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Sample records for nonequilibrium electron transport

  1. Non-equilibrium electron transport in degenerate nitride heterostructures-dynamic screening effects

    NASA Astrophysics Data System (ADS)

    Anderson, D. R.; Babiker, M.; Bennett, C. R.; Probert, M. I. J.

    2003-04-01

    We show how dynamic screening effects on non-equilibrium electron transport can be incorporated in the case of electronically dense GaN-based quantum wells. The theory is based on the Boltzmann equation, leading to evaluations of the momentum relaxation time and, hence, the electron mobility in these heterostructures. We find that both screening and anti-screening effects are manifest as the electron density varies. However, anti-screening dominates over a wide range of densities, with screening commencing at densities appropriate for phonon-plasmon coupling.

  2. Nonequilibrium mesoscopic transport: a genealogy

    NASA Astrophysics Data System (ADS)

    Das, Mukunda P.; Green, Frederick

    2012-05-01

    Models of nonequilibrium quantum transport underpin all modern electronic devices, from the largest scales to the smallest. Past simplifications such as coarse graining and bulk self-averaging served well to understand electronic materials. Such particular notions become inapplicable at mesoscopic dimensions, edging towards the truly quantum regime. Nevertheless a unifying thread continues to run through transport physics, animating the design of small-scale electronic technology: microscopic conservation and nonequilibrium dissipation. These fundamentals are inherent in quantum transport and gain even greater and more explicit experimental meaning in the passage to atomic-sized devices. We review their genesis, their theoretical context, and their governing role in the electronic response of meso- and nanoscopic systems.

  3. Emittance growth of an nonequilibrium intense electron beam in a transport channel with discrete focusing

    SciTech Connect

    Carlsten, B.E.

    1997-02-01

    The author analyzes the emittance growth mechanisms for a continuous, intense electron beam in a focusing transport channel, over distances short enough that the beam does not reach equilibrium. The emittance grows from the effect of nonlinear forces arising from (1) current density nonuniformities, (2) energy variations leading to nonlinearities in the space-charge force even if the current density is uniform, (3) axial variations in the radial vector potential, (4) an axial velocity shear along the beam, and (5) an energy redistribution of the beam as the beam compresses or expands. The emittance growth is studied analytically and numerically for the cases of balanced flow, tight focusing, and slight beam scalloping, and is additionally studied numerically for an existing 6-MeV induction linear accelerator. Rules for minimizing the emittance along a beamline are established. Some emittance growth will always occur, both from current density nonuniformities that arise along the transport and from beam radius changes along the transport.

  4. Quantum nonequilibrium approach for fast electron transport in open systems: photosynthetic reaction centers.

    PubMed

    Pudlak, M; Pichugin, K N; Nazmitdinov, R G; Pincak, R

    2011-11-01

    Creation of electrons or excitons by external fields in a system with initially statistically independent unrelaxed vibrational modes leads to an initial condition term. The contribution of this term in the time convolution generalized master-equation approach is studied in the second order of the perturbation theory in path-integral formalism. The developed approach, applied for the analysis of dynamics in the photosynthetic reaction center, exhibits the key role of the initial condition terms at the primary stage of electron transfer.

  5. Effective equilibrium theory of nonequilibrium quantum transport

    SciTech Connect

    Dutt, Prasenjit; Koch, Jens; Han, Jong; Le Hur, Karyn

    2011-12-15

    The theoretical description of strongly correlated quantum systems out of equilibrium presents several challenges and a number of open questions persist. Here, we focus on nonlinear electronic transport through an interacting quantum dot maintained at finite bias using a concept introduced by Hershfield [S. Hershfield, Phys. Rev. Lett. 70 2134 (1993)] whereby one can express such nonequilibrium quantum impurity models in terms of the system's Lippmann-Schwinger operators. These scattering operators allow one to reformulate the nonequilibrium problem as an effective equilibrium problem associated with a modified Hamiltonian. In this paper, we provide a pedagogical analysis of the core concepts of the effective equilibrium theory. First, we demonstrate the equivalence between observables computed using the Schwinger-Keldysh framework and the effective equilibrium approach, and relate Green's functions in the two theoretical frameworks. Second, we expound some applications of this method in the context of interacting quantum impurity models. We introduce a novel framework to treat effects of interactions perturbatively while capturing the entire dependence on the bias voltage. For the sake of concreteness, we employ the Anderson model as a prototype for this scheme. Working at the particle-hole symmetric point, we investigate the fate of the Abrikosov-Suhl resonance as a function of bias voltage and magnetic field. - Highlights: > Reformulation of steady-state nonequilibrium quantum transport, following Hershfield. > Derivation of effective equilibrium density operator using the 'open-system' approach. > Equivalence with the Keldysh description and formulas relating the two approaches. > Novel framework to treat interactions perturbatively. > Application to nonequilibrium Anderson model and fate of Abrikosov-Suhl resonance.

  6. Electron Systems Out of Equilibrium: Nonequilibrium Green's Function Approach

    NASA Astrophysics Data System (ADS)

    Špička, Václav Velický, Bedřich Kalvová, Anděla

    2015-10-01

    This review deals with the state of the art and perspectives of description of non-equilibrium many body systems using the non-equilibrium Green's function (NGF) method. The basic aim is to describe time evolution of the many-body system from its initial state over its transient dynamics to its long time asymptotic evolution. First, we discuss basic aims of transport theories to motivate the introduction of the NGF techniques. Second, this article summarizes the present view on construction of the electron transport equations formulated within the NGF approach to non-equilibrium. We discuss incorporation of complex initial conditions to the NGF formalism, and the NGF reconstruction theorem, which serves as a tool to derive simplified kinetic equations. Three stages of evolution of the non-equilibrium, the first described by the full NGF description, the second by a Non-Markovian Generalized Master Equation and the third by a Markovian Master Equation will be related to each other.

  7. Nonequilibrium transport in superconducting filaments

    NASA Technical Reports Server (NTRS)

    Arutyunov, K. YU.; Danilova, N. P.; Nikolaeva, A. A.

    1995-01-01

    The step-like current-voltage characteristics of highly homogeneous single-crystalline tin and indium thin filaments has been measured. The length of the samples L approximately 1 cm was much greater than the nonequilibrium quasiparticle relaxation length Lambda. It was found that the activation of a successive i-th voltage step occurs at current significantly greater than the one derived with the assumption that the phase slip centers are weakly interacting on a scale L much greater than Lambda. The observation of 'subharmonic' fine structure on the voltage-current characteristics of tin filaments confirms the hypothesis of the long-range phase slip centers interaction.

  8. Spin-Seebeck effect on the surface of a topological insulator due to nonequilibrium spin-polarization parallel to the direction of thermally driven electronic transport

    NASA Astrophysics Data System (ADS)

    Chang, Po-Hao; Mahfouzi, Farzad; Nagaosa, Naoto; Nikolić, Branislav K.

    2014-05-01

    We study the transverse spin-Seebeck effect (SSE) on the surface of a three-dimensional topological insulator (TI) thin film, such as Bi2Se3, which is sandwiched between two normal metal leads. The temperature bias ΔT applied between the leads generates surface charge current which becomes spin polarized due to strong spin-orbit coupling on the TI surface, with polarization vector acquiring a component Px≃60% parallel to the direction of transport. When the third nonmagnetic voltage probe is attached to the portion of the TI surface across its width Ly, pure spin current will be injected into the probe where the inverse spin Hall effect (ISHE) converts it into a voltage signal |VISHE|max/ΔT ≃2.5μV/K (assuming the SH angle of the Pt voltage probe and Ly=1 mm). The existence of predicted nonequilibrium spin polarization parallel to the direction of electronic transport and the corresponding electron-driven SSE crucially relies on orienting quintuple layers (QLs) of Bi2Se3 orthogonal to the TI surface and tilted by 45∘ with respect to the direction of transport. Our analysis is based on the Landauer-Büttiker-type formula for spin currents in the leads of a multiterminal quantum-coherent junction, which is constructed by using nonequilibrium Green function formalism within which we show how to take into account arbitrary orientation of QLs via the self-energy describing coupling between semi-infinite normal metal leads and the TI sample.

  9. Nonequilibrium Interlayer Transport in Pulsed Laser Deposition

    SciTech Connect

    Tischler, Jonathan Zachary; Eres, Gyula; Larson, Ben C; Rouleau, Christopher M; Zschack, P.; Lowndes, Douglas H

    2006-01-01

    We use time-resolved surface x-ray diffraction measurements with microsecond range resolution to study the growth kinetics of pulsed laser deposited SrTiO3. Time-dependent surface coverages corresponding to single laser shots were determined directly from crystal truncation rod intensity transients. Analysis of surface coverage evolution shows that extremely fast nonequilibrium interlayer transport, which occurs concurrently with the arrival of the laser plume, dominates the deposition process. A much smaller fraction of material, which is governed by the dwell time between successive laser shots, is transferred by slow, thermally driven interlayer transport processes.

  10. Light-induced electronic non-equilibrium in plasmonic particles.

    PubMed

    Kornbluth, Mordechai; Nitzan, Abraham; Seideman, Tamar

    2013-05-01

    We consider the transient non-equilibrium electronic distribution that is created in a metal nanoparticle upon plasmon excitation. Following light absorption, the created plasmons decohere within a few femtoseconds, producing uncorrelated electron-hole pairs. The corresponding non-thermal electronic distribution evolves in response to the photo-exciting pulse and to subsequent relaxation processes. First, on the femtosecond timescale, the electronic subsystem relaxes to a Fermi-Dirac distribution characterized by an electronic temperature. Next, within picoseconds, thermalization with the underlying lattice phonons leads to a hot particle in internal equilibrium that subsequently equilibrates with the environment. Here we focus on the early stage of this multistep relaxation process, and on the properties of the ensuing non-equilibrium electronic distribution. We consider the form of this distribution as derived from the balance between the optical absorption and the subsequent relaxation processes, and discuss its implication for (a) heating of illuminated plasmonic particles, (b) the possibility to optically induce current in junctions, and (c) the prospect for experimental observation of such light-driven transport phenomena. PMID:23656152

  11. Temporal Response of Nonequilibrium Correlated Electrons

    SciTech Connect

    Moritz, Brian; Devereaux, T.P.; Freericks, J.K.; /Georgetown U.

    2010-08-26

    In this work we examine the time-resolved, instantaneous current response for the spinless Falicov-Kimball model at half-filling, on both sides of the Mott-Hubbard metal-insulator transition, driven by a strong electric field pump pulse. The results are obtained using an exact, nonequilibrium, many-body impurity solution specifically designed to treat the out-of-equilibrium evolution of electrons in time-dependent fields. We provide a brief introduction to the method and its computational details. We find that the current develops Bloch oscillations, similar to the case of DC driving fields, with an additional amplitude modulation, characterized by beats and induced by correlation effects. Correlations primarily manifest themselves through an overall reduction in magnitude and shift in the onset time of the current response with increasing interaction strength.

  12. Electrolytes: transport properties and non-equilibrium thermodynamics

    SciTech Connect

    Miller, D.G.

    1980-12-01

    This paper presents a review on the application of non-equilibrium thermodynamics to transport in electrolyte solutions, and some recent experimental work and results for mutual diffusion in electrolyte solutions.

  13. Combined physical and chemical nonequilibrium transport model for solution conduits

    NASA Astrophysics Data System (ADS)

    Field, Malcolm S.; Leij, Feike J.

    2014-02-01

    Solute transport in karst aquifers is primarily constrained to relatively complex and inaccessible solution conduits where transport is often rapid, turbulent, and at times constrictive. Breakthrough curves generated from tracer tests in solution conduits are typically positively-skewed with long tails evident. Physical nonequilibrium models to fit breakthrough curves for tracer tests in solution conduits are now routinely employed. Chemical nonequilibrium processes are likely important interactions, however. In addition to partitioning between different flow domains, there may also be equilibrium and nonequilibrium partitioning between the aqueous and solid phases. A combined physical and chemical nonequilibrium (PCNE) model was developed for an instantaneous release similar to that developed by Leij and Bradford (2009) for a pulse release. The PCNE model allows for partitioning open space in solution conduits into mobile and immobile flow regions with first-order mass transfer between the two regions to represent physical nonequilibrium in the conduit. Partitioning between the aqueous and solid phases proceeds either as an equilibrium process or as a first-order process and represents chemical nonequilibrium for both the mobile and immobile regions. Application of the model to three example breakthrough curves demonstrates the applicability of the combined physical and chemical nonequilibrium model to tracer tests conducted in karst aquifers, with exceptionally good model fits to the data. The three models, each from a different state in the United States, exhibit very different velocities, dispersions, and other transport properties with most of the transport occurring via the fraction of mobile water. Fitting the model suggests the potentially important interaction of physical and chemical nonequilibrium processes.

  14. Generalized nonequilibrium vertex correction method in coherent medium theory for quantum transport simulation of disordered nanoelectronics

    NASA Astrophysics Data System (ADS)

    Yan, Jiawei; Ke, Youqi

    2016-07-01

    Electron transport properties of nanoelectronics can be significantly influenced by the inevitable and randomly distributed impurities/defects. For theoretical simulation of disordered nanoscale electronics, one is interested in both the configurationally averaged transport property and its statistical fluctuation that tells device-to-device variability induced by disorder. However, due to the lack of an effective method to do disorder averaging under the nonequilibrium condition, the important effects of disorders on electron transport remain largely unexplored or poorly understood. In this work, we report a general formalism of Green's function based nonequilibrium effective medium theory to calculate the disordered nanoelectronics. In this method, based on a generalized coherent potential approximation for the Keldysh nonequilibrium Green's function, we developed a generalized nonequilibrium vertex correction method to calculate the average of a two-Keldysh-Green's-function correlator. We obtain nine nonequilibrium vertex correction terms, as a complete family, to express the average of any two-Green's-function correlator and find they can be solved by a set of linear equations. As an important result, the averaged nonequilibrium density matrix, averaged current, disorder-induced current fluctuation, and averaged shot noise, which involve different two-Green's-function correlators, can all be derived and computed in an effective and unified way. To test the general applicability of this method, we applied it to compute the transmission coefficient and its fluctuation with a square-lattice tight-binding model and compared with the exact results and other previously proposed approximations. Our results show very good agreement with the exact results for a wide range of disorder concentrations and energies. In addition, to incorporate with density functional theory to realize first-principles quantum transport simulation, we have also derived a general form of

  15. Non-equilibrium STLS approach to transport properties of single impurity Anderson model

    NASA Astrophysics Data System (ADS)

    Rezai, Raheleh; Ebrahimi, Farshad

    2014-04-01

    In this work, using the non-equilibrium Keldysh formalism, we study the effects of the electron-electron interaction and the electron-spin correlation on the non-equilibrium Kondo effect and the transport properties of the symmetric single impurity Anderson model (SIAM) at zero temperature by generalizing the self-consistent method of Singwi, Tosi, Land, and Sjolander (STLS) for a single-band tight-binding model with Hubbard type interaction to out of equilibrium steady-states. We at first determine in a self-consistent manner the non-equilibrium spin correlation function, the effective Hubbard interaction, and the double-occupancy at the impurity site. Then, using the non-equilibrium STLS spin polarization function in the non-equilibrium formalism of the iterative perturbation theory (IPT) of Yosida and Yamada, and Horvatic and Zlatic, we compute the spectral density, the current-voltage characteristics and the differential conductance as functions of the applied bias and the strength of on-site Hubbard interaction. We compare our spectral densities at zero bias with the results of numerical renormalization group (NRG) and depict the effects of the electron-electron interaction and electron-spin correlation at the impurity site on the aforementioned properties by comparing our numerical result with the order U2 IPT. Finally, we show that the obtained numerical results on the differential conductance have a quadratic universal scaling behavior and the resulting Kondo temperature shows an exponential behavior.

  16. Nonequilibrium transport in superconducting tunneling structures.

    SciTech Connect

    Chtchelkatchev, N. M.; Vinokur, V. M.; Baturina, T. I.

    2010-12-01

    We derive the current-voltage (I-V) characteristics of far from equilibrium superconducting tunneling arrays and find that the energy relaxation ensuring the charge transfer occurs in two stages: (i) the energy exchange between charge carriers and the intermediate bosonic agent, environment, and (ii) relaxing the energy further to the (phonon) thermostat, the bath, provided the rate of the environmental modes-phonon interactions is slower than their energy exchange rate with the tunneling junction. For a single junction we find I {proportional_to} (V/R)ln({Lambda}/V), where R is the bare tunnel resistance of the junction and {Lambda} is the high energy cut-off of the electron-environment interaction. In large tunneling arrays comprised of macroscopic number of junctions, low-temperature transport is governed by the cotunneling processes losing energy to the electron-hole environment. Below some critical temperature, T*, the Coulomb interactions open a finite gap in the environment excitations spectrum blocking simultaneously Cooper pair and normal excitations currents through the array; this is the microscopic mechanism of the insulator-to-superinsulator transition.

  17. Non-equilibrium Transport in Carbon based Adsorbate Systems

    NASA Astrophysics Data System (ADS)

    Fürst, Joachim; Brandbyge, Mads; Stokbro, Kurt; Jauho, Antti-Pekka

    2007-03-01

    We have used the Atomistix Tool Kit(ATK) and TranSIESTA[1] packages to investigate adsorption of iron atoms on a graphene sheet. The technique of both codes is based on density functional theory using local basis sets[2], and non-equilibrium Green's functions (NEGF) to calculate the charge distribution under external bias. Spin dependent electronic structure calculations are performed for different iron coverages. These reveal adsorption site dependent charge transfer from iron to graphene leading to screening effects. Transport calculations show spin dependent scattering of the transmission which is analysed obtaining the transmission eigenchannels for each spin type. The phenomena of electromigration of iron in these systems at finite bias will be discussed, estimating the so-called wind force from the reflection[3]. [1] M. Brandbyge, J.-L. Mozos, P. Ordejon, J. Taylor, and K. Stokbro. Physical Review B (Condensed Matter and Materials Physics), 65(16):165401/11-7, 2002. [2] Jose M. Soler, Emilio Artacho, Julian D. Gale, Alberto Garcia, Javier Junquera, Pablo Ordejon, and Daniel Sanchez-Portal. Journal of Physics Condensed Matter, 14(11):2745-2779, 2002. [3] Sorbello. Theory of electromigration. Solid State Physics, 1997.

  18. Non-equilibrium STLS approach to transport properties of single impurity Anderson model

    SciTech Connect

    Rezai, Raheleh Ebrahimi, Farshad

    2014-04-15

    In this work, using the non-equilibrium Keldysh formalism, we study the effects of the electron–electron interaction and the electron-spin correlation on the non-equilibrium Kondo effect and the transport properties of the symmetric single impurity Anderson model (SIAM) at zero temperature by generalizing the self-consistent method of Singwi, Tosi, Land, and Sjolander (STLS) for a single-band tight-binding model with Hubbard type interaction to out of equilibrium steady-states. We at first determine in a self-consistent manner the non-equilibrium spin correlation function, the effective Hubbard interaction, and the double-occupancy at the impurity site. Then, using the non-equilibrium STLS spin polarization function in the non-equilibrium formalism of the iterative perturbation theory (IPT) of Yosida and Yamada, and Horvatic and Zlatic, we compute the spectral density, the current–voltage characteristics and the differential conductance as functions of the applied bias and the strength of on-site Hubbard interaction. We compare our spectral densities at zero bias with the results of numerical renormalization group (NRG) and depict the effects of the electron–electron interaction and electron-spin correlation at the impurity site on the aforementioned properties by comparing our numerical result with the order U{sup 2} IPT. Finally, we show that the obtained numerical results on the differential conductance have a quadratic universal scaling behavior and the resulting Kondo temperature shows an exponential behavior. -- Highlights: •We introduce for the first time the non-equilibrium method of STLS for Hubbard type models. •We determine the transport properties of SIAM using the non-equilibrium STLS method. •We compare our results with order-U2 IPT and NRG. •We show that non-equilibrium STLS, contrary to the GW and self-consistent RPA, produces the two Hubbard peaks in DOS. •We show that the method keeps the universal scaling behavior and correct

  19. Arrangement of a nanostructure array to control equilibrium and nonequilibrium transports of macromolecules.

    PubMed

    Yasui, Takao; Kaji, Noritada; Ogawa, Ryo; Hashioka, Shingi; Tokeshi, Manabu; Horiike, Yasuhiro; Baba, Yoshinobu

    2015-05-13

    Exploiting the nonequilibrium transport of macromolecules makes it possible to increase the separation speed without any loss of separation resolution. Here we report the arrangement of a nanostructure array in microchannels to control equilibrium and nonequilibrium transports of macromolecules. The direct observation and separation of macromolecules in the nanopillar array reported here are the first to reveal the nonequilibrium transport, which has a potential to overcome the intrinsic trade-off between the separation speed and resolution.

  20. Nonequilibrium phase transitions in cuprates observed by ultrafast electron crystallography.

    PubMed

    Gedik, Nuh; Yang, Ding-Shyue; Logvenov, Gennady; Bozovic, Ivan; Zewail, Ahmed H

    2007-04-20

    Nonequilibrium phase transitions, which are defined by the formation of macroscopic transient domains, are optically dark and cannot be observed through conventional temperature- or pressure-change studies. We have directly determined the structural dynamics of such a nonequilibrium phase transition in a cuprate superconductor. Ultrafast electron crystallography with the use of a tilted optical geometry technique afforded the necessary atomic-scale spatial and temporal resolutions. The observed transient behavior displays a notable "structural isosbestic" point and a threshold effect for the dependence of c-axis expansion (Deltac) on fluence (F), with Deltac/F = 0.02 angstrom/(millijoule per square centimeter). This threshold for photon doping occurs at approximately 0.12 photons per copper site, which is unexpectedly close to the density (per site) of chemically doped carriers needed to induce superconductivity. PMID:17446397

  1. Two-Temperature Model of Nonequilibrium Electron Relaxation:. a Review

    NASA Astrophysics Data System (ADS)

    Singh, Navinder

    The present paper is a review of the phenomena related to nonequilibrium electron relaxation in bulk and nano-scale metallic samples. The workable Two-Temperature Model (TTM) based on Boltzmann-Bloch-Peierls kinetic equation has been applied to study the ultra-fast (femto-second) electronic relaxation in various metallic systems. The advent of new ultra-fast (femto-second) laser technology and pump-probe spectroscopy has produced wealth of new results for micro- and nano-scale electronic technology. The aim of this paper is to clarify the TTM, conditions of its validity and nonvalidity, its modifications for nano-systems, to sum-up the progress, and to point out open problems in this field. We also give a phenomenological integro-differential equation for the kinetics of nondegenerate electrons that goes beyond the TTM.

  2. Combined physical and chemical nonequilibrium transport model: Analytical solution, moments, and application to colloids

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The transport of solutes and colloids in porous media is influenced by a variety of physical and chemical nonequilibrium processes. A combined physical–chemical nonequilibrium (PCNE) model was therefore used to describe general mass transport. The model partitions the pore space into “mobile” and “i...

  3. Non-Equilibrium Hyperbolic Transport in Transcriptional Regulation

    PubMed Central

    Hernández-Lemus, Enrique; Correa-Rodríguez, María D.

    2011-01-01

    In this work we studied memory and irreversible transport phenomena in a non-equilibrium thermodynamical model for genomic transcriptional regulation. Transcriptional regulation possess an extremely complex phenomenology, and it is, of course, of foremost importance in organismal cell development and in the pathogenesis of complex diseases. A better understanding of the way in which these processes occur is mandatory to optimize the construction of gene regulatory networks, but also to connect these networks with multi-scale phenomena (e.g. metabolism, signalling pathways, etc.) under an integrative Systems Biology-like vision. In this paper we analyzed three simple mechanisms of genetic stimulation: an instant pulse, a periodic biochemical signal and a saturation process with sigmoidal kinetics and from these we derived the system's thermodynamical response, in the form of, for example, anomalous transcriptional bursts. PMID:21754990

  4. Nonequilibrium spin-polarized thermal transport in ferromagnetic-quantum dot-metal system

    NASA Astrophysics Data System (ADS)

    Xu, Li; Li, Zhi-Jian; Niu, Pengbin; Nie, Yi-Hang

    2016-10-01

    We use nonequilibrium Green function to analyze the nonequilibrium spin-polarized thermal transport through the ferromagnetic-quantum dot-metal system, in which a quantum dot (QD) is coupled to the ferromagnetic and metal electrodes with the voltage bias and the temperature shift. The differential thermoelectric conductance L (θ) is always zero and has no relation with the temperature shift when ε is equal to the Fermi level. The positive and negative values of L (θ) manifest the thermoelectric characteristic of electron-like (or hole-like) carrier when the temperature shift is nonzero. The electrostatic potential U becomes spin-dependent, and makes the dot level renormalization when the ferromagnetic-quantum dot-metal system is driven by the voltage bias and the temperature shift. We define that the spin polarization of the currents between the spin current Is and the electric current Ic is denoted as Is /Ic. The spin polarization Is /Ic shows novel and unique physical phenomenon when the voltage bias and the temperature shift are changed in the nonequilibrium state. Another interesting phenomenon is that we can obtain the pure spin current and a zero point of the thermocurrent Ith by adjusting the voltage bias and the temperature shift.

  5. Methodology for determining the electronic thermal conductivity of metals via direct nonequilibrium ab initio molecular dynamics

    NASA Astrophysics Data System (ADS)

    Yue, Sheng-Ying; Zhang, Xiaoliang; Stackhouse, Stephen; Qin, Guangzhao; Di Napoli, Edoardo; Hu, Ming

    2016-08-01

    Many physical properties of metals can be understood in terms of the free electron model, as proven by the Wiedemann-Franz law. According to this model, electronic thermal conductivity can be inferred from the Boltzmann transport equation (BTE). However, the BTE does not perform well for some complex metals, such as Cu. Moreover, the BTE cannot clearly describe the origin of the thermal energy carried by electrons or how this energy is transported in metals. The charge distribution of conduction electrons in metals is known to reflect the electrostatic potential of the ion cores. Based on this premise, we develop a methodology for evaluating electronic thermal conductivity of metals by combining the free electron model and nonequilibrium ab initio molecular dynamics simulations. We confirm that the kinetic energy of thermally excited electrons originates from the energy of the spatial electrostatic potential oscillation, which is induced by the thermal motion of ion cores. This method directly predicts the electronic thermal conductivity of pure metals with a high degree of accuracy, without explicitly addressing any complicated scattering processes of free electrons. Our methodology offers a route to understand the physics of heat transfer by electrons at the atomistic level. The methodology can be further extended to the study of similar electron-involved problems in materials, such as electron-phonon coupling, which is underway currently.

  6. Mechanisms of nonequilibrium electron-phonon coupling and thermal conductance at interfaces

    NASA Astrophysics Data System (ADS)

    Giri, Ashutosh; Gaskins, John T.; Donovan, Brian F.; Szwejkowski, Chester; Warzoha, Ronald J.; Rodriguez, Mark A.; Ihlefeld, Jon; Hopkins, Patrick E.

    2015-03-01

    We study the electron and phonon thermal coupling mechanisms at interfaces between gold films with and without Ti adhesion layers on various substrates via pump-probe time-domain thermoreflectance. The coupling between the electronic and the vibrational states is increased by more than a factor of five with the inclusion of an ˜3 nm Ti adhesion layer between the Au film and the non-metal substrate. Furthermore, we show an increase in the rate of relaxation of the electron system with increasing electron and lattice temperatures induced by the laser power and attribute this to enhanced electron-electron scattering, a transport channel that becomes more pronounced with increased electron temperatures. The inclusion of the Ti layer also results in a linear dependence of the electron-phonon relaxation rate with temperature, which we attribute to the coupling of electrons at and near the Ti/substrate interface. This enhanced electron-phonon coupling due to electron-interface scattering is shown to have negligible influence on the Kapitza conductances between the Au/Ti and the substrates at longer time scales when the electrons and phonons in the metal have equilibrated. These results suggest that only during highly nonequilibrium conditions between the electrons and phonons (Te ≫ Tp) does electron-phonon scattering at an interface contribute to thermal boundary conductance.

  7. Mechanisms of nonequilibrium electron-phonon coupling and thermal conductance at interfaces

    SciTech Connect

    Giri, Ashutosh; Gaskins, John T.; Donovan, Brian F.; Szwejkowski, Chester; Hopkins, Patrick E.; Warzoha, Ronald J.; Rodriguez, Mark A.; Ihlefeld, Jon

    2015-03-14

    We study the electron and phonon thermal coupling mechanisms at interfaces between gold films with and without Ti adhesion layers on various substrates via pump-probe time-domain thermoreflectance. The coupling between the electronic and the vibrational states is increased by more than a factor of five with the inclusion of an ∼3 nm Ti adhesion layer between the Au film and the non-metal substrate. Furthermore, we show an increase in the rate of relaxation of the electron system with increasing electron and lattice temperatures induced by the laser power and attribute this to enhanced electron-electron scattering, a transport channel that becomes more pronounced with increased electron temperatures. The inclusion of the Ti layer also results in a linear dependence of the electron-phonon relaxation rate with temperature, which we attribute to the coupling of electrons at and near the Ti/substrate interface. This enhanced electron-phonon coupling due to electron-interface scattering is shown to have negligible influence on the Kapitza conductances between the Au/Ti and the substrates at longer time scales when the electrons and phonons in the metal have equilibrated. These results suggest that only during highly nonequilibrium conditions between the electrons and phonons (T{sub e} ≫ T{sub p}) does electron-phonon scattering at an interface contribute to thermal boundary conductance.

  8. Nonequilibrium thermal transport and its relation to linear response

    NASA Astrophysics Data System (ADS)

    Karrasch, C.; Ilan, R.; Moore, J. E.

    2013-11-01

    We study the real-time dynamics of spin chains driven out of thermal equilibrium by an initial temperature gradient TL≠TR using density matrix renormalization group methods. We demonstrate that the nonequilibrium energy current saturates fast to a finite value if the linear-response thermal conductivity is infinite, i.e., if the Drude weight D is nonzero. Our data suggest that a nonintegrable dimerized chain might support such dissipationless transport (D>0). We show that the steady-state value JE of the current for arbitrary TL≠TR is of the functional form JE=f(TL)-f(TR), i.e., it is completely determined by the linear conductance. We argue for this functional form, which is essentially a Stefan-Boltzmann law in this integrable model; for the XXX ferromagnet, f can be computed via the thermodynamic Bethe ansatz in good agreement with the numerics. Inhomogeneous systems exhibiting different bulk parameters as well as Luttinger liquid boundary physics induced by single impurities are discussed briefly.

  9. Field scale DNAPLs transport under nonequilibrium sorption conditions.

    PubMed

    Ahmed, Ashraf A; Chen, Daoyi

    2006-01-01

    The purpose of this work is to study the desorption of dense nonaqueous phase liquids (DNAPLs), TCE in particular, from solid particles in field scale heterogeneous aquifers upon their remediation. A computer program, capable of simulating the fate and transport of NAPLs in porous media, has been developed to work under nonequilibrium sorption conditions. The model has been applied to a field scale site at Hill Air Force Base, Utah, which has been contaminated by DNAPLs. The simulated domain was 155 ft (47.25 m) long, 60 ft (18.29 m) wide, and 15.5 ft (4.72 m) thick. This thickness represents only the saturated zone of the aquifer. Changes in permeability, grain size distribution, and sorptive properties throughout the site have been incorporated into the model. Immediately after the aquifer cleanup, the DNAPL concentration in the aqueous phase was assumed to be zero, and this was considered the start-off time for the simulation. Results show that, with an increase in time, the TCE diffused out of the solid particles, forming a plume. The rate of contaminant diffusion was observed to be very fast at the start, followed by a very slow stage, with a number of years required for substantial desorption of the contaminant from the solid particles. There were local variations in contaminant concentration in the fluid phase across the site due to aquifer heterogeneity. A comparison between numerical results and water samples taken from the site after the end of the cleanup operation is also presented.

  10. Non-equilibrium Green function method: theory and application in simulation of nanometer electronic devices

    NASA Astrophysics Data System (ADS)

    Do, Van-Nam

    2014-09-01

    We review fundamental aspects of the non-equilibrium Green function method in the simulation of nanometer electronic devices. The method is implemented into our recently developed computer package OPEDEVS to investigate transport properties of electrons in nano-scale devices and low-dimensional materials. Concretely, we present the definition of the four real-time Green functions, the retarded, advanced, lesser and greater functions. Basic relations among these functions and their equations of motion are also presented in detail as the basis for the performance of analytical and numerical calculations. In particular, we review in detail two recursive algorithms, which are implemented in OPEDEVS to solve the Green functions defined in finite-size opened systems and in the surface layer of semi-infinite homogeneous ones. Operation of the package is then illustrated through the simulation of the transport characteristics of a typical semiconductor device structure, the resonant tunneling diodes.

  11. The effect of electron-electron interaction induced dephasing on electronic transport in graphene nanoribbons

    SciTech Connect

    Kahnoj, Sina Soleimani; Touski, Shoeib Babaee; Pourfath, Mahdi E-mail: pourfath@iue.tuwien.ac.at

    2014-09-08

    The effect of dephasing induced by electron-electron interaction on electronic transport in graphene nanoribbons is theoretically investigated. In the presence of disorder in graphene nanoribbons, wavefunction of electrons can set up standing waves along the channel and the conductance exponentially decreases with the ribbon's length. Employing the non-equilibrium Green's function formalism along with an accurate model for describing the dephasing induced by electron-electron interaction, we show that this kind of interaction prevents localization and transport of electrons remains in the diffusive regime where the conductance is inversely proportional to the ribbon's length.

  12. Nonequilibrium electron dynamics: Formation of the quasiparticle peak

    NASA Astrophysics Data System (ADS)

    Sayyad, Sharareh; Eckstein, Martin

    We characterize how the narrow quasiparticle band of the one-band Hubbard model forms out of a bad metallic state in a time-dependent metal-insulator transition, using nonequilibrium slave-rotor dynamical mean field theory. Our results exhibit a nontrivial electronic timescale which is much longer than the width of the quasiparticle peak itself. To study this timescale, we perform a fast ramp from the insulating phase into the metallic region of the phase diagram, resulting in a highly excited state, and study the equilibration of the system with a weakly coupled phononic bath. The slow relaxation behavior is explained by surveilling the interplay between spinon and rotor degrees of freedom. Since the system is initially prepared in an insulating phase, the quasi-particle peak emerges when spinons catch up the metal-insulator crossover region, which is reached earlier by the rotor. At this point, spinon and rotor become weakly coupled, and the resulting very slow equilibration of the spinon is a bottleneck for the dynamics. After the birth of the quasiparticle peak, its height enhances by the construction of the low-energy spectrum of the rotor, which then lacks behind the relaxation of the spinon.

  13. Nonequilibrium itinerant-electron magnetism: A time-dependent mean-field theory

    NASA Astrophysics Data System (ADS)

    Secchi, A.; Lichtenstein, A. I.; Katsnelson, M. I.

    2016-08-01

    We study the dynamical magnetic susceptibility of a strongly correlated electronic system in the presence of a time-dependent hopping field, deriving a generalized Bethe-Salpeter equation that is valid also out of equilibrium. Focusing on the single-orbital Hubbard model within the time-dependent Hartree-Fock approximation, we solve the equation in the nonequilibrium adiabatic regime, obtaining a closed expression for the transverse magnetic susceptibility. From this, we provide a rigorous definition of nonequilibrium (time-dependent) magnon frequencies and exchange parameters, expressed in terms of nonequilibrium single-electron Green's functions and self-energies. In the particular case of equilibrium, we recover previously known results.

  14. Reactive species in non-equilibrium atmospheric-pressure plasmas: Generation, transport, and biological effects

    NASA Astrophysics Data System (ADS)

    Lu, X.; Naidis, G. V.; Laroussi, M.; Reuter, S.; Graves, D. B.; Ostrikov, K.

    2016-05-01

    Non-equilibrium atmospheric-pressure plasmas have recently become a topical area of research owing to their diverse applications in health care and medicine, environmental remediation and pollution control, materials processing, electrochemistry, nanotechnology and other fields. This review focuses on the reactive electrons and ionic, atomic, molecular, and radical species that are produced in these plasmas and then transported from the point of generation to the point of interaction with the material, medium, living cells or tissues being processed. The most important mechanisms of generation and transport of the key species in the plasmas of atmospheric-pressure plasma jets and other non-equilibrium atmospheric-pressure plasmas are introduced and examined from the viewpoint of their applications in plasma hygiene and medicine and other relevant fields. Sophisticated high-precision, time-resolved plasma diagnostics approaches and techniques are presented and their applications to monitor the reactive species and plasma dynamics in the plasma jets and other discharges, both in the gas phase and during the plasma interaction with liquid media, are critically reviewed. The large amount of experimental data is supported by the theoretical models of reactive species generation and transport in the plasmas, surrounding gaseous environments, and plasma interaction with liquid media. These models are presented and their limitations are discussed. Special attention is paid to biological effects of the plasma-generated reactive oxygen and nitrogen (and some other) species in basic biological processes such as cell metabolism, proliferation, survival, etc. as well as plasma applications in bacterial inactivation, wound healing, cancer treatment and some others. Challenges and opportunities for theoretical and experimental research are discussed and the authors' vision for the emerging convergence trends across several disciplines and application domains is presented to

  15. Understanding Nonequilibrium and Correlated Electron Behavior in Molecular Junctions

    NASA Astrophysics Data System (ADS)

    Wegewijs, Maarten

    2010-03-01

    I present an overview of the effects of the strong correlations in single-molecule junctions on non-linear transport, focusing on theory while comparing with several recent experiments. In the brief introduction I outline our real-time diagrammatic transport theory and its renormalization group extensions. In this approach a kinetic equation (generalized master equation) for the molecular density matrix incorporates both the quantum coherence and the strong correlations between electronic, vibrational and spin degrees of freedom of the device. The molecular state and non-linear current are calculated perturbatively beyond the lowest order in the coupling to the electrodes. As a first example, a detailed comparison with recent measurements on carbon-nanotube ``peapod'' devices is presented, indicating non-trivial hybridization and Coulomb interaction with the host nanotube quantum dot. The remainder of the talk focuses on predictions for specific electromechanical (electron-vibration coupling) and magnetic effects (spin-orbit coupling). I discuss non-linear transport signatures of vibrations when going beyond the simplified pictures of sequential tunneling (which breaks down due to quantum fluctuations) and the Born-Oppenheimer separation (its breakdown resulting in pseudo-Jahn-Teller coupling). Both effects have recently been observed. Finally, I address the interplay of transport with various aspects of molecular magnetism, such as antisymmetric (Dzyaloshinskii-Moriya) exchange and magnetic anisotropy. A comparison with recent transport experiments reveals the possibility of electric-field tunable molecular magnetism in an ``ferric-star'' molecular device.

  16. Unique characteristics of nonequilibrium carrier transport dynamics in an undoped GaAs/n-type GaAs epitaxial structure

    NASA Astrophysics Data System (ADS)

    Hasegawa, Takayuki; Nakayama, Masaaki

    2016-07-01

    We have investigated nonequilibrium carrier dynamics in an undoped GaAs/n-type GaAs epitaxial structure at room temperature using reflection-type pump–probe spectroscopy at different pump photon energies and Monte Carlo simulation. It was found that the transport process of photogenerated electrons in the undoped layer is characterized by the valance between the quasiballistic motion passing through the undoped layer and the intervalley scattering from the Γ valley to the L one as a function of the excess energy of photogenerated electrons. The Γ–L scattering component exhibits threshold-like appearance and then gradually increases with increasing excess energy.

  17. Typical pure nonequilibrium steady states and irreversibility for quantum transport.

    PubMed

    Monnai, Takaaki; Yuasa, Kazuya

    2016-07-01

    It is known that each single typical pure state in an energy shell of a large isolated quantum system well represents a thermal equilibrium state of the system. We show that such typicality holds also for nonequilibrium steady states (NESS's). We consider a small quantum system coupled to multiple infinite reservoirs. In the long run, the total system reaches a unique NESS. We identify a large Hilbert space from which pure states of the system are to be sampled randomly and show that the typical pure states well describe the NESS. We also point out that the irreversible relaxation to the unique NESS is important to the typicality of the pure NESS's.

  18. Typical pure nonequilibrium steady states and irreversibility for quantum transport

    NASA Astrophysics Data System (ADS)

    Monnai, Takaaki; Yuasa, Kazuya

    2016-07-01

    It is known that each single typical pure state in an energy shell of a large isolated quantum system well represents a thermal equilibrium state of the system. We show that such typicality holds also for nonequilibrium steady states (NESS's). We consider a small quantum system coupled to multiple infinite reservoirs. In the long run, the total system reaches a unique NESS. We identify a large Hilbert space from which pure states of the system are to be sampled randomly and show that the typical pure states well describe the NESS. We also point out that the irreversible relaxation to the unique NESS is important to the typicality of the pure NESS's.

  19. Typical pure nonequilibrium steady states and irreversibility for quantum transport.

    PubMed

    Monnai, Takaaki; Yuasa, Kazuya

    2016-07-01

    It is known that each single typical pure state in an energy shell of a large isolated quantum system well represents a thermal equilibrium state of the system. We show that such typicality holds also for nonequilibrium steady states (NESS's). We consider a small quantum system coupled to multiple infinite reservoirs. In the long run, the total system reaches a unique NESS. We identify a large Hilbert space from which pure states of the system are to be sampled randomly and show that the typical pure states well describe the NESS. We also point out that the irreversible relaxation to the unique NESS is important to the typicality of the pure NESS's. PMID:27575115

  20. Combined physical and chemical nonequilibrium transport model: Analytical solution, moments, and application to colloids

    NASA Astrophysics Data System (ADS)

    Leij, Feike J.; Bradford, Scott A.

    2009-11-01

    The transport of solutes and colloids in porous media is influenced by a variety of physical and chemical nonequilibrium processes. A combined physical-chemical nonequilibrium (PCNE) model was therefore used to describe general mass transport. The model partitions the pore space into "mobile" and "immobile" flow regions with first-order mass transfer between these two regions (i.e, "physical" nonequilibrium or PNE). Partitioning between the aqueous and solid phases can either proceed as an equilibrium or a first-order process (i.e, "chemical" nonequilibrium or CNE) for both the mobile and immobile regions. An analytical solution for the PCNE model is obtained using iterated Laplace transforms. This solution complements earlier semi-analytical and numerical approaches to model solute transport with the PCNE model. The impact of selected model parameters on solute breakthrough curves is illustrated. As is well known, nonequilibrium results in earlier solute breakthrough with increased tailing. The PCNE model allows greater flexibility to describe this trend; for example, a closer resemblance between solute input and effluent pulse. Expressions for moments and transfer functions are presented to facilitate the analytical use of the PCNE model. Contours of mean breakthrough time, variance, and spread of the colloid breakthrough curves as a function of PNE and CNE parameters demonstrate the utility of a model that accounts for both physical and chemical nonequilibrium processes. The model is applied to describe representative colloid breakthrough curves in Ottawa sands reported by Bradford et al. (2002). An equilibrium model provided a good description of breakthrough curves for the bromide tracer but could not adequately describe the colloid data. A considerably better description was provide by the simple CNE model but the best description, especially for the larger 3.2-µm colloids, was provided by the PCNE model.

  1. Combined physical and chemical nonequilibrium transport model: analytical solution, moments, and application to colloids.

    PubMed

    Leij, Feike J; Bradford, Scott A

    2009-11-20

    The transport of solutes and colloids in porous media is influenced by a variety of physical and chemical nonequilibrium processes. A combined physical-chemical nonequilibrium (PCNE) model was therefore used to describe general mass transport. The model partitions the pore space into "mobile" and "immobile" flow regions with first-order mass transfer between these two regions (i.e, "physical" nonequilibrium or PNE). Partitioning between the aqueous and solid phases can either proceed as an equilibrium or a first-order process (i.e, "chemical" nonequilibrium or CNE) for both the mobile and immobile regions. An analytical solution for the PCNE model is obtained using iterated Laplace transforms. This solution complements earlier semi-analytical and numerical approaches to model solute transport with the PCNE model. The impact of selected model parameters on solute breakthrough curves is illustrated. As is well known, nonequilibrium results in earlier solute breakthrough with increased tailing. The PCNE model allows greater flexibility to describe this trend; for example, a closer resemblance between solute input and effluent pulse. Expressions for moments and transfer functions are presented to facilitate the analytical use of the PCNE model. Contours of mean breakthrough time, variance, and spread of the colloid breakthrough curves as a function of PNE and CNE parameters demonstrate the utility of a model that accounts for both physical and chemical nonequilibrium processes. The model is applied to describe representative colloid breakthrough curves in Ottawa sands reported by Bradford et al. (2002). An equilibrium model provided a good description of breakthrough curves for the bromide tracer but could not adequately describe the colloid data. A considerably better description was provide by the simple CNE model but the best description, especially for the larger 3.2-microm colloids, was provided by the PCNE model.

  2. Nonequilibrium transport of InAs/GaAs(111)A heterostructures coupled with superconducting Nb electrodes

    NASA Astrophysics Data System (ADS)

    Akazaki, Tatsushi; Yamaguchi, Hiroshi; Takayanagi, Hideaki

    2004-04-01

    We have investigated the nonequilibrium transport of a two-dimensional electron gas (2DEG) in an InAs/GaAs(111)A heterostructure coupled with superconducting Nb electrodes. In the superconductor (S)/normal conductor (N) hybrid system, the transport properties of the N are affected by the superconducting proximity effect. According to the updated theory, this proximity correction to the conductance (PCC) shows the reentrant behaviour to be a function of energy. We observed reentrant behaviour in the voltage and temperature dependences of the conductance of the 2DEG. The conductance peak is observed at Tcmax ~ 6 K and the PCC reaches ~20% of the normal-state conductance and almost disappears at low energies. These values are one order of magnitude higher than those obtained in the previous works. These results are most likely achieved by diminishing the length of the N channel L because the PCC as well as the correlation energy (Thouless energy) is proportional to 1/L2. The measured conductance showed a very good agreement with that of the theory.

  3. Space charge corrected electron emission from an aluminum surface under non-equilibrium conditions

    SciTech Connect

    Wendelen, W.; Bogaerts, A.; Mueller, B. Y.; Rethfeld, B.; Autrique, D.

    2012-06-01

    A theoretical study has been conducted of ultrashort pulsed laser induced electron emission from an aluminum surface. Electron emission fluxes retrieved from the commonly employed Fowler-DuBridge theory were compared to fluxes based on a laser-induced non-equilibrium electron distribution. As a result, the two- and three-photon photoelectron emission parameters for the Fowler-DuBridge theory have been approximated. We observe that at regimes where photoemission is important, laser-induced electron emission evolves in a more smooth manner than predicted by the Fowler-DuBridge theory. The importance of the actual electron distribution decreases at higher laser fluences, whereas the contribution of thermionic emission increases. Furthermore, the influence of a space charge effect on electron emission was evaluated by a one dimensional particle-in-cell model. Depending on the fluences, the space charge reduces the electron emission by several orders of magnitude. The influence of the electron emission flux profiles on the effective electron emission was found to be negligible. However, a non-equilibrium electron velocity distribution increases the effective electron emission significantly. Our results show that it is essential to consider the non-equilibrium electron distribution as well as the space charge effect for the description of laser-induced photoemission.

  4. Biological Electron Transport Systems

    PubMed Central

    Cowan, Dwaine O.; Pasternak, Gavril; Kaufman, Frank

    1970-01-01

    The solid-state electrical conductivities of a number of ferredoxin model compounds are reported. For one of these compounds, (KFeS2)n, an electron transfer rate for a 25 Å unit is shown to be at least 1 × 108 electrons sec-1. The rate becomes proportionally larger for smaller molecular units. This rapid rate is consistant with a short pipe model for electron transport between two reaction sites. Some of the factors leading to this rapid transfer rate are considered. PMID:5269247

  5. Full counting statistics for a single-electron transistor: nonequilibrium effects at intermediate conductance.

    PubMed

    Utsumi, Yasuhiro; Golubev, Dmitri S; Schön, Gerd

    2006-03-01

    We evaluate the current distribution for a single-electron transistor with intermediate strength tunnel conductance. Using the Schwinger-Keldysh approach and the drone (Majorana) fermion representation, we account for the renormalization of system parameters. Nonequilibrium effects induce a lifetime broadening of the charge-state levels, which suppress large current fluctuations.

  6. Quantum dissipative effects on non-equilibrium transport through a single-molecular transistor: The Anderson-Holstein-Caldeira-Leggett model

    PubMed Central

    Raju, Ch. Narasimha; Chatterjee, Ashok

    2016-01-01

    The Anderson-Holstein model with Caldeira-Leggett coupling with environment is considered to describe the damping effect in a single molecular transistor (SMT) which comprises a molecular quantum dot (with electron-phonon interaction) mounted on a substrate (environment) and coupled to metallic electrodes. The electron-phonon interaction is first eliminated using the Lang-Firsov transformation and the spectral density function, charge current and differential conductance are then calculated using the non-equilibrium Keldysh Green function technique. The effects of damping rate, and electron-electron and electron-phonon interactions on the transport properties of SMT are studied at zero temperature. PMID:26732725

  7. Curl flux, coherence, and population landscape of molecular systems: Nonequilibrium quantum steady state, energy (charge) transport, and thermodynamics

    SciTech Connect

    Zhang, Z. D.; Wang, J.

    2014-06-28

    We established a theoretical framework in terms of the curl flux, population landscape, and coherence for non-equilibrium quantum systems at steady state, through exploring the energy and charge transport in molecular processes. The curl quantum flux plays the key role in determining transport properties and the system reaches equilibrium when flux vanishes. The novel curl quantum flux reflects the degree of non-equilibriumness and the time-irreversibility. We found an analytical expression for the quantum flux and its relationship to the environmental pumping (non-equilibriumness quantified by the voltage away from the equilibrium) and the quantum tunneling. Furthermore, we investigated another quantum signature, the coherence, quantitatively measured by the non-zero off diagonal element of the density matrix. Populations of states give the probabilities of individual states and therefore quantify the population landscape. Both curl flux and coherence depend on steady state population landscape. Besides the environment-assistance which can give dramatic enhancement of coherence and quantum flux with high voltage at a fixed tunneling strength, the quantum flux is promoted by the coherence in the regime of small tunneling while reduced by the coherence in the regime of large tunneling, due to the non-monotonic relationship between the coherence and tunneling. This is in contrast to the previously found linear relationship. For the systems coupled to bosonic (photonic and phononic) reservoirs the flux is significantly promoted at large voltage while for fermionic (electronic) reservoirs the flux reaches a saturation after a significant enhancement at large voltage due to the Pauli exclusion principle. In view of the system as a quantum heat engine, we studied the non-equilibrium thermodynamics and established the analytical connections of curl quantum flux to the transport quantities such as energy (charge) transfer efficiency, chemical reaction efficiency, energy

  8. Curl flux, coherence, and population landscape of molecular systems: nonequilibrium quantum steady state, energy (charge) transport, and thermodynamics.

    PubMed

    Zhang, Zhedong; Wang, Jin; Zhang, Z D; Wang, J

    2014-06-28

    We established a theoretical framework in terms of the curl flux, population landscape, and coherence for non-equilibrium quantum systems at steady state, through exploring the energy and charge transport in molecular processes. The curl quantum flux plays the key role in determining transport properties and the system reaches equilibrium when flux vanishes. The novel curl quantum flux reflects the degree of non-equilibriumness and the time-irreversibility. We found an analytical expression for the quantum flux and its relationship to the environmental pumping (non-equilibriumness quantified by the voltage away from the equilibrium) and the quantum tunneling. Furthermore, we investigated another quantum signature, the coherence, quantitatively measured by the non-zero off diagonal element of the density matrix. Populations of states give the probabilities of individual states and therefore quantify the population landscape. Both curl flux and coherence depend on steady state population landscape. Besides the environment-assistance which can give dramatic enhancement of coherence and quantum flux with high voltage at a fixed tunneling strength, the quantum flux is promoted by the coherence in the regime of small tunneling while reduced by the coherence in the regime of large tunneling, due to the non-monotonic relationship between the coherence and tunneling. This is in contrast to the previously found linear relationship. For the systems coupled to bosonic (photonic and phononic) reservoirs the flux is significantly promoted at large voltage while for fermionic (electronic) reservoirs the flux reaches a saturation after a significant enhancement at large voltage due to the Pauli exclusion principle. In view of the system as a quantum heat engine, we studied the non-equilibrium thermodynamics and established the analytical connections of curl quantum flux to the transport quantities such as energy (charge) transfer efficiency, chemical reaction efficiency, energy

  9. Numerical analysis of the non-equilibrium plasma flow in the gaseous electronics conference reference reactor

    NASA Astrophysics Data System (ADS)

    Bijie, Yang; Ning, Zhou; Quanhua, Sun

    2016-01-01

    The capacitively coupled plasma in the gaseous electronics conference reference reactor is numerically investigated for argon flow using a non-equilibrium plasma fluid model. The finite rate chemistry is adopted for the chemical non-equilibrium among species including neutral metastable, whereas a two-temperature model is employed to resolve the thermal non-equilibrium between electrons and heavy species. The predicted plasma density agrees very well with experimental data for the validation case. A strong thermal non-equilibrium is observed between heavy particles and electrons due to its low collision frequency, where the heavy species remains near ambient temperature for low pressure and low voltage conditions (0.1 Torr, 100 V). The effects of the operating parameters on the ion flux are also investigated, including the electrode voltage, chamber pressure, and gas flow rate. It is found that the ion flux can be increased by either elevating the electrode voltage or lowering the gas pressure. Project supported by the National Natural Science Foundation of China (Nos. 11372325, 11475239).

  10. Thermal Conductivity in Nanoporous Gold Films during Electron-Phonon Nonequilibrium

    DOE PAGESBeta

    Hopkins, Patrick E.; Norris, Pamela M.; Phinney, Leslie M.; Policastro, Steven A.; Kelly, Robert G.

    2008-01-01

    The reduction of nanodevices has given recent attention to nanoporous materials due to their structure and geometry. However, the thermophysical properties of these materials are relatively unknown. In this article, an expression for thermal conductivity of nanoporous structures is derived based on the assumption that the finite size of the ligaments leads to electron-ligament wall scattering. This expression is then used to analyze the thermal conductivity of nanoporous structures in the event of electron-phonon nonequilibrium.

  11. The nonextensive parameter for nonequilibrium electron gas in an electromagnetic field

    SciTech Connect

    Yu, Haining; Du, Jiulin

    2014-11-15

    The nonextensive parameter for nonequilibrium electron gas of the plasma in an electromagnetic field is studied. We exactly obtained an expression of the q-parameter based on Boltzmann kinetic theories for plasmas, where Coulombian interactions and Lorentz forces play dominant roles. We show that the q-parameter different from unity is related by an equation to temperature gradient, electric field strength, magnetic induction as well as overall bulk velocity of the gas. The effect of the magnetic field on the q-parameter depends on the overall bulk velocity. Thus the q-parameter for the electron gas in an electromagnetic field represents the nonequilibrium nature or nonisothermal configurations of the plasma with electromagnetic interactions. - Highlights: • An expression of the q-parameter is obtained for nonequilibrium plasma with electromagnetic interactions. • The q-parameter is related to temperature gradient, electric field strength, magnetic induction as well as overall bulk velocity of the plasma. • The q-parameter represents the nonequilibrium nature of the complex plasma with electromagnetic interactions.

  12. A non-equilibrium equation-of-motion approach to quantum transport utilizing projection operators

    NASA Astrophysics Data System (ADS)

    Ochoa, Maicol A.; Galperin, Michael; Ratner, Mark A.

    2014-11-01

    We consider a projection operator approach to the non-equilbrium Green function equation-of-motion (PO-NEGF EOM) method. The technique resolves problems of arbitrariness in truncation of an infinite chain of EOMs and prevents violation of symmetry relations resulting from the truncation (equivalence of left- and right-sided EOMs is shown and symmetry with respect to interchange of Fermi or Bose operators before truncation is preserved). The approach, originally developed by Tserkovnikov (1999 Theor. Math. Phys. 118 85) for equilibrium systems, is reformulated to be applicable to time-dependent non-equilibrium situations. We derive a canonical form of EOMs, thus explicitly demonstrating a proper result for the non-equilibrium atomic limit in junction problems. A simple practical scheme applicable to quantum transport simulations is formulated. We perform numerical simulations within simple models and compare results of the approach to other techniques and (where available) also to exact results.

  13. Electronic transport in graphene

    NASA Astrophysics Data System (ADS)

    Zhang, Yuanbo

    This dissertation focuses on the electronic transport properties of graphene, a single atomic layer of graphite. Graphene is a novel two-dimensional system in which electron transport is effectively governed by the relativistic quantum theory. We discover a variety of new phenomenon which stem from the "relativistic" nature of the electron dynamics in graphene. An unusual quantum Hall (QH) effect is discovered in graphene at low temperatures and strong magnetic fields. Unlike conventional two-dimensional electron systems, in graphene the observed quantization condition is characterized by half integers rather than integers. Our investigation of the magneto-oscillations in resistance reveals a Berry's phase of pi associated with the electron motion in graphene. The half-integer quantization, as well as the Berry's phase, is attributed to the peculiar topology of the graphene band structure with a linear dispersion relation and vanishing mass near the Dirac point, which can be described by relativistic quantum electrodynamics. This is further confirmed by our measurement of the effective carrier mass, m*, which obeys Einstein's equation: E = m*c*2 where c* ≈ c/300 is the effective speed of light for electrons in graphene. The availability of high magnetic fields up to 45 Tesla allows us to study the magneto-transport in graphene in the extreme quantum limit. Under such condition, we discover new sets of QH states at filling factors nu = 0, +/-1, +/-4, indicating the lifting of the four-fold degeneracy of the previously observed QH states at nu = +/-4(|n|+1/2), where n is the Landau level index. In particular, the presence of the nu = 0, +/-1 QH states indicates that the Landau level at the charge neutral Dirac point splits into four sub-levels, lifting both sublattice and spin degeneracy, thereby potentially indicating a many-body correlation in this LL. The QH effect at nu = +/-4 is investigated in tilted magnetic fields and is attributed to lifting of the n

  14. Investigation of non-equilibrium electron-hole plasma in nanowires by THz spectroscopy

    NASA Astrophysics Data System (ADS)

    Cirlin, G. E.; Buyskih, A. C.; Bouravlev, A. D.; Samsonenko, Yu. B.; Kaliteevski, M. A.; Gallant, A. J.; Zeze, D.

    2016-05-01

    Efficient emission of THz radiation by AlGaAs nanowires via excitation of photocurrent by femtosecond optical pulses in nanowires was observed. Dynamics of photoinduced charge carrier was studied via influence of electron-hole plasma on THz radiation by optical pump THz probe method. It was found that characteristic time of screening of contact field is about 15 ps. Recombination of non-equilibrium occurs in two stages: fast recombination of free electron and holes (with relaxation time about 700 ps), and slow recombination (with relaxation time about 15 ns), which involves a capture of electrons and holes on the defects of crystalline structure of nanowires.

  15. Nonequilibrium electron-vibration coupling and conductance fluctuations in a C60 junction

    NASA Astrophysics Data System (ADS)

    Ulstrup, Søren; Frederiksen, Thomas; Brandbyge, Mads

    2012-12-01

    We investigate chemical bond formation and conductance in a molecular C60 junction under finite bias voltage using first-principles calculations based on density functional theory and nonequilibrium Green's functions (DFT-NEGF). At the point of contact formation we identify a remarkably strong coupling between the C60 motion and the molecular electronic structure. This is only seen for positive sample bias, although the conductance itself is not strongly polarity dependent. The nonequilibrium effect is traced back to a sudden shift in the position of the voltage drop with a small C60 displacement. Combined with a vibrational heating mechanism we construct a model from our results that explain the polarity-dependent two-level conductance fluctuations observed in recent scanning tunneling microscopy (STM) experiments [N. Néel , Nano Lett.NALEFD1530-698410.1021/nl201327c 11, 3593 (2011)]. These findings highlight the significance of nonequilibrium effects in chemical bond formation/breaking and in electron-vibration coupling in molecular electronics.

  16. Hierarchical Equation of Motion Investigation of Decoherence and Relaxation Dynamics in Nonequilibrium Transport through Interacting Quantum Dots

    NASA Astrophysics Data System (ADS)

    Hartle, Rainer; Cohen, Guy; Reichman, David R.; Millis, Andrew J.

    2014-03-01

    A recently developed hierarchical quantum master equation approach is used to investigate nonequilibrium electron transport through an interacting double quantum dot system in the regime where the inter-dot coupling is weaker than the coupling to the electrodes. The corresponding eigenstates provide tunneling paths that may interfere constructively or destructively, depending on the energy of the tunneling electrons. Electron-electron interactions are shown to quench these interference effects in bias-voltage dependent ways, leading, in particular, to negative differential resistance, population inversion and an enhanced broadening of resonances in the respective transport characteristics. Relaxation times are found to be very long, and to be correlated with very slow dynamics of the inter-dot coherences (off diagonal density matrix elements). The ability of the hierarchical quantum master equation approach to access very long time scales is crucial for the study of this physics. This work is supported by the National Science Foundation (NSF DMR-1006282 and NSF CHE-1213247), the Yad Hanadiv-Rothschild Foundation (via a Rothschild Fellowship for GC) and the Alexander von Humboldt Foundation (via a Feodor Lynen fellowship for RH).

  17. Electron Broadening of Isolated Lines with Stationary Non-Equilibrium Level Populations

    SciTech Connect

    Iglesias, C A

    2005-01-12

    It is shown that a quantum kinetic theory approach to line broadening, extended to stationary non-equilibrium states, yields corrections to the standard electron impact widths of isolated lines that depend on the population of the radiator internal levels. A consistent classical limit from a general quantum treatment of the perturbing electrons also introduces corrections to the isolated line widths. Both effects are essential in preserving detailed-balance relations. Preliminary analysis indicates that these corrections may resolve existing discrepancies between theoretical and experimental widths of isolated lines. An experimental test of the results is proposed.

  18. Dynamics of nonequilibrium electrons on neutral center states of interstitial magnesium donors in silicon

    NASA Astrophysics Data System (ADS)

    Pavlov, S. G.; Deßmann, N.; Pohl, A.; Shuman, V. B.; Portsel, L. M.; Lodygin, A. N.; Astrov, Yu. A.; Winnerl, S.; Schneider, H.; Stavrias, N.; van der Meer, A. F. G.; Tsyplenkov, V. V.; Kovalevsky, K. A.; Zhukavin, R. Kh.; Shastin, V. N.; Abrosimov, N. V.; Hübers, H.-W.

    2016-08-01

    Subnanosecond dynamics of optically excited electrons bound to excited states of neutral magnesium donor centers in silicon has been investigated. Lifetimes of nonequilibrium electrons have been derived from the decay of the differential transmission at photon energies matching the intracenter and the impurity-to-conduction band transitions. In contrast to hydrogenlike shallow donors in silicon, significantly longer lifetimes have been observed. This indicates weaker two-phonon and off-resonant interactions dominate the relaxation processes in contrast to the single-intervalley-phonon-assisted impurity-phonon interactions in the case of shallow donors in silicon.

  19. Electron and phonon drag in thermoelectric transport through coherent molecular conductors

    NASA Astrophysics Data System (ADS)

    Lü, Jing-Tao; Wang, Jian-Sheng; Hedegârd, Per; Brandbyge, Mads

    2016-05-01

    We study thermoelectric transport through a coherent molecular conductor connected to two electron and two phonon baths using the nonequilibrium Green's function method. We focus on the mutual drag between electron and phonon transport as a result of `momentum' transfer, which happens only when there are at least two phonon degrees of freedom. After deriving expressions for the linear drag coefficients, obeying the Onsager relation, we further investigate their effect on nonequilibrium transport. We show that the drag effect is closely related to two other phenomena: (1) adiabatic charge pumping through a coherent conductor; (2) the current-induced nonconservative and effective magnetic forces on phonons.

  20. Nonequilibrium GREEN’S Functions for High-Field Quantum Transport Theory

    NASA Astrophysics Data System (ADS)

    Bertoncini, Rita

    A formulation of the Kadanoff-Baym-Keldysh theory of nonequilibrium quantum statistical mechanics is developed in order to describe nonperturbatively the effects of the electric field on electron-phonon scattering in nondegenerate semiconductors. We derive an analytic, gauge-invariant model for the spectral density of energy states that accounts for both intracollisional field effect and collisional broadening simultaneously. A kinetic equation for the quantum distribution function is derived and solved numerically. The nonlinear drift velocity versus applied field characteristics is also evaluated numerically. Many features of our nonlinear theory bear formal resemblance to linear-response theory.

  1. Experimental determination of nonequilibrium transport parameters reflecting the competitive sorption between Cu and Pb in slag-sand column.

    PubMed

    Chung, Jaeshik; Kim, Young-Jin; Lee, Gwanghun; Nam, Kyoungphile

    2016-07-01

    Competitive sorption and resulting nonequilibrium transport of Cu and Pb were investigated using slag as a primary sorbent. A series of estimation models were applied based on the equilibrium, and nonequilibrium sorption respectively, and finally calibrated by incorporating the experimentally determined batch kinetic data. When applied individually, the behavior of metals in slag-sand column were well predicted by both equilibrium and nonequilibrium models in CXTFIT code. However, coexisting Cu and Pb exhibited competition for sorption sites, generating an irregular breakthrough curves such as overshoot (higher concentration in effluent than the feed concentration) of Cu and corresponding earlier peak of Pb followed by gradual re-rising. Although two-site nonequilibrium model further considers coupled hydrochemical process, desorption of the Cu from competition made the model prediction inaccurate. However, the parameter estimation could be improved by incorporating the experimentally determined mass transfer rate, ωexp from batch kinetics. Based on the calibrated model, the fraction of instantaneous retardation, βexp of Pb decreased from 0.41 in the single system to 0.30 in the binary system, indicating the shift from equilibrium to nonequilibrium state, where which of Cu increased from 0.39 to 0.94, representing the shift towards equilibrium. The modified results were also compared with five-step sequential extraction data, confirming that the shift of particular metal fractions from the competition triggered the nonequilibrium transport. PMID:27060642

  2. Nonequilibrium fluctuation-dissipation relations for one- and two-particle correlation functions in steady-state quantum transport

    SciTech Connect

    Ness, H.; Dash, L. K.

    2014-04-14

    We study the non-equilibrium (NE) fluctuation-dissipation (FD) relations in the context of quantum thermoelectric transport through a two-terminal nanodevice in the steady-state. The FD relations for the one- and two-particle correlation functions are derived for a model of the central region consisting of a single electron level. Explicit expressions for the FD relations of the Green's functions (one-particle correlations) are provided. The FD relations for the current-current and charge-charge (two-particle) correlations are calculated numerically. We use self-consistent NE Green's functions calculations to treat the system in the absence and in the presence of interaction (electron-phonon) in the central region. We show that, for this model, there is no single universal FD theorem for the NE steady state. There are different FD relations for each different class of problems. We find that the FD relations for the one-particle correlation function are strongly dependent on both the NE conditions and the interactions, while the FD relations of the current-current correlation function are much less dependent on the interaction. The latter property suggests interesting applications for single-molecule and other nanoscale transport experiments.

  3. Electron-Impact Excitation Cross Sections for Modeling Non-Equilibrium Gas

    NASA Technical Reports Server (NTRS)

    Huo, Winifred M.; Liu, Yen; Panesi, Marco; Munafo, Alessandro; Wray, Alan; Carbon, Duane F.

    2015-01-01

    In order to provide a database for modeling hypersonic entry in a partially ionized gas under non-equilibrium, the electron-impact excitation cross sections of atoms have been calculated using perturbation theory. The energy levels covered in the calculation are retrieved from the level list in the HyperRad code. The downstream flow-field is determined by solving a set of continuity equations for each component. The individual structure of each energy level is included. These equations are then complemented by the Euler system of equations. Finally, the radiation field is modeled by solving the radiative transfer equation.

  4. Kinetic theory of transport processes in partially ionized reactive plasma, II: Electron transport properties

    NASA Astrophysics Data System (ADS)

    Zhdanov, V. M.; Stepanenko, A. A.

    2016-11-01

    The previously obtained in (Zhdanov and Stepanenko, 2016) general transport equations for partially ionized reactive plasma are employed for analysis of electron transport properties in molecular and atomic plasmas. We account for both elastic and inelastic interaction channels of electrons with atoms and molecules of plasma and also the processes of electron impact ionization of neutral particles and three-body ion-electron recombination. The system of scalar transport equations for electrons is discussed and the expressions for non-equilibrium corrections to electron ionization and recombination rates and the diagonal part of the electron pressure tensor are derived. Special attention is paid to analysis of electron energy relaxation during collisions with plasma particles having internal degrees of freedom and the expression for the electron coefficient of inelastic energy losses is deduced. We also derive the expressions for electron vector and tensorial transport fluxes and the corresponding transport coefficients for partially ionized reactive plasma, which represent a generalization of the well-known results obtained by Devoto (1967). The results of numerical evaluation of contribution from electron inelastic collisions with neutral particles to electron transport properties are presented for a series of molecular and atomic gases.

  5. Nonequilibrium Keldysh formalism for interacting leads—Application to quantum dot transport driven by spin bias

    NASA Astrophysics Data System (ADS)

    Li, Yuan; Jalil, M. B. A.; Tan, Seng Ghee

    2012-06-01

    The conductance through a mesoscopic system of interacting electrons coupled to two adjacent leads is conventionally derived via the Keldysh nonequilibrium Green's function technique, in the limit of noninteracting leads [Y. Meir, N.S. Wingreen, Phys. Rev. Lett. 68 (1992) 2512]. We extend the standard formalism to cater for a quantum dot system with Coulombic interactions between the quantum dot and the leads. The general current expression is obtained by considering the equation of motion of the time-ordered Green's function of the system. The nonequilibrium effects of the interacting leads are then incorporated by determining the contour-ordered Green's function over the Keldysh loop and applying Langreth's theorem. The dot-lead interactions significantly increase the height of the Kondo peaks in density of states of the quantum dot. This translates into two Kondo peaks in the spin differential conductance when the magnitude of the spin bias equals that of the Zeeman splitting. There also exists a plateau in the charge differential conductance due to the combined effect of spin bias and the Zeeman splitting. The low-bias conductance plateau with sharp edges is also a characteristic of the Kondo effect. The conductance plateau disappears for the case of asymmetric dot-lead interaction.

  6. First-principles transport calculation method based on real-space finite-difference nonequilibrium Green's function scheme

    NASA Astrophysics Data System (ADS)

    Ono, Tomoya; Egami, Yoshiyuki; Hirose, Kikuji

    2012-11-01

    We demonstrate an efficient nonequilibrium Green's function transport calculation procedure based on the real-space finite-difference method. The direct inversion of matrices for obtaining the self-energy terms of electrodes is computationally demanding in the real-space method because the matrix dimension corresponds to the number of grid points in the unit cell of electrodes, which is much larger than that of sites in the tight-binding approach. The procedure using the ratio matrices of the overbridging boundary-matching technique [Y. Fujimoto and K. Hirose, Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.67.195315 67, 195315 (2003)], which is related to the wave functions of a couple of grid planes in the matching regions, greatly reduces the computational effort to calculate self-energy terms without losing mathematical strictness. In addition, the present procedure saves computational time to obtain the Green's function of the semi-infinite system required in the Landauer-Büttiker formula. Moreover, the compact expression to relate Green's functions and scattering wave functions, which provide a real-space picture of the scattering process, is introduced. An example of the calculated results is given for the transport property of the BN ring connected to (9,0) carbon nanotubes. The wave-function matching at the interface reveals that the rotational symmetry of wave functions with respect to the tube axis plays an important role in electron transport. Since the states coming from and going to electrodes show threefold rotational symmetry, the states in the vicinity of the Fermi level, the wave function of which exhibits fivefold symmetry, do not contribute to the electron transport through the BN ring.

  7. Consistent multi-internal-temperature models for vibrational and electronic nonequilibrium in hypersonic nitrogen plasma flows

    SciTech Connect

    Guy, Aurélien Bourdon, Anne Perrin, Marie-Yvonne

    2015-04-15

    In this work, a state-to-state vibrational and electronic collisional model is developed to investigate nonequilibrium phenomena behind a shock wave in an ionized nitrogen flow. In the ionization dynamics behind the shock wave, the electron energy budget is of key importance and it is found that the main depletion term corresponds to the electronic excitation of N atoms, and conversely the major creation terms are the electron-vibration term at the beginning, then replaced by the electron ions elastic exchange term. Based on these results, a macroscopic multi-internal-temperature model for the vibration of N{sub 2} and the electronic levels of N atoms is derived with several groups of vibrational levels of N{sub 2} and electronic levels of N with their own internal temperatures to model the shape of the vibrational distribution of N{sub 2} and of the electronic excitation of N, respectively. In this model, energy and chemistry source terms are calculated self-consistently from the rate coefficients of the state-to-state database. For the shock wave condition studied, a good agreement is observed on the ionization dynamics as well as on the atomic bound-bound radiation between the state-to-state model and the macroscopic multi-internal temperature model with only one group of vibrational levels of N{sub 2} and two groups of electronic levels of N.

  8. Optimizing Water Transport through Graphene-Based Membranes: Insights from Nonequilibrium Molecular Dynamics.

    PubMed

    Muscatello, Jordan; Jaeger, Frederike; Matar, Omar K; Müller, Erich A

    2016-05-18

    Recent experimental results suggest that stacked layers of graphene oxide exhibit strong selective permeability to water. To construe this observation, the transport mechanism of water permeating through a membrane consisting of layered graphene sheets is investigated via nonequilibrium and equilibrium molecular dynamics simulations. The effect of sheet geometry is studied by changing the offset between the entrance and exit slits of the membrane. The simulation results reveal that the permeability is not solely dominated by entrance effects; the path traversed by water molecules has a considerable impact on the permeability. We show that contrary to speculation in the literature, water molecules do not pass through the membrane as a hydrogen-bonded chain; instead, they form well-mixed fluid regions confined between the graphene sheets. The results of the present work are used to provide guidelines for the development of graphene and graphene oxide membranes for desalination and solvent separation.

  9. Optimizing Water Transport through Graphene-Based Membranes: Insights from Nonequilibrium Molecular Dynamics.

    PubMed

    Muscatello, Jordan; Jaeger, Frederike; Matar, Omar K; Müller, Erich A

    2016-05-18

    Recent experimental results suggest that stacked layers of graphene oxide exhibit strong selective permeability to water. To construe this observation, the transport mechanism of water permeating through a membrane consisting of layered graphene sheets is investigated via nonequilibrium and equilibrium molecular dynamics simulations. The effect of sheet geometry is studied by changing the offset between the entrance and exit slits of the membrane. The simulation results reveal that the permeability is not solely dominated by entrance effects; the path traversed by water molecules has a considerable impact on the permeability. We show that contrary to speculation in the literature, water molecules do not pass through the membrane as a hydrogen-bonded chain; instead, they form well-mixed fluid regions confined between the graphene sheets. The results of the present work are used to provide guidelines for the development of graphene and graphene oxide membranes for desalination and solvent separation. PMID:27121070

  10. Scale Invariance and Self-Similarity of 1-Dimensional Non-equilibrium Suspended Sediment Transport

    NASA Astrophysics Data System (ADS)

    Carr, K. J.; Ercan, A.; Kavvas, M. L.

    2014-12-01

    The conditions under which the governing equation for non-equilibrium one-dimensional suspended sediment transport in unsteady flows is scale-invariant and self-similar are examined by applying the one-parameter Lie group of point scaling transformations. Self-similarity conditions imposed due to initial and boundary conditions are also examined. Furthermore, one-parameter Lie group point scaling transformations required to physically scale the transport process without scaling the sediment material properties are identified and investigated. Preserving sediment density and diameter is believed to eliminate some of the scale errors encountered in traditional scaling methods. Under these conditions, not only are sediment diameter and density unscaled, but so too are the critical and total shear, kinematic viscosity and particle Reynolds number. The similarity of suspended sediment transport is increased through more accurate representation of suspended sediment concentration and carrying capacity of flow. The proposed method meets the needs of modelers by; maintaining the benefits found from distortion such as reduced cost, space, and model run-time; removing the need to apply scaled sediment or surrogate sediment; avoiding some of the scale effects and resulting errors of traditional flow and sediment transport scaling.

  11. Methods development for electron transport

    NASA Astrophysics Data System (ADS)

    Ganapol, Barry D.

    1992-04-01

    This report consists of two code manuals and an article recently published in the proceedings of the American Nuclear Society Mathematics and Computation Topical Meeting held in Pittsburgh. In these presentations, deterministic calculational methods simulating electron transport in solids are detailed. The first method presented (Section 2) is for the solution of the Spencer-Lewis equation in which electron motion is characterized by continuous slowing down theory and a pathlength formulation. The FN solution to the standard monoenergetic transport equation for electron transport with isotropic scattering in finite media is given in Section 3. For both codes, complete flow charts, operational instructions and sample problems are included. Finally, in Section 4, an application of the multigroup formulation of electron transport in an infinite medium is used to verify an equivalent SN formulation. For this case, anisotropic scattering is also included.

  12. Electron-Transport Properties of Few-Layer Black Phosphorus.

    PubMed

    Xu, Yuehua; Dai, Jun; Zeng, Xiao Cheng

    2015-06-01

    We perform the first-principles computational study of the effect of number of stacking layers and stacking style of the few-layer black phosphorus (BPs) on the electronic properties, including transport gap, current-voltage (i-v) relation, and differential conductance. Our computation is based on the nonequilibrium Green's function approach combined with density functional theory calculations. Specifically, we compute electron-transport properties of monolayer BP, bilayer BP, and trilayer BP as well as bilayer BPs with AB-, AA-, or AC-stacking. We find that the stacking number has greater influence on the transport gap than the stacking type. Conversely, the stacking type has greater influence on i-v curve and differential conductance than on the transport gap. This study offers useful guidance for determining the number of stacking layers and the stacking style of few-layer BP sheets in future experimental measurements and for potential applications in nanoelectronic devices.

  13. Nonequilibrium atmospheric pressure plasma with ultrahigh electron density and high performance for glass surface cleaning

    SciTech Connect

    Iwasaki, Masahiro; Matsudaira, Yuto; Hori, Masaru; Inui, Hirotoshi; Kano, Hiroyuki; Yoshida, Naofumi; Ito, Masafumi

    2008-02-25

    We produced a nonequilibrium atmospheric pressure plasma by applying an alternative current between two electrodes. The gas temperature and electron density were evaluated using optical emission spectroscopy. It was found that the plasma had gas temperatures from 1800 to 2150 K and ultrahigh electron densities in the order of 10{sup 16} cm{sup -3}. A remarkably high oxygen radical concentration of 1.6x10{sup 15} cm{sup -3} was obtained at a 1% O{sub 2}/Ar gas flow rate of 15 slm (standard liters per minute). Contact angles below 10 deg. were obtained in the process of glass cleaning with a plasma exposure time of 23 ms.

  14. Regimes of suprathermal electron transport

    SciTech Connect

    Glinsky, M.E.

    1995-07-01

    Regimes of the one-dimensional (1-D) transport of suprathermal electrons into a cold background plasma are delineated. A well ordered temporal progression is found through eras where {ital J}{center_dot}{ital E} heating, hot electron--cold electron collisional heating, and diffusive heat flow dominate the cold electron energy equation. Scaling relations for how important quantities such as the width and temperature of the heated layer of cold electrons evolve with time are presented. These scaling relations are extracted from a simple 1-D model of the transport which can be written in dimensionless form with one free parameter. The parameter is shown to be the suprathermal electron velocity divided by the drift velocity of cold electrons which balances the suprathermal current. Special attention is paid to the assumptions which allow the reduction from the collisional Vlasov equation, using a Fokker--Planck collision operator, to this simple model. These model equations are numerically solved and compared to both the scaling relations and a more complete multigroup electron diffusion transport. Implications of the scaling relations on fast ion generation, magnetic field generation, and electric field inhibition of electron transport are examined as they apply to laser heated plasmas. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  15. Heat Transfer and Fluid Transport of Supercritical CO2 in Enhanced Geothermal System with Local Thermal Non-equilibrium Model

    DOE PAGESBeta

    Zhang, Le; Luo, Feng; Xu, Ruina; Jiang, Peixue; Liu, Huihai

    2014-12-31

    The heat transfer and fluid transport of supercritical CO2 in enhanced geothermal system (EGS) is studied numerically with local thermal non-equilibrium model, which accounts for the temperature difference between solid matrix and fluid components in porous media and uses two energy equations to describe heat transfer in the solid matrix and in the fluid, respectively. As compared with the previous results of our research group, the effect of local thermal non-equilibrium mainly depends on the volumetric heat transfer coefficient ah, which has a significant effect on the production temperature at reservoir outlet and thermal breakthrough time. The uniformity of volumetricmore » heat transfer coefficient ah has little influence on the thermal breakthrough time, but the temperature difference become more obvious with time after thermal breakthrough with this simulation model. The thermal breakthrough time reduces and the effect of local thermal non-equilibrium becomes significant with decreasing ah.« less

  16. Contactless electronic transport in a bio-molecular junction

    SciTech Connect

    Hossain, Faruque M. Al-Dirini, Feras; Skafidas, Efstratios

    2014-07-28

    Molecular electronics hold promise for next generation ultra-low power, nano-scale integrated electronics. The main challenge in molecular electronics is to make a reliable interface between molecules and metal electrodes. Interfacing metals and molecules detrimentally affects the characteristics of nano-scale molecular electronic devices. It is therefore essential to investigate alternative arrangements such as contact-less tunneling gaps wherever such configurations are feasible. We conduct ab initio density functional theory and non-equilibrium Green's functions calculations to investigate the transport properties of a biocompatible glycine molecular junction. By analyzing the localized molecular orbital energy distributions and transmission probabilities in the transport-gap, we find a glycine molecule confined between two gold electrodes, without making a contact, is energetically stable and possesses high tunneling current resembling an excellent ohmic-like interface.

  17. The stationary non-equilibrium plasma of cosmic-ray electrons and positrons

    NASA Astrophysics Data System (ADS)

    Tomaschitz, Roman

    2016-06-01

    The statistical properties of the two-component plasma of cosmic-ray electrons and positrons measured by the AMS-02 experiment on the International Space Station and the HESS array of imaging atmospheric Cherenkov telescopes are analyzed. Stationary non-equilibrium distributions defining the relativistic electron-positron plasma are derived semi-empirically by performing spectral fits to the flux data and reconstructing the spectral number densities of the electronic and positronic components in phase space. These distributions are relativistic power-law densities with exponential cutoff, admitting an extensive entropy variable and converging to the Maxwell-Boltzmann or Fermi-Dirac distributions in the non-relativistic limit. Cosmic-ray electrons and positrons constitute a classical (low-density high-temperature) plasma due to the low fugacity in the quantized partition function. The positron fraction is assembled from the flux densities inferred from least-squares fits to the electron and positron spectra and is subjected to test by comparing with the AMS-02 flux ratio measured in the GeV interval. The calculated positron fraction extends to TeV energies, predicting a broad spectral peak at about 1 TeV followed by exponential decay.

  18. Visualizing non-equilibrium lithiation of spinel oxide via in situ transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    He, Kai; Zhang, Sen; Li, Jing; Yu, Xiqian; Meng, Qingping; Zhu, Yizhou; Hu, Enyuan; Sun, Ke; Yun, Hongseok; Yang, Xiao-Qing; Zhu, Yimei; Gan, Hong; Mo, Yifei; Stach, Eric A.; Murray, Christopher B.; Su, Dong

    2016-05-01

    Spinel transition metal oxides are important electrode materials for lithium-ion batteries, whose lithiation undergoes a two-step reaction, whereby intercalation and conversion occur in a sequential manner. These two reactions are known to have distinct reaction dynamics, but it is unclear how their kinetics affects the overall electrochemical response. Here we explore the lithiation of nanosized magnetite by employing a strain-sensitive, bright-field scanning transmission electron microscopy approach. This method allows direct, real-time, high-resolution visualization of how lithiation proceeds along specific reaction pathways. We find that the initial intercalation process follows a two-phase reaction sequence, whereas further lithiation leads to the coexistence of three distinct phases within single nanoparticles, which has not been previously reported to the best of our knowledge. We use phase-field theory to model and describe these non-equilibrium reaction pathways, and to directly correlate the observed phase evolution with the battery's discharge performance.

  19. Visualizing non-equilibrium lithiation of spinel oxide via in situ transmission electron microscopy.

    PubMed

    He, Kai; Zhang, Sen; Li, Jing; Yu, Xiqian; Meng, Qingping; Zhu, Yizhou; Hu, Enyuan; Sun, Ke; Yun, Hongseok; Yang, Xiao-Qing; Zhu, Yimei; Gan, Hong; Mo, Yifei; Stach, Eric A; Murray, Christopher B; Su, Dong

    2016-01-01

    Spinel transition metal oxides are important electrode materials for lithium-ion batteries, whose lithiation undergoes a two-step reaction, whereby intercalation and conversion occur in a sequential manner. These two reactions are known to have distinct reaction dynamics, but it is unclear how their kinetics affects the overall electrochemical response. Here we explore the lithiation of nanosized magnetite by employing a strain-sensitive, bright-field scanning transmission electron microscopy approach. This method allows direct, real-time, high-resolution visualization of how lithiation proceeds along specific reaction pathways. We find that the initial intercalation process follows a two-phase reaction sequence, whereas further lithiation leads to the coexistence of three distinct phases within single nanoparticles, which has not been previously reported to the best of our knowledge. We use phase-field theory to model and describe these non-equilibrium reaction pathways, and to directly correlate the observed phase evolution with the battery's discharge performance.

  20. Heating of nonequilibrium electrons by laser radiation in solid transparent dielectrics

    SciTech Connect

    Nikiforov, A. M. Epifanov, A. S.; Garnov, S. V.

    2011-01-15

    A computer simulation of the heating of nonequilibrium electrons by an intense high-frequency electromagnetic field leading to the bulk damage of solid transparent dielectrics under single irradiation has been carried out. The dependences of the avalanche ionization rate on threshold field strength have been derived. Using the Fokker-Planck equation with a flux-doubling boundary condition is shown to lead to noticeable errors even at a ratio of the photon energy to the band gap {approx}0.1. The series of dependences of the critical fields on pulse duration have been constructed for various initial lattice temperatures and laser wavelengths, which allow the electron avalanche to be identified as a limiting breakdown mechanism. The ratio of the energy stored in the electron subsystem to the excess (with respect to the equilibrium state) energy of the phonon subsystem by the end of laser pulse action has been calculated both with and without allowance for phonon heating. The influence of phonon heating on the impact avalanche ionization rate is analyzed.

  1. Nonequilibrium quantum dynamics and transport: from integrability to many-body localization

    NASA Astrophysics Data System (ADS)

    Vasseur, Romain; Moore, Joel E.

    2016-06-01

    We review the non-equilibrium dynamics of many-body quantum systems after a quantum quench with spatial inhomogeneities, either in the Hamiltonian or in the initial state. We focus on integrable and many-body localized systems that fail to self-thermalize in isolation and for which the standard hydrodynamical picture breaks down. The emphasis is on universal dynamics, non-equilibrium steady states and new dynamical phases of matter, and on phase transitions far from thermal equilibrium. We describe how the infinite number of conservation laws of integrable and many-body localized systems lead to complex non-equilibrium states beyond the traditional dogma of statistical mechanics.

  2. Electron transport in bipyridinium films.

    PubMed

    Raymo, Françisco M; Alvarado, Robert J

    2004-01-01

    Bipyridinium dications are versatile building blocks for the assembly of functional materials. In particular, their reliable electrochemical response has encouraged the design of electroactive films. Diverse and elegant experimental strategies to coat metallic and semiconducting electrodes with bipyridinium compounds have, in fact, emerged over the past two decades. The resulting interfacial assemblies span from a few nanometers to several micrometers in thickness. They incorporate from a single molecular layer to large collections of entangled polymer chains. They transport electrons efficiently from the electrode surface to the film/solution interface and vice versa. Electron self-exchange between and the physical diffusion of the bipyridinium building blocks conspire in defining the charge transport properties of these fascinating electroactive assemblies. Often, the matrix of electron-deficient bipyridinium dications can be exploited to entrap electron-rich analytes. Electrostatic interactions promote the supramolecular association of the guests with the surface-confined host matrix. Furthermore, chromophoric sites can be coupled to the bipyridinium dications to produce photosensitive arrays capable of harvesting light and generating current. Thus, thorough investigations on the fundamental properties of these functional molecule-based materials can lead to promising applications in electroanalysis and solar energy conversion, while contributing to advances in the basic understanding of electron transport in interfacial assemblies.

  3. A review of reaction rates and thermodynamic and transport properties for an 11-species air model for chemical and thermal nonequilibrium calculations to 30000 K

    NASA Technical Reports Server (NTRS)

    Gupta, Roop N.; Yos, Jerrold M.; Thompson, Richard A.; Lee, Kam-Pui

    1990-01-01

    Reaction rate coefficients and thermodynamic and transport properties are reviewed and supplemented for the 11-species air model which can be used for analyzing flows in chemical and thermal nonequilibrium up to temperatures of 3000 K. Such flows will likely occur around currently planned and future hypersonic vehicles. Guidelines for determining the state of the surrounding environment are provided. Curve fits are given for the various species properties for their efficient computation in flowfield codes. Approximate and more exact formulas are provided for computing the properties of partially ionized air mixtures in a high energy environment. Limitations of the approximate mixing laws are discussed for a mixture of ionized species. An electron number-density correction for the transport properties of the charged species is obtained. This correction has been generally ignored in the literature.

  4. Chemical kinetics and relaxation of non-equilibrium air plasma generated by energetic photon and electron beams

    NASA Astrophysics Data System (ADS)

    Maulois, Melissa; Ribière, Maxime; Eichwald, Olivier; Yousfi, Mohammed; Azaïs, Bruno

    2016-04-01

    The comprehension of electromagnetic perturbations of electronic devices, due to air plasma-induced electromagnetic field, requires a thorough study on air plasma. In the aim to understand the phenomena at the origin of the formation of non-equilibrium air plasma, we simulate, using a volume average chemical kinetics model (0D model), the time evolution of a non-equilibrium air plasma generated by an energetic X-ray flash. The simulation is undertaken in synthetic air (80% N2 and 20% O2) at ambient temperature and atmospheric pressure. When the X-ray flash crosses the gas, non-relativistic Compton electrons (low energy) and a relativistic Compton electron beam (high energy) are simultaneously generated and interact with the gas. The considered chemical kinetics scheme involves 26 influent species (electrons, positive ions, negative ions, and neutral atoms and molecules in their ground or metastable excited states) reacting following 164 selected reactions. The kinetics model describing the plasma chemistry was coupled to the conservation equation of the electron mean energy, in order to calculate at each time step of the non-equilibrium plasma evolution, the coefficients of reactions involving electrons while the energy of the heavy species (positive and negative ions and neutral atoms and molecules) is assumed remaining close to ambient temperature. It has been shown that it is the relativistic Compton electron beam directly created by the X-ray flash which is mainly responsible for the non-equilibrium plasma formation. Indeed, the low energy electrons (i.e., the non-relativistic ones) directly ejected from molecules by Compton collisions contribute to less than 1% on the creation of electrons in the plasma. In our simulation conditions, a non-equilibrium plasma with a low electron mean energy close to 1 eV and a concentration of charged species close to 1013 cm-3 is formed a few nanoseconds after the peak of X-ray flash intensity. 200 ns after the flash

  5. Electronic Transport in Carbon Nanomaterials

    SciTech Connect

    Lopez-Benzanilla, Alejandro; Meunier, Vincent; Sumpter, Bobby G; Roche, Stephan; Cruz Silva, Eduardo

    2012-01-01

    Over the past decade, transport measurements on individual single-wall nanotubes have played a prominent role in developing our understanding of this novel carbon conductor. These measurements have identified both metallic and semiconducting nanotubes, determined their dominant electronic scattering mechanisms, and elucidated in great detail the properties of their quantized energy spectrum. Recent technological breakthroughs in nanotube device fabrication and electronic measurement have made possible experiments of unprecedented precision that reveal new and surprising phenomena. In this review, we present the fundamental properties of nanotubes side by side with the newest discoveries and also discuss some of the most exciting emerging directions.

  6. Mesoscopic electronics beyond DC transport

    NASA Astrophysics Data System (ADS)

    di Carlo, Leonardo

    Since the inception of mesoscopic electronics in the 1980's, direct current (dc) measurements have underpinned experiments in quantum transport. Novel techniques complementing dc transport are becoming paramount to new developments in mesoscopic electronics, particularly as the road is paved toward quantum information processing. This thesis describes seven experiments on GaAs/AlGaAs and graphene nanostructures unified by experimental techniques going beyond traditional dc transport. Firstly, dc current induced by microwave radiation applied to an open chaotic quantum dot is investigated. Asymmetry of mesoscopic fluctuations of induced current in perpendicular magnetic field is established as a tool for separating the quantum photovoltaic effect from classical rectification. A differential charge sensing technique is next developed using integrated quantum point contacts to resolve the spatial distribution of charge inside a double quantum clot. An accurate method for determining interdot tunnel coupling and electron temperature using charge sensing is demonstrated. A two-channel system for detecting current noise in mesoscopic conductors is developed, enabling four experiments where shot noise probes transmission properties not available in dc transport and Johnson noise serves as an electron thermometer. Suppressed shot noise is observed in quantum point contacts at zero parallel magnetic field, associated with the 0.7 structure in conductance. This suppression evolves with increasing field into the shot-noise signature of spin-lifted mode degeneracy. Quantitative agreement is found with a phenomenological model for density-dependent mode splitting. Shot noise measurements of multi-lead quantum-dot structures in the Coulomb blockade regime distill the mechanisms by which Coulomb interaction and quantum indistinguishability correlate electron flow. Gate-controlled sign reversal of noise cross correlation in two capacitively-coupled dots is observed, and shown to

  7. Electron Transport in Hall Thrusters

    NASA Astrophysics Data System (ADS)

    McDonald, Michael Sean

    Despite high technological maturity and a long flight heritage, computer models of Hall thrusters remain dependent on empirical inputs and a large part of thruster development to date has been heavily experimental in nature. This empirical approach will become increasingly unsustainable as new high-power thrusters tax existing ground test facilities and more exotic thruster designs stretch and strain the boundaries of existing design experience. The fundamental obstacle preventing predictive modeling of Hall thruster plasma properties and channel erosion is the lack of a first-principles description of electron transport across the strong magnetic fields between the cathode and anode. In spite of an abundance of proposed transport mechanisms, accurate assessments of the magnitude of electron current due to any one mechanism are scarce, and comparative studies of their relative influence on a single thruster platform simply do not exist. Lacking a clear idea of what mechanism(s) are primarily responsible for transport, it is understandably difficult for the electric propulsion scientist to focus his or her theoretical and computational tools on the right targets. This work presents a primarily experimental investigation of collisional and turbulent Hall thruster electron transport mechanisms. High-speed imaging of the thruster discharge channel at tens of thousands of frames per second reveals omnipresent rotating regions of elevated light emission, identified with a rotating spoke instability. This turbulent instability has been shown through construction of an azimuthally segmented anode to drive significant cross-field electron current in the discharge channel, and suggestive evidence points to its spatial extent into the thruster near-field plume as well. Electron trajectory simulations in experimentally measured thruster electromagnetic fields indicate that binary collisional transport mechanisms are not significant in the thruster plume, and experiments

  8. Electron transport in granular metals.

    PubMed

    Altland, Alexander; Glazman, Leonid I; Kamenev, Alex

    2004-01-16

    We consider thermodynamic and transport properties of a long granular array with strongly connected grains (intergrain conductance g>1). We find that the system's conductance and differential capacitance exhibits activated behavior, approximately exp([-T(*)/T]. The gap T(*) represents the energy needed to create a long single-electron charge soliton propagating through the array. This scale is parametrically larger than the energy at which conventional perturbation theory breaks down.

  9. Electronic transport in unconventional superconductors

    SciTech Connect

    Graf, M.J.

    1998-12-31

    The author investigates the electron transport coefficients in unconventional superconductors at low temperatures, where charge and heat transport are dominated by electron scattering from random lattice defects. He discusses the features of the pairing symmetry, Fermi surface, and excitation spectrum which are reflected in the low temperature heat transport. For temperatures {kappa}{sub B}T {approx_lt} {gamma} {much_lt} {Delta}{sub 0}, where {gamma} is the bandwidth of impurity induced Andreev states, certain eigenvalues become universal, i.e., independent of the impurity concentration and phase shift. Deep in the superconducting phase ({kappa}{sub B}T {approx_lt} {gamma}) the Wiedemann-Franz law, with Sommerfeld`s value of the Lorenz number, is recovered. He compares the results for theoretical models of unconventional superconductivity in high-{Tc} and heavy fermion superconductors with experiment. The findings show that impurities are a sensitive probe of the low-energy excitation spectrum, and that the zero-temperature limit of the transport coefficients provides an important test of the order parameter symmetry.

  10. Visualizing non-equilibrium lithiation of spinel oxide via in situ transmission electron microscopy.

    PubMed

    He, Kai; Zhang, Sen; Li, Jing; Yu, Xiqian; Meng, Qingping; Zhu, Yizhou; Hu, Enyuan; Sun, Ke; Yun, Hongseok; Yang, Xiao-Qing; Zhu, Yimei; Gan, Hong; Mo, Yifei; Stach, Eric A; Murray, Christopher B; Su, Dong

    2016-01-01

    Spinel transition metal oxides are important electrode materials for lithium-ion batteries, whose lithiation undergoes a two-step reaction, whereby intercalation and conversion occur in a sequential manner. These two reactions are known to have distinct reaction dynamics, but it is unclear how their kinetics affects the overall electrochemical response. Here we explore the lithiation of nanosized magnetite by employing a strain-sensitive, bright-field scanning transmission electron microscopy approach. This method allows direct, real-time, high-resolution visualization of how lithiation proceeds along specific reaction pathways. We find that the initial intercalation process follows a two-phase reaction sequence, whereas further lithiation leads to the coexistence of three distinct phases within single nanoparticles, which has not been previously reported to the best of our knowledge. We use phase-field theory to model and describe these non-equilibrium reaction pathways, and to directly correlate the observed phase evolution with the battery's discharge performance. PMID:27157119

  11. Visualizing non-equilibrium lithiation of spinel oxide via in situ transmission electron microscopy

    PubMed Central

    He, Kai; Zhang, Sen; Li, Jing; Yu, Xiqian; Meng, Qingping; Zhu, Yizhou; Hu, Enyuan; Sun, Ke; Yun, Hongseok; Yang, Xiao-Qing; Zhu, Yimei; Gan, Hong; Mo, Yifei; Stach, Eric A.; Murray, Christopher B.; Su, Dong

    2016-01-01

    Spinel transition metal oxides are important electrode materials for lithium-ion batteries, whose lithiation undergoes a two-step reaction, whereby intercalation and conversion occur in a sequential manner. These two reactions are known to have distinct reaction dynamics, but it is unclear how their kinetics affects the overall electrochemical response. Here we explore the lithiation of nanosized magnetite by employing a strain-sensitive, bright-field scanning transmission electron microscopy approach. This method allows direct, real-time, high-resolution visualization of how lithiation proceeds along specific reaction pathways. We find that the initial intercalation process follows a two-phase reaction sequence, whereas further lithiation leads to the coexistence of three distinct phases within single nanoparticles, which has not been previously reported to the best of our knowledge. We use phase-field theory to model and describe these non-equilibrium reaction pathways, and to directly correlate the observed phase evolution with the battery's discharge performance. PMID:27157119

  12. Ignition conditions relaxation for central hot-spot ignition with an ion-electron non-equilibrium model

    NASA Astrophysics Data System (ADS)

    Fan, Zhengfeng; Liu, Jie; Liu, Bin; Yu, Chengxin; He, X. T.

    2016-01-01

    Fusion ignition experiments on the National Ignition Facility have demonstrated >5 keV hot spot with ρRh lower than 0.3 g/cm2 [Döppner et al., Phys. Rev. Lett. 115, 055001 (2015)]. We present an ion-electron non-equilibrium model, in which the hot-spot ion temperature is higher than its electron temperature so that the hot-spot nuclear reactions are enhanced while energy leaks are considerably reduced. Theoretical analysis shows that the ignition region would be significantly enlarged in the hot-spot ρR-T space as compared with the commonly used equilibrium model. Simulations show that shocks could be utilized to create and maintain non-equilibrium conditions within the hot spot, and the hot-spot ρR requirement is remarkably reduced for achieving self-heating.

  13. Transport properties of dense fluid mixtures using nonequilibrium molecular dynamics. Final report, September 15, 1987--March 14, 1997

    SciTech Connect

    Murad, S.

    1997-05-01

    Computer Simulation Studies were carried out using the method of equilibrium and nonequilibrium molecular dynamics (NEMD) to examine a wide range of transport processes in both fluids and fluid mixtures. This included testing a wide range of mixing rules for thermal conductivity and viscosity. In addition a method was developed to calculate the internal rotational contributions to thermal conductivity and the accuracy of current methods for predicting these contributions were examined. These comparisons were then used to suggest possible ways of improving these theories. The method of NEMD was also used to examine the critical enhancements of thermal conductivity. Finally, molecular simulations were carried out to study the various transport coefficients of fluids confined by membranes, as well as important transport processes such as osmosis, and reverse osmosis.

  14. Secondary electron emissions and dust charging currents in the nonequilibrium dusty plasma with power-law distributions

    SciTech Connect

    Gong Jingyu; Du Jiulin

    2012-06-15

    We study the secondary electron emissions induced by the impact of electrons on dust grains and the resulting dust charging processes in the nonequilibrium dusty plasma with power-law distributions. We derive new expressions of the secondary emitted electron flux and the dust charging currents that are generalized by the power-law q-distributions, where the nonlinear core functions are numerically studied for the nonextensive parameter q. Our numerical analyses show that the power-law q-distribution of the primary electrons has a significant effect on both the secondary emitted electron flux and the dust charging currents, and this effect depends strongly on the ratio of the electrostatic potential energy of the primary electrons at the dust grain's surface to the thermodynamic energy, implying that a competition in the dusty plasma between these two energies plays a crucial role in this novel effect.

  15. Nonequilibrium transport through a Kondo dot in a magnetic field: perturbation theory and poor man's scaling.

    PubMed

    Rosch, A; Paaske, J; Kroha, J; Wölfle, P

    2003-02-21

    We consider electron transport through a quantum dot described by the Kondo model in the regime of large transport voltage V in the presence of a magnetic field B with max((V,B)>T(K). The electric current I and the local magnetization M are found to be universal functions of V/T(K) and B/T(K), where T(K) is the equilibrium Kondo temperature. We present a generalization of the perturbative renormali-zation group to frequency dependent coupling functions, as necessitated by the structure of bare perturbation theory. We calculate I and M within a poor man's scaling approach and find excellent agreement with experiment. PMID:12633260

  16. The effect of magnetic field and disorders on the electronic transport in graphene nanoribbons.

    PubMed

    Kumar, S Bala; Jalil, M B A; Tan, S G; Liang, Gengchiau

    2010-09-22

    We developed a unified mesoscopic transport model for graphene nanoribbons, which combines the nonequilibrium Green's function (NEGF) formalism with the real-space π-orbital model. Based on this model, we probe the spatial distribution of electrons under a magnetic field, in order to obtain insights into the various signature Hall effects in disordered armchair graphene nanoribbons (AGNR). In the presence of a uniform perpendicular magnetic field (B[Symbol: see text]-field), a perfect AGNR shows three distinct spatial current profiles at equilibrium, depending on its width. Under nonequilibrium conditions (i.e. in the presence of an applied bias), the net electron flow is restricted to the edges and occurs in opposite directions depending on whether the Fermi level lies within the valence or conduction band. For electrons at an energy level below the conduction window, the B[Symbol: see text]-field gives rise to local electron flux circulation, although the global flux is zero. Our study also reveals the suppression of electron backscattering as a result of the edge transport which is induced by the B[Symbol: see text]-field. This phenomenon can potentially mitigate the undesired effects of disorder, such as bulk and edge vacancies, on the transport properties of AGNR. Lastly, we show that the effect of [Formula: see text]-field on electronic transport is less significant in the multimode compared to the single-mode electron transport.

  17. Nonequilibrium solvent effects in Born-Oppenheimer molecular dynamics for ground and excited electronic states.

    PubMed

    Bjorgaard, J A; Velizhanin, K A; Tretiak, S

    2016-04-21

    The effects of solvent on molecular processes such as excited state relaxation and photochemical reaction often occurs in a nonequilibrium regime. Dynamic processes such as these can be simulated using excited statemolecular dynamics. In this work, we describe methods of simulating nonequilibrium solvent effects in excited statemolecular dynamics using linear-response time-dependent density functional theory and apparent surface charge methods. These developments include a propagation method for solvent degrees of freedom and analytical energy gradients for the calculation of forces. Molecular dynamics of acetaldehyde in water or acetonitrile are demonstrated where the solute-solvent system is out of equilibrium due to photoexcitation and emission. PMID:27389206

  18. Nonequilibrium solvent effects in Born-Oppenheimer molecular dynamics for ground and excited electronic states

    NASA Astrophysics Data System (ADS)

    Bjorgaard, J. A.; Velizhanin, K. A.; Tretiak, S.

    2016-04-01

    The effects of solvent on molecular processes such as excited state relaxation and photochemical reaction often occurs in a nonequilibrium regime. Dynamic processes such as these can be simulated using excited state molecular dynamics. In this work, we describe methods of simulating nonequilibrium solvent effects in excited state molecular dynamics using linear-response time-dependent density functional theory and apparent surface charge methods. These developments include a propagation method for solvent degrees of freedom and analytical energy gradients for the calculation of forces. Molecular dynamics of acetaldehyde in water or acetonitrile are demonstrated where the solute-solvent system is out of equilibrium due to photoexcitation and emission.

  19. Nonequilibrium transport in the Anderson-Holstein model with interfacial screening

    NASA Astrophysics Data System (ADS)

    Perfetto, Enrico; Stefanucci, Gianluca

    Image charge effects in nanoscale junctions with strong electron-phonon coupling open the way to unexplored physical scenarios. Here we present a comprehensive study of the transport properties of the Anderson-Holstein model in the presence of dot-lead repulsion. We propose an accurate many-body approach to deal with the simultaneous occurrence of the Franck-Condon blockade and the screening-induced enhancement of the polaron mobility. Remarkably, we find that a novel mechanism of negative differential conductance origins from the competition between the charge blocking due to the electron-phonon interaction and the charge deblocking due to the image charges. An experimental setup to observe this phenomenon is discussed. References [1]E. Perfetto, G. Stefanucci and M. Cini, Phys. Rev. B 85, 165437 (2012). [2] E. Perfetto and G. Stefanucci, Phys. Rev. B 88, 245437 (2013). [3] E. Perfetto and G. Stefanucci, Journal of Computational Electronics 14, 352 (2015). E.P. and G.S. acknowledge funding by MIUR FIRB Grant No. RBFR12SW0J.

  20. Effects of partial hydrogenation on electronic transport properties in C60 molecular devices

    NASA Astrophysics Data System (ADS)

    Chen, L. N.; Cao, C.; Wu, X. Z.; Ma, S. S.; Huang, W. R.; Xu, H.

    2012-12-01

    By using nonequilibrium Green's functions in combination with the density-function theory, we investigate electronic transport properties of molecular devices with pristine and partial hydrogenation. The calculated results show that the electronic transport properties of molecular devices can be modulated by partial hydrogenation. Interestingly, our results exhibit negative differential resistance behavior in the case of the imbalance H-adsorption in C60 molecular devices under low bias. However, negative differential resistance behavior cannot be observed in the case of the balance H-adsorption. A mechanism is proposed for the hydrogenation and negative differential resistance behavior.

  1. Open XXZ spin chain: nonequilibrium steady state and a strict bound on ballistic transport.

    PubMed

    Prosen, Tomaž

    2011-05-27

    An explicit matrix product ansatz is presented, in the first two orders in the (weak) coupling parameter, for the nonequilibrium steady state of the homogeneous, nearest neighbor Heisenberg XXZ spin 1/2 chain driven by Lindblad operators which act only at the edges of the chain. The first order of the density operator becomes, in the thermodynamic limit, an exact pseudolocal conservation law and yields-via the Mazur inequality-a rigorous lower bound on the high-temperature spin Drude weight. Such a Mazur bound is a nonvanishing fractal function of the anisotropy parameter Δ for |Δ|<1. PMID:21699339

  2. Electronic transport properties of a quinone-based molecular switch

    NASA Astrophysics Data System (ADS)

    Zheng, Ya-Peng; Bian, Bao-An; Yuan, Pei-Pei

    2016-09-01

    In this paper, we carried out first-principles calculations based on density functional theory and non-equilibrium Green's function to investigate the electronic transport properties of a quinone-based molecule sandwiched between two Au electrodes. The molecular switch can be reversibly switched between the reduced hydroquinone (HQ) and oxidized quinone (Q) states via redox reactions. The switching behavior of two forms is analyzed through their I- V curves, transmission spectra and molecular projected self-consistent Hamiltonian at zero bias. Then we discuss the transmission spectra of the HQ and Q forms at different bias, and explain the oscillation of current according to the transmission eigenstates of LUMO energy level for Q form. The results suggest that this kind of a quinone-based molecule is usable as one of the good candidates for redox-controlled molecular switches.

  3. Electronic transport characteristics in silicon nanotube field-effect transistors

    NASA Astrophysics Data System (ADS)

    Shan, Guangcun; Wang, Yu; Huang, Wei

    2011-07-01

    The successful synthesis of silicon nanotubes (SiNTs) has been reported, making these nanostructures a new novel candidate for future nanodevices. By self-consistently solving the Poisson equations using the non-equilibrium Green's function (NEGF) formalism, we investigate the electronic transport and the role of gate bias in affecting the drive current of single-walled silicon nanotube (SW-SiNT) field-effect transistors (FETs). By comparison of a SW-CNT FET, it is found that the SW-SiNT with a high- k HfO gate oxide is a promising candidate for nanotube transistor with better performance. The results discussed here would serve as a versatile and powerful guideline for future experimental studies of SW-SiNT-based transistor with the purpose of exploring device application for nanoelectronics.

  4. Effects of nitrogen substitutional doping on the electronic transport of carbon nanotube

    NASA Astrophysics Data System (ADS)

    Wei, Jianwei; Hu, Huifang; Zeng, Hui; Zhou, Zhipeng; Yang, Weiwei; Peng, Ping

    2008-01-01

    We have studied the effects of nitrogen substitutional doping on the transport properties of single-wall carbon nanotube (8, 0) using density functional theory and non-equilibrium Green's functions. The results reveal that the nanotube changes from the semiconducting to the quasi-metallic state because of the dopants, and their structures strongly dominate their electrical properties. Our calculations indicate that transport properties of the doped nanotubes are sensitive not only to the concentration of nitrogen atoms but also to their distribution. The doping effects on the electronic transport of the carbon nanotube are discussed.

  5. Nonequilibrium spin polarization induced charge Hall effect

    NASA Astrophysics Data System (ADS)

    Hou, Dazhi; Qiu, Z.; Iguchi, R.; Sato, K.; Uchida, K.; Bauer, G. W.; Saitoh, Eiji

    2015-03-01

    The nonequilibrium spin polarization lies at the heart of information processing in spin-based devices. The generation and manipulation of the spin polarization have been realized by various approaches, however, the spin polarization is usually considered to have negligible effect on the electric transport property, especially for systems of high electron concentration like metals (ɛF ~ eV). Here we show that the nonequilibrium spin polarization can cause a novel Hall voltage in a conventional metallic alloy at room temperature, which is due to a new mechanism and closely related to the spin Nernst effect.

  6. Kinetics of band bending and electron affinity at GaAs(001) surface with nonequilibrium cesium overlayers

    SciTech Connect

    Zhuravlev, A. G.; Savchenko, M. L.; Paulish, A. G.; Alperovich, V. L.; Scheibler, H. E.; Jaroshevich, A. S.

    2013-12-04

    The dosage dependences of surface band bending and effective electron affinity under cesium deposition on the Ga-rich GaAs(001) surface, along with the relaxation of these electronic properties after switching off the Cs source are experimentally studied by means of modified photoreflectance spectroscopy and photoemission quantum yield spectroscopy. At small Cs coverages, below half of a monolayer, additional features in the dosage dependence and subsequent downward relaxation of the photoemission current are determined by the variations of band bending. At coverages above half of a monolayer the upward relaxation of the photocurrent is caused supposedly by the decrease of the electron affinity due to restructuring in the nonequilibrium cesium overlayer.

  7. Nonequilibrium diagrammatic technique for nanoscale devices

    NASA Astrophysics Data System (ADS)

    Zebrev, G. I.

    2006-05-01

    A general approach based on gauge invariance requirements has been developed for automatic construction of quantum kinetic equation in electron systems, far for equilibrium. Proposed theoretical scheme has high generality and automatism and capable to treat nonequilibrium effects of electron transport, quantum interference and energy dissipation. Dissipative and quantum-interference effects can be consequentially incorporated in the computational scheme through solution of dynamic Dyson equation for self-energies in the framework of conventional diagrammatic technique.

  8. Density Functional Theory for Steady-State Nonequilibrium Molecular Junctions

    PubMed Central

    Liu, Shuanglong; Nurbawono, Argo; Zhang, Chun

    2015-01-01

    We present a density functional theory (DFT) for steady-state nonequilibrium quantum systems such as molecular junctions under a finite bias. Based on the steady-state nonequilibrium statistics that maps nonequilibrium to an effective equilibrium, we show that ground-state DFT (GS-DFT) is not applicable in this case and two densities, the total electron density and the density of current-carrying electrons, are needed to uniquely determine the properties of the corresponding nonequilibrium system. A self-consistent mean-field approach based on two densities is then derived. The theory is implemented into SIESTA computational package and applied to study nonequilibrium electronic/transport properties of a realistic carbon-nanotube (CNT)/Benzene junction. Results obtained from our steady-state DFT (SS-DFT) are compared with those of conventional GS-DFT based transport calculations. We show that SS-DFT yields energetically more stable nonequilibrium steady state, predicts significantly lower electric current, and is able to produce correct electronic structures in local equilibrium under a limiting case. PMID:26472080

  9. Non-canonical distribution and non-equilibrium transport beyond weak system-bath coupling regime: A polaron transformation approach

    NASA Astrophysics Data System (ADS)

    Xu, Dazhi; Cao, Jianshu

    2016-08-01

    The concept of polaron, emerged from condense matter physics, describes the dynamical interaction of moving particle with its surrounding bosonic modes. This concept has been developed into a useful method to treat open quantum systems with a complete range of system-bath coupling strength. Especially, the polaron transformation approach shows its validity in the intermediate coupling regime, in which the Redfield equation or Fermi's golden rule will fail. In the polaron frame, the equilibrium distribution carried out by perturbative expansion presents a deviation from the canonical distribution, which is beyond the usual weak coupling assumption in thermodynamics. A polaron transformed Redfield equation (PTRE) not only reproduces the dissipative quantum dynamics but also provides an accurate and efficient way to calculate the non-equilibrium steady states. Applications of the PTRE approach to problems such as exciton diffusion, heat transport and light-harvesting energy transfer are presented.

  10. Electronic transport in fullerene C20 bridge assisted by molecular vibrations.

    PubMed

    Yamamoto, Takahiro; Watanabe, Kazuyuki; Watanabe, Satoshi

    2005-08-01

    The effect of molecular vibrations on electronic transport is investigated with the smallest fullerene C20 bridge, utilizing the Keldysh nonequilibrium Green's function techniques combined with the tight-binding molecular-dynamics method. Large discontinuous steps appear in the differential conductance when the applied bias voltage matches particular vibrational energies. The magnitude of the step is found to vary considerably with the vibrational mode and to depend on the local electronic states besides the strength of electron-vibration coupling. On the basis of this finding, a novel way to control the molecular motion by adjusting the gate voltage is proposed.

  11. Two-channel model for nonequilibrium thermal transport in pump-probe experiments

    NASA Astrophysics Data System (ADS)

    Wilson, R. B.; Feser, Joseph P.; Hohensee, Gregory T.; Cahill, David G.

    2013-10-01

    We present an analytic solution for heat flow in a multilayer two-channel system for the interpretation of time-domain thermoreflectance (TDTR) experiments where nonequilibrium effects are important. The two-channel solution is used to analyze new room temperature TDTR measurements of Al/Cu and Al/Si0.99Ge0.01 systems. Cu and Si0.99Ge0.01 are examples of materials well suited for analysis with a two-channel model because thermal excitations responsible for the vast majority of the heat capacity in these solids contribute little to their thermal conductivity. Nonequilibrium effects are found to be unimportant for the interpretation of the Al/Cu TDTR data but dramatic for the Al/Si0.99Ge0.01 TDTR data. The two-channel model predicts a significant reduction in the effective thermal conductivity of Si0.99Ge0.01 in a region within 150 nm of the Al/Si0.99Ge0.01 interface. The extra thermal resistance in this region is a result of the disparate heat flux boundary conditions for low- and high-frequency phonons in combination with weak coupling between low- and high-frequency phonons. When the experimental data are analyzed with a single-channel model, both the conductance and thermal conductivity appear to depend on pump-modulation frequency, consistent with the two-channel model's predictions. Finally, we compare the results of our diffusive two-channel model to a nonlocal description for steady-state heat flow near a boundary and show they yield nearly identical results.

  12. Coupled electron-photon radiation transport

    SciTech Connect

    Lorence, L.; Kensek, R.P.; Valdez, G.D.; Drumm, C.R.; Fan, W.C.; Powell, J.L.

    2000-01-17

    Massively-parallel computers allow detailed 3D radiation transport simulations to be performed to analyze the response of complex systems to radiation. This has been recently been demonstrated with the coupled electron-photon Monte Carlo code, ITS. To enable such calculations, the combinatorial geometry capability of ITS was improved. For greater geometrical flexibility, a version of ITS is under development that can track particles in CAD geometries. Deterministic radiation transport codes that utilize an unstructured spatial mesh are also being devised. For electron transport, the authors are investigating second-order forms of the transport equations which, when discretized, yield symmetric positive definite matrices. A novel parallelization strategy, simultaneously solving for spatial and angular unknowns, has been applied to the even- and odd-parity forms of the transport equation on a 2D unstructured spatial mesh. Another second-order form, the self-adjoint angular flux transport equation, also shows promise for electron transport.

  13. The Moving Lines on Electron Spectra as Charge Reflexes on Non-equilibrium States of Nanostructured Surfaces.

    PubMed

    Mishchuk, Oleg A

    2016-12-01

    The experimental results present the phenomenon of moving lines on electron spectra which are linked spatially and in time with the localization and durability of the processes of new surface producing in folds and grain boundaries. This effect was also realized for a thin-layer composite "organic on metal films on dielectric substrate" in modeling non-equilibrium conditions which are created by the intensive electron beam pulse impact. It was found that the nature of the inceptive adsorption layer, in addition to the metal film, determines the initial positions of moving lines on the spectra. The main accents in these investigations were in observations of appearance of the moving lines, dynamics of their displacements on the spectra, final stages when these lines vanished, and finding the general regularities between the spontaneous and induced events.

  14. The Moving Lines on Electron Spectra as Charge Reflexes on Non-equilibrium States of Nanostructured Surfaces

    NASA Astrophysics Data System (ADS)

    Mishchuk, Oleg A.

    2016-04-01

    The experimental results present the phenomenon of moving lines on electron spectra which are linked spatially and in time with the localization and durability of the processes of new surface producing in folds and grain boundaries. This effect was also realized for a thin-layer composite "organic on metal films on dielectric substrate" in modeling non-equilibrium conditions which are created by the intensive electron beam pulse impact. It was found that the nature of the inceptive adsorption layer, in addition to the metal film, determines the initial positions of moving lines on the spectra. The main accents in these investigations were in observations of appearance of the moving lines, dynamics of their displacements on the spectra, final stages when these lines vanished, and finding the general regularities between the spontaneous and induced events.

  15. The Moving Lines on Electron Spectra as Charge Reflexes on Non-equilibrium States of Nanostructured Surfaces.

    PubMed

    Mishchuk, Oleg A

    2016-12-01

    The experimental results present the phenomenon of moving lines on electron spectra which are linked spatially and in time with the localization and durability of the processes of new surface producing in folds and grain boundaries. This effect was also realized for a thin-layer composite "organic on metal films on dielectric substrate" in modeling non-equilibrium conditions which are created by the intensive electron beam pulse impact. It was found that the nature of the inceptive adsorption layer, in addition to the metal film, determines the initial positions of moving lines on the spectra. The main accents in these investigations were in observations of appearance of the moving lines, dynamics of their displacements on the spectra, final stages when these lines vanished, and finding the general regularities between the spontaneous and induced events. PMID:27083583

  16. Heat Transfer and Fluid Transport of Supercritical CO2 in Enhanced Geothermal System with Local Thermal Non-equilibrium Model

    SciTech Connect

    Zhang, Le; Luo, Feng; Xu, Ruina; Jiang, Peixue; Liu, Huihai

    2014-12-31

    The heat transfer and fluid transport of supercritical CO2 in enhanced geothermal system (EGS) is studied numerically with local thermal non-equilibrium model, which accounts for the temperature difference between solid matrix and fluid components in porous media and uses two energy equations to describe heat transfer in the solid matrix and in the fluid, respectively. As compared with the previous results of our research group, the effect of local thermal non-equilibrium mainly depends on the volumetric heat transfer coefficient ah, which has a significant effect on the production temperature at reservoir outlet and thermal breakthrough time. The uniformity of volumetric heat transfer coefficient ah has little influence on the thermal breakthrough time, but the temperature difference become more obvious with time after thermal breakthrough with this simulation model. The thermal breakthrough time reduces and the effect of local thermal non-equilibrium becomes significant with decreasing ah.

  17. Electron transport through single endohedral Ce@C82 metallofullerenes

    NASA Astrophysics Data System (ADS)

    Kaneko, Satoshi; Wang, Lu; Luo, Guangfu; Lu, Jing; Nagase, Shigeru; Sato, Satoru; Yamada, Michio; Slanina, Zdenek; Akasaka, Takeshi; Kiguchi, Manabu

    2012-10-01

    The electron transport through a single endohedral Ce@C82 metallofullerene bridging between metal electrodes was investigated with experimental (break junction) as well as theoretical (density functional theory coupled with the nonequilibrium Green's function formalism) techniques. The single Ce@C82 molecule junction showing a high and fixed conductance value was fabricated by direct binding of the metallofullerene to Ag electrodes. The junction had a conductance of 0.28(±0.05)G0 (G0 = 2e2/h), which was much larger than that of single molecule junctions having anchoring groups (<0.01G0), but only half that of the single C60 molecule junction of 0.5G0. The unexpected reduced conductance of the single Ce@C82 molecule junction compared with that of the single C60 molecule junction was supported by the ab initio quantum transport calculations and was explained in terms of the localization of electrons in the C82 cage. In the case of the Au electrodes, the single Ce@C82 molecule junction was not formed by the break junction technique because the Ce@C82 molecule could not be trapped in the large Au nanogap, which was formed just after breaking the Au contacts.

  18. Time-dependent and steady-state Gutzwiller approach for nonequilibrium transport in nanostructures

    NASA Astrophysics Data System (ADS)

    Lanatà, Nicola; Strand, Hugo U. R.

    2012-09-01

    We extend the time-dependent Gutzwiller variational approach, recently introduced by Schirò and Fabrizio [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.105.076401 105, 076401 (2010)], to impurity problems. Furthermore, we derive a consistent theory for the steady state, and show its equivalence with the previously introduced nonequilibrium steady-state extension of the Gutzwiller approach. The method is shown to be able to capture dissipation in the leads, so that a steady state is reached after a sufficiently long relaxation time. The time-dependent method is applied to the single-orbital Anderson impurity model at half filling, modeling a quantum dot coupled to two leads. In these exploratory calculations, the Gutzwiller projector is limited to act only on the impurity. The strengths and the limitations of this approximation are assessed via comparison with state-of-the-art continuous-time quantum Monte Carlo results. Finally, we discuss how the method can be systematically improved by extending the region of action of the Gutzwiller projector.

  19. Vibration-induced inelastic effects in the electron transport through multisite molecular bridges.

    PubMed

    Zimbovskaya, Natalya A; Kuklja, Maija M

    2009-09-21

    We theoretically analyzed inelastic effects in the electron transport through molecular junctions originating from electron-vibron interactions. The molecular bridge was simulated by a periodical chain of identical hydrogenlike atoms with the nearest neighbors interaction thus providing a set of energy states for the electron tunneling. To avoid difficulties inevitably arising when advanced computational techniques are employed to study inelastic electron transport through multilevel bridges, we propose and develop a semiphenomenological approach. The latter is based on Buttiker's dephasing model within the scattering matrix formalism. We apply the proposed approach to describe features associated with electron energy transfer to vibrational phonons that appear in the second derivative of the current in the junction with respect to the bias voltage. In the particular case of a single level bridge our results agree with those obtained by proper calculations carried out within the nonequilibrium Green's functions method indicating the usefulness of the suggested approach.

  20. Theoretical study of electronic transport properties of a graphene-silicene bilayer

    NASA Astrophysics Data System (ADS)

    Berdiyorov, G. R.; Bahlouli, H.; Peeters, F. M.

    2015-06-01

    Electronic transport properties of a graphene-silicene bilayer system are studied using density-functional theory in combination with the nonequilibrium Green's function formalism. Depending on the energy of the electrons, the transmission can be larger in this system as compared to the sum of the transmissions of separated graphene and silicene monolayers. This effect is related to the increased electron density of states in the bilayer sample. At some energies, the electronic states become localized in one of the layers, resulting in the suppression of the electron transmission. The effect of an applied voltage on the transmission becomes more pronounced in the layered sample as compared to graphene due to the larger variation of the electrostatic potential profile. Our findings will be useful when creating hybrid nanoscale devices where enhanced transport properties will be desirable.

  1. Theoretical study of electronic transport properties of a graphene-silicene bilayer

    SciTech Connect

    Berdiyorov, G. R.; Bahlouli, H.; Peeters, F. M.

    2015-06-14

    Electronic transport properties of a graphene-silicene bilayer system are studied using density-functional theory in combination with the nonequilibrium Green's function formalism. Depending on the energy of the electrons, the transmission can be larger in this system as compared to the sum of the transmissions of separated graphene and silicene monolayers. This effect is related to the increased electron density of states in the bilayer sample. At some energies, the electronic states become localized in one of the layers, resulting in the suppression of the electron transmission. The effect of an applied voltage on the transmission becomes more pronounced in the layered sample as compared to graphene due to the larger variation of the electrostatic potential profile. Our findings will be useful when creating hybrid nanoscale devices where enhanced transport properties will be desirable.

  2. Nonlinear thermoelectric transport in single-molecule junctions: the effect of electron-phonon interactions

    NASA Astrophysics Data System (ADS)

    Zimbovskaya, Natalya A.

    2016-07-01

    In this paper, we theoretically analyze steady-state thermoelectric transport through a single-molecule junction with a vibrating bridge. The thermally induced charge current in the system is explored using a nonequilibrium Green function formalism. We study the combined effects of Coulomb interactions between charge carriers on the bridge and electron-phonon interactions on the thermocurrent beyond the linear response regime. It is shown that electron-vibron interactions may significantly affect both the magnitude and the direction of the thermocurrent, and vibrational signatures may appear.

  3. Parameters describing nonequilibrium transport of polycyclic aromatic hydrocarbons through contaminated soil columns: estimability analysis, correlation, and optimization.

    PubMed

    Ngo, Viet V; Michel, Julien; Gujisaite, Valérie; Latifi, Abderrazak; Simonnot, Marie-Odile

    2014-03-01

    reasons behind the optimization problems and indicate the type of experimental information additionally needed for parameter identification. To overcome the parameterization issues of PAH non-equilibrium transport, the experimental design, timescale, and model refinement need further improvement. The conclusions presented in this paper are not limited necessarily to PAHs, but may also be relevant to other organic contaminants with similar leaching behavior.

  4. Plasmon-Mediated Electron Transport in Tip-Enhanced Raman Spectroscopic Junctions.

    PubMed

    Pal, Partha Pratim; Jiang, Nan; Sonntag, Matthew D; Chiang, Naihao; Foley, Edward T; Hersam, Mark C; Van Duyne, Richard P; Seideman, Tamar

    2015-11-01

    We combine experiment, theory, and first-principles-based calculations to study the light-induced plasmon-mediated electron transport characteristics of a molecular-scale junction. The experimental data show a nonlinear increase in electronic current perturbation when the focus of a chopped laser beam moves laterally toward the tip-sample junction. To understand this behavior and generalize it, we apply a combined theory of the electronic nonequilibrium formed upon decoherence of an optically triggered plasmon and first-principles transport calculations. Our model illustrates that the current via an adsorbed molecular monolayer increases nonlinearly as more energy is pumped into the junction due to the increasing availability of virtual molecular orbital channels for transport with higher injection energies. Our results thus illustrate light-triggered, plasmon-enhanced tunneling current in the presence of a molecular linker. PMID:26538036

  5. Communication: Electronic and transport properties of molecular junctions under a finite bias: A dual mean field approach

    SciTech Connect

    Liu, Shuanglong; Feng, Yuan Ping; Zhang, Chun

    2013-11-21

    We show that when a molecular junction is under an external bias, its properties cannot be uniquely determined by the total electron density in the same manner as the density functional theory for ground state properties. In order to correctly incorporate bias-induced nonequilibrium effects, we present a dual mean field (DMF) approach. The key idea is that the total electron density together with the density of current-carrying electrons are sufficient to determine the properties of the system. Two mean fields, one for current-carrying electrons and the other one for equilibrium electrons can then be derived. Calculations for a graphene nanoribbon junction show that compared with the commonly used ab initio transport theory, the DMF approach could significantly reduce the electric current at low biases due to the non-equilibrium corrections to the mean field potential in the scattering region.

  6. Effects of electron-phonon interaction on thermal and electrical transport through molecular nano-conductors

    SciTech Connect

    Lü, Jing-Tao; Zhou, Hangbo; Jiang, Jin-Wu; Wang, Jian-Sheng

    2015-05-15

    The topic of this review is the effects of electron-phonon interaction (EPI) on the transport properties of molecular nano-conductors. A nano-conductor connects to two electron leads and two phonon leads, possibly at different temperatures or chemical potentials. The EPI appears only in the nano-conductor. We focus on its effects on charge and energy transport. We introduce three approaches. For weak EPI, we use the nonequilibrium Green’s function method to treat it perturbatively. We derive the expressions for the charge and heat currents. For weak system-lead couplings, we use the quantum master equation approach. In both cases, we use a simple single level model to study the effects of EPI on the system’s thermoelectric transport properties. It is also interesting to look at the effect of currents on the dynamics of the phonon system. For this, we derive a semi-classical generalized Langevin equation to describe the nano-conductor’s atomic dynamics, taking the nonequilibrium electron system, as well as the rest of the atomic degrees of freedom as effective baths. We show simple applications of this approach to the problem of energy transfer between electrons and phonons.

  7. Transport experiments with Dirac electrons

    NASA Astrophysics Data System (ADS)

    Checkelsky, Joseph George

    This thesis presents transport experiments performed on solid state systems in which the behavior of the charge carriers can be described by the Dirac equation. Unlike the massive carriers in a typical material, in these systems the carriers behave like massless fermions with a photon-like dispersion predicted to greatly modify their spin and charge transport properties. The first system studied is graphene, a crystalline monolayer of carbon arranged in a hexagonal lattice. The band structure calculated from the hexagonal lattice has the form of the massless Dirac Hamiltonian. At the charge neutral Dirac point, we find that application of a magnetic field drives a transition to an insulating state. We also study the thermoelectric properties of graphene and find that the states near the Dirac point have a unique response compared to those at higher charge density. The second system is the 3D topological insulator Bi2Se3, where a Dirac-like dispersion for states on the 2D surface of the insulating 3D crystal arises as a result of the topology of the 3D bands and time reversal symmetry. To access the transport properties of the 2D states, we suppress the remnant bulk conduction channel by chemical doping and electrostatic gating. In bulk crystals we find strong quantum corrections to transport at low temperature when the bulk conduction channel is maximally suppressed. In microscopic crystals we are able better to isolate the surface conduction channel properties. We identify in-gap conducting states that have relatively high mobility compared to the bulk and exhibit weak anti-localization, consistent with predictions for protected 2D surface states with strong spin-orbit coupling.

  8. The Electron Transport Chain: An Interactive Simulation

    ERIC Educational Resources Information Center

    Romero, Chris; Choun, James

    2014-01-01

    This activity provides students an interactive demonstration of the electron transport chain and chemiosmosis during aerobic respiration. Students use simple, everyday objects as hydrogen ions and electrons and play the roles of the various proteins embedded in the inner mitochondrial membrane to show how this specific process in cellular…

  9. Inelastic transport in the Coulomb blockade regime within a nonequilibrium atomic limit

    NASA Astrophysics Data System (ADS)

    Galperin, Michael; Nitzan, Abraham; Ratner, Mark A.

    2008-09-01

    A method developed by Sandalov [Int. J. Quantum Chem. 94, 113 (2003)] is applied to inelastic transport in the case of strong correlations on the molecule, which is relatively weakly coupled to contacts. The ability of the approach to deal with the transport in the language of many-body molecular states as well as to take into account charge-specific normal modes and nonadiabatic couplings is stressed. We demonstrate the capabilities of the technique within simple model calculations and compare it to previously published approaches.

  10. Monte Carlo electron/photon transport

    SciTech Connect

    Mack, J.M.; Morel, J.E.; Hughes, H.G.

    1985-01-01

    A review of nonplasma coupled electron/photon transport using Monte Carlo method is presented. Remarks are mainly restricted to linerarized formalisms at electron energies from 1 keV to 1000 MeV. Applications involving pulse-height estimation, transport in external magnetic fields, and optical Cerenkov production are discussed to underscore the importance of this branch of computational physics. Advances in electron multigroup cross-section generation is reported, and its impact on future code development assessed. Progress toward the transformation of MCNP into a generalized neutral/charged-particle Monte Carlo code is described. 48 refs.

  11. Electron transport through single carbon nanotubes

    SciTech Connect

    Schenkel, Thomas; Chai, G.; Heinrich, H.; Chow, L.; Schenkel, T.

    2007-08-01

    We report on the transport of energetic electrons through single, well aligned multi-wall carbon nanotubes (CNT). Embedding of CNTs in a protective carbon fiber coating enables the application of focused ion beam based sample preparation techniques for the non-destructive isolation and alignment of individual tubes. Aligned tubes with lengths of 0.7 to 3 mu m allow transport of 300 keV electrons in a transmission electron microscope through their hollow cores at zero degree incident angles and for a misalignment of up to 1 degree.

  12. Non-equilibrium ionization by a periodic electron beam. I. Synthetic coronal spectra and implications for interpretation of observations

    NASA Astrophysics Data System (ADS)

    Dzifčáková, E.; Dudík, J.; Mackovjak, Š.

    2016-05-01

    Context. Coronal heating is currently thought to proceed via the mechanism of nanoflares, small-scale and possibly recurring heating events that release magnetic energy. Aims: We investigate the effects of a periodic high-energy electron beam on the synthetic spectra of coronal Fe ions. Methods: Initially, the coronal plasma is assumed to be Maxwellian with a temperature of 1 MK. The high-energy beam, described by a κ-distribution, is then switched on every period P for the duration of P/ 2. The periods are on the order of several tens of seconds, similar to exposure times or cadences of space-borne spectrometers. Ionization, recombination, and excitation rates for the respective distributions are used to calculate the resulting non-equilibrium ionization state of Fe and the instantaneous and period-averaged synthetic spectra. Results: Under the presence of the periodic electron beam, the plasma is out of ionization equilibrium at all times. The resulting spectra averaged over one period are almost always multithermal if interpreted in terms of ionization equilibrium for either a Maxwellian or a κ-distribution. Exceptions occur, however; the EM-loci curves appear to have a nearly isothermal crossing-point for some values of κs. The instantaneous spectra show fast changes in intensities of some lines, especially those formed outside of the peak of the respective EM(T) distributions if the ionization equilibrium is assumed. Movies 1-5 are available in electronic form at http://www.aanda.org

  13. A review of reaction rates and thermodynamic and transport properties for the 11-species air model for chemical and thermal nonequilibrium calculations to 30000 K

    NASA Technical Reports Server (NTRS)

    Gupta, Roop N.; Yos, Jerrold M.; Thompson, Richard A.

    1989-01-01

    Reaction rate coefficients and thermodynamic and transport properties are provided for the 11-species air model which can be used for analyzing flows in chemical and thermal nonequilibrium. Such flows will likely occur around currently planned and future hypersonic vehicles. Guidelines for determining the state of the surrounding environment are provided. Approximate and more exact formulas are provided for computing the properties of partially ionized air mixtures in such environments.

  14. Implicit Water Simulations of Non-Equilibrium Charge Transport in Ion Channels

    NASA Astrophysics Data System (ADS)

    Ravaioli, U.; van der Straaten, T. A.; Kathawala, G.

    Ion channels are natural nano-channels found in the membranes of all living cells, which exhibit a broad range of specific device-like functions to help regulate cell physiology. The study of charge transport in ion channels is imperative to understand how charge regulation is accomplished at the molecular level if one is to develop nanoscale artificial systems that mimic biological function and detection. Although Molecular Dynamics is the most popular approach to simulate ion channel behavior, the computational cost of representing all water molecules and ions in the system is prohibitive to study the timescales required to resolve ionic current and lead to structure design. A hierarchy of models of decreasing complexity is needed to address simulation of different time and space scales, similar to the set of models developed to study transport in semiconductors. This paper discusses the application of Monte Carlo and Drift-diffusion methods to simulate transport in ion channels, using the ompF porin channel as a prototype.

  15. Separation of angular and energy relaxations of nonequilibrium electrons in a solid

    NASA Astrophysics Data System (ADS)

    Bakaleinikov, L. A.; Tropp, E. A.; Flegontova, E. Yu.

    2016-08-01

    We demonstrate that the collision integral of the kinetic equation for the interaction of hot electrons with phonons can be split into substantially different parts that correspond to elastic and inelastic collisions. In particular, this applies to electrons with energies of about 1 eV that propagate in semiconductors. The difference in the characteristic energy and momentum relaxation times makes it possible to separate the angular and energy relaxation processes. If the differential cross section of elastic scattering depends, not on the scattering angle, but on the directions of incident and scattered electrons (which is observed, e.g., for the interaction of an electron with piezoelectric lattice vibrations in AIIIBV compounds), the Laplacian in the equation that describes the spatial and energy distributions of electrons can be replaced by an elliptical operator; i.e., the electron diffusion turns out to be anisotropic.

  16. Nonequilibrium Dynamics in a Quasi-Two-Dimensional Electron Plasma after Ultrafast Intersubband Excitation

    SciTech Connect

    Lutgen, S.; Kaindl, R.A.; Woerner, M.; Elsaesser, T.; Hase, A.; Kuenzel, H.; Gulia, M.; Meglio, D.; Lugli, P.

    1996-10-01

    The dynamics of electrons in GaInAs/AlInAs quantum wells is studied after excitation from the {ital n}=1 to the {ital n}=2 conduction subband. Femtosecond pump-probe experiments demonstrate for the first time athermal distributions of {ital n}=1 electrons on a surprisingly long time scale of 2ps. Thermalization involves intersubband scattering of excited electrons via optical phonon emission with a time constant of 1ps and intrasubband Coulomb and phonon scattering. Ensemble Monte Carlo simulations show that the slow electron equilibration results from Pauli blocking and screening of carrier-carrier scattering. {copyright} {ital 1996 The American Physical Society.}

  17. Electronic Transport in Organic Molecules

    NASA Astrophysics Data System (ADS)

    Tian, W.; Samanta, M. P.; Henderson, J. I.; Kubiak, C. P.; Datta, S.

    1996-03-01

    A systematic theoretical study of the conductance of a class of organic molecules connected between two gold cantact pads will be presented. This class of molecules consists of oligomers of benzene rings linked at their para-positions and terminated with suitable ligand end groups designed to bond to gold substrates. Such molecules are currently being investigated experimentally for use as interconnectors in nanoscale electronic devices (J.Guay et al, J.Am.Chem.Soc., 115,1869, (1993); M.Dorogi et al, Phys. Rev. B52,9071,(1995); D.B.Janes et al, Superlatt. and Microstruc., in press). Analytical and numerical results will be presented illustrating effects of Metal Induced Gap States (MIGS), end group atoms, geometric and molecular structure on the measured conductance.

  18. A new perspective on the electron transfer: recovering the Butler-Volmer equation in non-equilibrium thermodynamics.

    PubMed

    Dreyer, Wolfgang; Guhlke, Clemens; Müller, Rüdiger

    2016-09-28

    Electron transfer reactions are commonly described by the phenomenological Butler-Volmer equation which has its origin in kinetic theories. The Butler-Volmer equation relates interfacial reaction rates to bulk quantities like the electrostatic potential and electrolyte concentrations. Although the general structure of the equation is well accepted, for modern electrochemical systems like batteries and fuel cells there is still intensive discussion about the specific dependencies of the coefficients. A general guideline for the derivation of Butler-Volmer type equations is missing in the literature. We derive very general relations of Butler-Volmer structure which are based on a rigorous non-equilibrium thermodynamic model and allow for adaption to a wide variety of electrochemical systems. We discuss the application of the new thermodynamic approach to different scenarios like the classical electron transfer reactions at metal electrodes and the intercalation process in lithium-iron-phosphate electrodes. Furthermore we show that under appropriate conditions also adsorption processes can lead to Butler-Volmer equations. We illustrate the application of our theory by a strongly simplified example of electroplating. PMID:27560993

  19. Effect of substitutional impurities on the electronic transport properties of graphene

    NASA Astrophysics Data System (ADS)

    Berdiyorov, G. R.; Bahlouli, H.; Peeters, F. M.

    2016-10-01

    Density-functional theory in combination with the nonequilibrium Green's function formalism is used to study the effect of substitutional doping on the electronic transport properties of hydrogen passivated zig-zag graphene nanoribbon devices. B, N and Si atoms are used to substitute carbon atoms located at the center or at the edge of the sample. We found that Si-doping results in better electronic transport as compared to the other substitutions. The transmission spectrum also depends on the location of the substitutional dopants: for single atom doping the largest transmission is obtained for edge substitutions, whereas substitutions in the middle of the sample give larger transmission for double carbon substitutions. The obtained results are explained in terms of electron localization in the system due to the presence of impurities.

  20. Electronic and transport properties of PSi@MoS2 nanocables.

    PubMed

    Sun, Cuicui; Zhang, Guiling; Shang, Yan; Yang, Zhao-Di; Sun, Xiaojun

    2016-02-14

    Electronic structures and transport properties of prototype MoS2 nanotube (15, 0) nanocables, including undoped PSi@MoS2 and B- and P-doped PSi@MoS2 (where PSi refers to polysilane), are investigated using the density functional theory (DFT) and the non-equilibrium Green's function (NEGF) methods. It is found that transport properties of two-probe systems by sandwiching finite long nanocables between two Au electrodes are basically in agreement with the electronic structures of their corresponding infinitely long systems. Encapsulating undoped and doped PSi nanowires inside the MoS2 nanotubes could not significantly affect the electronic and transport properties. B-doping and P-doping upon PSi play different roles in the electronic and transport properties. B-doping may exert constructive and destructive effects on electron transport depending on its position and applied bias direction, while P-doping displays a negligible effect. In addition, we found that bi-doping by two adjacent B atoms could slightly enhance the conductivity. These results could offer some clues for conducting experiments to achieve nanoelectronic devices with intrinsic transport properties of MoS2 nanotubes.

  1. Resistive Plate Chambers: electron transport and modeling

    NASA Astrophysics Data System (ADS)

    Bošnjaković, D.; Petrović, Z. Lj; Dujko, S.

    2014-12-01

    We study the electron transport in gas mixtures used by Resistive Plate Chambers (RPCs) in high energy physics experiments at CERN. Calculations are performed using a multi term theory for solving the Boltzmann equation. We identify the effects induced by non-conservative nature of electron attachment, including attachment heating of electrons and negative differential conductivity (NDC). NDC was observed only in the bulk component of drift velocity. Using our Monte Carlo technique, we calculate the spatially resolved transport properties in order to investigate the origin of these effects. We also present our microscopic approach to modeling of RPCs which is based on Monte Carlo method. Calculated results for a timing RPC show good agreement with an analytical model and experimental data. Different cross section sets for electron scattering in C2H2F4 are used for comparison and analysis.

  2. Electronic transport properties of tetracyclopentadienyl modified with C and Si atoms

    NASA Astrophysics Data System (ADS)

    Yang, Li-Hua; Yang, Chuan-Lu; Wang, Mei-Shan; Ma, Xiao-Guang

    2015-09-01

    The electronic transport characteristics for three tetracyclopentadienyl systems with C and Si atoms have been investigated on the basis of density-functional theory and non-equilibrium Green's function. Ohmic conductance, current-voltage curves, and differential conductance are obtained and analyzed. Switch and negative differential resistance behavior is observed in these systems. The novel characteristics of these systems are attributed to the highest occupied molecular orbital and lowest unoccupied molecular orbital and to the change in transmission spectra within the bias range.

  3. Electron transport property of cobalt-centered porphyrin-armchair graphene nanoribbon (AGNR) junction

    SciTech Connect

    Mondal, Rajkumar; Sarkar, Utpal

    2015-06-24

    We have investigated the electron transport properties of Cobalt-centered (Co-centered) porphyrin molecule using the density functional theory and non-equilibrium greens function method. Here we have reported transmission coefficient as well as current voltage characteristics of Co-centered porphyrine molecule connected between armchair graphene nanoribbons. It has been found that at low bias region i.e., 0 V to 0.3 V it does not contribute any current. Gradual increase of bias voltage results different order of magnitude of current in different bias region.

  4. Energy deposition and non-equilibrium infared radiation of energetic auroral electrons

    NASA Astrophysics Data System (ADS)

    Wu, Yadong; Gao, Bo; Zhu, Guangsheng; Li, Ziguang

    2016-07-01

    Infrared radiation caused by energetic auroral electrons plays an important role in the thermospheric hear budget, and may be seen as background by infrared surveillance sensors. The auroral electron deposition leads to the ionization, excitation, and dissociation of neutral species(N2,O2,and O), and initiates a series of chemical reaction in the upper atmosphere, finally causes the optical emission of infared excited emitters. In this study, the whole progress from the initial auroral electrons energy deposition to the final infrared emissions has been modeled, which including space plasma, atmospheric physical chemistry, and radiative transfer. The initial atmosphere parameters before auroral disturbing are given by MSIS00 model. The primary electron flux at the top of atmosphere is given by a statistical fitting with the sum of three distribution terms, a power law, a Maxwellian and a Guassian. A semi-emprical model is used in the calculation of energy depositon of single primary electron. The total integral ion pairs production rate is obtained after combining with the initial primary electron flux. The production rate and flux of secondary electrons are modeled with a continuous slow down approximation, using different excitation, ionization, dissociation cross sections of N2, O2, and O to electrons. The photochemical reactions with auroral disturbance is analysed, and its calculation model is established. A "three-step" calculation method is created to obtain number densities of eleven species in the hight between 90-160 km, which containing N2+, O2+, O+, O2+(a4Π), O+(2D), O+(2P), N2(A3Σ), N(2D), N(4S), NO+, and N+. Number densities of different vibraional levels of NO and NO+ are got with steady state assumption, considering 1-12 vibrational levels of NO and 1-14 vibrational levels of NO+. The infared emissions and the spectral lines of the two radiating bodies are calculated with a fuzzy model of spectral band.

  5. A non-equilibrium model for soil heating and moisture transport during extreme surface heating

    NASA Astrophysics Data System (ADS)

    Massman, William

    2016-04-01

    The increasing use of prescribed fire by land managers and increasing likelihood of wildfires due to climate change requires an improved modeling capability of extreme heating of soils during fires. This study describes a new model of soil evaporation and transport of heat, soil moisture, and water vapor, for use during fires. The model is based on conservation equations of energy and mass and its performance is evaluated against dynamic soil temperature and moisture observations obtained during laboratory experiments on soil samples exposed to surface heat fluxes ranging between 10,000 and 50,000 Wm2. In general, the model simulates the observed temperature dynamics quite well, but is less precise (but still good) at capturing the moisture dynamics. The model emulates the observed increase in soil moisture ahead of the drying front and the hiatus in the soil temperature rise during the strongly evaporative stage of drying. It also captures the observed rapid evaporation of soil moisture that occurs at relatively low temperatures (50-90 C), and can provide quite accurate predictions of the total amount of soil moisture evaporated during the laboratory experiments. Overall, this new model provides a much more physically realistic simulation over all previous models developed for the same purpose.

  6. NEQAIR96,Nonequilibrium and Equilibrium Radiative Transport and Spectra Program: User's Manual

    NASA Technical Reports Server (NTRS)

    Whiting, Ellis E.; Park, Chul; Liu, Yen; Arnold, James O.; Paterson, John A.

    1996-01-01

    This document is the User's Manual for a new version of the NEQAIR computer program, NEQAIR96. The program is a line-by-line and a line-of-sight code. It calculates the emission and absorption spectra for atomic and diatomic molecules and the transport of radiation through a nonuniform gas mixture to a surface. The program has been rewritten to make it easy to use, run faster, and include many run-time options that tailor a calculation to the user's requirements. The accuracy and capability have also been improved by including the rotational Hamiltonian matrix formalism for calculating rotational energy levels and Hoenl-London factors for dipole and spin-allowed singlet, doublet, triplet, and quartet transitions. Three sample cases are also included to help the user become familiar with the steps taken to produce a spectrum. A new user interface is included that uses check location, to select run-time options and to enter selected run data, making NEQAIR96 easier to use than the older versions of the code. The ease of its use and the speed of its algorithms make NEQAIR96 a valuable educational code as well as a practical spectroscopic prediction and diagnostic code.

  7. Defect engineering of the electronic transport through cuprous oxide interlayers

    NASA Astrophysics Data System (ADS)

    Fadlallah, Mohamed M.; Eckern, Ulrich; Schwingenschlögl, Udo

    2016-06-01

    The electronic transport through Au–(Cu2O)n–Au junctions is investigated using first-principles calculations and the nonequilibrium Green’s function method. The effect of varying the thickness (i.e., n) is studied as well as that of point defects and anion substitution. For all Cu2O thicknesses the conductance is more enhanced by bulk-like (in contrast to near-interface) defects, with the exception of O vacancies and Cl substitutional defects. A similar transmission behavior results from Cu deficiency and N substitution, as well as from Cl substitution and N interstitials for thick Cu2O junctions. In agreement with recent experimental observations, it is found that N and Cl doping enhances the conductance. A Frenkel defect, i.e., a superposition of an O interstitial and O substitutional defect, leads to a remarkably high conductance. From the analysis of the defect formation energies, Cu vacancies are found to be particularly stable, in agreement with earlier experimental and theoretical work.

  8. Defect engineering of the electronic transport through cuprous oxide interlayers

    PubMed Central

    Fadlallah, Mohamed M.; Eckern, Ulrich; Schwingenschlögl, Udo

    2016-01-01

    The electronic transport through Au–(Cu2O)n–Au junctions is investigated using first-principles calculations and the nonequilibrium Green’s function method. The effect of varying the thickness (i.e., n) is studied as well as that of point defects and anion substitution. For all Cu2O thicknesses the conductance is more enhanced by bulk-like (in contrast to near-interface) defects, with the exception of O vacancies and Cl substitutional defects. A similar transmission behavior results from Cu deficiency and N substitution, as well as from Cl substitution and N interstitials for thick Cu2O junctions. In agreement with recent experimental observations, it is found that N and Cl doping enhances the conductance. A Frenkel defect, i.e., a superposition of an O interstitial and O substitutional defect, leads to a remarkably high conductance. From the analysis of the defect formation energies, Cu vacancies are found to be particularly stable, in agreement with earlier experimental and theoretical work. PMID:27256905

  9. Stark broadening for diagnostics of the electron density in non-equilibrium plasma utilizing isotope hydrogen alpha lines

    SciTech Connect

    Yang, Lin; Tan, Xiaohua; Wan, Xiang; Chen, Lei; Jin, Dazhi; Qian, Muyang; Li, Gongping

    2014-04-28

    Two Stark broadening parameters including FWHM (full width at half maximum) and FWHA (full width at half area) of isotope hydrogen alpha lines are simultaneously introduced to determine the electron density of a pulsed vacuum arc jet. To estimate the gas temperature, the rotational temperature of the C{sub 2} Swan system is fit to 2500 ± 100 K. A modified Boltzmann-plot method with b{sub i}-factor is introduced to determine the modified electron temperature. The comparison between results of atomic and ionic lines indicates the jet is in partial local thermodynamic equilibrium and the electron temperature is close to 13 000 ± 400 K. Based on the computational results of Gig-Card calculation, a simple and precise interpolation algorithm for the discrete-points tables can be constructed to obtain the traditional n{sub e}-T{sub e} diagnostic maps of two Stark broadening parameters. The results from FWHA formula by the direct use of FWHM = FWHA and these from the diagnostic map are different. It can be attributed to the imprecise FWHA formula form and the deviation between FWHM and FWHA. The variation of the reduced mass pair due to the non-equilibrium effect contributes to the difference of the results derived from two hydrogen isotope alpha lines. Based on the Stark broadening analysis in this work, a corrected method is set up to determine n{sub e} of (1.10 ± 0.08) × 10{sup 21} m{sup −3}, the reference reduced mass μ{sub 0} pair of (3.30 ± 0.82 and 1.65 ± 0.41), and the ion kinetic temperature of 7900 ± 1800 K.

  10. Nonequilibrium Pump–Probe Photoexcitation as a Tool for Analyzing Unoccupied Equilibrium States of Correlated Electrons

    NASA Astrophysics Data System (ADS)

    Yamaji, Youhei; Imada, Masatoshi

    2016-09-01

    Relaxation of electrons in a Hubbard ring coupled to a dissipative bosonic bath is studied to simulate the pump-probe photoemission measurement. From this insight, we propose an experimental method of eliciting the unoccupied part of single-particle spectra at the equilibrium of doped Mott insulators. We reveal first that the effective temperatures of distribution functions and electronic spectra are different during the relaxation, which makes the frequently employed thermalization picture inappropriate. Contrary to the conventional analysis, we show that the unoccupied spectra at equilibrium can be detected as the states that relax faster.

  11. Nonequilibrium Pump-Probe Photoexcitation as a Tool for Analyzing Unoccupied Equilibrium States of Correlated Electrons

    NASA Astrophysics Data System (ADS)

    Yamaji, Youhei; Imada, Masatoshi

    2016-09-01

    Relaxation of electrons in a Hubbard ring coupled to a dissipative bosonic bath is studied to simulate the pump-probe photoemission measurement. From this insight, we propose an experimental method of eliciting the unoccupied part of single-particle spectra at the equilibrium of doped Mott insulators. We reveal first that the effective temperatures of distribution functions and electronic spectra are different during the relaxation, which makes the frequently employed thermalization picture inappropriate. Contrary to the conventional analysis, we show that the unoccupied spectra at equilibrium can be detected as the states that relax faster.

  12. NEQAIRv14.0 Release Notes: Nonequilibrium and Equilibrium Radiative Transport Spectra Program

    NASA Technical Reports Server (NTRS)

    Brandis, Aaron Michael; Cruden, Brett A.

    2014-01-01

    NEQAIR v14.0 is the first parallelized version of NEQAIR. Starting from the last version of the code that went through the internal software release process at NASA Ames (NEQAIR 2008), there have been significant updates to the physics in the code and the computational efficiency. NEQAIR v14.0 supersedes NEQAIR v13.2, v13.1 and the suite of NEQAIR2009 versions. These updates have predominantly been performed by Brett Cruden and Aaron Brandis from ERC Inc at NASA Ames Research Center in 2013 and 2014. A new naming convention is being adopted with this current release. The current and future versions of the code will be named NEQAIR vY.X. The Y will refer to a major release increment. Minor revisions and update releases will involve incrementing X. This is to keep NEQAIR more in line with common software release practices. NEQAIR v14.0 is a standalone software tool for line-by-line spectral computation of radiative intensities and/or radiative heat flux, with one-dimensional transport of radiation. In order to accomplish this, NEQAIR v14.0, as in previous versions, requires the specification of distances (in cm), temperatures (in K) and number densities (in parts/cc) of constituent species along lines of sight. Therefore, it is assumed that flow quantities have been extracted from flow fields computed using other tools, such as CFD codes like DPLR or LAURA, and that lines of sight have been constructed and written out in the format required by NEQAIR v14.0. There are two principal modes for running NEQAIR v14.0. In the first mode NEQAIR v14.0 is used as a tool for creating synthetic spectra of any desired resolution (including convolution with a specified instrument/slit function). The first mode is typically exercised in simulating/interpreting spectroscopic measurements of different sources (e.g. shock tube data, plasma torches, etc.). In the second mode, NEQAIR v14.0 is used as a radiative heat flux prediction tool for flight projects. Correspondingly, NEQAIR has

  13. Numerical solution of the electron transport equation

    NASA Astrophysics Data System (ADS)

    Woods, Mark

    The electron transport equation has been solved many times for a variety of reasons. The main difficulty in its numerical solution is that it is a very stiff boundary value problem. The most common numerical methods for solving boundary value problems are symmetric collocation methods and shooting methods. Both of these types of methods can only be applied to the electron transport equation if the boundary conditions are altered with unrealistic assumptions because they require too many points to be practical. Further, they result in oscillating and negative solutions, which are physically meaningless for the problem at hand. For these reasons, all numerical methods for this problem to date are a bit unusual because they were designed to try and avoid the problem of extreme stiffness. This dissertation shows that there is no need to introduce spurious boundary conditions or invent other numerical methods for the electron transport equation. Rather, there already exists methods for very stiff boundary value problems within the numerical analysis literature. We demonstrate one such method in which the fast and slow modes of the boundary value problem are essentially decoupled. This allows for an upwind finite difference method to be applied to each mode as is appropriate. This greatly reduces the number of points needed in the mesh, and we demonstrate how this eliminates the need to define new boundary conditions. This method is verified by showing that under certain restrictive assumptions, the electron transport equation has an exact solution that can be written as an integral. We show that the solution from the upwind method agrees with the quadrature evaluation of the exact solution. This serves to verify that the upwind method is properly solving the electron transport equation. Further, it is demonstrated that the output of the upwind method can be used to compute auroral light emissions.

  14. Electronic and spin transport properties of graphene nanoribbon mediated by metal adatoms: a study by the QUAMBO-NEGF approach

    SciTech Connect

    Zhang, G. P.; Liu, Xiaojie; Wang, C. Z.; Yao, Y. X.; Zhang, Jian; Ho, K. M.

    2013-02-12

    Structural and electronic properties, including deformation, magnetic moment, Mulliken population, bond order, as well as electronic transport properties, of zigzag graphene nanoribbon (ZGNR) with Co adatoms on hollow sites are investigated by quasi-atomic minimal basis orbits (QUAMBOs), a first-principles tight binding (TB) scheme based on density functional theory (DFT), combined with a non-equilibrium Green's function. For electronic transport, below the Fermi level the transmission is strongly suppressed and spin dependent as a result of magnetism by Co adatom adsorption, while above the Fermi level the transmission is slightly distorted and spin independent. Due to the local environment dependence of QUAMBOs–TB parameters, we construct QUAMBOs–TB parameters of ZGNR leads and ZGNR with Co adatoms on hollow center sites by a divide-and-conquer approach, and accurately reproduce the electronic transmission behavior. Our QUAMBO–NEGF method is a new and promising way of examining electronic transport in large-scale systems.

  15. Electron Transport Through Single Fullerene Molecules (abstract)

    NASA Astrophysics Data System (ADS)

    Stróżecka, Anna; Muthukumar, Kaliappan; Larsson, J. Andreas; Voigtländer, Bert

    2009-04-01

    Fullerenes show potential for applications in nanotechnology due to the possibility of tuning their properties by doping or functionalization. In particular, the endohedral doping of the hollow carbon cage with metal atoms allows changing the electronic and magnetic properties of the molecule without distorting the geometry of the outer shell. Here we present a low temperature scanning tunneling microscopy (STM) and spectroscopy study of the vibrational and transport properties of Ce2atC80 metallofullerenes. We observe that electron transport through the endohedral fullerene is strongly mediated by excitation of molecular vibrations, especially the dynamics of encapsulated atoms. We measure the conductance of the single-molecule junction upon contact between the molecule and the STM tip. To determine the role of doping atoms we compare the results obtained for the endohedrally doped species with those for a hollow fullerene. Analysis shows that localization of electron density on encapsulated atoms hinders the conduction process through the fullerene.

  16. Nonequilibrium theory of a hot-electron bolometer with normal metal-insulator-superconductor tunnel junction

    SciTech Connect

    Golubev, Dmitri; Kuzmin, Leonid

    2001-06-01

    The operation of the hot-electron bolometer with normal metal-insulator-superconductor (NIS) tunnel junction as a temperature sensor is analyzed theoretically. The responsivity and the noise equivalent power (NEP) of the bolometer are obtained numerically for typical experimental parameters. Relatively simple approximate analytical expressions for these values are derived. The time constant of the device is also found. We demonstrate that the effect of the electron cooling by the NIS junction, which serves as a thermometer, can improve the sensitivity. This effect is also useful in the presence of the finite background power load. We discuss the effect of the correlation of the shot noise and the heat flow noise in the NIS junction. {copyright} 2001 American Institute of Physics.

  17. Geometric effects in nonequilibrium electron transfer statistics in adiabatically driven quantum junctions

    NASA Astrophysics Data System (ADS)

    Goswami, Himangshu Prabal; Agarwalla, Bijay Kumar; Harbola, Upendra

    2016-05-01

    Cyclic Pancharatnam-Berry (PB) and adiabatic noncyclic geometric (ANG) effects are investigated in a single electron orbital system connected to two metal contacts with externally driven chemical potential and/or temperatures. The PB contribution doesn't affect the density matrix evolution, but has a quantitative effect on the statistics (fluctuations) of electron transfer. The ANG contribution, on the other hand, affects the net flux across the junction. Unlike the PB, the ANG contribution is nonzero when two parameters are identically driven. Closed analytical expressions are derived for the ANG contribution to the flux, and the PB contribution to the first two leading order fluctuations. Fluctuations can be modified by manipulating the relative phases of the drivings. Interestingly, we find that the fluctuations of the pumped charge do not satisfy the steady state fluctuation theorem in presence of nonzero geometric contribution, but can be recovered for a vanishing geometric contribution even in presence of the external driving.

  18. Screening and sheath formation in a nonequilibrium mixed Cairns-Tsallis electron distribution

    SciTech Connect

    Bouzit, Omar; Gougam, Leila Ait; Tribeche, Mouloud

    2015-05-15

    The effects of electron nonextensivity for a given nonthermality state, on Debye shielding and electrostatic sheath formation are examined. A physically meaningful Cairns-Tsallis distribution is outlined and a generalized expression for the Debye screening length λ{sub D}{sup q,α} is obtained. It is shown that an increase of the entropic index q causes λ{sub D}{sup q,α} to decrease whatever the amount of plasma nonthermality α. In addition, smaller pertinent values of q along with relatively higher values of α provide larger values of λ{sub D}{sup q,α}. The shielded electrostatic potential falls off as a function of distance more slowly as α increases, a result somewhat analogous to the dynamical shielding decrease (albeit in a different context) of a free charge as it begins to move. Moreover, smaller pertinent values of q along with relatively higher values of α are found to involve higher ion drift speed v{sub i0} for proper sheath formation. As α increases, the sheath electrostatic potential-gradient dΨ{sub s}/dξ becomes abruptly steep slowing down the energetic electrons leakage to the wall. Moreover, the sheath thickness broadens as the electron nonthermality strengthens.

  19. The electronic transport behavior of hybridized zigzag graphene and boron nitride nanoribbons

    SciTech Connect

    Zhou, Yuhong; Zhang, Jianbing; Miao, Xiangshui; Zhang, Daoli; Ye, Cong

    2014-03-21

    In this present work, we have investigated the electronic transport properties of the hybridized structure constructed by the zigzag graphene and boron-nitride (BN) nanoribbons (Z-B{sub n}N{sub m}C{sub p}, n + m + p = 16) through employing nonequilibrium Green's functions in combination with the density-functional theory. The results demonstrate that the electronic transport properties of the hybridized Z-B{sub n}N{sub m}C{sub p} nanoribbons are strongly dependent on the width of boron-nitride or graphene nanoribbons. When the numbers of n and m are not equal, the negative differential resistance behavior is observed, which can be modulated by varying the width of BN nanoribbons. The conductance of the hybridized Z-B{sub n}N{sub m}C{sub p} nanoribbons with odd numbers of zigzag carbon chains also increases by the width of BN nanoribbons.

  20. Visualizing non-equilibrium lithiation of spinel oxide via in situ transmission electron microscopy

    DOE PAGESBeta

    He, Kai; Zhang, Sen; Li, Jing; Yu, Xiqian; Meng, Qingping; Zhu, Yizhou; Hu, Enyuan; Sun, Ke; Yun, Hongseok; Yang, Xiao -Qing; et al

    2016-05-09

    In this study, spinel transition metal oxides are an important class of materials that are being considered as electrodes for lithium-ion batteries, due to their low cost and high theoretical capacity. The lithiation of these compounds is known to undergo a two-step reaction, whereby intercalation and conversion occur in a sequential fashion. These two reactions are known to have distinct reaction dynamics, but it is unclear how the kinetics of these processes affect the overall electrochemical response. Here, we explore the lithiation of nanosized magnetite (Fe3O4) by employing a new strain-sensitive, bright-field scanning transmission electron microscopy approach.

  1. Ground state cooling of a nanomechanical resonator using electron transport in hybrid systems

    NASA Astrophysics Data System (ADS)

    Rastelli, Gianluca; Stadler, Pascal; Belzig, Wolfgang

    A still open challenge in nanoelectromechanical systems is the achievement of the quantum regime via active cooling and using electron transport. I will discuss active ground state cooling in a bottom-up device, viz. a carbon nanotube quantum dot suspended between two electric nano-contacts, and for two different coherent transport regimes: (i) spin-polarized current between two ferromagnets and (ii) sub-gap Andreev current between a superconductor and a normal metal. I will show that efficient ground state cooling of the resonator can be achieved for realistic parameters of the system and varying the transport parameters, e.g. gate voltage, magnetic field, etc. Finally I will discuss the signatures in the current-voltage characteristics of the non-equilibrium state of the nanoresonator. Zukunftskolleg of the University of Konstanz; DFG through SFB 767 and BE 3803/5.

  2. The transport properties of the molecular-scale B2C and BC3 electronic devices

    NASA Astrophysics Data System (ADS)

    Li, Guiqin; Li, Runqin

    2012-09-01

    The transport properties of the molecular-scale B2C and BC3 electronic devices are investigated with an ab initio method combined with a nonequilibrium Green function technique. The effects of different BC graphenes and ribbon lengths on the transport properties of the devices are significant. The results show that the devices with different BC graphenes and sizes have unusual transmission coefficients, which leads to special current transport mechanisms for the devices. Notably, the current strength of the device with the shortest ribbon length is the largest in three B2C devices, but the current strength of the device with the shortest ribbon length is the smallest for BC3 device.

  3. Regulation of Photosynthetic Electron Transport and Photoinhibition

    PubMed Central

    Roach, Thomas; Krieger-Liszkay, Anja Krieger

    2014-01-01

    Photosynthetic organisms and isolated photosystems are of interest for technical applications. In nature, photosynthetic electron transport has to work efficiently in contrasting environments such as shade and full sunlight at noon. Photosynthetic electron transport is regulated on many levels, starting with the energy transfer processes in antenna and ending with how reducing power is ultimately partitioned. This review starts by explaining how light energy can be dissipated or distributed by the various mechanisms of non-photochemical quenching, including thermal dissipation and state transitions, and how these processes influence photoinhibition of photosystem II (PSII). Furthermore, we will highlight the importance of the various alternative electron transport pathways, including the use of oxygen as the terminal electron acceptor and cyclic flow around photosystem I (PSI), the latter which seem particularly relevant to preventing photoinhibition of photosystem I. The control of excitation pressure in combination with the partitioning of reducing power influences the light-dependent formation of reactive oxygen species in PSII and in PSI, which may be a very important consideration to any artificial photosynthetic system or technical device using photosynthetic organisms. PMID:24678670

  4. Electron ripple injection concept for transport control

    SciTech Connect

    Choe, W.; Ono, M.; Hwang, Y.S.

    1992-01-01

    Recent experiments in many devices have provided firm evidence that the edge radial electric field profile differs between L- and H-modes, and that these fields can greatly modify transport in tokamak plasmas. A nonintrusive method for inducing radial electric field based on electron ripple injection is being developed by the CDX-U group. This technique utilizes a pair of special coils to create a local magnetic field ripple to trap the electrons at the edge of the plasma. The trapped electrons then drift into the plasma due to the [del]B drift. An ECH power is applied to accelerate electrons to sufficient perpendicular energy to penetrate into the plasma. Application of ECH power to the trapped electrons should provide the desired 20 A of electron current with electrons of a few keV of energy and v[perpendicular]/v[parallel] [much gt] 1. A controlled experiment to investigate the physics of ECH aided ripple injection has been designed on CDX-U. With the set of ripple coils designed for CDX-U, a ripple fraction of [delta] ([double bond] [del]B/B[sub av]) [approximately] 5% is attainable. At this ripple fraction, electrons are trapped if v[perpendicular]/v[parallel] [much gt] 1> (2[delta])[sup [minus][1/2

  5. Self-consistent electron transport in tokamaks

    SciTech Connect

    Gatto, R.; Chavdarovski, I.

    2007-09-15

    Electron particle, momentum, and energy fluxes in axisymmetric toroidal devices are derived from a version of the action-angle collision operator that includes both diffusion and drag in action-space [D. A. Hitchcock, R. D. Hazeltine, and S. M. Mahajan, Phys. Fluids 26, 2603 (1983); H. E. Mynick, J. Plasma Phys. 39, 303 (1988)]. A general result of the theory is that any contribution to transport originating directly from the toroidal frequency of the particle motion is constrained to be zero when the electron temperature is equal to the ion temperature. In particular, this constraint applies to those components of the particle and energy fluxes that are proportional to the magnetic shear, independent of the underlying turbulence and of whether the particles are trapped or untrapped. All the total fluxes describing collisionless transport of passing electrons in steady-state magnetic turbulence contain contributions proportional to the conventional thermodynamic drives, which are always outward, and contributions proportional to the magnetic shear, which have both magnitude and sign dependent on the ion-electron temperature ratio. The turbulent generalization of Ohm's law includes a hyper-resistive term, which flattens the current density profile on a fast time scale, and a turbulent electric field, which can have both signs depending on the electron-ion temperature ratio.

  6. Single-molecule junctions beyond electronic transport.

    PubMed

    Aradhya, Sriharsha V; Venkataraman, Latha

    2013-06-01

    The idea of using individual molecules as active electronic components provided the impetus to develop a variety of experimental platforms to probe their electronic transport properties. Among these, single-molecule junctions in a metal-molecule-metal motif have contributed significantly to our fundamental understanding of the principles required to realize molecular-scale electronic components from resistive wires to reversible switches. The success of these techniques and the growing interest of other disciplines in single-molecule-level characterization are prompting new approaches to investigate metal-molecule-metal junctions with multiple probes. Going beyond electronic transport characterization, these new studies are highlighting both the fundamental and applied aspects of mechanical, optical and thermoelectric properties at the atomic and molecular scales. Furthermore, experimental demonstrations of quantum interference and manipulation of electronic and nuclear spins in single-molecule circuits are heralding new device concepts with no classical analogues. In this Review, we present the emerging methods being used to interrogate multiple properties in single molecule-based devices, detail how these measurements have advanced our understanding of the structure-function relationships in molecular junctions, and discuss the potential for future research and applications.

  7. Electronic transport in smectic liquid crystals

    NASA Astrophysics Data System (ADS)

    Shiyanovskaya, I.; Singer, K. D.; Twieg, R. J.; Sukhomlinova, L.; Gettwert, V.

    2002-04-01

    Time-of-flight measurements of transient photoconductivity have revealed bipolar electronic transport in phenylnaphthalene and biphenyl liquid crystals (LC), which exhibit several smectic mesophases. In the phenylnaphthalene LC, the hole mobility is significantly higher than the electron mobility and exhibits different temperature and phase behavior. Electron mobility in the range ~10-5 cm2/V s is temperature activated and remains continuous at the phase transitions. However, hole mobility is nearly temperature independent within the smectic phases, but is very sensitive to smectic order, 10-3 cm2/V s in the smectic-B (Sm-B) and 10-4 cm2/V s in the smectic-A (Sm-A) mesophases. The different behavior for holes and electron transport is due to differing transport mechanisms. The electron mobility is apparently controlled by rate-limiting multiple shallow trapping by impurities, but hole mobility is not. To explain the lack of temperature dependence for hole mobility within the smectic phases we consider two possible polaron transport mechanisms. The first mechanism is based on the hopping of Holstein small polarons in the nonadiabatic limit. The polaron binding energy and transfer integral values, obtained from the model fit, turned out to be sensitive to the molecular order in smectic mesophases. A second possible scenario for temperature-independent hole mobility involves the competion between two different polaron mechanisms involving so-called nearly small molecular polarons and small lattice polarons. Although the extracted transfer integrals and binding energies are reasonable and consistent with the model assumptions, the limited temperature range of the various phases makes it difficult to distinguish between any of the models. In the biphenyl LCs both electron and hole mobilities exhibit temperature activated behavior in the range of 10-5 cm2/V s without sensitivity to the molecular order. The dominating transport mechanism is considered as multiple trapping

  8. Electronic transport in methylated fragments of DNA

    SciTech Connect

    Almeida, M. L. de; Oliveira, J. I. N.; Lima Neto, J. X.; Gomes, C. E. M.; Fulco, U. L. Albuquerque, E. L.; Freire, V. N.; Caetano, E. W. S.; Moura, F. A. B. F. de; Lyra, M. L.

    2015-11-16

    We investigate the electronic transport properties of methylated deoxyribonucleic-acid (DNA) strands, a biological system in which methyl groups are added to DNA (a major epigenetic modification in gene expression), sandwiched between two metallic platinum electrodes. Our theoretical simulations apply an effective Hamiltonian based on a tight-binding model to obtain current-voltage curves related to the non-methylated/methylated DNA strands. The results suggest potential applications in the development of novel biosensors for molecular diagnostics.

  9. Electronic transport in methylated fragments of DNA

    NASA Astrophysics Data System (ADS)

    de Almeida, M. L.; Oliveira, J. I. N.; Lima Neto, J. X.; Gomes, C. E. M.; Fulco, U. L.; Albuquerque, E. L.; Freire, V. N.; Caetano, E. W. S.; de Moura, F. A. B. F.; Lyra, M. L.

    2015-11-01

    We investigate the electronic transport properties of methylated deoxyribonucleic-acid (DNA) strands, a biological system in which methyl groups are added to DNA (a major epigenetic modification in gene expression), sandwiched between two metallic platinum electrodes. Our theoretical simulations apply an effective Hamiltonian based on a tight-binding model to obtain current-voltage curves related to the non-methylated/methylated DNA strands. The results suggest potential applications in the development of novel biosensors for molecular diagnostics.

  10. Electron transport fluxes in potato plateau regime

    SciTech Connect

    Shaing, K.C.; Hazeltine, R.D.

    1997-12-01

    Electron transport fluxes in the potato plateau regime are calculated from the solutions of the drift kinetic equation and fluid equations. It is found that the bootstrap current density remains finite in the region close to the magnetic axis, although it decreases with increasing collision frequency. This finite amount of the bootstrap current in the relatively collisional regime is important in modeling tokamak startup with 100{percent} bootstrap current. {copyright} {ital 1997 American Institute of Physics.}

  11. Electron ripple injection concept for transport control

    SciTech Connect

    Choe, W.; Ono, M.; Hwang, Y.S.

    1992-10-01

    Recent experiments in many devices have provided firm evidence that the edge radial electric field profile differs between L- and H-modes, and that these fields can greatly modify transport in tokamak plasmas. A nonintrusive method for inducing radial electric field based on electron ripple injection is being developed by the CDX-U group. This technique utilizes a pair of special coils to create a local magnetic field ripple to trap the electrons at the edge of the plasma. The trapped electrons then drift into the plasma due to the {del}B drift. An ECH power is applied to accelerate electrons to sufficient perpendicular energy to penetrate into the plasma. Application of ECH power to the trapped electrons should provide the desired 20 A of electron current with electrons of a few keV of energy and v{perpendicular}/v{parallel} {much_gt} 1. A controlled experiment to investigate the physics of ECH aided ripple injection has been designed on CDX-U. With the set of ripple coils designed for CDX-U, a ripple fraction of {delta} ({double_bond} {del}B/B{sub av}) {approximately} 5% is attainable. At this ripple fraction, electrons are trapped if v{perpendicular}/v{parallel} {much_gt} 1> (2{delta}){sup {minus}{1/2}} {approx}3. A resonant cavity box was fabricated for efficient heating of the trapped electrons. It is also capable of measuring the effect of the field ripple in conjunction with trapped electrons. Some preliminary results are given.

  12. Transport of electrons in monolithic hot electron Si transistors

    NASA Astrophysics Data System (ADS)

    Berz, F.

    1986-12-01

    The transport of electrons across the base of monolithic hot electron transistors is studied using a simplified model. The base is assumed to be limited by abrupt barriers and no account is taken of backscattering from the collector region. The collisions in the base are considered to be of only one type which represents an average between interactions with optical and acoustic phonons. A fundamental part in the analysis is played by the function PEX( i, x), ( i = 1, 2, …) which gives the total probability of exit into the collector of an electron whose ith collision occurs at a point of abscissa x within the base. The function PEX( i, x) is determined iteratively for decreasing values of i, using the theorem of compound probabilities, and from there the transport factor α across the base is derived. Programs have been written to this effect, and the results are illustrated by means of examples which demonstrate the effect on the transport factor α of the various parameters of the device, and show some comparisons with a previous theory[4].

  13. Conditioner for a helically transported electron beam

    SciTech Connect

    Wang, Changbiao

    1992-05-01

    The kinetic theory is developed to investigate a conditioner for a helically transported electron beam. Linear expressions for axial velocity spread are derived. Numerical simulation is used to check the theoretical results and examine nonlinear aspects of the conditioning process. The results show that in the linear regime the action of the beam conditioner on a pulsed beam mainly depends on the phase at which the beam enters the conditioner and depends only slightly on the operating wavelength. In the nonlinear regime, however, the action of the conditioner strongly depends on the operating wavelength and only slightly upon the entrance phase. For a properly chosen operating wavelength, a little less than the electron`s relativistic cyclotron wavelength, the conditioner can decrease the axial velocity spread of a pulsed beam down to less than one-third of its initial value.

  14. Electron transport parameters in NF3

    NASA Astrophysics Data System (ADS)

    Lisovskiy, V.; Yegorenkov, V.; Ogloblina, P.; Booth, J.-P.; Martins, S.; Landry, K.; Douai, D.; Cassagne, V.

    2014-03-01

    We present electron transport parameters (the first Townsend coefficient, the dissociative attachment coefficient, the fraction of electron energy lost by collisions with NF3 molecules, the average and characteristic electron energy, the electron mobility and the drift velocity) in NF3 gas calculated from published elastic and inelastic electron-NF3 collision cross-sections using the BOLSIG+ code. Calculations were performed for the combined RB (Rescigno 1995 Phys. Rev. E 52 329, Boesten et al 1996 J. Phys. B: At. Mol. Opt. Phys. 29 5475) momentum-transfer cross-section, as well as for the JB (Joucoski and Bettega 2002 J. Phys. B: At. Mol. Opt. Phys. 35 783) momentum-transfer cross-section. In addition, we have measured the radio frequency (rf) breakdown curves for various inter-electrode gaps and rfs, and from these we have determined the electron drift velocity in NF3 from the location of the turning point in these curves. These drift velocity values are in satisfactory agreement with those calculated by the BOLSIG+ code employing the JB momentum-transfer cross-section.

  15. Electronic transport in graphene-based heterostructures

    SciTech Connect

    Tan, J. Y.; Avsar, A.; Balakrishnan, J.; Taychatanapat, T.; O'Farrell, E. C. T.; Eda, G.; Castro Neto, A. H.; Koon, G. K. W.; Özyilmaz, B.; Watanabe, K.; Taniguchi, T.

    2014-05-05

    While boron nitride (BN) substrates have been utilized to achieve high electronic mobilities in graphene field effect transistors, it is unclear how other layered two dimensional (2D) crystals influence the electronic performance of graphene. In this Letter, we study the surface morphology of 2D BN, gallium selenide (GaSe), and transition metal dichalcogenides (tungsten disulfide (WS{sub 2}) and molybdenum disulfide (MoS{sub 2})) crystals and their influence on graphene's electronic quality. Atomic force microscopy analysis shows that these crystals have improved surface roughness (root mean square value of only ∼0.1 nm) compared to conventional SiO{sub 2} substrate. While our results confirm that graphene devices exhibit very high electronic mobility (μ) on BN substrates, graphene devices on WS{sub 2} substrates (G/WS{sub 2}) are equally promising for high quality electronic transport (μ ∼ 38 000 cm{sup 2}/V s at room temperature), followed by G/MoS{sub 2} (μ ∼ 10 000 cm{sup 2}/V s) and G/GaSe (μ ∼ 2200 cm{sup 2}/V s). However, we observe a significant asymmetry in electron and hole conduction in G/WS{sub 2} and G/MoS{sub 2} heterostructures, most likely due to the presence of sulphur vacancies in the substrate crystals. GaSe crystals are observed to degrade over time even under ambient conditions, leading to a large hysteresis in graphene transport making it a less suitable substrate.

  16. Electronic and thermoelectric transport properties for a zigzag graphene-silicene-graphene heterojunction modulated by external field

    NASA Astrophysics Data System (ADS)

    Zhou, Benhu; Zhou, Benliang; Zeng, Yangsu; Zhou, Guanghui; Duan, Manyi

    2016-04-01

    we investigate the electronic and thermoelectric transport properties for a graphene-silicene-graphene (GSG) heterojunction with zigzag-edge nanoribbons under the modulation of the effective spin-orbit coupling (SOC) and potential energy. Using the nonequilibrium Green's function method, it is demonstrated that both the transmission coefficient T and the charge Seebeck coefficient SC display the oscillatory behavior and can be effectively modulated by effective SOC λSO and the potential energy V0. Furthermore, the even-odd difference in transport and thermoelectric properties disappears in the GSG heterojunction. Additionally, the dependence of the transmission coefficient and the charge Seebeck coefficient on Anderson disorder strength has been studied.

  17. Bond breaks of nucleotides by dissociative electron transfer of nonequilibrium prehydrated electrons: a new molecular mechanism for reductive DNA damage.

    PubMed

    Wang, Chun-Rong; Nguyen, Jenny; Lu, Qing-Bin

    2009-08-19

    DNA damage is a central mechanism in the pathogenesis and treatment of human diseases, notably cancer. Little is known about reductive DNA damage in causing genetic mutations during oncogenesis and killing cancer cells during radiotherapy. The prehydrated electron (e(-)(pre)) has the highest yield among all the radicals generated in cells during ionizing radiation and has subpicosecond lifetimes (10(-13) s) and energies below 0 eV, but its role in DNA damage is unknown. In this work, our real-time measurements by femtosecond time-resolved laser spectroscopy have revealed that while adenine and cytosine can effectively trap an e(-)(pre) to form stable anions, thymidine and especially guanine are highly susceptible to dissociative electron transfer of e(-)(pre), leading to bond dissociation in DNA. Our finding demonstrates a dissociative electron transfer pathway for reductive DNA damage that might be related to various diseases such as cancer and stroke. Moreover, this finding challenges the conventional notion that damage to the genome is mainly induced by the oxidizing OH* radical and might eventually lead to improved radiotherapy of cancer and radioprotection of humans.

  18. Spatial interferences in the electron transport of heavy-fermion materials

    NASA Astrophysics Data System (ADS)

    Zhang, Shu-feng; Liu, Yu; Song, Hai-Feng; Yang, Yi-feng

    2016-08-01

    The scanning tunneling microscopy/spectroscopy and the point contact spectroscopy represent major progress in recent heavy-fermion research. Both have revealed important information on the composite nature of the emergent heavy-electron quasiparticles. However, a detailed and thorough microscopic understanding of the similarities and differences in the underlying physical processes of these techniques is still lacking. Here we study the electron transport in the normal state of the periodic Anderson lattice by using the Keldysh nonequilibrium Green's function technique. In addition to the well-known Fano interference between the conduction and f -electron channels, our results further reveal the effect of spatial interference between different spatial paths at the interface on the differential conductance and their interesting interplay with the band features such as the hybridization gap and the Van Hove singularity. We find that the spatial interference leads to a weighted average in the momentum space for the electron transport and could cause suppression of the electronic band features under certain circumstances. In particular, it reduces the capability of probing the f -electron spectral weight near the edges of the hybridization gap for large interface depending on the Fermi surface of the lead. Our results indicate an intrinsic inefficiency of the point contact spectroscopy in probing the f electrons.

  19. Study of transport of laser-driven relativistic electrons in solid materials

    NASA Astrophysics Data System (ADS)

    Leblanc, Philippe

    With the ultra intense lasers available today, it is possible to generate very hot electron beams in solid density materials. These intense laser-matter interactions result in many applications which include the generation of ultrashort secondary sources of particles and radiation such as ions, neutrons, positrons, x-rays, or even laser-driven hadron therapy. For these applications to become reality, a comprehensive understanding of laser-driven energy transport including hot electron generation through the various mechanisms of ionization, and their subsequent transport in solid density media is required. This study will focus on the characterization of electron transport effects in solid density targets using the state-of- the-art particle-in-cell code PICLS. A number of simulation results will be presented on the topics of ionization propagation in insulator glass targets, non-equilibrium ionization modeling featuring electron impact ionization, and electron beam guiding by the self-generated resistive magnetic field. An empirically derived scaling relation for the resistive magnetic in terms of the laser parameters and material properties is presented and used to derive a guiding condition. This condition may prove useful for the design of future laser-matter interaction experiments.

  20. Electron Transport in Short Peptide Single Molecules

    NASA Astrophysics Data System (ADS)

    Cui, Jing; Brisendine, Joseph; Ng, Fay; Nuckolls, Colin; Koder, Ronald; Venkarataman, Latha

    We present a study of the electron transport through a series of short peptides using scanning tunneling microscope-based break junction method. Our work is motivated by the need to gain a better understanding of how various levels of protein structure contribute to the remarkable capacity of proteins to transport charge in biophysical processes such as respiration and photosynthesis. We focus here on short mono, di and tri-peptides, and probe their conductance when bound to gold electrodes in a native buffer environment. We first show that these peptides can bind to gold through amine, carboxyl, thiol and methyl-sulfide termini. We then focus on two systems (glycine and alanine) and show that their conductance decays faster than alkanes terminated by the same linkers. Importantly, our results show that the peptide bond is less conductive than a sigma carbon-carbon bond. This work was supported in part by NSF-DMR 1507440.

  1. Electronic transport properties of silicon clusters

    NASA Astrophysics Data System (ADS)

    Matsuura, Yukihito

    2016-02-01

    The electronic transport properties of silicon clusters were examined via theoretical calculations using the first-principles method. Additionally, p-type doping and n-type doping were analyzed by calculating conductance and current of boron- and phosphorus-doped silicon clusters. The p-type doping and n-type doping provided a new transmission peak at an energy level around the Fermi level to increase conductance. Furthermore, simultaneous boron and phosphorus doping resulted in noticeable rectifying characteristics, with the current drive in forward bias being three times higher than that in the reverse bias. A p-n junction was achieved even on a molecular scale.

  2. Inelastic electron transport in granular arrays

    SciTech Connect

    Altland, A.; Glazman, L.I.; Kamenev, A.; Meyer, J.S. . E-mail: jmeyer@mps.ohio-state.edu

    2006-11-15

    Transport properties of granular systems are governed by Coulomb blockade effects caused by the discreteness of the electron charge. We show that, in the limit of vanishing mean level spacing on the grains, the low-temperature behavior of 1d and 2d arrays is insulating at any inter-grain coupling (characterized by a dimensionless conductance g). In 2d and g >> 1, there is a sharp Berezinskii-Kosterlitz-Thouless crossover to the conducting phase at a certain temperature, T {sub BKT}. These results are obtained by applying an instanton analysis to map the conventional 'phase' description of granular arrays onto the dual 'charge' representation.

  3. Inelastic electron transport in granular arrays.

    SciTech Connect

    Altland, A.; Glazman, L. I.; Kamenev, A.; Meyer, J. S.; Materials Science Division; Univ. zu Koln; Univ. Minnesota; Ohio State Univ.

    2006-01-01

    Transport properties of granular systems are governed by Coulomb blockade effects caused by the discreteness of the electron charge. We show that, in the limit of vanishing mean level spacing on the grains, the low-temperature behavior of 1d and 2d arrays is insulating at any inter-grain coupling (characterized by a dimensionless conductance g). In 2d and g 1, there is a sharp Berezinskii-Kosterlitz-Thouless crossover to the conducting phase at a certain temperature, T{sub BKT}. These results are obtained by applying an instanton analysis to map the conventional 'phase' description of granular arrays onto the dual 'charge' representation.

  4. Electron heat transport down steep temperature gradients

    SciTech Connect

    Matte, J.P.; Virmont, J.

    1982-12-27

    Electron heat transport is studied by numerically solving the Fokker-Planck equation, with a spherical harmonic representation of the distribution function. The first two terms (f/sub 0/, f/sub 1/) suffice, even in steep temperature gradients. Deviations from the Spitzer-Haerm law appear for lambda/L/sub T/ ((mean free path)/(temperature gradient length))> or approx. =0.01, as a result of non-Maxwellian f/sub 0/. For lambda/L/sub T/> or approx. =1, the heat flux is (1/3) of the free-streaming value. In intermediate cases, a harmonic law describes well the hottest part of the plasma.

  5. Electronic transport properties of (fluorinated) metal phthalocyanine

    NASA Astrophysics Data System (ADS)

    Fadlallah, M. M.; Eckern, U.; Romero, A. H.; Schwingenschlögl, U.

    2016-01-01

    The magnetic and transport properties of the metal phthalocyanine (MPc) and F16MPc (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn and Ag) families of molecules in contact with S-Au wires are investigated by density functional theory within the local density approximation, including local electronic correlations on the central metal atom. The magnetic moments are found to be considerably modified under fluorination. In addition, they do not depend exclusively on the configuration of the outer electronic shell of the central metal atom (as in isolated MPc and F16MPc) but also on the interaction with the leads. Good agreement between the calculated conductance and experimental results is obtained. For M = Ag, a high spin filter efficiency and conductance is observed, giving rise to a potentially high sensitivity for chemical sensor applications.

  6. Conditioner for a helically transported electron beam

    SciTech Connect

    Wang, Changbiao.

    1992-05-01

    The kinetic theory is developed to investigate a conditioner for a helically transported electron beam. Linear expressions for axial velocity spread are derived. Numerical simulation is used to check the theoretical results and examine nonlinear aspects of the conditioning process. The results show that in the linear regime the action of the beam conditioner on a pulsed beam mainly depends on the phase at which the beam enters the conditioner and depends only slightly on the operating wavelength. In the nonlinear regime, however, the action of the conditioner strongly depends on the operating wavelength and only slightly upon the entrance phase. For a properly chosen operating wavelength, a little less than the electron's relativistic cyclotron wavelength, the conditioner can decrease the axial velocity spread of a pulsed beam down to less than one-third of its initial value.

  7. Spin-dependent electron transport in zinc- and manganese-doped adenine molecules

    SciTech Connect

    Simchi, Hamidreza; Esmaeilzadeh, Mahdi Mazidabadi, Hossein

    2014-01-28

    The spin-dependent electron transport properties of zinc- and manganese-doped adenine molecules connected to zigzag graphene leads are studied in the zero bias regime using the non-equilibrium Green's function method. The conductance of the adenine molecule increased and became spin-dependent when a zinc or manganese atom was doped into the molecules. The effects of a transverse electric field on the spin-polarization of the transmitted electrons were investigated and the spin-polarization was controlled by changing the transverse electric field. Under the presence of a transverse electric field, both the zinc- and manganese-doped adenine molecules acted as spin-filters. The maximum spin-polarization of the manganese-doped adenine molecule was greater than the molecule doped with zinc.

  8. Nonequilibrium kinetics of the electron-phonon sybsystem of a crystal in a strong electric field as a base of the electroplastic effect

    NASA Astrophysics Data System (ADS)

    Karas, V. I.; Vlasenko, A. M.; Sokolenko, V. I.; Zakharov, V. E.

    2015-09-01

    We present the results of a kinetic analysis of nonequilibrium dynamics of the electron-phonon system of a crystal in a strong electric field based on the proposed method of numerically solving a set of Boltzmann equations for electron and phonon distribution functions without expanding the electron distribution function into a series in the phonon energy. It is shown that the electric field action excites the electron subsystem, which by transferring energy to the phonon subsystem creates a large amount of short-wave phonons that effectively influence the lattice defects (point, lines, boundaries of different phases), which results in a redistribution of and decrease in the lattice defect density, in damage healing, in a decrease in the local peak stress, and a decrease in the degradation level of the construction material properties.

  9. Quantum mechanical simulation of electronic transport in nanostructured devices by efficient self-consistent pseudopotential calculation

    NASA Astrophysics Data System (ADS)

    Jiang, Xiang-Wei; Li, Shu-Shen; Xia, Jian-Bai; Wang, Lin-Wang

    2011-03-01

    We present a new empirical pseudopotential (EPM) calculation approach to simulate the million atom nanostructured semiconductor devices under potential bias using periodic boundary conditions. To treat the nonequilibrium condition, instead of directly calculating the scattering states from the source and drain, we calculate the stationary states by the linear combination of bulk band method and then decompose the stationary wave function into source and drain injecting scattering states according to an approximated top of the barrier splitting (TBS) scheme based on physical insight of ballistic and tunneling transports. The decomposed electronic scattering states are then occupied according to the source/drain Fermi-Levels to yield the occupied electron density which is then used to solve the potential, forming a self-consistent loop. The TBS is tested in a one-dimensional effective mass model by comparing with the direct scattering state calculation results. It is also tested in a three-dimensional 22 nm double gate ultra-thin-body field-effect transistor study, by comparing the TBS-EPM result with the nonequilibrium Green's function tight-binding result. We expected the TBS scheme will work whenever the potential in the barrier region is smoother than the wave function oscillations and it does not have local minimum, thus there is no multiple scattering as in a resonant tunneling diode, and when a three-dimensional problem can be represented as a quasi-one-dimensional problem, e.g., in a variable separation approximation. Using our approach, a million atom nonequilibrium nanostructure device can be simulated with EPM on a single processor computer.

  10. Electron Transport, Energy Transfer, and Optical Response in Single Molecule Junctions

    NASA Astrophysics Data System (ADS)

    White, Alexander James

    The last decade has seen incredible growth in the quality of experiments being done on single molecule junctions. Contemporary experimental measurements have expanded far beyond simple electron transport. Measurement of vibronic eects, quantum interference and decoherence eects, molecular optical response (Raman spectroscopy), and molecular spintronics are just some of the continuing areas of research in single molecule junctions. Experimental advancements demand advanced theoretical treatments, which can be used accurately within appropriate physical regimes, in order to understand measured phenomena and predict interesting directions for future study. In this dissertation we will study systems with strong intra-system interactions using a many-body states based approach. We will be focused on three related processes in molecular junctions: electron transport, electronic energy transfer, and molecular excitation. Inelastic electron transport in the regime of strong and nonlinear electron-vibration coupling within and outside of the Born-Oppenheimer regime will be investigated. To understand their appropriateness, we will compare simple semi-classical approximations in molecular redox junctions and electron-counting devices to fully quantum calculations based on many-body system states. The role of coherence and quantum interference in energy and electron transfer in molecular junctions is explored. Experiments that simultaneously measure surface enhanced Raman scattering and electron conduction have revealed a strong interaction between conducting electrons and molecular excitation. We investigate the role of the molecular response to a classical surface plasmon enhanced electric eld considering the back action of the oscillating molecular dipole. Raman scattering is quantum mechanical by nature and involves strong interaction between surface plasmons in the contacts and the molecular excitation. We develop a scheme for treating strong plasmon-molecular excitation

  11. Status of electron transport in MCNP{trademark}

    SciTech Connect

    Hughes, H.G.

    1995-09-01

    In recent years, an ongoing project within the radiation transport group (XTM) at Los Alamos National Laboratory has been the implementation and validation of an electron transport capability in the Monte Carlo code NICNP. In this paper the authors document the continuous-energy electron transport methods currently in use in MCNP, and describes a recent improvement of the energy-loss straggling algorithm. MCNP also supports electron transport calculations in a multigroup mode.

  12. Electronic transport of recrystallized freestanding graphene nanoribbons.

    PubMed

    Qi, Zhengqing John; Daniels, Colin; Hong, Sung Ju; Park, Yung Woo; Meunier, Vincent; Drndić, Marija; Johnson, A T Charlie

    2015-01-01

    The use of graphene and other two-dimensional materials in next-generation electronics is hampered by the significant damage caused by conventional lithographic processing techniques employed in device fabrication. To reduce the density of defects and increase mobility, Joule heating is often used since it facilitates lattice reconstruction and promotes self-repair. Despite its importance, an atomistic understanding of the structural and electronic enhancements in graphene devices enabled by current annealing is still lacking. To provide a deeper understanding of these mechanisms, atomic recrystallization and electronic transport in graphene nanoribbon (GNR) devices are investigated using a combination of experimental and theoretical methods. GNR devices with widths below 10 nm are defined and electrically measured in situ within the sample chamber of an aberration-corrected transmission electron microscope. Immediately after patterning, we observe few-layer polycrystalline GNRs with irregular sp(2)-bonded edges. Continued structural recrystallization toward a sharp, faceted edge is promoted by increasing application of Joule heat. Monte Carlo-based annealing simulations reveal that this is a result of concentrated local currents at lattice defects, which in turn promotes restructuring of unfavorable edge structures toward an atomically sharp state. We establish that intrinsic conductance doubles to 2.7 e(2)/h during the recrystallization process following an almost 3-fold reduction in device width, which is attributed to improved device crystallinity. In addition to the observation of consistent edge bonding in patterned GNRs, we further motivate the use of bonded bilayer GNRs for future nanoelectronic components by demonstrating how electronic structure can be tailored by an appropriate modification of the relative twist angle of the bonded bilayer.

  13. Ion age transport: developing devices beyond electronics

    NASA Astrophysics Data System (ADS)

    Demming, Anna

    2014-03-01

    There is more to current devices than conventional electronics. Increasingly research into the controlled movement of ions and molecules is enabling a range of new technologies. For example, as Weihua Guan, Sylvia Xin Li and Mark Reed at Yale University explain, 'It offers a unique opportunity to integrate wet ionics with dry electronics seamlessly'. In this issue they provide an overview of voltage-gated ion and molecule transport in engineered nanochannels. They cover the theory governing these systems and fabrication techniques, as well as applications, including biological and chemical analysis, and energy conversion [1]. Studying the movement of particles in nanochannels is not new. The transport of materials in rock pores led Klinkenberg to describe an analogy between diffusion and electrical conductivity in porous rocks back in 1951 [2]. And already in 1940, Harold Abramson and Manuel Gorin noted that 'When an electric current is applied across the living human skin, the skin may be considered to act like a system of pores through which transfer of substances like ragweed pollen extract may be achieved both by electrophoretic and by diffusion phenomena' [3]. Transport in living systems through pore structures on a much smaller scale has attracted a great deal of research in recent years as well. The selective transport of ions and small organic molecules across the cell membrane facilitates a number of functions including communication between cells, nerve conduction and signal transmission. Understanding these processes may benefit a wide range of potential applications such as selective separation, biochemical sensing, and controlled release and drug delivery processes. In Germany researchers have successfully demonstrated controlled ionic transport through nanopores functionalized with amine-terminated polymer brushes [4]. The polymer nanobrushes swell and shrink in response to changes in temperature, thus opening and closing the nanopore passage to ionic

  14. Ion age transport: developing devices beyond electronics

    NASA Astrophysics Data System (ADS)

    Demming, Anna

    2014-03-01

    There is more to current devices than conventional electronics. Increasingly research into the controlled movement of ions and molecules is enabling a range of new technologies. For example, as Weihua Guan, Sylvia Xin Li and Mark Reed at Yale University explain, 'It offers a unique opportunity to integrate wet ionics with dry electronics seamlessly'. In this issue they provide an overview of voltage-gated ion and molecule transport in engineered nanochannels. They cover the theory governing these systems and fabrication techniques, as well as applications, including biological and chemical analysis, and energy conversion [1]. Studying the movement of particles in nanochannels is not new. The transport of materials in rock pores led Klinkenberg to describe an analogy between diffusion and electrical conductivity in porous rocks back in 1951 [2]. And already in 1940, Harold Abramson and Manuel Gorin noted that 'When an electric current is applied across the living human skin, the skin may be considered to act like a system of pores through which transfer of substances like ragweed pollen extract may be achieved both by electrophoretic and by diffusion phenomena' [3]. Transport in living systems through pore structures on a much smaller scale has attracted a great deal of research in recent years as well. The selective transport of ions and small organic molecules across the cell membrane facilitates a number of functions including communication between cells, nerve conduction and signal transmission. Understanding these processes may benefit a wide range of potential applications such as selective separation, biochemical sensing, and controlled release and drug delivery processes. In Germany researchers have successfully demonstrated controlled ionic transport through nanopores functionalized with amine-terminated polymer brushes [4]. The polymer nanobrushes swell and shrink in response to changes in temperature, thus opening and closing the nanopore passage to ionic

  15. Electronic transport and dynamics in correlated heterostructures

    NASA Astrophysics Data System (ADS)

    Mazza, G.; Amaricci, A.; Capone, M.; Fabrizio, M.

    2015-05-01

    We investigate by means of the time-dependent Gutzwiller approximation the transport properties of a strongly correlated slab subject to Hubbard repulsion and connected with to two metallic leads kept at a different electrochemical potential. We focus on the real-time evolution of the electronic properties after the slab is connected to the leads and consider both metallic and Mott insulating slabs. When the correlated slab is metallic, the system relaxes to a steady state that sustains a finite current. The zero-bias conductance is finite and independent of the degree of correlations within the slab as long as the system remains metallic. On the other hand, when the slab is in a Mott insulating state, the external bias leads to currents that are exponentially activated by charge tunneling across the Mott-Hubbard gap, consistent with the Landau-Zener dielectric breakdown scenario.

  16. Effects of Cu deficiency on photosynthetic electron transport

    SciTech Connect

    Droppa, M.; Terry, N.; Horvath, G.

    1984-04-01

    The role of copper (Cu) in photosynthetic electron transport was explored by using Cu deficiency in sugar beet as an experimental approach. Copper influenced electron transport at two sites in addition to plastocyanin. Under mild deficiency (0.84 nmol of Cu per cm/sup 2/ of leaf area), electron transport between the two photosystems (PS) is inhibited but not electron transport within PS I or PS II measured separately. The chlorophyll/plastoquinone ratio was normal in Cu-deficient plants. However, the breakpoint in the Arrhenius plot of electron transport was shifted towards a higher temperature. It is concluded that Cu is necessary to maintain the appropriate membrane fluidity to ensure the mobility of plastoquinone molecules to transfer electrons between the two photosystems. Under severe deficiency (0.22 nmol of Cu per cm/sup 2/ of leaf area) both PS II and PS I electron transports were inhibited and to the same extent. PS II electron transport activity could not be restored by adding artifical electron donors. Polypeptides with M/sub r/s of 28,000 and 13,500 were missing in Cu-deficient chloroplast membranes. In PS II particles prepared from normal chloroplasts of spinach, 2 atoms of Cu per reaction center are present. We conclude that Cu influences PS II electron transport either directly, by participation in electron transfer as a constituent of an electron carrier, or indirectly, via the polypeptide composition of the membrane in the PS II complex.

  17. Electron scattering and transport in liquid argon

    SciTech Connect

    Boyle, G. J.; Cocks, D. G.; White, R. D.; McEachran, R. P.

    2015-04-21

    The transport of excess electrons in liquid argon driven out of equilibrium by an applied electric field is revisited using a multi-term solution of Boltzmann’s equation together with ab initio liquid phase cross-sections calculated using the Dirac-Fock scattering equations. The calculation of liquid phase cross-sections extends previous treatments to consider multipole polarisabilities and a non-local treatment of exchange, while the accuracy of the electron-argon potential is validated through comparison of the calculated gas phase cross-sections with experiment. The results presented highlight the inadequacy of local treatments of exchange that are commonly used in liquid and cluster phase cross-section calculations. The multi-term Boltzmann equation framework accounting for coherent scattering enables the inclusion of the full anisotropy in the differential cross-section arising from the interaction and the structure factor, without an a priori assumption of quasi-isotropy in the velocity distribution function. The model, which contains no free parameters and accounts for both coherent scattering and liquid phase screening effects, was found to reproduce well the experimental drift velocities and characteristic energies.

  18. Electronic transport through carbon nanotubes - effect of contacts, topological defects, dopants and chemisorbed impurities

    SciTech Connect

    Maiti, A; Hoekstra, J; Andzelm, J; Govind, N; Ricca, A; Svizhenko, A; Mehrez, H; Anantram, M P

    2005-02-11

    Electronics based on carbon nanotubes (CNT) has received a lot of attention recently because of its tremendous application potential, such as active components and interconnects in nanochips, nanoelectromechanical systems (NEMS), display devices, and chemical and biological sensors. However, as with most nanoelectronic systems, successful commercial deployment implies structural control at the molecular level. To this end, it is clearly necessary to understand the effect of contacts, topological defects, dopants, and chemisorbed atoms and molecules on the electronic transport through CNT's. This paper summarizes our computational efforts to address some of the above questions. Examples include: wetting properties and bonding strength of metal contacts on the CNT surface, the effect of Stone-Wales defects on the chemisorption of O{sub 2} and NH3, and how such chemisorbed species and defects effect the electronic transmission and conductance. Our approach is based on first-principles density functional theory (DFT) to compute equilibrium structures, and nonequilibrium Green's function (NEGF) methods, using both DFT and semi-empirical tight-binding formalisms, for computing electronic transport properties.

  19. Effect of interfaces on electron transport properties of MoS2-Au Contacts

    NASA Astrophysics Data System (ADS)

    Aminpour, Maral; Hapala, Prokop; Le, Duy; Jelinek, Pavel; Rahman, Talat S.; Rahman's Group Collaboration; Nanosurf Lab Collaboration

    2014-03-01

    Single layer MoS2 is a promising material for future electronic devices such as transistors since it has good transport characteristics with mobility greater than 200 cm-1V-1s-1 and on-off current ratios up to 108. However, before MoS2 can become a mainstream electronic material for the semiconductor industry, the design of low resistive metal-semiconductor junctions as contacts of the electronic devices needs to be addressed and studied systematically. We have examined the effect of Au contacts on the electronic transport properties of single layer MoS2 using density functional theory in combination with the non-equilibrium Green's function method. The Schottky barrier between Au contact and MoS2, transmission spectra, and I-V curves will be reported and discussed as a function of MoS2 and Au interfaces of varying geometry. This work is supported in part by the US Department of Energy under grant DE-FG02-07ER15842.

  20. Electronic and thermoelectric transport properties for an armchair graphene-silicene-graphene heterojunction modulated by external field

    NASA Astrophysics Data System (ADS)

    Zhou, Benhu; Zhou, Benliang; Zeng, Yangsu; Zhou, Guanghui; Duan, Manyi

    2016-08-01

    We analytically investigate effective spin-orbit coupling (SOC) and potential energy on electronic and thermoelectric transport properties for a graphene-silicene-graphene (GSG) heterojunction with armchair-edge nanoribbons using nonequilibrium Green's function method. The calculation shows that the transmission coefficient T and the charge Seebeck coefficient SC for armchair-edge GSG junctions display the oscillatory behavior and depend sensitively on both effective SOC λSO and the potential energy V0. Compared with zigzag-edge GSG heterojunctions, armchair-edge GSG heterojunctions are found to posses superior thermoelectric performance, their charge Seebeck coefficients can be improved by one order of magnitude.

  1. Introduction to Nonequilibrium Statistical Mechanics with Quantum Field Theory

    NASA Astrophysics Data System (ADS)

    Kita, T.

    2010-04-01

    microscopically with quantum field theory, including fluctuations. We also discuss a derivation of the quantum transport equations for electrons in electromagnetic fields based on the gauge-invariant Wigner transformation so that the Lorentz force is reproduced naturally. As for (iii), the Gibbs entropy of equilibrium statistical mechanics suffers from the flaw that it does not evolve in time. We show here that a microscopic expression of nonequilibrium dynamical entropy can be derived from the quantum transport equations so as to be compatible with the law of increase in entropy as well as equilibrium statistical mechanics.

  2. Structural, electronic, mechanical, and transport properties of phosphorene nanoribbons: Negative differential resistance behavior

    NASA Astrophysics Data System (ADS)

    Maity, Ajanta; Singh, Akansha; Sen, Prasenjit; Kibey, Aniruddha; Kshirsagar, Anjali; Kanhere, Dilip G.

    2016-08-01

    Structural, electronic, mechanical, and transport properties of two different types of phosphorene nanoribbons are calculated within the density functional theory and nonequilibrium Green's function formalisms. Armchair nanoribbons turn out to be semiconductors at all widths considered. Zigzag nanoribbons are metallic in their layer-terminated structure, but undergo Peierls-like transition at the edges. Armchair nanoribbons have smaller Young's modulus compared to a monolayer, while zigzag nanoribbons have larger Young's modulus. Edge reconstruction further increases the Young's modulus of zigzag nanoribbons. A two-terminal device made of zigzag nanoribbons show negative differential resistance behavior that is robust with respect to edge reconstruction. We have also calculated the I -V characteristics for two nonzero gate voltages. The results show that the zigzag nanoribbons display strong p -type character.

  3. Effect of gas flow on electronic transport in a DNA-decorated carbon nanotube.

    PubMed

    Poonam, P; Deo, N

    2011-05-20

    We calculate the two-time current correlation function using the experimental data of the current-time characteristics of the Gas-DNA-decorated carbon nanotube field effect transistor. The pattern of the correlation function is a measure of the sensitivity and selectivity of the sensors and suggest that these gas flow sensors may also be used as DNA sequence detectors. The system is modelled by a one-dimensional tight-binding Hamiltonian and we present analytical calculations of quantum electronic transport for the system using the time-dependent nonequilibrium Green's function formalism and the adiabatic expansion. The zeroth and first order contributions to the current I(0)(t) and I(1)(t) are calculated, where I(0)(t) is the Landauer formula. The formula for the time-dependent current is then used to compare the theoretical results with the experiment.

  4. Vibrationally dependent electron-electron interactions in resonant electron transport through single-molecule junctions

    NASA Astrophysics Data System (ADS)

    Erpenbeck, A.; Härtle, R.; Bockstedte, M.; Thoss, M.

    2016-03-01

    We investigate the role of electronic-vibrational coupling in resonant electron transport through single-molecule junctions, taking into account that the corresponding coupling strengths may depend on the charge and excitation state of the molecular bridge. Within an effective-model Hamiltonian approach for a molecule with multiple electronic states, this requires to extend the commonly used model and include vibrationally dependent electron-electron interaction. We use Born-Markov master equation methods and consider selected models to exemplify the effect of the additional interaction on the transport characteristics of a single-molecule junction. In particular, we show that it has a significant influence on local cooling and heating mechanisms, it may result in negative differential resistance, and it may cause pronounced asymmetries in the conductance map of a single-molecule junction.

  5. Nonequilibrium green function approach to elastic and inelastic spin-charge transport in topological insulator-based heterostructures and magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Mahfouzi, Farzad

    Current and future technological needs increasingly motivate the intensive scientific research of the properties of materials at the nano-scale. One of the most important domains in this respect at present concerns nano-electronics and its diverse applications. The great interest in this domain arises from the potential reduction of the size of the circuit components, maintaining their quality and functionality, and aiming at greater efficiency, economy, and storage characteristics for the corresponding physical devices. The aim of this thesis is to present a contribution to the analysis of the electronic charge and spin transport phenomena that occur at the quantum level in nano-structures. This thesis spans the areas of quantum transport theory through time-dependent systems, electron-boson interacting systems and systems of interest to spintronics. A common thread in the thesis is to develop the theoretical foundations and computational algorithms to numerically simulate such systems. In order to optimize the numerical calculations I resort to different techniques (such as graph theory in finding inverse of a sparse matrix, adaptive grids for integrations and programming languages (e.g., MATLAB and C++) and distributed computing tools (MPI, CUDA). Outline of the Thesis: After giving an introduction to the topics covered in this thesis in Chapter 1, I present the theoretical foundations to the field of non-equilibrium quantum statistics in Chapter 2. The applications of this formalism and the results are covered in the subsequent chapters as follows: Spin and charge quantum pumping in time-dependent systems: Covered in Chapters 3, 4 and 5, this topics was initially motivated by experiments on measuring voltage signal from a magnetic tunnel junction (MTJ) exposed to a microwave radiation in ferromagnetic resonance (FMR) condition. In Chapter 3 we found a possible explanation for the finite voltage signal measured from a tunnel junction consisting of only a single

  6. Designing a beam transport system for RHIC's electron lens

    SciTech Connect

    Gu, X.; Pikin, A.; Okamura, M.; Fischer, W.; Luo, Y.; Gupta, R.; Hock, J.; Raparia, D.

    2011-03-28

    We designed two electron lenses to apply head-on beam-beam compensation for RHIC; they will be installed near IP10. The electron-beam transport system is an important subsystem of the entire electron-lens system. Electrons are transported from the electron gun to the main solenoid and further to the collector. The system must allow for changes of the electron beam size inside the superconducting magnet, and for changes of the electron position by 5 mm in the horizontal- and vertical-planes.

  7. Transition in Electron Transport in a Cylindrical Hall Thruster

    SciTech Connect

    J.B. Parker, Y. Raitses, and N.J. Fisch

    2010-06-02

    Through the use of high-speed camera and Langmuir probe measurements in a cylindrical Hall thruster, we report the discovery of a rotating spoke of increased plasma density and light emission which correlates with increased electron transport across the magnetic field. As cathode electron emission is increased, a sharp transition occurs where the spoke disappears and electron transport decreases. This suggests that a significant fraction of the electron current might be directed through the spoke.

  8. Transition in electron transport in a cylindrical Hall thruster

    SciTech Connect

    Parker, J. B.; Raitses, Y.; Fisch, N. J.

    2010-08-30

    Through the use of high-speed camera and Langmuir probe measurements in a cylindrical Hall thruster, we report the discovery of a rotating spoke of increased plasma density and light emission which correlates with increased electron transport across the magnetic field. As cathode electron emission is increased, a sharp transition occurs where the spoke disappears and electron transport decreases. This suggests that a significant fraction of the electron current might be directed through the spoke.

  9. Effect of lithium and sodium ion adsorption on the electronic transport properties of Ti3C2 MXene

    NASA Astrophysics Data System (ADS)

    Berdiyorov, G. R.

    2015-12-01

    MXenes are found to be promising electrode materials for energy storage applications. Recent theoretical and experimental studies indicate the possibility of using these novel low dimensional materials for metal-ion batteries. Herein, we use density-functional theory in combination with the nonequilibrium Green's function formalism to study the effect of lithium and sodium ion adsorption on the electronic transport properties of the MXene, Ti3C2. Oxygen, hydroxyl and fluorine terminated species are considered and the obtained results are compared with the ones for the pristine MXene. We found that the ion adsorption results in reduced electronic transport in the pristine MXene: depending on the type of the ions and the bias voltage, the current in the system can be reduced by more than 30%. On the other hand, transport properties of the oxygen terminated sample can be improved by the ion adsorption: for both types of ions the current in the system can be increased by more than a factor of 4. However, the electronic transport is less affected by the ions in fluorinated and hydroxylated samples. These two samples show enhanced electronic transport as compared to the pristine MXene. The obtained results are explained in terms of electron localization in the system.

  10. Fano Antiresonance and Kondo Resonance for Electronic Transport Through a Laterally Coupled Carbon-Nanotube Quantum-Dot System

    NASA Astrophysics Data System (ADS)

    Huo, Dong-Ming

    2015-10-01

    We present nonequilibrium Green function calculations for electronic transport through a laterally coupled carbon-nanotube quantum-dot system. In this system, a one-dimensional double carbon nanotube quantum dot attached to polarised electrodes forms a main channel for electronic tunnelling. Each carbon nanotube quantum dot in the main channel couples to a dangling carbon nanotube quantum dot. Then, the conductance spectrum is calculated. The insulating band and resonance peak in this spectrum, due to Fano antiresonance and Kondo resonance, are discussed. The intradot electron's Coulomb interaction effect on the insulating band is also investigated. By controlling the coupling coefficient between the quantum dots, we can realise mutual transformation between Kondo resonance and Fano antiresonance at the Fermi level. The spin-orbit coupling and magnetic field's influence on the Kondo resonance peak are discussed in detail. Finally, spin magnetic moment and orbital magnetic moment of electrons in the quantum dot by applying parallel magnetic field are also predicted.

  11. Electronic and Ionic Transport Dynamics in Organolead Halide Perovskites.

    PubMed

    Li, Dehui; Wu, Hao; Cheng, Hung-Chieh; Wang, Gongming; Huang, Yu; Duan, Xiangfeng

    2016-07-26

    Ion migration has been postulated as the underlying mechanism responsible for the hysteresis in organolead halide perovskite devices. However, the electronic and ionic transport dynamics and how they impact each other in organolead halide perovskites remain elusive to date. Here we report a systematic investigation of the electronic and ionic transport dynamics in organolead halide perovskite microplate crystals and thin films using temperature-dependent transient response measurements. Our study reveals that thermally activated ionic and electronic conduction coexist in perovskite devices. The extracted activation energies suggest that the electronic transport is easier, but ions migrate harder in microplates than in thin films, demonstrating that the crystalline quality and grain boundaries can fundamentally modify electronic and ionic transport in perovskites. These findings offer valuable insight on the electronic and ionic transport dynamics in organolead halide perovskites, which is critical for optimizing perovskite devices with reduced hysteresis and improved stability and efficiency.

  12. The induction of microsomal electron transport enzymes.

    PubMed

    Waterman, M R; Estabrook, R W

    1983-01-01

    Liver endoplasmic reticulum contains as NADPH-dependent electron transport complex where the family of hemeproteins, termed cytochrome P-450, serve as catalysts for the oxidation of a variety of different organic chemicals. The content and inventory of the types of cytochrome P-450 is readily modified following in vivo treatment of animals with 'inducing agents' such as barbiturates, steroids and polycyclic hydrocarbons. Recent studies have applied the methods of molecular biology to evaluate changes in the transcription and translation of genomic information occurring concomitant with the initiation of synthesis of various types of cytochrome P-450. The ability to isolate unique cytochrome P-450 proteins and to prepare specific antibodies now permits the study of in vitro translation of mRNA and the preparation of specific cDNAs. The present review summarizes the historic background leading to current concepts of cytochrome P-450 induction and describes recent advances in our knowledge of the regulation of cytochrome P-450 synthesis in the liver. PMID:6353196

  13. Estimates of nonequilibrium radiation for Venus entry. [generated by chemical reactions in shock layers

    NASA Technical Reports Server (NTRS)

    Grose, W. L.; Nealy, J. E.

    1975-01-01

    The present investigation is an analysis of the radiation from the chemical nonequilibrium region in the shock layer about a vehicle during Venus entry. The radiation and the flow were assumed to be uncoupled. An inviscid, nonequilibrium flowfield was calculated and an effective electronic temperature was determined for the predominant radiating species. Species concentrations and electronic temperature were then input into a radiation transport code to calculate heating rates. The present results confirm earlier investigations which indicate that the radiation should be calculated using electronic temperatures for the radiating species. These temperatures are not related in a simple way to the local translational temperature. For the described mission, the nonequilibrium radiative heating rate is approximately twice the corresponding equilibrium value at peak heating.

  14. Steady-State Density Functional Theory for Non-equilibrium Quantum Systems

    NASA Astrophysics Data System (ADS)

    Shuanglong, Liu

    Recently, electron transport properties of molecular junctions under finite bias voltages have attracted a lot of attention because of the potential application of molecular electronic devices. When a molecular junction is under zero bias voltage at zero temperature, it is in equilibrium ground state and all its properties can be solved by ground-state density functional theory (GS-DFT) where ground-state electron density determines everything. Under finite bias voltage, the molecular junction is in non-equilibrium steady state. According to Hershfield's non-equilibrium statistics, a system in non-equilibrium steady state corresponds to an effective equilibrium system. This correspondence provides the basis for the steady-state density functional theory (SS-DFT) which will be developed in this thesis. (Abstract shortened by UMI.).

  15. INTRODUCTION: Nonequilibrium Processes in Plasmas

    NASA Astrophysics Data System (ADS)

    Petrović, Zoran; Marić, Dragana; Malović, Gordana

    2009-07-01

    cosmos collapsed from the uniform plasma stage into stars and empty space, practically nothing is in real equilibrium only in local equilibrium. How wrong we were. As our focus turned to anti particles, positrons and positronium, we realized that even in those early stages there was major non-equilibrium between matter and anti matter originating from the earliest stages of the Big Bang. Thus it is safe to correct the famous quote by the renowned natural philosopher Sheldon Cooper into: 'If you know the laws of [non-equilibrium] physics anything is possible'. From the matter-anti-matter ratio in the universe to life itself. But do we really need such farfetched introductory remarks to justify our scientific choices? It suffices to focus on non-equilibrium plasmas and transport of pollutants in the air and see how many new methods for diagnostics and treatment have been proposed for medicine in the past 10 years. So in addition to the past major achievements such as plasma etching for integrated circuit production, the field is full of possibilities and truly, almost anything is possible. We hope that some of the papers presented here summarize well how we learn about the laws of non-equilibrium physics in the given context of plasmas and air pollution and how we open new possibilities for further understanding and further applications. A wide range of topics is covered in this volume. This time we start with elementary collisional processes and a review of the data for excitation of polyatomic molecules obtained by the binary collision experiments carried out at the Institute of Physics in Belgrade by the group of Bratislav Marinković. A wide range of activities on the foundation of gaseous positronics ranging from new measurements in the binary regime to the simulation of collective transport in dense gases is presented by James Sullivan and coworkers. This work encompasses three continents, half a dozen groups and several lectures at the workshops while also covering

  16. Full counting statistics of vibrationally assisted electronic conduction: Transport and fluctuations of thermoelectric efficiency

    NASA Astrophysics Data System (ADS)

    Agarwalla, Bijay Kumar; Jiang, Jian-Hua; Segal, Dvira

    2015-12-01

    We study the statistical properties of charge and energy transport in electron conducting junctions with electron-phonon interactions, specifically, the thermoelectric efficiency and its fluctuations. The system comprises donor and acceptor electronic states, representing a two-site molecule or a double-quantum-dot system. Electron transfer between metals through the two molecular sites is coupled to a particular vibrational mode which is taken to be either harmonic or anharmonic, a truncated (two-state) spectrum. Considering these models we derive the cumulant generating function in steady state for charge and energy transfer, correct to second order in the electron-phonon interaction, but exact to all orders in the metal-molecule coupling strength. This is achieved by using the nonequilibrium Green's function approach (harmonic mode) and a kinetic quantum master-equation method (anharmonic mode). From the cumulant generating function we calculate the charge current and its noise and the large-deviation function for the thermoelectric efficiency. We demonstrate that at large bias the charge current, differential conductance, and the current noise can identify energetic and structural properties of the junction. We further examine the operation of the junction as a thermoelectric engine and show that while the macroscopic thermoelectric efficiency is indifferent to the nature of the mode (harmonic or anharmonic), efficiency fluctuations do reflect this property.

  17. Effect of compression on the electronic, optical and transport properties of MoS2/graphene-based junctions

    NASA Astrophysics Data System (ADS)

    Ghorbani-Asl, Mahdi; Bristowe, Paul D.; Koziol, K.; Heine, Thomas; Kuc, Agnieszka

    2016-06-01

    Electronic, optical and transport properties of the MoS2/graphene heterostructure have been investigated as function of applied uniaxial compression normal to the interface plane using first principles calculations and a non-equilibrium Green’s function approach. The results show that a small compressive load (∼1 GPa) can open up the band gap (∼12 meV), reduce the optical absorption coefficient (∼7%), redshift the absorption spectrum, and create non-Ohmic I –V characteristics that depend on the magnitude of applied bias. This suggests that graphene/MoS2 heterostructure can be suitable for electromechanical and photomechanical devices where the electronic, optical and transport properties can be tuned by an appropriate application of bias and mechanical deformations.

  18. Nonequilibrium thermodynamics of an interface

    NASA Astrophysics Data System (ADS)

    Schweizer, Marco; Öttinger, Hans Christian; Savin, Thierry

    2016-05-01

    Interfacial thermodynamics has deep ramifications in understanding the boundary conditions of transport theories. We present a formulation of local equilibrium for interfaces that extends the thermodynamics of the "dividing surface," as introduced by Gibbs, to nonequilibrium settings such as evaporation or condensation. By identifying the precise position of the dividing surface in the interfacial region with a gauge degree of freedom, we exploit gauge-invariance requirements to consistently define the intensive variables for the interface. The model is verified under stringent conditions by employing high-precision nonequilibrium molecular-dynamics simulations of a coexisting vapor-liquid Lennard-Jones fluid. We conclude that the interfacial temperature is determined using the surface tension as a "thermometer," and it can be significantly different from the temperatures of the adjacent phases. Our findings lay foundations for nonequilibrium interfacial thermodynamics.

  19. Nonequilibrium thermodynamics of an interface.

    PubMed

    Schweizer, Marco; Öttinger, Hans Christian; Savin, Thierry

    2016-05-01

    Interfacial thermodynamics has deep ramifications in understanding the boundary conditions of transport theories. We present a formulation of local equilibrium for interfaces that extends the thermodynamics of the "dividing surface," as introduced by Gibbs, to nonequilibrium settings such as evaporation or condensation. By identifying the precise position of the dividing surface in the interfacial region with a gauge degree of freedom, we exploit gauge-invariance requirements to consistently define the intensive variables for the interface. The model is verified under stringent conditions by employing high-precision nonequilibrium molecular-dynamics simulations of a coexisting vapor-liquid Lennard-Jones fluid. We conclude that the interfacial temperature is determined using the surface tension as a "thermometer," and it can be significantly different from the temperatures of the adjacent phases. Our findings lay foundations for nonequilibrium interfacial thermodynamics.

  20. Nonequilibrium thermodynamics of an interface.

    PubMed

    Schweizer, Marco; Öttinger, Hans Christian; Savin, Thierry

    2016-05-01

    Interfacial thermodynamics has deep ramifications in understanding the boundary conditions of transport theories. We present a formulation of local equilibrium for interfaces that extends the thermodynamics of the "dividing surface," as introduced by Gibbs, to nonequilibrium settings such as evaporation or condensation. By identifying the precise position of the dividing surface in the interfacial region with a gauge degree of freedom, we exploit gauge-invariance requirements to consistently define the intensive variables for the interface. The model is verified under stringent conditions by employing high-precision nonequilibrium molecular-dynamics simulations of a coexisting vapor-liquid Lennard-Jones fluid. We conclude that the interfacial temperature is determined using the surface tension as a "thermometer," and it can be significantly different from the temperatures of the adjacent phases. Our findings lay foundations for nonequilibrium interfacial thermodynamics. PMID:27300960

  1. Electron transport theory in magnetic nanostructures

    NASA Astrophysics Data System (ADS)

    Choy, Tat-Sang

    Magnetic nanostructure has been a new trend because of its application in making magnetic sensors, magnetic memories, and magnetic reading heads in hard disks drives. Although a variety of nanostructures have been realized in experiments in recent years by innovative sample growth techniques, the theoretical study of these devices remain a challenge. On one hand, atomic scale modeling is often required for studying the magnetic nanostructures; on the other, these structures often have a dimension on the order of one micrometer, which makes the calculation numerically intensive. In this work, we have studied the electron transport theory in magnetic nanostructures, with special attention to the giant magnetoresistance (GMR) structure. We have developed a model that includes the details of the band structure and disorder, both of which are both important in obtaining the conductivity. We have also developed an efficient algorithm to compute the conductivity in magnetic nanostructures. The model and the algorithm are general and can be applied to complicated structures. We have applied the theory to current-perpendicular-to-plane GMR structures and the results agree with experiments. Finally, we have searched for the atomic configuration with the highest GMR using the simulated annealing algorithm. This method is computationally intensive because we have to compute the GMR for 103 to 104 configurations. However it is still very efficient because the number of steps it takes to find the maximum is much smaller than the number of all possible GMR structures. We found that ultra-thin NiCu superlattices have surprisingly large GMR even at the moderate disorder in experiments. This finding may be useful in improving the GMR technology.

  2. Nonequilibrium green function approach to elastic and inelastic spin-charge transport in topological insulator-based heterostructures and magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Mahfouzi, Farzad

    Current and future technological needs increasingly motivate the intensive scientific research of the properties of materials at the nano-scale. One of the most important domains in this respect at present concerns nano-electronics and its diverse applications. The great interest in this domain arises from the potential reduction of the size of the circuit components, maintaining their quality and functionality, and aiming at greater efficiency, economy, and storage characteristics for the corresponding physical devices. The aim of this thesis is to present a contribution to the analysis of the electronic charge and spin transport phenomena that occur at the quantum level in nano-structures. This thesis spans the areas of quantum transport theory through time-dependent systems, electron-boson interacting systems and systems of interest to spintronics. A common thread in the thesis is to develop the theoretical foundations and computational algorithms to numerically simulate such systems. In order to optimize the numerical calculations I resort to different techniques (such as graph theory in finding inverse of a sparse matrix, adaptive grids for integrations and programming languages (e.g., MATLAB and C++) and distributed computing tools (MPI, CUDA). Outline of the Thesis: After giving an introduction to the topics covered in this thesis in Chapter 1, I present the theoretical foundations to the field of non-equilibrium quantum statistics in Chapter 2. The applications of this formalism and the results are covered in the subsequent chapters as follows: Spin and charge quantum pumping in time-dependent systems: Covered in Chapters 3, 4 and 5, this topics was initially motivated by experiments on measuring voltage signal from a magnetic tunnel junction (MTJ) exposed to a microwave radiation in ferromagnetic resonance (FMR) condition. In Chapter 3 we found a possible explanation for the finite voltage signal measured from a tunnel junction consisting of only a single

  3. Reverse electron transport effects on NADH formation and metmyoglobin reduction.

    PubMed

    Belskie, K M; Van Buiten, C B; Ramanathan, R; Mancini, R A

    2015-07-01

    The objective was to determine if NADH generated via reverse electron flow in beef mitochondria can be used for electron transport-mediated reduction and metmyoglobin reductase pathways. Beef mitochondria were isolated from bovine hearts (n=5) and reacted with combinations of succinate, NAD, and mitochondrial inhibitors to measure oxygen consumption and NADH formation. Mitochondria and metmyoglobin were reacted with succinate, NAD, and mitochondrial inhibitors to measure electron transport-mediated metmyoglobin reduction and metmyoglobin reductase activity. Addition of succinate and NAD increased oxygen consumption, NADH formation, electron transport-mediated metmyoglobin reduction, and reductase activity (p<0.05). Addition of antimycin A prevented electron flow beyond complex III, therefore, decreasing oxygen consumption and electron transport-mediated metmyoglobin reduction. Addition of rotenone prevented reverse electron flow, increased oxygen consumption, increased electron transport-mediated metmyoglobin reduction, and decreased NADH formation. Succinate and NAD can generate NADH in bovine tissue postmortem via reverse electron flow and this NADH can be used by both electron transport-mediated and metmyoglobin reductase pathways. PMID:25828162

  4. Reverse electron transport effects on NADH formation and metmyoglobin reduction.

    PubMed

    Belskie, K M; Van Buiten, C B; Ramanathan, R; Mancini, R A

    2015-07-01

    The objective was to determine if NADH generated via reverse electron flow in beef mitochondria can be used for electron transport-mediated reduction and metmyoglobin reductase pathways. Beef mitochondria were isolated from bovine hearts (n=5) and reacted with combinations of succinate, NAD, and mitochondrial inhibitors to measure oxygen consumption and NADH formation. Mitochondria and metmyoglobin were reacted with succinate, NAD, and mitochondrial inhibitors to measure electron transport-mediated metmyoglobin reduction and metmyoglobin reductase activity. Addition of succinate and NAD increased oxygen consumption, NADH formation, electron transport-mediated metmyoglobin reduction, and reductase activity (p<0.05). Addition of antimycin A prevented electron flow beyond complex III, therefore, decreasing oxygen consumption and electron transport-mediated metmyoglobin reduction. Addition of rotenone prevented reverse electron flow, increased oxygen consumption, increased electron transport-mediated metmyoglobin reduction, and decreased NADH formation. Succinate and NAD can generate NADH in bovine tissue postmortem via reverse electron flow and this NADH can be used by both electron transport-mediated and metmyoglobin reductase pathways.

  5. Gate controlled electronic transport in monolayer MoS{sub 2} field effect transistor

    SciTech Connect

    Zhou, Y. F.; Wang, B.; Yu, Y. J.; Wei, Y. D. E-mail: jianwang@hku.hk; Xian, H. M.; Wang, J. E-mail: jianwang@hku.hk

    2015-03-14

    The electronic spin and valley transport properties of a monolayer MoS{sub 2} are investigated using the non-equilibrium Green's function formalism combined with density functional theory. Due to the presence of strong Rashba spin orbit interaction (RSOI), the electronic valence bands of monolayer MoS{sub 2} are split into spin up and spin down Zeeman-like texture near the two inequivalent vertices K and K′ of the first Brillouin zone. When the gate voltage is applied in the scattering region, an additional strong RSOI is induced which generates an effective magnetic field. As a result, electron spin precession occurs along the effective magnetic field, which is controlled by the gate voltage. This, in turn, causes the oscillation of conductance as a function of the magnitude of the gate voltage and the length of the gate region. This current modulation due to the spin precession shows the essential feature of the long sought Datta-Das field effect transistor (FET). From our results, the oscillation periods for the gate voltage and gate length are found to be approximately 2.2 V and 20.03a{sub B} (a{sub B} is Bohr radius), respectively. These observations can be understood by a simple spin precessing model and indicate that the electron behaviors in monolayer MoS{sub 2} FET are both spin and valley related and can easily be controlled by the gate.

  6. Thermally activated long range electron transport in living biofilms.

    PubMed

    Yates, Matthew D; Golden, Joel P; Roy, Jared; Strycharz-Glaven, Sarah M; Tsoi, Stanislav; Erickson, Jeffrey S; El-Naggar, Mohamed Y; Calabrese Barton, Scott; Tender, Leonard M

    2015-12-28

    Microbial biofilms grown utilizing electrodes as metabolic electron acceptors or donors are a new class of biomaterials with distinct electronic properties. Here we report that electron transport through living electrode-grown Geobacter sulfurreducens biofilms is a thermally activated process with incoherent redox conductivity. The temperature dependency of this process is consistent with electron-transfer reactions involving hemes of c-type cytochromes known to play important roles in G. sulfurreducens extracellular electron transport. While incoherent redox conductivity is ubiquitous in biological systems at molecular-length scales, it is unprecedented over distances it appears to occur through living G. sulfurreducens biofilms, which can exceed 100 microns in thickness. PMID:26611733

  7. Ultrafast electronic transport in low dimensional semiconductor nanostructures

    NASA Astrophysics Data System (ADS)

    Choi, Hyunyong; Norris, Theodore B.; Faist, Jérôme; Capasso, Federico

    2009-02-01

    Ultrafast time-resolved pump-probe measurements are used to study low energy excitations and dynamics of electronic transport in various semiconductor nanostructures. In quantum cascade lasers, we observe ultrafast gain recovery dynamics due to electronic transport in the structures. In particular, the nature of electronic transport had been addressed by using ultrafast optical techniques. Sub-picosecond resonant tunneling injection from the quantum cascade laser injector ground state into the upper lasing state was found to be incoherent due to strong dephasing in the active subband. We also observed the strong coupling of the electronic transport to the intra-cavity photon density, which we term "photon-driven transport". Note that this invited paper reviews the details of our recent observations (H. Choi et al., Phys. Rev. Lett., 100, 167401, 2008 and H. Choi, et al., Appl. Phys. Lett. 92, 122114 (2008)).

  8. The effect of molecular mobility on electronic transport in carbon nanotube-polymer composites and networks

    SciTech Connect

    Shenogin, Sergei; Lee, Jonghoon; Voevodin, Andrey A.; Roy, Ajit K.

    2014-12-21

    A multiscale modeling approach to the prediction of electrical conductivity in carbon nanotube (CNT)–polymer composite materials is developed, which takes into account thermally activated molecular mobility of the matrix and the CNTs. On molecular level, a tight-binding density functional theory and non-equilibrium Green's function method are used to calculate the static electron transmission function in the contact between two metallic carbon nanotubes that corresponds to electron transport at 0 K. For higher temperatures, the statistical distribution of effective contact resistances is considered that originates from thermal fluctuations of intermolecular distances caused by molecular mobility of carbon nanotube and the polymer matrix. Based on this distribution and using effective medium theory, the temperature dependence of macroscopic electrical resistivity for CNT-polymer composites and CNT mats is calculated. The predicted data indicate that the electrical conductivity of the CNT-polymer composites increases linearly with temperature above 50 K, which is in a quantitative agreement with the experiments. Our model predicts a slight nonlinearity in temperature dependence of electric conductivity at low temperatures for percolated composites with small CNT loading. The model also explains the effect of glass transition and other molecular relaxation processes in the polymer matrix on the composite electrical conductivity. The developed multiscale approach integrates the atomistic charge transport mechanisms in percolated CNT-polymer composites with the macroscopic response and thus enables direct comparison of the prediction with the measurements of macroscopic material properties.

  9. The effect of molecular mobility on electronic transport in carbon nanotube-polymer composites and networks

    NASA Astrophysics Data System (ADS)

    Shenogin, Sergei; Lee, Jonghoon; Voevodin, Andrey A.; Roy, Ajit K.

    2014-12-01

    A multiscale modeling approach to the prediction of electrical conductivity in carbon nanotube (CNT)-polymer composite materials is developed, which takes into account thermally activated molecular mobility of the matrix and the CNTs. On molecular level, a tight-binding density functional theory and non-equilibrium Green's function method are used to calculate the static electron transmission function in the contact between two metallic carbon nanotubes that corresponds to electron transport at 0 K. For higher temperatures, the statistical distribution of effective contact resistances is considered that originates from thermal fluctuations of intermolecular distances caused by molecular mobility of carbon nanotube and the polymer matrix. Based on this distribution and using effective medium theory, the temperature dependence of macroscopic electrical resistivity for CNT-polymer composites and CNT mats is calculated. The predicted data indicate that the electrical conductivity of the CNT-polymer composites increases linearly with temperature above 50 K, which is in a quantitative agreement with the experiments. Our model predicts a slight nonlinearity in temperature dependence of electric conductivity at low temperatures for percolated composites with small CNT loading. The model also explains the effect of glass transition and other molecular relaxation processes in the polymer matrix on the composite electrical conductivity. The developed multiscale approach integrates the atomistic charge transport mechanisms in percolated CNT-polymer composites with the macroscopic response and thus enables direct comparison of the prediction with the measurements of macroscopic material properties.

  10. Computational Study of the Thermal and Electronic Transport Properties of Rigidly-Interconnected Carbon Nano Foam

    NASA Astrophysics Data System (ADS)

    Park, Sora; Kwon, Young-Kyun; Tománek, David

    2012-02-01

    We study the thermal and electronic transport properties of rigidly-interconnected structures having sp^2 carbon minimal surface called schwarzites. The system consists of core parts composed of schwarzite and interconnection parts with (4,4) carbon nanotube segments [1]. Using direct molecular dynamics simulations with the Tersoff potential, we compute the thermal conductivity of various configurations to explore the dependence on the number of core parts and on the length of interconnection parts. Our calculations show that each core part plays as a scattering center, which reduces the phonon mean free path and thus the thermal conductivity. We also investigate the electronic transport properties of the system by applying the non-equilibrium Green function approach in combination with density functional theory. We explore the effects of different core connectivity and structural defects introduced near the core parts on the electrical conductance. These thermal and electonic properties may be connected to the thermoelectric properties of the schwarzite system.[1] S. Park, K. Kittimanapun, J. S. Ahn, Y.-K. Kwon and D. Tom'anek, J. Phys.: Condens. Matter 22, 334220 (2010).

  11. PREFACE: Progress in Nonequilibrium Green's Functions IV

    NASA Astrophysics Data System (ADS)

    Bonitz, Michael; Balzer, Karsten

    2010-04-01

    This is the fourth volume1 of articles on the theory of Nonequilibrium Green's functions (NEGF) and their modern application in various fields such as plasma physics, semiconductor physics, molecular electronics and high energy physics. It contains 23 articles written by experts in many-body theory and quantum transport who summarize recent progress in their respective area of research. The articles are based on talks given at the interdisciplinary conference Progress in Nonequilibrium Green's functions IV which was held 17-21 August 2009 at the University of Glasgow, Scotland. This conference continues the tradition of the previous meetings which started in 1999 and which aimed at an informal exchange across field boundaries. The previous meetings and the earlier proceedings proved to be very stimulating not only for young researchers but also for experienced scientists, and we are convinced that this fourth volume will be as successful as the previous ones. As before, this volume includes only extended review-type papers which are written in a way that they are understandable to a broad interdisciplinary audience. All papers published in this volume of Journal of Physics: Conference Series have been peer reviewed through processes administrated by the Editors assuring highest scientific standards. In the review process some papers were substantially revised and improved and some were rejected. This conference would not have been possible without the remarkable work of the local organizing team around John Barker and Scott Roy and the generous financial support from the University of Glasgow and the Deutsche Forschungsgemeinschaft via SFB-Transregio 24. Michael Bonitz and Karsten Balzer Kiel, February 2010 1 The first two volumes are Progress in Nonequilibrium Green's functions, M Bonitz (ed) and Progress in Nonequilibrium Green's functions II, M Bonitz and D Semkat (eds), which were published by World Scientific (Singapore), in 2000 and 2003, respectively (ISBN

  12. Collisional-radiative nonequilibrium in partially ionized atomic nitrogen

    NASA Technical Reports Server (NTRS)

    Kunc, J. A.; Soon, W. H.

    1989-01-01

    A nonlinear collisional-radiative model for determination of nonequilibrium production of electrons, excited atoms, and bound-bound, dielectronic and continuum line intensities in stationary partially ionized atomic nitrogen is presented. Populations of 14 atomic levels and line intensities are calculated in plasma with T(e) = 8000-15,000 K and N(t) = 10 to the 12th - 10 to the 18th/cu cm. Transport of radiation is included by coupling the rate equations of production of the electrons and excited atoms with the radiation escape factors, which are not constant but depend on plasma conditions.

  13. Spin transport in tilted electron vortex beams

    NASA Astrophysics Data System (ADS)

    Basu, Banasri; Chowdhury, Debashree

    2014-12-01

    In this paper we have enlightened the spin related issues of tilted Electron vortex beams. We have shown that in the skyrmionic model of electron we can have the spin Hall current considering the tilted type of electron vortex beam. We have considered the monopole charge of the tilted vortex as time dependent and through the time variation of the monopole charge we can explain the spin Hall effect of electron vortex beams. Besides, with an external magnetic field we can have a spin filter configuration.

  14. Spin transport in tilted electron vortex beams

    SciTech Connect

    Basu, Banasri; Chowdhury, Debashree

    2014-12-10

    In this paper we have enlightened the spin related issues of tilted Electron vortex beams. We have shown that in the skyrmionic model of electron we can have the spin Hall current considering the tilted type of electron vortex beam. We have considered the monopole charge of the tilted vortex as time dependent and through the time variation of the monopole charge we can explain the spin Hall effect of electron vortex beams. Besides, with an external magnetic field we can have a spin filter configuration.

  15. Tuning anisotropic electronic transport properties of phosphorene via substitutional doping.

    PubMed

    Guo, Caixia; Xia, Congxin; Fang, Lizhen; Wang, Tianxing; Liu, Yufang

    2016-10-01

    Using first-principles calculations, we studied the anisotropic electronic transport properties of pristine and X-doped phosphorene (X = B, Al, Ga, C, Si, Ge, N, As, O, S, and Se atoms). The results show that doping different elements can induce obviously different electronic transport characteristics. Moreover, isovalent doping maintains semiconducting characteristics and anisotropic transport properties, while group IV and VI atoms doping can induce metal properties. Meanwhile, Al and Ga substituting P decrease the anisotropic behaviors of transport, and other atom doping still preserves anisotropic characteristics. Interestingly, obvious negative differential resistance behaviors can be observed in C, Si, Ge, O, S, and Se-doped phosphorene.

  16. Terahertz electromodulation spectroscopy of electron transport in GaN

    SciTech Connect

    Engelbrecht, S. G.; Arend, T. R.; Kersting, R.; Zhu, T.; Kappers, M. J.

    2015-03-02

    Time-resolved terahertz (THz) electromodulation spectroscopy is applied to investigate the high-frequency transport of electrons in gallium nitride at different doping concentrations and densities of threading dislocations. At THz frequencies, all structures reveal Drude transport. The analysis of the spectral response provides the fundamental transport properties, such as the electron scattering time and the electrons' conductivity effective mass. We observe the expected impact of ionized-impurity scattering and that scattering at threading dislocations only marginally affects the high-frequency mobility.

  17. Non-nuclear electron transport channels in hollow molecules

    NASA Astrophysics Data System (ADS)

    Zhao, Jin; Petek, Hrvoje

    2014-08-01

    Electron transport in inorganic semiconductors and metals occurs through delocalized bands formed by overlapping electron orbitals. Strong correlation of electronic wave functions with the ionic cores couples the electron and lattice motions, leading to efficient interaction and scattering that degrades coherent charge transport. By contrast, unoccupied electronic states at energies near the vacuum level with diffuse molecular orbitals may form nearly-free-electron bands with density maxima in non-nuclear interstitial voids, which are subject to weaker electron-phonon interaction. The position of such bands typically above the frontier orbitals, however, renders them unstable with respect to electronic interband relaxation and therefore unsuitable for charge transport. Through electronic-structure calculations, we engineer stable, non-nuclear, nearly-free-electron conduction channels in low-dimensional molecular materials by tailoring their electrostatic and polarization potentials. We propose quantum structures of graphane-derived Janus molecular sheets with spatially isolated conducting and insulating regions that potentially exhibit emergent electronic properties, as a paradigm for molecular-scale non-nuclear charge conductors; we also describe tuning of their electronic properties by application of external fields and calculate their electron-acoustic-phonon interaction.

  18. Photosynthetic, respiratory and extracellular electron transport pathways in cyanobacteria.

    PubMed

    Lea-Smith, David J; Bombelli, Paolo; Vasudevan, Ravendran; Howe, Christopher J

    2016-03-01

    Cyanobacteria have evolved elaborate electron transport pathways to carry out photosynthesis and respiration, and to dissipate excess energy in order to limit cellular damage. Our understanding of the complexity of these systems and their role in allowing cyanobacteria to cope with varying environmental conditions is rapidly improving, but many questions remain. We summarize current knowledge of cyanobacterial electron transport pathways, including the possible roles of alternative pathways in photoprotection. We describe extracellular electron transport, which is as yet poorly understood. Biological photovoltaic devices, which measure electron output from cells, and which have been proposed as possible means of renewable energy generation, may be valuable tools in understanding cyanobacterial electron transfer pathways, and enhanced understanding of electron transfer may allow improvements in the efficiency of power output. This article is part of a Special Issue entitled Organization and dynamics of bioenergetic systems in bacteria, edited by Conrad Mullineaux.

  19. Photosynthetic, respiratory and extracellular electron transport pathways in cyanobacteria.

    PubMed

    Lea-Smith, David J; Bombelli, Paolo; Vasudevan, Ravendran; Howe, Christopher J

    2016-03-01

    Cyanobacteria have evolved elaborate electron transport pathways to carry out photosynthesis and respiration, and to dissipate excess energy in order to limit cellular damage. Our understanding of the complexity of these systems and their role in allowing cyanobacteria to cope with varying environmental conditions is rapidly improving, but many questions remain. We summarize current knowledge of cyanobacterial electron transport pathways, including the possible roles of alternative pathways in photoprotection. We describe extracellular electron transport, which is as yet poorly understood. Biological photovoltaic devices, which measure electron output from cells, and which have been proposed as possible means of renewable energy generation, may be valuable tools in understanding cyanobacterial electron transfer pathways, and enhanced understanding of electron transfer may allow improvements in the efficiency of power output. This article is part of a Special Issue entitled Organization and dynamics of bioenergetic systems in bacteria, edited by Conrad Mullineaux. PMID:26498190

  20. Ballistic electron transport in wrinkled superlattices

    NASA Astrophysics Data System (ADS)

    Mitran, T. L.; Nemnes, G. A.; Ion, L.; Dragoman, Daniela

    2016-07-01

    Inspired by the problem of elastic wave scattering on wrinkled interfaces, we studied the scattering of ballistic electrons on a wrinkled potential energy region. The electron transmission coefficient depends on both wrinkle amplitude and periodicity, having different behaviors for positive and negative scattering potential energies. For scattering on potential barriers, minibands appear in the electron transmission, as in superlattices, whereas for scattering on periodic potential wells the transmission coefficient has a more complex form. Besides suggesting that tuning of electron transmission is possible by modifying the scattering potential via voltages on wrinkled gate electrodes, our results emphasize the analogies between ballistic electrons and elastic waves even in scattering problems on non-typical configurations.

  1. Fast electron generation and transport in a turbulent, magnetized plasma

    SciTech Connect

    Stoneking, W.R.

    1994-05-01

    The nature of fast electron generation and transport in the Madison Symmetric Torus (MST) reversed field pinch (RFP) is investigated using two electron energy analyzer (EEA) probes and a thermocouple calorimeter. The parallel velocity distribution of the fast electron population is well fit by a drifted Maxwellian distribution with temperature of about 100 eV and drift velocity of about 2 {times} 10{sup 6} m/s. Cross-calibration of the EEA with the calorimeter provides a measurement of the fast electron perpendicular temperature of 30 eV, much lower than the parallel temperature, and is evidence that the kinetic dynamo mechanism (KDT) is not operative in MST. The fast electron current is found to match to the parallel current at the edge, and the fast electron density is about 4 {times} 10{sup 11} cm{sup {minus}3} independent of the ratio of the applied toroidal electric field to the critical electric field for runaways. First time measurements of magnetic fluctuation induced particle transport are reported. By correlating electron current fluctuations with radial magnetic fluctuations the transported flux of electrons is found to be negligible outside r/a{approximately}0.9, but rises the level of the expected total particle losses inside r/a{approximately}0.85. A comparison of the measured diffusion coefficient is made with the ausilinear stochastic diffusion coefficient. Evidence exists that the reduction of the transport is due to the presence of a radial ambipolar electric field of magnitude 500 V/m, that acts to equilibrate the ion and electron transport rates. The convective energy transport associated with the measured particle transport is large enough to account for the observed magnetic fluctuation induced energy transport in MST.

  2. Ion current rectification inversion in conic nanopores: nonequilibrium ion transport biased by ion selectivity and spatial asymmetry.

    PubMed

    Yan, Yu; Wang, Lin; Xue, Jianming; Chang, Hsueh-Chia

    2013-01-28

    We show both theoretically and experimentally that the ion-selectivity of a conic nanopore, as defined by a normalized density of the surface charge, significantly affects ion current rectification across the pore. For weakly selective negatively charged pores, intra-pore ion transport controls the current and internal ion enrichment/depletion at positive/reverse biased voltage (current enters/leaves through the tip, respectively), which is responsible for current rectification. For strongly selective negatively charged pores under positive bias, the current can be reduced by external field focusing and concentration depletion at the tip at low ionic strengths and high voltages, respectively. These external phenomena produce a rectification inversion for highly selective pores at high (low) voltage (ionic strength). With an asymptotic analysis of the intra-pore and external ion transport, we derive simple scaling laws to quantitatively capture empirical and numerical data for ion current rectification and rectification inversion of conic nanopores.

  3. Non-nuclear Electron Transport Channels in Hollow Molecules

    SciTech Connect

    Zhao, Jin; Petek, Hrvoje

    2014-08-15

    Electron transport in inorganic semiconductors and metals occurs through delocalized bands formed by overlapping electron orbitals. Strong correlation of electronic wave functions with the ionic cores couples the electron and lattice motions, leading to efficient interaction and scattering that degrades coherent charge transport. By contrast, unoccupied electronic states at energies near the vacuum level with diffuse molecular orbitals may form nearly-free-electron bands with density maxima in non-nuclear interstitial voids, which are subject to weaker electron-phonon interaction. The position of such bands typically above the frontier orbitals, however, renders them unstable with respect to electronic interband relaxation and therefore unsuitable for charge transport. Through electronic-structure calculations, we engineer stable, non-nuclear, nearly-free-electron conduction channels in low-dimensional molecular materials by tailoring their electrostatic and polarization potentials. We propose quantum structures of graphane-derived Janus molecular sheets with spatially isolated conducting and insulating regions that potentially exhibit emergent electronic properties, as a paradigm for molecular-scale non-nuclear charge conductors; we also describe tuning of their electronic properties by application of external fields and calculate their electron–acoustic-phonon interaction.

  4. Nonequilibrium superconducting detectors

    NASA Astrophysics Data System (ADS)

    Cristiano, R.; Ejrnaes, M.; Esposito, E.; Lisitskyi, M. P.; Nappi, C.; Pagano, S.; Perez de Lara, D.

    2006-03-01

    Nonequilibrium superconducting detectors exploit the early stages of the energy down cascade which occur after the absorption of radiation. They operate on a short temporal scale ranging from few microseconds down to tens of picoseconds. In such a way they provide fast counting capability, high time discrimination and also, for some devices, energy sensitivity. Nonequilibrium superconducting detectors are developed for their use both in basic science and in practical applications for detection of single photons or single ionized macromolecules. In this paper we consider two devices: distributed readout imaging detectors (DROIDs) based on superconducting tunnel junctions (STJs), which are typically used for high-speed energy spectroscopy applications, and hot-electron superconductive detectors (HESDs), which are typically used as fast counters and time discriminators. Implementation of the DROID geometry to use a single superconductor is discussed. Progress in the fabrication technology of NbN nanostructured HESDs is presented. The two detectors share the high sensitivity that makes them able to efficiently detect even single photons down to infrared energy.

  5. A non-equilibrium model for soil heating and moisture transport during extreme surface heating: the soil (heat-moisture-vapor) HMV-Model Version 1

    NASA Astrophysics Data System (ADS)

    Massman, W. J.

    2015-11-01

    Increased use of prescribed fire by land managers and the increasing likelihood of wildfires due to climate change require an improved modeling capability of extreme heating of soils during fires. This issue is addressed here by developing and testing the soil (heat-moisture-vapor) HMV-model, a 1-D (one-dimensional) non-equilibrium (liquid-vapor phase change) model of soil evaporation that simulates the coupled simultaneous transport of heat, soil moisture, and water vapor. This model is intended for use with surface forcing ranging from daily solar cycles to extreme conditions encountered during fires. It employs a linearized Crank-Nicolson scheme for the conservation equations of energy and mass and its performance is evaluated against dynamic soil temperature and moisture observations, which were obtained during laboratory experiments on soil samples exposed to surface heat fluxes ranging between 10 000 and 50 000 W m-2. The Hertz-Knudsen equation is the basis for constructing the model's non-equilibrium evaporative source term. Some unusual aspects of the model that were found to be extremely important to the model's performance include (1) a dynamic (temperature and moisture potential dependent) condensation coefficient associated with the evaporative source term, (2) an infrared radiation component to the soil's thermal conductivity, and (3) a dynamic residual soil moisture. This last term, which is parameterized as a function of temperature and soil water potential, is incorporated into the water retention curve and hydraulic conductivity functions in order to improve the model's ability to capture the evaporative dynamics of the strongly bound soil moisture, which requires temperatures well beyond 150 °C to fully evaporate. The model also includes film flow, although this phenomenon did not contribute much to the model's overall performance. In general, the model simulates the laboratory-observed temperature dynamics quite well, but is less precise (but

  6. Nonequilibrium Green's function formulation of intersubband absorption for nonparabolic single-band effective mass Hamiltonian

    NASA Astrophysics Data System (ADS)

    Kolek, Andrzej

    2015-05-01

    The formulas are derived that enable calculations of intersubband absorption coefficient within nonequilibrium Green's function method applied to a single-band effective-mass Hamiltonian with the energy dependent effective mass. The derivation provides also the formulas for the virtual valence band components of the two-band Green's functions which can be used for more exact estimation of the density of states and electrons and more reliable treatment of electronic transport in unipolar n-type heterostructure semiconductor devices.

  7. Nonequilibrium Green's function formulation of intersubband absorption for nonparabolic single-band effective mass Hamiltonian

    SciTech Connect

    Kolek, Andrzej

    2015-05-04

    The formulas are derived that enable calculations of intersubband absorption coefficient within nonequilibrium Green's function method applied to a single-band effective-mass Hamiltonian with the energy dependent effective mass. The derivation provides also the formulas for the virtual valence band components of the two-band Green's functions which can be used for more exact estimation of the density of states and electrons and more reliable treatment of electronic transport in unipolar n-type heterostructure semiconductor devices.

  8. Electronic transport and lasing in microstructures

    SciTech Connect

    Lax, M.

    1992-01-01

    We consider the interaction of hot carriers with hot phonons in a quantum well. Transport is considered in the transverse direction and tunneling through the well barriers. Time-dependent transport effects down to the femto-second regime are included, as are strong and/or microwave fields, with negative resistance effects. Resonant tunneling assisted by phonon relaxation and infra-red radiation will be explored. The limitations on transmission of information due to partition noise, as influenced by the design of semiconductor feedback lasers will be considered. The use of light scattering and decision theory to detect shell-like aerosols is examined.

  9. Thermochemical nonequilibrium in atomic hydrogen at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Scott, R. K.

    1972-01-01

    A numerical study of the nonequilibrium flow of atomic hydrogen in a cascade arc was performed to obtain insight into the physics of the hydrogen cascade arc. A rigorous mathematical model of the flow problem was formulated, incorporating the important nonequilibrium transport phenomena and atomic processes which occur in atomic hydrogen. Realistic boundary conditions, including consideration of the wall electrostatic sheath phenomenon, were included in the model. The governing equations of the asymptotic region of the cascade arc were obtained by writing conservation of mass and energy equations for the electron subgas, an energy conservation equation for heavy particles and an equation of state. Finite-difference operators for variable grid spacing were applied to the governing equations and the resulting system of strongly coupled, stiff equations were solved numerically by the Newton-Raphson method.

  10. RHIC electron lens beam transport system design considerations

    SciTech Connect

    Gu, X.; Pikin, A.; Okamura, M.; Fischer, W.; Luo, Y.; Gupta, R.; Hock, J.; Jain, A.; Raparia, D.

    2010-10-01

    To apply head-on beam-beam compensation for RHIC, two electron lenses are designed and will be installed at IP10. Electron beam transport system is one of important subsystem, which is used to transport electron beam from electron gun side to collector side. This system should be able to change beam size inside superconducting magnet and control beam position with 5 mm in horizontal and vertical plane. Some other design considerations for this beam transport system are also reported in this paper. The head-on beam-beam effect is one of important nonlinear source in storage ring and linear colliders, which have limited the luminosity improvement of many colliders, such as SppS, Tevatron and RHIC. In order to enhance the performance of colliders, beam-beam effects can be compensated with direct space charge compensation, indirect space charge compensation or betatron phase cancellation scheme. Like other colliders, indirect space charge compensation scheme (Electron Lens) was also proposed for Relativistic Heavy Ion Collider (RHIC) beam-beam compensation at Brookhaven National Laboratory. The two similar electron lenses are located in IR10 between the DX magnets. One RHIC electron lens consists of one DC electron gun, one superconducting magnet, one electron collector and beam transport system.

  11. Energy-filtered cold electron transport at room temperature

    PubMed Central

    Bhadrachalam, Pradeep; Subramanian, Ramkumar; Ray, Vishva; Ma, Liang-Chieh; Wang, Weichao; Kim, Jiyoung; Cho, Kyeongjae; Koh, Seong Jin

    2014-01-01

    Fermi-Dirac electron thermal excitation is an intrinsic phenomenon that limits functionality of various electron systems. Efforts to manipulate electron thermal excitation have been successful when the entire system is cooled to cryogenic temperatures, typically <1 K. Here we show that electron thermal excitation can be effectively suppressed at room temperature, and energy-suppressed electrons, whose energy distribution corresponds to an effective electron temperature of ~45 K, can be transported throughout device components without external cooling. This is accomplished using a discrete level of a quantum well, which filters out thermally excited electrons and permits only energy-suppressed electrons to participate in electron transport. The quantum well (~2 nm of Cr2O3) is formed between source (Cr) and tunnelling barrier (SiO2) in a double-barrier-tunnelling-junction structure having a quantum dot as the central island. Cold electron transport is detected from extremely narrow differential conductance peaks in electron tunnelling through CdSe quantum dots, with full widths at half maximum of only ~15 mV at room temperature. PMID:25204839

  12. Signatures of the electronic nature of pairing in high-T(c) superconductors obtained by non-equilibrium boson spectroscopy.

    PubMed

    Krasnov, Vladimir M; Katterwe, Sven-Olof; Rydh, Andreas

    2013-01-01

    Understanding the pairing mechanism that gives rise to high-temperature superconductivity is one of the longest-standing problems of condensed-matter physics. Almost three decades after its discovery, even the question of whether or not phonons are involved remains a point of contention to some. Here we describe a technique for determining the spectra of bosons generated during the formation of Cooper pairs on recombination of hot electrons as they tunnel between the layers of a cuprate superconductor. The results obtained indicate that the bosons that mediate pairing decay over micrometre-scale distances and picosecond timescales, implying that they propagate at a speed of around 10⁶ m s⁻¹. This value is more than two orders of magnitude greater than the phonon propagation speed but close to Fermi velocity for electrons, suggesting that the pairing mechanism is mediated by unconventional repulsive electron-electron, rather than attractive electron-phonon, interactions. PMID:24336159

  13. Influence of nonequilibrium lipid transport, membrane compartmentalization, and membrane proteins on the lateral organization of the plasma membrane

    NASA Astrophysics Data System (ADS)

    Fan, Jun; Sammalkorpi, Maria; Haataja, Mikko

    2010-01-01

    Compositional lipid domains (lipid rafts) in plasma membranes are believed to be important components of many cellular processes. The mechanisms by which cells regulate the sizes, lifetimes, and spatial localization of these domains are rather poorly understood at the moment. We propose a robust mechanism for the formation of finite-sized lipid raft domains in plasma membranes, the competition between phase separation in an immiscible lipid system and active cellular lipid transport processes naturally leads to the formation of such domains. Simulations of a continuum model reveal that the raft size distribution is broad and the average raft size is strongly dependent on the rates of cellular and interlayer lipid transport processes. We demonstrate that spatiotemporal variations in the recycling may enable the cell to localize larger raft aggregates at specific parts along the membrane. Moreover, we show that membrane compartmentalization may further facilitate spatial localization of the raft domains. Finally, we demonstrate that local interactions with immobile membrane proteins can spatially localize the rafts and lead to further clustering.

  14. Computer modeling of electron and proton transport in chloroplasts.

    PubMed

    Tikhonov, Alexander N; Vershubskii, Alexey V

    2014-07-01

    Photosynthesis is one of the most important biological processes in biosphere, which provides production of organic substances from atmospheric CO2 and water at expense of solar energy. In this review, we contemplate computer models of oxygenic photosynthesis in the context of feedback regulation of photosynthetic electron transport in chloroplasts, the energy-transducing organelles of the plant cell. We start with a brief overview of electron and proton transport processes in chloroplasts coupled to ATP synthesis and consider basic regulatory mechanisms of oxygenic photosynthesis. General approaches to computer simulation of photosynthetic processes are considered, including the random walk models of plastoquinone diffusion in thylakoid membranes and deterministic approach to modeling electron transport in chloroplasts based on the mass action law. Then we focus on a kinetic model of oxygenic photosynthesis that includes key stages of the linear electron transport, alternative pathways of electron transfer around photosystem I (PSI), transmembrane proton transport and ATP synthesis in chloroplasts. This model includes different regulatory processes: pH-dependent control of the intersystem electron transport, down-regulation of photosystem II (PSII) activity (non-photochemical quenching), the light-induced activation of the Bassham-Benson-Calvin (BBC) cycle. The model correctly describes pH-dependent feedback control of electron transport in chloroplasts and adequately reproduces a variety of experimental data on induction events observed under different experimental conditions in intact chloroplasts (variations of CO2 and O2 concentrations in atmosphere), including a complex kinetics of P700 (primary electron donor in PSI) photooxidation, CO2 consumption in the BBC cycle, and photorespiration. Finally, we describe diffusion-controlled photosynthetic processes in chloroplasts within the framework of the model that takes into account complex architecture of

  15. Study of Electron Transport and Amplification in Diamond

    SciTech Connect

    Ben-Zvi, Ilan; Muller, Erik

    2015-01-05

    The development of the Diamond Amplified Photocathode (DAP) has produced significant results under our previous HEP funded efforts both on the fabrication of working devices and the understanding of the underlying physics governing its performance. The results presented here substantiate the use of diamond as both a secondary electron amplifier for high-brightness, high-average-current electron sources and as a photon and particle detector in harsh radiation environments. Very high average current densities (>10A/cm2) have been transported through diamond material. The transport has been measured as a function of incident photon energy and found to be in good agreement with theoretical models. Measurements of the charge transport for photon energies near the carbon K-edge (290 eV for sp3 bonded carbon) have provided insight into carrier loss due to diffusion; modeling of this aspect of charge transport is underway. The response of diamond to nanosecond x-ray pulses has been measured; in this regime the charge transport is as expected. Electron emission from hydrogenated diamond has been measured using both electron and x-ray generated carriers; a gain of 178 has been observed for electron-generated carriers. The energy spectrum of the emitted electrons has been measured, providing insight into the electron affinity and ultimately the thermal emittance. The origin of charge trapping in diamond has been investigated for both bulk and surface trapping

  16. Electron transport in one-dimensional plasmas

    SciTech Connect

    Wienke, B.R.

    1983-11-01

    A one-dimensional, multigroup, discrete ordinates technique for computing electron energy deposition in plasmas is detailed. The Fokker-Planck collision operator is employed in the continuous approximation and electric fields (considered external) are included in the equation. Bremsstrahlung processes are not treated. Comparisons with analytic and Monte Carlo results are given. Fits to deposition profiles and energy scaling are proposed and discussed for monoenergetic and Maxwellian sources in the range, 0 to 150 keV, with and without uniform fields. The techniques employed to track electrons are generally useful in situations where the background plasma temperature is an order of magnitude smaller than the electron energy and collective plasma effects are negligible. We have used the approach successfully in laser pellet implosion applications.

  17. Conditioner for a helically transported electron beam

    SciTech Connect

    Wang, C.

    1992-05-01

    The kinetic theory is developed to investigate a conditioner for a helically imported electron beam. Linear expressions for axial velocity spread are derived. Numerical simulation is used to check the theoretical results and examine nonlinear aspects of the conditioning process. The results show that in the linear regime the action of the beam conditioner on a pulsed beam mainly depends on the phase at which the beam enters the conditioner and depends only slightly on the operating wavelength. In the nonlinear regime, however, the action of the conditioner strongly depends on the operating wavelength and only slightly upon the entrance phase. For a properly chosen operating wavelength, a little less than the electron`s relativistic cyclotron wavelength, the conditioner can decrease the axial velocity spread of a pulsed beam down to less than one-third of its initial value.

  18. Coherent electron transport in a helical nanotube

    NASA Astrophysics Data System (ADS)

    Liang, Guo-Hua; Wang, Yong-Long; Du, Long; Jiang, Hua; Kang, Guang-Zhen; Zong, Hong-Shi

    2016-09-01

    The quantum dynamics of carriers bound to helical tube surfaces is investigated in a thin-layer quantization scheme. By numerically solving the open-boundary Schrödinger equation in curvilinear coordinates, geometric effect on the coherent transmission spectra is analysed in the case of single propagating mode as well as multimode. It is shown that, the coiling endows the helical nanotube with different transport properties from a bent cylindrical surface. Fano resonance appears as a purely geometric effect in the conductance, the corresponding energy of quasibound state is obviously influenced by the torsion and length of the nanotube. We also find new plateaus in the conductance. The transport of double-degenerate mode in this geometry is reminiscent of the Zeeman coupling between the magnetic field and spin angular momentum in quasi-one-dimensional structure.

  19. A Deterministic Transport Code for Space Environment Electrons

    NASA Technical Reports Server (NTRS)

    Nealy, John E.; Chang, C. K.; Norman, Ryan B.; Blattnig, Steve R.; Badavi, Francis F.; Adamczyk, Anne M.

    2010-01-01

    A deterministic computational procedure has been developed to describe transport of space environment electrons in various shield media. This code is an upgrade and extension of an earlier electron code. Whereas the former code was formulated on the basis of parametric functions derived from limited laboratory data, the present code utilizes well established theoretical representations to describe the relevant interactions and transport processes. The shield material specification has been made more general, as have the pertinent cross sections. A combined mean free path and average trajectory approach has been used in the transport formalism. Comparisons with Monte Carlo calculations are presented.

  20. Neoclassical electron transport in tokamaks with neutral-beam injection

    SciTech Connect

    Helander, P.; Akers, R.J.

    2005-04-15

    The collisional interaction between neutral-beam ions and bulk plasma electrons leads to convective transport of particles and energy similar to the well-known Ware pinch. These transport fluxes are calculated, and it is found that the particle flux is outward when the neutral beams are in the same direction as the plasma current and inward otherwise, while the opposite holds for the electron heat transport. This effectively shifts the neutral-beam fueling profile approximately one fast-ion banana width outward during coinjection and inward during counterinjection, and could help to explain why very different plasma behavior is sometimes observed when the direction of the plasma current is reversed.

  1. Ghost transmission: How large basis sets can make electron transport calculations worse

    SciTech Connect

    Herrmann, Carmen; Solomon, Gemma C.; Subotnik, Joseph E.; Mujica, Vladimiro; Ratner, Mark A.

    2010-01-01

    The Landauer approach has proven to be an invaluable tool for calculating the electron transport properties of single molecules, especially when combined with a nonequilibrium Green’s function approach and Kohn–Sham density functional theory. However, when using large nonorthogonal atom-centered basis sets, such as those common in quantum chemistry, one can find erroneous results if the Landauer approach is applied blindly. In fact, basis sets of triple-zeta quality or higher sometimes result in an artificially high transmission and possibly even qualitatively wrong conclusions regarding chemical trends. In these cases, transport persists when molecular atoms are replaced by basis functions alone (“ghost atoms”). The occurrence of such ghost transmission is correlated with low-energy virtual molecular orbitals of the central subsystem and may be interpreted as a biased and thus inaccurate description of vacuum transmission. An approximate practical correction scheme is to calculate the ghost transmission and subtract it from the full transmission. As a further consequence of this study, it is recommended that sensitive molecules be used for parameter studies, in particular those whose transmission functions show antiresonance features such as benzene-based systems connected to the electrodes in meta positions and other low-conducting systems such as alkanes and silanes.

  2. Photon-assisted electronic and spin transport in a junction containing precessing molecular spin

    NASA Astrophysics Data System (ADS)

    Filipović, Milena; Belzig, Wolfgang

    2016-02-01

    We study the ac charge and -spin transport through an orbital of a magnetic molecule with spin precessing in a constant magnetic field. We assume that the source and drain contacts have time-dependent chemical potentials. We employ the Keldysh nonequilibrium Green's functions method to calculate the spin and charge currents to linear order in the time-dependent potentials. The molecular and electronic spins are coupled via exchange interaction. The time-dependent molecular spin drives inelastic transitions between the molecular quasienergy levels, resulting in a rich structure in the transport characteristics. The time-dependent voltages allow us to reveal the internal precession time scale (the Larmor frequency) by a dc conductance measurement if the ac frequency matches the Larmor frequency. In the low-ac-frequency limit the junction resembles a classical electric circuit. Furthermore, we show that the setup can be used to generate dc-spin currents, which are controlled by the molecular magnetization direction and the relative phases between the Larmor precession and the ac voltage.

  3. Transport of secondary electrons and reactive species in ion tracks

    NASA Astrophysics Data System (ADS)

    Surdutovich, Eugene; Solov'yov, Andrey V.

    2015-08-01

    The transport of reactive species brought about by ions traversing tissue-like medium is analysed analytically. Secondary electrons ejected by ions are capable of ionizing other molecules; the transport of these generations of electrons is studied using the random walk approximation until these electrons remain ballistic. Then, the distribution of solvated electrons produced as a result of interaction of low-energy electrons with water molecules is obtained. The radial distribution of energy loss by ions and secondary electrons to the medium yields the initial radial dose distribution, which can be used as initial conditions for the predicted shock waves. The formation, diffusion, and chemical evolution of hydroxyl radicals in liquid water are studied as well. COST Action Nano-IBCT: Nano-scale Processes Behind Ion-Beam Cancer Therapy.

  4. Catalytic photoinduced electron transport across a lipid bilayer mediated by a membrane-soluble electron relay.

    PubMed

    Limburg, B; Bouwman, E; Bonnet, S

    2015-12-14

    Unidirectional photocatalytic electron transfer from a hydrophilic electron donor encapsulated in the interior of a liposome, to a hydrophilic electron acceptor on the other side of the membrane, has been achieved using the simple membrane-soluble electron relay 1-methoxy-N-methylphenazinium (MMP(+)). The total amount of photoproduct (>140 nmol) exceeds the number of moles of MMP(+) present (125 nmol), thus showing that the transport of electrons is catalytic.

  5. Electron Trapping and Charge Transport by Large Amplitude Whistlers

    NASA Technical Reports Server (NTRS)

    Kellogg, P. J.; Cattell, C. A.; Goetz, K.; Monson, S. J.; Wilson, L. B., III

    2010-01-01

    Trapping of electrons by magnetospheric whistlers is investigated using data from the Waves experiment on Wind and the S/WAVES experiment on STEREO. Waveforms often show a characteristic distortion which is shown to be due to electrons trapped in the potential of the electrostatic part of oblique whistlers. The density of trapped electrons is significant, comparable to that of the unperturbed whistler. Transport of these trapped electrons to new regions can generate potentials of several kilovolts, Trapping and the associated potentials may play an important role in the acceleration of Earth's radiation belt electrons.

  6. A Deterministic Computational Procedure for Space Environment Electron Transport

    NASA Technical Reports Server (NTRS)

    Nealy, John E.; Chang, C. K.; Norman, Ryan B.; Blattnig, Steve R.; Badavi, Francis F.; Adamcyk, Anne M.

    2010-01-01

    A deterministic computational procedure for describing the transport of electrons in condensed media is formulated to simulate the effects and exposures from spectral distributions typical of electrons trapped in planetary magnetic fields. The primary purpose for developing the procedure is to provide a means of rapidly performing numerous repetitive transport calculations essential for electron radiation exposure assessments for complex space structures. The present code utilizes well-established theoretical representations to describe the relevant interactions and transport processes. A combined mean free path and average trajectory approach is used in the transport formalism. For typical space environment spectra, several favorable comparisons with Monte Carlo calculations are made which have indicated that accuracy is not compromised at the expense of the computational speed.

  7. Electron transport through nuclear pasta in magnetized neutron stars

    NASA Astrophysics Data System (ADS)

    Yakovlev, D. G.

    2015-10-01

    We present a simple model for electron transport in a possible layer of exotic nuclear clusters (in the so-called nuclear pasta layer) between the crust and liquid core of a strongly magnetized neutron star. The electron transport there can be strongly anisotropic and gyrotropic. The anisotropy is produced by different electron effective collision frequencies along and across local symmetry axis in domains of exotic ordered nuclear clusters and by complicated effects of the magnetic field. We also calculate averaged kinetic coefficients in case local domains are freely oriented. Possible applications of the obtained results and open problems are outlined.

  8. Multidimensional electron-photon transport with standard discrete ordinates codes

    SciTech Connect

    Drumm, C.R.

    1995-12-31

    A method is described for generating electron cross sections that are compatible with standard discrete ordinates codes without modification. There are many advantages of using an established discrete ordinates solver, e.g. immediately available adjoint capability. Coupled electron-photon transport capability is needed for many applications, including the modeling of the response of electronics components to space and man-made radiation environments. The cross sections have been successfully used in the DORT, TWODANT and TORT discrete ordinates codes. The cross sections are shown to provide accurate and efficient solutions to certain multidimensional electronphoton transport problems.

  9. Treating electron transport in MCNP{sup trademark}

    SciTech Connect

    Hughes, H.G.

    1996-12-31

    The transport of electrons and other charged particles is fundamentally different from that of neutrons and photons. A neutron, in aluminum slowing down from 0.5 MeV to 0.0625 MeV will have about 30 collisions; a photon will have fewer than ten. An electron with the same energy loss will undergo 10{sup 5} individual interactions. This great increase in computational complexity makes a single- collision Monte Carlo approach to electron transport unfeasible for many situations of practical interest. Considerable theoretical work has been done to develop a variety of analytic and semi-analytic multiple-scattering theories for the transport of charged particles. The theories used in the algorithms in MCNP are the Goudsmit-Saunderson theory for angular deflections, the Landau an theory of energy-loss fluctuations, and the Blunck-Leisegang enhancements of the Landau theory. In order to follow an electron through a significant energy loss, it is necessary to break the electron`s path into many steps. These steps are chosen to be long enough to encompass many collisions (so that multiple-scattering theories are valid) but short enough that the mean energy loss in any one step is small (for the approximations in the multiple-scattering theories). The energy loss and angular deflection of the electron during each step can then be sampled from probability distributions based on the appropriate multiple- scattering theories. This subsumption of the effects of many individual collisions into single steps that are sampled probabilistically constitutes the ``condensed history`` Monte Carlo method. This method is exemplified in the ETRAN series of electron/photon transport codes. The ETRAN codes are also the basis for the Integrated TIGER Series, a system of general-purpose, application-oriented electron/photon transport codes. The electron physics in MCNP is similar to that of the Integrated TIGER Series.

  10. Theoretical study of particle transport in electron internal transport barriers in TCV

    SciTech Connect

    Fable, E.; Sauter, O.; Marinoni, A.; Zucca, C.

    2006-11-30

    Previous results from the analysis of fully non inductively sustained electron internal transport barriers (eITBs) in TCV show that a strong coupling exists between electron temperature and density profiles inside the barrier. A phenomenology that is completely different from the standard L-mode is observed . New experimental results assess transient phases to calculate particle convection and diffusion coefficients, allowing also to discuss the role of neoclassical transport. Gyrokinetic and gyrofluid analysis of steady-state eITBs provide tools to understand the mechanism that drive the observed density peaking in advanced scenarios with internal transport barriers and dominant electron heating.

  11. Electronic transport in ultranarrow zigzag graphene nanoribbons with edge disorders

    NASA Astrophysics Data System (ADS)

    Liu, Y. L.; Xu, G. L.; Zhang, X. W.

    2016-11-01

    We investigate the transport properties of ultranarrow zigzag graphene nanoribbons (ZGNRs) with edge vacancies by using recursive Green's function method. Transport gaps are observed when the vacancies are distributed uniformly on both sides. In addition, ZGNRs with symmetrical structure have much larger transport gaps than the asymmetrical ones. This phenomenon results from the different band structures between them. We also calculate the conductance of ZGNRs with edge vacancies distributed randomly. It shows that transport gaps decrease exponentially with the increasing of ZGNRs width because the symmetry of structure is broken by the random edge vacancies. Localization analysis reveals that the electronic transport channels around Fermi energy are blockaded so that they are not responsible for electron transmission.

  12. Visualizing the non-equilibrium dynamics of photoinduced intramolecular electron transfer with femtosecond X-ray pulses

    SciTech Connect

    Canton, Sophie E.; Kjær, Kasper S.; Vankó, György; van Driel, Tim B.; Adachi, Shin -ichi; Bordage, Amélie; Bressler, Christian; Chabera, Pavel; Christensen, Morten; Dohn, Asmus O.; Galler, Andreas; Gawelda, Wojciech; Gosztola, David; Haldrup, Kristoffer; Harlang, Tobias; Liu, Yizhu; Møller, Klaus B.; Németh, Zoltán; Nozawa, Shunsuke; Pápai, Mátyás; Sato, Tokushi; Sato, Takahiro; Suarez-Alcantara, Karina; Togashi, Tadashi; Tono, Kensuke; Uhlig, Jens; Vithanage, Dimali A.; Wärnmark, Kenneth; Yabashi, Makina; Zhang, Jianxin; Sundström, Villy; Nielsen, Martin M.

    2015-03-02

    Ultrafast photoinduced electron transfer preceding energy equilibration still poses many experimental and conceptual challenges to the optimization of photoconversion since an atomic-scale description has so far been beyond reach. Here we combine femtosecond transient optical absorption spectroscopy with ultrafast X-ray emission spectroscopy and diffuse X-ray scattering at the SACLA facility to track the non-equilibrated electronic and structural dynamics within a bimetallic donor–acceptor complex that contains an optically dark centre. Exploiting the 100-fold increase in temporal resolution as compared with storage ring facilities, these measurements constitute the first X-ray-based visualization of a non-equilibrated intramolecular electron transfer process over large interatomic distances. Thus experimental and theoretical results establish that mediation through electronically excited molecular states is a key mechanistic feature. The present study demonstrates the extensive potential of femtosecond X-ray techniques as diagnostics of non-adiabatic electron transfer processes in synthetic and biological systems, and some directions for future studies, are outlined.

  13. Visualizing the non-equilibrium dynamics of photoinduced intramolecular electron transfer with femtosecond X-ray pulses

    DOE PAGESBeta

    Canton, Sophie E.; Kjær, Kasper S.; Vankó, György; van Driel, Tim B.; Adachi, Shin -ichi; Bordage, Amélie; Bressler, Christian; Chabera, Pavel; Christensen, Morten; Dohn, Asmus O.; et al

    2015-03-02

    Ultrafast photoinduced electron transfer preceding energy equilibration still poses many experimental and conceptual challenges to the optimization of photoconversion since an atomic-scale description has so far been beyond reach. Here we combine femtosecond transient optical absorption spectroscopy with ultrafast X-ray emission spectroscopy and diffuse X-ray scattering at the SACLA facility to track the non-equilibrated electronic and structural dynamics within a bimetallic donor–acceptor complex that contains an optically dark centre. Exploiting the 100-fold increase in temporal resolution as compared with storage ring facilities, these measurements constitute the first X-ray-based visualization of a non-equilibrated intramolecular electron transfer process over large interatomic distances.more » Thus experimental and theoretical results establish that mediation through electronically excited molecular states is a key mechanistic feature. The present study demonstrates the extensive potential of femtosecond X-ray techniques as diagnostics of non-adiabatic electron transfer processes in synthetic and biological systems, and some directions for future studies, are outlined.« less

  14. Visualizing the non-equilibrium dynamics of photoinduced intramolecular electron transfer with femtosecond X-ray pulses

    PubMed Central

    Canton, Sophie E.; Kjær, Kasper S.; Vankó, György; van Driel, Tim B.; Adachi, Shin-ichi; Bordage, Amélie; Bressler, Christian; Chabera, Pavel; Christensen, Morten; Dohn, Asmus O.; Galler, Andreas; Gawelda, Wojciech; Gosztola, David; Haldrup, Kristoffer; Harlang, Tobias; Liu, Yizhu; Møller, Klaus B.; Németh, Zoltán; Nozawa, Shunsuke; Pápai, Mátyás; Sato, Tokushi; Sato, Takahiro; Suarez-Alcantara, Karina; Togashi, Tadashi; Tono, Kensuke; Uhlig, Jens; Vithanage, Dimali A.; Wärnmark, Kenneth; Yabashi, Makina; Zhang, Jianxin; Sundström, Villy; Nielsen, Martin M.

    2015-01-01

    Ultrafast photoinduced electron transfer preceding energy equilibration still poses many experimental and conceptual challenges to the optimization of photoconversion since an atomic-scale description has so far been beyond reach. Here we combine femtosecond transient optical absorption spectroscopy with ultrafast X-ray emission spectroscopy and diffuse X-ray scattering at the SACLA facility to track the non-equilibrated electronic and structural dynamics within a bimetallic donor–acceptor complex that contains an optically dark centre. Exploiting the 100-fold increase in temporal resolution as compared with storage ring facilities, these measurements constitute the first X-ray-based visualization of a non-equilibrated intramolecular electron transfer process over large interatomic distances. Experimental and theoretical results establish that mediation through electronically excited molecular states is a key mechanistic feature. The present study demonstrates the extensive potential of femtosecond X-ray techniques as diagnostics of non-adiabatic electron transfer processes in synthetic and biological systems, and some directions for future studies, are outlined. PMID:25727920

  15. Conformation-controlled electron transport in single-molecule junctions containing oligo(phenylene ethynylene) derivatives.

    PubMed

    Wang, Le-Jia; Yong, Ai; Zhou, Kai-Ge; Tan, Lin; Ye, Jian; Wu, Guo-Ping; Xu, Zhu-Guo; Zhang, Hao-Li

    2013-08-01

    Understanding the relationships between the molecular structure and electronic transport characteristics of single-molecule junctions is of fundamental and technological importance for future molecular electronics. Herein, we report a combined experimental and theoretical study on the single-molecule conductance of a series of oligo(phenylene ethynylene) (OPE) molecular wires, which consist of two phenyl-ethynyl-phenyl π units with different dihedral angles. The molecular conductance was studied by scanning tunneling microscopy (STM)-based break-junction techniques under different conditions, including variable temperature and bias potential, which suggested that a coherent tunneling mechanism takes place in the OPE molecular wires with a length of 2.5 nm. The conductance of OPE molecular junctions are strongly affected by the coupling strength between the two π systems, which can be tuned by controlling their intramolecular conformation. A cos(2)θ dependence was revealed between the molecular conductance and dihedral angles between the two conjugated units. Theoretical investigations on the basis of density functional theory and nonequilibrium Green's functions (NEGF) gave consistent results with the experimental observations and provided insights into the conformation-dominated molecular conductance.

  16. First principles study on the electronic transport properties of C60 and B80 molecular bridges

    NASA Astrophysics Data System (ADS)

    Zheng, X. H.; Hao, H.; Lan, J.; Wang, X. L.; Shi, X. Q.; Zeng, Z.

    2014-08-01

    The electronic transport properties of molecular bridges constructed by C60 and B80 molecules which have the same symmetry are investigated by first principles calculations combined with a non-equilibrium Green's function technique. It is found that, like C60, monomer B80 is a good conductor arising from the charge transfer from the leads to the molecule, while the dimer (B80)2 and (C60)2 are both insulators due to the potential barrier formed at the molecule-molecule interface. Our further study shows that, although both the homogeneous dimer (B80)2 and (C60)2 display poor conductivity, the heterogeneous dimer B80C60 shows a very high conductance as a result from the decreased HOMO-LUMO gap and the excess charge redistribution. Finally, we find that the conductivity of both (B80)2 and (C60)2 can be significantly improved by electron doping, for example, by doping C in (B80)2 and doping N in (C60)2.

  17. Study of electron transport in hydrocarbon gases

    NASA Astrophysics Data System (ADS)

    Hasegawa, H.; Date, H.

    2015-04-01

    The drift velocity and the effective ionization coefficient of electrons in the organic gases, C2H2, C2H4, C2H6, CH3OH, C2H5OH, C6H6, and C6H5CH3, have been measured over relatively wide ranges of density-reduced electric fields (E/N) at room temperature (around 300 K). The drift velocity was measured, based on the arrival-time spectra of electrons by using a double-shutter drift tube over the E/N range from 300 to 2800 Td, and the effective ionization coefficient (α - η) was determined by the steady-state Townsend method from 150 to 3000 Td. Whenever possible, these parameters were compared with those available in the literature. It has been shown that the swarm parameters for these gases have specific tendencies, depending on their molecular configurations.

  18. Conditioner for a helically transported electron beam

    SciTech Connect

    Wang, C.

    1992-05-01

    The kinetic theory is developed to investigate a conditioner for a helically imported electron beam. Linear expressions for axial velocity spread are derived. Numerical simulation is used to check the theoretical results and examine nonlinear aspects of the conditioning process. The results show that in the linear regime the action of the beam conditioner on a pulsed beam mainly depends on the phase at which the beam enters the conditioner and depends only slightly on the operating wavelength. In the nonlinear regime, however, the action of the conditioner strongly depends on the operating wavelength and only slightly upon the entrance phase. For a properly chosen operating wavelength, a little less than the electron's relativistic cyclotron wavelength, the conditioner can decrease the axial velocity spread of a pulsed beam down to less than one-third of its initial value.

  19. Nonequilibrium electronic phenomena and the chemical energy accommodation during heterogeneous recombination of atomic hydrogen on the manganese doped willemite

    NASA Astrophysics Data System (ADS)

    Grankin, D. V.; Grankin, V. P.; Styrov, V. V.; Sushchikh, M.

    2016-03-01

    The surface chemiluminescence of Zn2SiO4-Mn phosphor (λmax = 525 nm) has been studied under excitation by exoergic interaction of H-atoms with its surface. We have found that the pre-irradiation of the Zn2SiO4-Mn by UV light results in the transient increase in the luminescence intensity by two orders of magnitude. On the other hand, deposition of Pd-nanoparticles on the surface leads to luminescence quenching. These two effects are associated with the energy accommodation in the gas-surface interaction via electronic channel by the filled electron traps of the insulating phosphor or by metallic electrons of the Pd-nanoparticles.

  20. Signatures of the electronic nature of pairing in high-Tc superconductors obtained by non-equilibrium boson spectroscopy

    PubMed Central

    Krasnov, Vladimir M.; Katterwe, Sven-Olof; Rydh, Andreas

    2013-01-01

    Understanding the pairing mechanism that gives rise to high-temperature superconductivity is one of the longest-standing problems of condensed-matter physics. Almost three decades after its discovery, even the question of whether or not phonons are involved remains a point of contention to some. Here we describe a technique for determining the spectra of bosons generated during the formation of Cooper pairs on recombination of hot electrons as they tunnel between the layers of a cuprate superconductor. The results obtained indicate that the bosons that mediate pairing decay over micrometre-scale distances and picosecond timescales, implying that they propagate at a speed of around 106 m s−1. This value is more than two orders of magnitude greater than the phonon propagation speed but close to Fermi velocity for electrons, suggesting that the pairing mechanism is mediated by unconventional repulsive electron–electron, rather than attractive electron–phonon, interactions. PMID:24336159

  1. Comparison of equilibrium ohmic and nonequilibrium swarm models for monitoring conduction electron evolution in high-altitude EMP calculations

    DOE PAGESBeta

    Pusateri, Elise N.; Morris, Heidi E.; Nelson, Eric; Ji, Wei

    2016-10-17

    Here, atmospheric electromagnetic pulse (EMP) events are important physical phenomena that occur through both man-made and natural processes. Radiation-induced currents and voltages in EMP can couple with electrical systems, such as those found in satellites, and cause significant damage. Due to the disruptive nature of EMP, it is important to accurately predict EMP evolution and propagation with computational models. CHAP-LA (Compton High Altitude Pulse-Los Alamos) is a state-of-the-art EMP code that solves Maxwell inline images equations for gamma source-induced electromagnetic fields in the atmosphere. In EMP, low-energy, conduction electrons constitute a conduction current that limits the EMP by opposing themore » Compton current. CHAP-LA calculates the conduction current using an equilibrium ohmic model. The equilibrium model works well at low altitudes, where the electron energy equilibration time is short compared to the rise time or duration of the EMP. At high altitudes, the equilibration time increases beyond the EMP rise time and the predicted equilibrium ionization rate becomes very large. The ohmic model predicts an unphysically large production of conduction electrons which prematurely and abruptly shorts the EMP in the simulation code. An electron swarm model, which implicitly accounts for the time evolution of the conduction electron energy distribution, can be used to overcome the limitations exhibited by the equilibrium ohmic model. We have developed and validated an electron swarm model previously in Pusateri et al. (2015). Here we demonstrate EMP damping behavior caused by the ohmic model at high altitudes and show improvements on high-altitude, upward EMP modeling obtained by integrating a swarm model into CHAP-LA.« less

  2. Surface excitations in the modelling of electron transport for electron-beam-induced deposition experiments

    PubMed Central

    Valentí, Roser; Werner, Wolfgang S

    2015-01-01

    Summary The aim of the present overview article is to raise awareness of an essential aspect that is usually not accounted for in the modelling of electron transport for focused-electron-beam-induced deposition (FEBID) of nanostructures: Surface excitations are on the one hand responsible for a sizeable fraction of the intensity in reflection-electron-energy-loss spectra for primary electron energies of up to a few kiloelectronvolts and, on the other hand, they play a key role in the emission of secondary electrons from solids, regardless of the primary energy. In this overview work we present a general perspective of recent works on the subject of surface excitations and on low-energy electron transport, highlighting the most relevant aspects for the modelling of electron transport in FEBID simulations. PMID:26171301

  3. Dynamics of charge transfer: Rate processes formulated with nonequilibrium Green's functions

    SciTech Connect

    Yeganeh, Sina; Ratner, Mark A.; Mujica, Vladimiro

    2007-04-28

    The authors examine the connection between electron transport under bias in a junction and nonadiabatic intramolecular electron transfer (ET). It is shown that under certain assumptions it is possible to define a stationary current that allows the computation of the intramolecular transfer rate using the same formalism that is employed in the description of transport. They show that the nonequilibrium Green's function formalism of quantum transport can be used to calculate the ET rate. The formal connection between electron transport and electron transfer is made, and they work out the simple case of an electronic level coupled to a vibrational mode representing a thermal bath and show that the result is the same as expected from a Fermi golden rule treatment, and in the high-temperature limit yields the Marcus electron transfer theory. The usefulness of this alternative formulation of rates is discussed.

  4. Electron Transport in Graphene Nanoribbon Field-Effect Transistor under Bias and Gate Voltages: Isochemical Potential Approach.

    PubMed

    Yun, Jeonghun; Lee, Geunsik; Kim, Kwang S

    2016-07-01

    Zigzag graphene nanoribbon (zGNR) of narrow width has a moderate energy gap in its antiferromagnetic ground state. So far, first-principles electron transport calculations have been performed using nonequilibrium Green function (NEGF) method combined with density functional theory (DFT). However, the commonly practiced bottom-gate control has not been studied computationally due to the need to simulate an electron reservoir that fixes the chemical potential of electrons in the zGNR and electrodes. Here, we present the isochemical potential scheme to describe the top/back-gate effect using external potential. Then, we examine the change in electronic state under the modulation of chemical potential and the subsequent electron transport phenomena in zGNR transistor under substantial top-/back-gate and bias voltages. The gate potential can activate the device states resulting in a boosted current. This gate-controlled current-boosting could be utilized for designing novel zGNR field effect transistors (FETs). PMID:27299184

  5. Study of electron transport in hydrocarbon gases

    SciTech Connect

    Hasegawa, H.; Date, H.

    2015-04-07

    The drift velocity and the effective ionization coefficient of electrons in the organic gases, C{sub 2}H{sub 2}, C{sub 2}H{sub 4}, C{sub 2}H{sub 6}, CH{sub 3}OH, C{sub 2}H{sub 5}OH, C{sub 6}H{sub 6}, and C{sub 6}H{sub 5}CH{sub 3}, have been measured over relatively wide ranges of density-reduced electric fields (E/N) at room temperature (around 300 K). The drift velocity was measured, based on the arrival-time spectra of electrons by using a double-shutter drift tube over the E/N range from 300 to 2800 Td, and the effective ionization coefficient (α − η) was determined by the steady-state Townsend method from 150 to 3000 Td. Whenever possible, these parameters were compared with those available in the literature. It has been shown that the swarm parameters for these gases have specific tendencies, depending on their molecular configurations.

  6. Evidence for global electron transportation into the jovian inner magnetosphere.

    PubMed

    Yoshioka, K; Murakami, G; Yamazaki, A; Tsuchiya, F; Kimura, T; Kagitani, M; Sakanoi, T; Uemizu, K; Kasaba, Y; Yoshikawa, I; Fujimoto, M

    2014-09-26

    Jupiter's magnetosphere is a strong particle accelerator that contains ultrarelativistic electrons in its inner part. They are thought to be accelerated by whistler-mode waves excited by anisotropic hot electrons (>10 kiloelectron volts) injected from the outer magnetosphere. However, electron transportation in the inner magnetosphere is not well understood. By analyzing the extreme ultraviolet line emission from the inner magnetosphere, we show evidence for global inward transport of flux tubes containing hot plasma. High-spectral-resolution scanning observations of the Io plasma torus in the inner magnetosphere enable us to generate radial profiles of the hot electron fraction. It gradually decreases with decreasing radial distance, despite the short collisional time scale that should thermalize them rapidly. This indicates a fast and continuous resupply of hot electrons responsible for exciting the whistler-mode waves.

  7. Evidence for global electron transportation into the jovian inner magnetosphere.

    PubMed

    Yoshioka, K; Murakami, G; Yamazaki, A; Tsuchiya, F; Kimura, T; Kagitani, M; Sakanoi, T; Uemizu, K; Kasaba, Y; Yoshikawa, I; Fujimoto, M

    2014-09-26

    Jupiter's magnetosphere is a strong particle accelerator that contains ultrarelativistic electrons in its inner part. They are thought to be accelerated by whistler-mode waves excited by anisotropic hot electrons (>10 kiloelectron volts) injected from the outer magnetosphere. However, electron transportation in the inner magnetosphere is not well understood. By analyzing the extreme ultraviolet line emission from the inner magnetosphere, we show evidence for global inward transport of flux tubes containing hot plasma. High-spectral-resolution scanning observations of the Io plasma torus in the inner magnetosphere enable us to generate radial profiles of the hot electron fraction. It gradually decreases with decreasing radial distance, despite the short collisional time scale that should thermalize them rapidly. This indicates a fast and continuous resupply of hot electrons responsible for exciting the whistler-mode waves. PMID:25258073

  8. Evidence for global electron transportation into the jovian inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Yoshioka, K.; Murakami, G.; Yamazaki, A.; Tsuchiya, F.; Kimura, T.; Kagitani, M.; Sakanoi, T.; Uemizu, K.; Kasaba, Y.; Yoshikawa, I.; Fujimoto, M.

    2014-09-01

    Jupiter’s magnetosphere is a strong particle accelerator that contains ultrarelativistic electrons in its inner part. They are thought to be accelerated by whistler-mode waves excited by anisotropic hot electrons (>10 kiloelectron volts) injected from the outer magnetosphere. However, electron transportation in the inner magnetosphere is not well understood. By analyzing the extreme ultraviolet line emission from the inner magnetosphere, we show evidence for global inward transport of flux tubes containing hot plasma. High-spectral-resolution scanning observations of the Io plasma torus in the inner magnetosphere enable us to generate radial profiles of the hot electron fraction. It gradually decreases with decreasing radial distance, despite the short collisional time scale that should thermalize them rapidly. This indicates a fast and continuous resupply of hot electrons responsible for exciting the whistler-mode waves.

  9. Probing in Space and Time the Nuclear Motion Driven by Nonequilibrium Electronic Dynamics in Ultrafast Pumped N2.

    PubMed

    Ajay, J; Šmydke, J; Remacle, F; Levine, R D

    2016-05-19

    An ultrafast electronic excitation of N2 in the vacuum ultraviolet creates a nonstationary coherent linear superposition of interacting valence and Rydberg states resulting in a net oscillating dipole moment. There is therefore a linear response to an electrical field that can be queried by varying the time delay between the pump and a second optical probe pulse. Both the pump and probe pulses are included in our computation as part of the Hamiltonian, and the time-dependent wave function for both electronic and nuclear dynamics is computed using a grid representation for the internuclear coordinate. Even on an ultrafast time scale there are several processes that can be discerned beyond the expected coherence oscillations. In particular, the coupling between the excited valence and Rydberg states of the same symmetry is very evident and can be directly probed by varying the delay between pulse and probe. For quite a number of vibrations the nuclear motion does not dephase the electronic disequilibrium. However, the nuclear motion does modulate the dipolar response by taking the wave packet in and out of the Franck-Condon region and by its strong influence on the coupling of the Rydberg and valence states. A distinct isotope effect arises from the dependence of the interstate coupling on the nuclear mass.

  10. Dissipationless electron transport in photon-dressed nanostructures.

    PubMed

    Kibis, O V

    2011-09-01

    It is shown that the electron coupling to photons in field-dressed nanostructures can result in the ground electron-photon state with a nonzero electric current. Since the current is associated with the ground state, it flows without the Joule heating of the nanostructure and is nondissipative. Such a dissipationless electron transport can be realized in strongly coupled electron-photon systems with the broken time-reversal symmetry--particularly, in quantum rings and chiral nanostructures dressed by circularly polarized photons. PMID:21981519

  11. Optical spectroscopy of molecular junctions: Nonequilibrium Green's functions perspective

    NASA Astrophysics Data System (ADS)

    Gao, Yi; Galperin, Michael

    2016-05-01

    We consider optical spectroscopy of molecular junctions from the quantum transport perspective when radiation field is quantized and optical response of the system is simulated as photon flux. Using exact expressions for photon and electronic fluxes derived within the nonequilibrium Green function (NEGF) methodology and utilizing fourth order diagrammatic perturbation theory (PT) in molecular coupling to radiation field, we perform simulations employing realistic parameters. Results of the simulations are compared to the bare PT which is usually employed in studies on nonlinear optical spectroscopy to classify optical processes. We show that the bare PT violates conservation laws, while flux conserving NEGF formulation mixes optical processes.

  12. Optical spectroscopy of molecular junctions: Nonequilibrium Green's functions perspective.

    PubMed

    Gao, Yi; Galperin, Michael

    2016-05-01

    We consider optical spectroscopy of molecular junctions from the quantum transport perspective when radiation field is quantized and optical response of the system is simulated as photon flux. Using exact expressions for photon and electronic fluxes derived within the nonequilibrium Green function (NEGF) methodology and utilizing fourth order diagrammatic perturbation theory (PT) in molecular coupling to radiation field, we perform simulations employing realistic parameters. Results of the simulations are compared to the bare PT which is usually employed in studies on nonlinear optical spectroscopy to classify optical processes. We show that the bare PT violates conservation laws, while flux conserving NEGF formulation mixes optical processes. PMID:27155631

  13. Effect of dephasing on DNA sequencing via transverse electronic transport

    SciTech Connect

    Zwolak, Michael; Krems, Matt; Pershin, Yuriy V; Di Ventra, Massimiliano

    2009-01-01

    We study theoretically the effects of dephasing on DNA sequencing in a nanopore via transverse electronic transport. To do this, we couple classical molecular dynamics simulations with transport calculations using scattering theory. Previous studies, which did not include dephasing, have shown that by measuring the transverse current of a particular base multiple times, one can get distributions of currents for each base that are distinguishable. We introduce a dephasing parameter into transport calculations to simulate the effects of the ions and other fluctuations. These effects lower the overall magnitude of the current, but have little effect on the current distributions themselves. The results of this work further implicate that distinguishing DNA bases via transverse electronic transport has potential as a sequencing tool.

  14. Status of electron transport in MCNP{trademark}

    SciTech Connect

    Hughes, H.G.

    1997-10-01

    The latest version of MCNP, the Los Alamos Monte Carlo transport code, has now been officially released. A variety of new features are available in MCNP4B. Among these are differential operator perturbations, cross section plotting capabilities, enhanced diagnostics for transport in repeated structures and lattices, improved efficiency in distributed memory multiprocessing, corrected particle lifetime and lifespan estimators, and expanded software quality assurance procedures and testing, including testing of the multigroup Boltzmann Fokker Planck capability. New and improved cross section sets in the form of ENDF/B-VI evaluations have also been recently released and can be used in MCNP4B. Perhaps most significant for the interests of this special session, the electron transport algorithm has been improved, especially in the collisional energy loss straggling and the angular deflection treatments. In this paper, I shall concentrate on a fairly complete documentation of the current status of the electron transport methods in MCNP.

  15. Mitochondrial ROS Produced via Reverse Electron Transport Extend Animal Lifespan

    PubMed Central

    Scialò, Filippo; Sriram, Ashwin; Fernández-Ayala, Daniel; Gubina, Nina; Lõhmus, Madis; Nelson, Glyn; Logan, Angela; Cooper, Helen M.; Navas, Plácido; Enríquez, Jose Antonio; Murphy, Michael P.; Sanz, Alberto

    2016-01-01

    Summary Increased production of reactive oxygen species (ROS) has long been considered a cause of aging. However, recent studies have implicated ROS as essential secondary messengers. Here we show that the site of ROS production significantly contributes to their apparent dual nature. We report that ROS increase with age as mitochondrial function deteriorates. However, we also demonstrate that increasing ROS production specifically through respiratory complex I reverse electron transport extends Drosophila lifespan. Reverse electron transport rescued pathogenesis induced by severe oxidative stress, highlighting the importance of the site of ROS production in signaling. Furthermore, preventing ubiquinone reduction, through knockdown of PINK1, shortens lifespan and accelerates aging; phenotypes that are rescued by increasing reverse electron transport. These results illustrate that the source of a ROS signal is vital in determining its effects on cellular physiology and establish that manipulation of ubiquinone redox state is a valid strategy to delay aging. PMID:27076081

  16. Mitochondrial ROS Produced via Reverse Electron Transport Extend Animal Lifespan.

    PubMed

    Scialò, Filippo; Sriram, Ashwin; Fernández-Ayala, Daniel; Gubina, Nina; Lõhmus, Madis; Nelson, Glyn; Logan, Angela; Cooper, Helen M; Navas, Plácido; Enríquez, Jose Antonio; Murphy, Michael P; Sanz, Alberto

    2016-04-12

    Increased production of reactive oxygen species (ROS) has long been considered a cause of aging. However, recent studies have implicated ROS as essential secondary messengers. Here we show that the site of ROS production significantly contributes to their apparent dual nature. We report that ROS increase with age as mitochondrial function deteriorates. However, we also demonstrate that increasing ROS production specifically through respiratory complex I reverse electron transport extends Drosophila lifespan. Reverse electron transport rescued pathogenesis induced by severe oxidative stress, highlighting the importance of the site of ROS production in signaling. Furthermore, preventing ubiquinone reduction, through knockdown of PINK1, shortens lifespan and accelerates aging; phenotypes that are rescued by increasing reverse electron transport. These results illustrate that the source of a ROS signal is vital in determining its effects on cellular physiology and establish that manipulation of ubiquinone redox state is a valid strategy to delay aging.

  17. Nonequilibrium structural condition in the medical TiNi-based alloy surface layer treated by electron beam

    SciTech Connect

    Neiman, Aleksei A. Lotkov, Aleksandr I.; Meisner, Ludmila L. Semin, Viktor O.; Koval, Nikolai N.; Teresov, Anton D.

    2014-11-14

    The research is devoted to study the structural condition and their evolution from the surface to the depth of TiNi specimens treated by low-energy high-current electron beams with surface melting at a beam energy density E = 10 J/cm{sup 2}, number of pulses N = 10, and pulse duration τ = 50 μs. Determined thickness of the remelted layer, found that it has a layered structure in which each layer differs in phase composition and structural phase state. Refinement B2 phase lattice parameters in local areas showed the presence of strong inhomogeneous lattice strain.

  18. Progress in Simulating Turbulent Electron Thermal Transport in NSTX

    SciTech Connect

    Guttenfelder, Walter; Kaye, S. M.; Ren, Y.; Bell, R. E.; Hammett, G. W.; LeBlanc, B. P.; Mikkelsen, D. R.; Peterson, J. L.; Nevins, W. M.; Candy, J.; Yuh, H.

    2013-07-17

    Nonlinear simulations based on multiple NSTX discharge scenarios have progressed to help differentiate unique instability mechanisms and to validate with experimental turbulence and transport data. First nonlinear gyrokinetic simulations of microtearing (MT) turbulence in a high-beta NSTX H-mode discharge predict experimental levels of electron thermal transport that are dominated by magnetic flutter and increase with collisionality, roughly consistent with energy confinement times in dimensionless collisionality scaling experiments. Electron temperature gradient (ETG) simulations predict significant electron thermal transport in some low and high beta discharges when ion scales are suppressed by E x B shear. Although the predicted transport in H-modes is insensitive to variation in collisionality (inconsistent with confinement scaling), it is sensitive to variations in other parameters, particularly density gradient stabilization. In reversed shear (RS) Lmode discharges that exhibit electron internal transport barriers, ETG transport has also been shown to be suppressed nonlinearly by strong negative magnetic shear, s<<0. In many high beta plasmas, instabilities which exhibit a stiff beta dependence characteristic of kinetic ballooning modes (KBM) are sometimes found in the core region. However, they do not have a distinct finite beta threshold, instead transitioning gradually to a trapped electron mode (TEM) as beta is reduced to zero. Nonlinear simulations of this "hybrid" TEM/KBM predict significant transport in all channels, with substantial contributions from compressional magnetic perturbations. As multiple instabilities are often unstable simultaneously in the same plasma discharge, even on the same flux surface, unique parametric dependencies are discussed which may be useful for distinguishing the different mechanisms experimentally.

  19. Coherently driven, ultrafast electron-phonon dynamics in transport junctions

    SciTech Connect

    Szekely, Joshua E.; Seideman, Tamar

    2014-07-28

    Although the vast majority of studies of transport via molecular-scale heterojunctions have been conducted in the (static) energy domain, experiments are currently beginning to apply time domain approaches to the nanoscale transport problem, combining spatial with temporal resolution. It is thus an opportune time for theory to develop models to explore both new phenomena in, and new potential applications of, time-domain, coherently driven molecular electronics. In this work, we study the interaction of a molecular phonon with an electronic wavepacket transmitted via a conductance junction within a time-domain model that treats the electron and phonon on equal footing and spans the weak to strong electron-phonon coupling strengths. We explore interference between two coherent energy pathways in the electronic subspace, thus complementing previous studies of coherent phenomena in conduction junctions, where the stationary framework was used to study interference between spatial pathways. Our model provides new insights into phase decoherence and population relaxation within the electronic subspace, which have been conventionally treated by density matrix approaches that often rely on phenomenological parameters. Although the specific case of a transport junction is explored, our results are general, applying also to other instances of coupled electron-phonon systems.

  20. Transport Properties of III-N Hot Electron Transistors

    NASA Astrophysics Data System (ADS)

    Suntrup, Donald J., III

    Unipolar hot electron transistors (HETs) represent a tantalizing alternative to established bipolar transistor technologies. During device operation electrons are injected over a large emitter barrier into the base where they travel along the device axis with very high velocity. Upon arrival at the collector barrier, high-energy electrons pass over the barrier and contribute to collector current while low-energy electrons are quantum mechanically reflected back into the base. Designing the base with thickness equal to or less than the hot electron mean free path serves to minimize scattering events and thus enable quasi-ballistic operation. Large current gain is achieved by increasing the ratio of transmitted to reflected electrons. Although III-N HETs have undergone substantial development in recent years, there remain ample opportunities to improve key device metrics. In order to engineer improved device performance, a deeper understanding of the operative transport physics is needed. Fortunately, the HET provides fertile ground for studying several prominent electron transport phenomena. In this thesis we present results from several studies that use the III-N HET as both emitter and analyzer of hot electron momentum states. The first provides a measurement of the hot electron mean free path and the momentum relaxation rate in GaN; the second relies on a new technique called electron injection spectroscopy to investigate the effects of barrier height inhomogeneity in the emitter. To supplement our analysis we develop a comprehensive theory of coherent electron transport that allows us to model the transfer characteristics of complex heterojunctions. Such a model provides a theoretical touchstone with which to compare our experimental results. While these studies are of potential interest in their own right, we interpret the results with an eye toward improving next-generation device performance.

  1. Simulation of electron transport in quantum well devices

    NASA Technical Reports Server (NTRS)

    Miller, D. R.; Gullapalli, K. K.; Reddy, V. R.; Neikirk, D. P.

    1992-01-01

    Double barrier resonant tunneling diodes (DBRTD) have received much attention as possible terahertz devices. Despite impressive experimental results, the specifics of the device physics (i.e., how the electrons propagate through the structure) are only qualitatively understood. Therefore, better transport models are warranted if this technology is to mature. In this paper, the Lattice Wigner function is used to explain the important transport issues associated with DBRTD device behavior.

  2. Anomalous electronic transport in dual-nanostructured lead telluride.

    PubMed

    He, J Q; Sootsman, J R; Xu, L Q; Girard, S N; Zheng, J C; Kanatzidis, M G; Dravid, V P

    2011-06-15

    The Pb- and Sb- dual nanostructured PbTe system exhibits anomalous electronic transport behavior wherein the carrier mobility first increases and then decreases with increase in temperature. By combining in situ transmission electron microscopy observations and theoretical calculations based on energy filtering of charge carriers, we propose a plausible mechanism of charge transport based on interphase potential that is mediated by interdiffusion between coexisting Pb and Sb precipitates. These findings promise new strategies to enhance thermoelectric figure of merit via dual and multinanostructuring of miscible precipitates. PMID:21557606

  3. Signatures of electron-magnon interaction in charge and spin currents through magnetic tunnel junctions: A nonequilibrium many-body perturbation theory approach

    NASA Astrophysics Data System (ADS)

    Mahfouzi, Farzad; Nikolić, Branislav K.

    2014-07-01

    We develop a numerically exact scheme for resumming certain classes of Feynman diagrams in the self-consistent perturbative expansion for the electron and magnon self-energies in the nonequilibrium Green function formalism applied to a coupled electron-magnon (e-m) system driven out of equilibrium by the applied finite bias voltage. Our scheme operates with the electronic and magnonic GFs and the corresponding self-energies viewed as matrices in the Keldysh space, rather than conventionally extracting their retarded and lesser components, which greatly simplifies translation of diagrams into compact mathematical expressions and their computational implementation. This is employed to understand the effect of inelastic e-m scattering on charge and spin current vs bias voltage Vb in F/I/F (F-ferromagnet; I-insulating barrier) magnetic tunnel junctions (MTJs), which are modeled on a quasi-one-dimensional (quasi-1D) tight-binding lattice for the electronic subsystem and quasi-1D Heisenberg model for the magnonic subsystem. For this purpose, we evaluate the Fock diagram for the electronic self-energy and the electron-hole polarization bubble diagram for the magnonic self-energy. The respective electronic and magnonic GF lines within these diagrams are the fully interacting ones, thereby requiring to solve the ensuing coupled system of nonlinear integral equations self-consistently. Despite using the quasi-1D model and treating e-m interaction in many-body fashion only within a small active region consisting of few lattice sites around the F/I interface, our analysis captures essential features of the so-called zero-bias anomaly observed [V. Drewello, J. Schmalhorst, A. Thomas, and G. Reiss, Phys. Rev. B 77, 014440 (2008), 10.1103/PhysRevB.77.014440] in both MgO- and AlOx-based realistic 3D MTJs where the second derivative d2I /dVb2 (i.e., inelastic electron tunneling spectrum) of charge current exhibits sharp peaks of opposite sign on either side Vb=0. We show that this

  4. Electronic transport in polycrystalline samples of icosahedral phases

    NASA Astrophysics Data System (ADS)

    Vekilov, Yu. Kh.; Chernikov, M. A.; Dolinichek, Ya.

    2016-01-01

    The low-temperature electronic transport in polycrystals of quasicrystalline phases with an icosahedral structure has been analyzed within the model of the granular electronic system. In this model, the grains (drops) of a metallic icosahedral phase are surrounded by extended defects and grain boundaries, which create an insulating environment. The electron transport in this model is determined by the size quantization of electronic states inside metallic grains, by intergranular tunneling, and by electrostatic barriers. Depending on the temperature and structural state of the system, the hopping conductivity with variable lengths of jumps in the Efros-Shklovskii or Mott regime is observed with predominantly elastic cotunneling. In the case of strong intergranular coupling, the system passes into the metallic regime with the exponential temperature dependence of the electrical conductivity.

  5. Role of Inelastic Electron–Phonon Scattering in Electron Transport through Ultra-Scaled Amorphous Phase Change Material Nanostructures

    SciTech Connect

    Liu, Jie; Xu, Xu; Anantram, M.P.

    2014-09-01

    The electron transport through ultra-scaled amorphous phase change material (PCM) GeTe is investigated by using ab initio molecular dynamics, density functional theory, and non-equilibrium Green’s function, and the inelastic electron–phonon scattering is accounted for by using the Born approximation. It is shown that, in ultra-scaled PCM device with 6 nm channel length, < 4 % of the energy carried by the incident electrons from the source is transferred to the atomic lattice before reaching the drain, indicating that the electron transport is largely elastic. Our simulation results show that the inelastic electron–phonon scattering, which plays an important role to excite trapped electrons in bulk PCM devices, exerts very limited influence on the current density value and the shape of current–voltage curve of ultra-scaled PCM devices. The analysis reveals that the Poole–Frenkel law and the Ohm’s law, which are the governing physical mechanisms of the bulk PCM devices, cease to be valid in the ultra-scaled PCM devices.

  6. Inelastic electron transport: IETS, NDR, switching, and hysteresis

    NASA Astrophysics Data System (ADS)

    Galperin, Michael; Nitzan, Abraham; Ratner, Mark

    2005-03-01

    We study the effect of the mutual influence between the phonon and the electron subsystems using nonequilibrium Green function (NEGF) formalism at the level of self-consistent Born approximation. Regarding the inelastic spectrum, two types of inelastic contributions are discussed. Features associated with real and virtual energy transfer to phonons are usually observed in the second derivative of the current I with respect to the voltage V. Signatures of resonant tunneling driven by an intermediate molecular ion appear as peaks in the first derivative dI/dV and may show phonon sidebands. The dependence of the observed vibrationally induced lineshapes on the junction characteristics, and the linewidths associated with these features are also discussed. Polaron formation on a molecular wire as a possible mechanism for observed NDR, switching and/or hysteresis in the I/V characteristic of molecular junctions is discussed within a simple mean-field model (self-consistent Hartree approximation). This mechanism differs from earlier proposed mechanisms of charging and conformational change. The polaron model captures the essential physics and provides qualitative correspondence with experimental data. The importance of active redox centers in the molecule is indicated.

  7. Non equilibrium electronic transport in multilayered nanostructures

    NASA Astrophysics Data System (ADS)

    Cruz-Rojas, Jesus

    Recent advances in strongly correlated materials have produced systems with novel and interesting properties like high Tc superconductors, Mott insulators and others. These novel properties have sparked an interest in industry as well as in academia as new devices are being developed. One such kind of device that can be fabricated is a heterostructure, in which layers of different compounds are stacked in a single direction. Modern deposition techniques like electron beam epitaxy, in which atomic layers of different materials are deposited one at a time creating the device, are capable of fabricating heterostructures with atomic precision. We propose a technique to study heterostructures composed of strongly correlated materials out of equilibrium. By using the Keldysh Green's function formalism in the dynamical mean field theory (DMFT) framework the properties of a multilayered device are analyzed. The system is composed of infinite dimensional 2D lattices, stacked in the z direction. The first and last planes are then connected to a bulk reservoir, and several metallic planes are used to connect the bulk reservoir to the barrier region. The barrier region is the system of interest, also known as the device. The device is composed of a number of planes where the system correlations have been turned on. The correlations are then model by using the Falicov-Kimball Hamiltonian. The device is then connected to the bulk once again from the opposite side using metallic planes creating a symmetric system. In order to study the non equilibrium properties of the device a linear vector potential A(t) = A0 + tE is turned on a long time in the past for a unit of time and then turned off. This in turn will create a current in the bulk, in effect current biasing the device, as opposed to a voltage bias in which opposite sides of the device are held to a different potential. In this document we will explain the importance of the subject, we will derive and develop the algorithm

  8. Study of Electron Transport and Amplification in Diamond

    SciTech Connect

    Muller, Erik M.; Ben-Zvi, Ilan

    2013-03-31

    As a successful completion of this award, my group has demonstrated world-leading electron gain from diamond for use in a diamond-amplified photocathode. Also, using high-resolution photoemission measurements we were able to uncover exciting new physics of the electron emission mechanisms from hydrogen terminated diamond. Our work, through the continued support of HEP, has resulted in a greater understanding of the diamond material science, including current limits, charge transport modeling, and spatial uniformity.

  9. Origin of electronic transport of lithium phthalocyanine iodine crystal

    SciTech Connect

    Koike, Noritake; Oda, Masato; Shinozuka, Yuzo

    2013-12-04

    The electronic structures of Lithium Phthalocyanine Iodine are investigated using density functional theory. Comparing the band structures of several model crystals, the metallic conductivity of highly doped LiPcI{sub x} can be explained by the band of doped iodine. These results reveal that there is a new mechanism for electronic transport of doped organic semiconductors that the dopant band plays the main role.

  10. Two-stream approach to electron transport and thermalization

    SciTech Connect

    Stamnes, K.

    1981-04-01

    An explicit solution to the electron transport and energy degradation problem is presented in the two-stream approximation. The validity of this simple approach is discussed, and it is shown that it can be extended to high electron energies (appropriate for applications to auroras) provided the coupling between the two streams, described by the backscatter ratio, is correctly estimated. A simple formula for the backscatter ratio which can be used at all energies is derived.

  11. Simulation of electron transport during electron-beam-induced deposition of nanostructures

    PubMed Central

    Jeschke, Harald O; Valentí, Roser

    2013-01-01

    Summary We present a numerical investigation of energy and charge distributions during electron-beam-induced growth of tungsten nanostructures on SiO2 substrates by using a Monte Carlo simulation of the electron transport. This study gives a quantitative insight into the deposition of energy and charge in the substrate and in the already existing metallic nanostructures in the presence of the electron beam. We analyze electron trajectories, inelastic mean free paths, and the distribution of backscattered electrons in different compositions and at different depths of the deposit. We find that, while in the early stages of the nanostructure growth a significant fraction of electron trajectories still interacts with the substrate, when the nanostructure becomes thicker the transport takes place almost exclusively in the nanostructure. In particular, a larger deposit density leads to enhanced electron backscattering. This work shows how mesoscopic radiation-transport techniques can contribute to a model that addresses the multi-scale nature of the electron-beam-induced deposition (EBID) process. Furthermore, similar simulations can help to understand the role that is played by backscattered electrons and emitted secondary electrons in the change of structural properties of nanostructured materials during post-growth electron-beam treatments. PMID:24367747

  12. Electron transport in magnetrons by a posteriori Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    Costin, C.; Minea, T. M.; Popa, G.

    2014-02-01

    Electron transport across magnetic barriers is crucial in all magnetized plasmas. It governs not only the plasma parameters in the volume, but also the fluxes of charged particles towards the electrodes and walls. It is particularly important in high-power impulse magnetron sputtering (HiPIMS) reactors, influencing the quality of the deposited thin films, since this type of discharge is characterized by an increased ionization fraction of the sputtered material. Transport coefficients of electron clouds released both from the cathode and from several locations in the discharge volume are calculated for a HiPIMS discharge with pre-ionization operated in argon at 0.67 Pa and for very short pulses (few µs) using the a posteriori Monte Carlo simulation technique. For this type of discharge electron transport is characterized by strong temporal and spatial dependence. Both drift velocity and diffusion coefficient depend on the releasing position of the electron cloud. They exhibit minimum values at the centre of the race-track for the secondary electrons released from the cathode. The diffusion coefficient of the same electrons increases from 2 to 4 times when the cathode voltage is doubled, in the first 1.5 µs of the pulse. These parameters are discussed with respect to empirical Bohm diffusion.

  13. Fluctuating-bias controlled electron transport in molecular junctions

    NASA Astrophysics Data System (ADS)

    Ridley, Michael; MacKinnon, Angus; Kantorovich, Lev

    2016-05-01

    We consider the problem of transport through a multiterminal molecular junction in the presence of a stochastic bias, which can also be used to describe transport through fluctuating molecular energy levels. To describe these effects, we first make a simple extension of our previous work [Phys. Rev. B 91, 125433 (2015), 10.1103/PhysRevB.91.125433] to show that the problem of tunneling through noisy energy levels can be mapped onto the problem of a noisy driving bias, which appears in the Kadanoff-Baym equations for this system in an analogous manner to the driving term in the Langevin equation for a classical circuit. This formalism uses the nonequilibrium Green's function method to obtain analytically closed formulas for transport quantities within the wide-band limit approximation for an arbitrary time-dependent bias and it is automatically partition free. We obtain exact closed formulas for both the colored and white noise-averaged current at all times. In the long-time limit, these formulas possess a Landauer-Büttiker-type structure which enables the extraction of an effective transmission coefficient for the transport. Expanding the Fermi function into a series of simple poles, we find an exact formal relation between the parameters which characterize the bias fluctuations and the poles of the Fermi function. This enables us to describe the effect of the temperature and the strength of the fluctuations on the averaged current which we interpret as a quantum analog to the classical fluctuation-dissipation theorem. We use these results to convincingly refute some recent results on the multistability of the current through a fluctuating level, simultaneously verifying that our formalism satisfies some well-known theorems on the asymptotic current. Finally, we present numerical results for the current through a molecular chain which demonstrate a transition from nonlinear to linear I -V characteristics as the strength of fluctuations is increased, as well as a

  14. Effect of uniaxial strain on the electronic transport through disordered graphene p-n junctions

    NASA Astrophysics Data System (ADS)

    Deng, Min; Wang, Yong-Jian; Gang, Yu; Chen, Jian-Fei

    2016-09-01

    Using the non-equilibrium Green’s function method, we investigated theoretically the electron transport through a disordered graphene p-n junction under a perpendicular magnetic field. A uniaxial strain is applied to the graphene sheet. It is found that the conductance versus the on-site energy of the right electrode exhibits the successive step-like structure in the n-n region, however, a zero value plateau followed by the successive oscillation peaks in the p-n region. When the longitudinal or transverse strain is applied, the zero value plateau almost remains intact, while the oscillation peaks are greatly enhanced with increasing the strain strength, and depending on the orientation of the applied strain, the oscillation peaks shift towards the positive or negative energy upon increasing the strain. In the presence of the disorder, the characteristic conductance plateaus emerge at e2/h, (3/2)e2/h, etc. for the appropriate disorder strength. With the rise of the strain, the original plateau structure is destroyed, instead, the conductance exhibits new plateaus whose amplitude and position strongly depend on the strain strength and direction.

  15. Electronic transport through a graphene-based ferromagnetic/normal/ferromagnetic junction.

    PubMed

    Chen, Jiang-chai; Cheng, Shu-guang; Shen, Shun-qing; Sun, Qing-feng

    2010-01-27

    Electronic transport in a graphene-based ferromagnetic/normal/ferromagnetic junction is investigated by means of the Landauer-Büttiker formalism and the nonequilibrium Green function technique. For the zigzag edge case, the results show that the conductance is always larger than e(2)/h for the parallel configuration of lead magnetizations, but for the antiparallel configuration the conductance becomes zero because of the band-selective rule. Therefore, a magnetoresistance (MR) plateau emerges with the value 100% when the Fermi energy is located around the Dirac point. In addition, choosing narrower graphene ribbons can yield wider 100% MR plateaus and the length change of the central graphene region does not affect the 100% MR plateaus. Although the disorder will reduce the MR plateau, the plateau value can still be kept about 50% even in a large disorder strength case. In addition, when the magnetizations of the left and right leads have a relative angle, the conductance changes as a cosine function of the angle. What is more, for the armchair edge case, the MR is usually small. So, it is more favorable to fabricate a graphene-based spin valve device by using a zigzag edge graphene ribbon. PMID:21386283

  16. Nonequilibrium is different

    NASA Astrophysics Data System (ADS)

    Kirkpatrick, T. R.; Dorfman, J. R.

    2015-08-01

    Nonequilibrium and equilibrium fluid systems differ due to the existence of long-range correlations in nonequilibrium that are not present in equilibrium, except at critical points. Here we examine fluctuations of the temperature, of the pressure tensor, and of the heat current in a fluid maintained in a nonequilibrium stationary state (NESS) with a fixed temperature gradient, a system in which the nonequilibrium correlations are especially long-ranged. For this particular NESS, our results show that (i) the mean-squared fluctuations in nonequilibrium differ markedly in their system-size scaling compared to their equilibrium counterparts, and (ii) there are large, nonlocal correlations of the normal stress in this NESS. These terms provide important corrections to the fluctuating normal stress in linearized Landau-Lifshitz fluctuating hydrodynamics.

  17. Photosynthetic electron transport system promotes synthesis of Au-nanoparticles.

    PubMed

    Shabnam, Nisha; Pardha-Saradhi, P

    2013-01-01

    In this communication, a novel, green, efficient and economically viable light mediated protocol for generation of Au-nanoparticles using most vital organelle, chloroplasts, of the plant system is portrayed. Thylakoids/chloroplasts isolated from Potamogeton nodosus (an aquatic plant) and Spinacia oleracea (a terrestrial plant) turned Au³⁺ solutions purple in presence of light of 600 µmol m⁻² s⁻¹ photon flux density (PFD) and the purple coloration intensified with time. UV-Vis spectra of these purple colored solutions showed absorption peak at ∼545 nm which is known to arise due to surface plasmon oscillations specific to Au-nanoparticles. However, thylakoids/chloroplasts did not alter color of Au³⁺ solutions in dark. These results clearly demonstrated that photosynthetic electron transport can reduce Au³⁺ to Au⁰ which nucleate to form Au-nanoparticles in presence of light. Transmission electron microscopic studies revealed that Au-nanoparticles generated by light driven photosynthetic electron transport system of thylakoids/chloroplasts were in range of 5-20 nm. Selected area electron diffraction and powder X-ray diffraction indicated crystalline nature of these nanoparticles. Energy dispersive X-ray confirmed that these nanoparticles were composed of Au. To confirm the potential of light driven photosynthetic electron transport in generation of Au-nanoparticles, thylakoids/chloroplasts were tested for their efficacy to generate Au-nanoparticles in presence of light of PFD ranging from 60 to 600 µmol m⁻² s⁻¹. The capacity of thylakoids/chloroplasts to generate Au-nanoparticles increased remarkably with increase in PFD, which further clearly demonstrated potential of light driven photosynthetic electron transport in reduction of Au³⁺ to Au⁰ to form nanoparticles. The light driven donation of electrons to metal ions by thylakoids/chloroplasts can be exploited for large scale production of nanoparticles. PMID:23976990

  18. Photosynthetic electron transport system promotes synthesis of Au-nanoparticles.

    PubMed

    Shabnam, Nisha; Pardha-Saradhi, P

    2013-01-01

    In this communication, a novel, green, efficient and economically viable light mediated protocol for generation of Au-nanoparticles using most vital organelle, chloroplasts, of the plant system is portrayed. Thylakoids/chloroplasts isolated from Potamogeton nodosus (an aquatic plant) and Spinacia oleracea (a terrestrial plant) turned Au³⁺ solutions purple in presence of light of 600 µmol m⁻² s⁻¹ photon flux density (PFD) and the purple coloration intensified with time. UV-Vis spectra of these purple colored solutions showed absorption peak at ∼545 nm which is known to arise due to surface plasmon oscillations specific to Au-nanoparticles. However, thylakoids/chloroplasts did not alter color of Au³⁺ solutions in dark. These results clearly demonstrated that photosynthetic electron transport can reduce Au³⁺ to Au⁰ which nucleate to form Au-nanoparticles in presence of light. Transmission electron microscopic studies revealed that Au-nanoparticles generated by light driven photosynthetic electron transport system of thylakoids/chloroplasts were in range of 5-20 nm. Selected area electron diffraction and powder X-ray diffraction indicated crystalline nature of these nanoparticles. Energy dispersive X-ray confirmed that these nanoparticles were composed of Au. To confirm the potential of light driven photosynthetic electron transport in generation of Au-nanoparticles, thylakoids/chloroplasts were tested for their efficacy to generate Au-nanoparticles in presence of light of PFD ranging from 60 to 600 µmol m⁻² s⁻¹. The capacity of thylakoids/chloroplasts to generate Au-nanoparticles increased remarkably with increase in PFD, which further clearly demonstrated potential of light driven photosynthetic electron transport in reduction of Au³⁺ to Au⁰ to form nanoparticles. The light driven donation of electrons to metal ions by thylakoids/chloroplasts can be exploited for large scale production of nanoparticles.

  19. Transport Experiments on 2D Correlated Electron Physics in Semiconductors

    SciTech Connect

    Tsui, Daniel

    2014-03-24

    This research project was designed to investigate experimentally the transport properties of the 2D electrons in Si and GaAs, two prototype semiconductors, in several new physical regimes that were previously inaccessible to experiments. The research focused on the strongly correlated electron physics in the dilute density limit, where the electron potential energy to kinetic energy ratio rs>>1, and on the fractional quantum Hall effect related physics in nuclear demagnetization refrigerator temperature range on samples with new levels of purity and controlled random disorder.

  20. Electron energy transport and magnetic curvature driven modes

    SciTech Connect

    Coppi, B.; Tang, W.M.

    1984-10-01

    A transport coefficient for anomalous electron thermal conduction is constructed on the basis of the so-called Principle of Profile Consistency. It is assumed that the relevant modes in plasma where a substantial fraction of the electron population is magnetically trapped produce magnetic reconnection at a microscopic level and are driven by the combined effects of the plasma pressure gradient and the magnetic field curvature. Consequently, the scaling for the electron energy confinement time exhibits a strongly favorable dependence on the radius of magnetic curvature.

  1. Investigation of electron beam transport in a helical undulator

    SciTech Connect

    Jeong, Y.U.; Lee, B.C.; Kim, S.K.

    1995-12-31

    Lossless transport of electrons through the undulator is essential for CW operation of the FELs driven by recirculating electrostatic accelerators. We calculate the transport ratio of an electron beam in a helical undulator by using a 3-D simulation code and compare the results with the experimental results. The energy and the current of the electron beam are 400 keV and 2 A, respectively. The 3-D distribution of the magnetic field of a practical permanent-magnet helical undulator is measured and is used in the calculations. The major parameters of the undutlator are : period = 32 mm, number of periods = 20, number of periods in adiabatic region = 3.5, magnetic field strength = 1.3 kG. The transport ratio is very sensitive to the injection condition of the electron beam such as the emittance, the diameter, the divergence, etc.. The injection motion is varied in the experiments by changing the e-gun voltage or the field strength of the focusing magnet located at the entrance of the undulator. It is confirmed experimentally and with simulations that most of the beam loss occurs at the adiabatic region of the undulator regardless of the length of the adiabatic region The effect of axial guiding magnetic field on the beam finish is investigated. According to the simulations, the increase of the strength of axial magnetic field from 0 to 1 kG results in the increase of the transport ratio from 15 % to 95%.

  2. ELECTRONIC AND TRANSPORT PROPERTIES OF THERMOELECTRIC Ru2Si3

    NASA Astrophysics Data System (ADS)

    Singh, David J.; Parker, David

    2013-10-01

    We report calculations of the doping and temperature dependent thermopower of Ru2Si3 based on Boltzmann transport theory and the first principles electronic structure. We find that the performance reported to date can be significantly improved by optimization of the doping level and that ultimately n-type should have higher ZT than p-type.

  3. Requirement for Coenzyme Q in Plasma Membrane Electron Transport

    NASA Astrophysics Data System (ADS)

    Sun, I. L.; Sun, E. E.; Crane, F. L.; Morre, D. J.; Lindgren, A.; Low, H.

    1992-12-01

    Coenzyme Q is required in the electron transport system of rat hepatocyte and human erythrocyte plasma membranes. Extraction of coenzyme Q from the membrane decreases NADH dehydrogenase and NADH:oxygen oxidoreductase activity. Addition of coenzyme Q to the extracted membrane restores the activity. Partial restoration of activity is also found with α-tocopherylquinone, but not with vitamin K_1. Analogs of coenzyme Q inhibit NADH dehydrogenase and oxidase activity and the inhibition is reversed by added coenzyme Q. Ferricyanide reduction by transmembrane electron transport from HeLa cells is inhibited by coenzyme Q analogs and restored with added coenzyme Q10. Reduction of external ferricyanide and diferric transferrin by HeLa cells is accompanied by proton release from the cells. Inhibition of the reduction by coenzyme Q analogs also inhibits the proton release, and coenzyme Q10 restores the proton release activity. Trans-plasma membrane electron transport stimulates growth of serum-deficient cells, and added coenzyme Q10 increases growth of HeLa (human adenocarcinoma) and BALB/3T3 (mouse fibroblast) cells. The evidence is consistent with a function for coenzyme Q in a trans-plasma membrane electron transport system which influences cell growth.

  4. Neoclassical electron and ion transport in toroidally rotating plasmas

    SciTech Connect

    Sugama, H.; Horton, W.

    1997-06-01

    Neoclassical transport processes of electrons and ions are investigated in detail for toroidally rotating axisymmetric plasmas with large flow velocities on the order of the ion thermal speed. The Onsager relations for the flow-dependent neoclassical transport coefficients are derived from the symmetry properties of the drift kinetic equation with the self-adjoint collision operator. The complete neoclassical transport matrix with the Onsager symmetry is obtained for the rotating plasma consisting of electrons and single-species ions in the Pfirsch{endash}Schl{umlt u}ter and banana regimes. It is found that the inward banana fluxes of particles and toroidal momentum are driven by the parallel electric field, which are phenomena coupled through the Onsager symmetric off-diagonal coefficients to the parallel currents caused by the radial thermodynamic forces conjugate to the inward fluxes, respectively. {copyright} {ital 1997 American Institute of Physics.}

  5. Relativistic electron transport and bremsstrahlung production in solar flares

    NASA Astrophysics Data System (ADS)

    Miller, James A.; Ramaty, Reuven

    1989-09-01

    A Monte Carlo simulation of ultrarelativistic electron transport in solar flare magnetic loops has been developed. It includes Coulomb, synchrotron, and bremsstrahlung energy losses; pitch-angle scattering by Alfven and whistler turbulence in the coronal region of the loop; and magnetic mirroring in the converging magnetic flux tubes beneath the transition region. Depth distributions, time profiles, energy spectra, and angular distributions of the resulting bremsstrahlung emission are calculated. It is found that both the preferential detection of solar flares with greater than 10 MeV emission near the limb of the sun and the observation of ultrarelativistic electron bremsstrahlung from flares on the disk are consequences of the loop transport model. The declining portions of the observed time profiles of greater than 10 MeV emission from solar flares can also be accounted for, and it is proposed that these portions are determined by transport and not acceleration.

  6. Energy-filtered Electron Transport Structures for Low-power Low-noise 2-D Electronics

    PubMed Central

    Pan, Xuan; Qiu, Wanzhi; Skafidas, Efstratios

    2016-01-01

    In addition to cryogenic techniques, energy filtering has the potential to achieve high-performance low-noise 2-D electronic systems. Assemblies based on graphene quantum dots (GQDs) have been demonstrated to exhibit interesting transport properties, including resonant tunnelling. In this paper, we investigate GQDs based structures with the goal of producing energy filters for next generation lower-power lower-noise 2-D electronic systems. We evaluate the electron transport properties of the proposed GQD device structures to demonstrate electron energy filtering and the ability to control the position and magnitude of the energy passband by appropriate device dimensioning. We also show that the signal-to-thermal noise ratio performance of the proposed nanoscale device can be modified according to device geometry. The tunability of two-dimensional GQD structures indicates a promising route for the design of electron energy filters to produce low-power and low-noise electronics. PMID:27796343

  7. Electron transport mechanisms in polymer-carbon sphere composites

    NASA Astrophysics Data System (ADS)

    Nieves, Cesar A.; Ramos, Idalia; Pinto, Nicholas J.; Zimbovskaya, Natalya A.

    2016-07-01

    A set of uniform carbon microspheres (CSs) whose diameters have the order of 0.125 μm to 10 μm was prepared from aqueous sucrose solution by means of hydrothermal carbonization of sugar molecules. A pressed pellet was composed by mixing CSs with polyethylene oxide (PEO). Electrical characterization of the pellet was carried out showing Ohmic current-voltage characteristics and temperature-dependent conductivity in the range of 80 K electron transport. It was shown that thermally induced electron tunneling between adjacent spheres may take on an important part in the electron transport through the CS/PEO composites.

  8. Electron transport in naphthylamine-based organic compounds

    NASA Astrophysics Data System (ADS)

    Tse, S. C.; Kwok, K. C.; So, S. K.

    2006-12-01

    Two naphthylamine-based hole transporters, namely, N ,N'-diphenyl-N ,N'-bis(1-naphthyl)(1,1'-biphenyl)-4,4'diamine (NPB) and 4,4',4″-tris(n-(2-naphthyl)-n-phenyl-amino)-triphenylamine (2TNATA), were found to possess electron transporting (ET) abilities. From time-of-flight measurements, values of electron mobilities for NPB and 2TNATA are (6-9)×10-4 and (1-3)×10-4cm2/Vs, respectively, under an applied electric field range of 0.04-0.8MV/cm at 290K. An organic light-emitting diode that employed NPB as the ET material was demonstrated. The electron conducting mechanism of NPB and 2TNATA in relation to the Marcus theory [Rev. Mod. Phys. 65, 599 (1993)] from quantum chemistry will be discussed.

  9. Electronic transport experiments on osmium-adatom-decorated graphene

    NASA Astrophysics Data System (ADS)

    Elias, Jamie; Henriksen, Erik

    Monolayer graphene is theoretically predicted to inherit a spin-orbit coupling from a dilute coating of certain transition metal adatoms. To explore these predictions we have constructed a cryogenic probe capable of in situ thermal annealing of graphene followed immediately by electronic transport measurements and controlled deposition of sub-monolayer coatings of most any metal. Previously a light coating of indium on graphene was investigated, and found to transfer electrons to graphene and reduce the mobility although no evidence of an induced spin-orbit coupling was seen. We are now depositing osmium and tungsten on graphene devices. Our initial results show an unexpected hole-doping and a sizable increase in resistance of the sample. We will report our progress on characterizing these samples by electronic transport measurements.

  10. Transport in nanoscale systems: hydrodynamics, turbulence, and local electron heating

    NASA Astrophysics Data System (ADS)

    di Ventra, Massimiliano

    2007-03-01

    Transport in nanoscale systems is usually described as an open-boundary scattering problem. This picture, however, says nothing about the dynamical onset of steady states, their microscopic nature, or their dependence on initial conditions [1]. In order to address these issues, I will first describe the dynamical many-particle state via an effective quantum hydrodynamic theory [2]. This approach allows us to predict a series of novel phenomena like turbulence of the electron liquid [2], local electron heating in nanostructures [3], and the effect of electron viscosity on resistance [4]. I will provide both analytical results and numerical examples of first-principles electron dynamics in nanostructures using the above approach. I will also discuss possible experimental tests of our predictions. Work supported in part by NSF and DOE. [1] N. Bushong, N. Sai and M. Di Ventra, ``Approach to steady-state transport in nanoscale systems'' Nano Letters, 5 2569 (2005); M. Di Ventra and T.N. Todorov, ``Transport in nanoscale systems: the microcanonical versus grand-canonical picture,'' J. Phys. Cond. Matt. 16, 8025 (2004). [2] R. D'Agosta and M. Di Ventra, ``Hydrodynamic approach to transport and turbulence in nanoscale conductors,'' cond-mat/05123326; J. Phys. Cond. Matt., in press. [3] R. D'Agosta, N. Sai and M. Di Ventra, ``Local electron heating in nanoscale conductors,'' cond-mat/0605312; Nano Letters, in press. [4] N. Sai, M. Zwolak, G. Vignale and M. Di Ventra, ``Dynamical corrections to the DFT-LDA electron conductance in nanoscale systems,'' Phys. Rev. Lett. 94, 186810 (2005).

  11. Application of Momentum Transfer Theory for Ion and Electron Transport in Pure Gases and in Gas Mixtures

    SciTech Connect

    Jovanovic, J.V.; Vrhovac, S. B.

    2004-12-01

    In this paper we have presented two applications of Momentum Transfer Theory (MTT), which were both aimed at obtaining reliable data for modeling of non-equilibrium plasma. Transport properties of ion swarms in presence of Resonant Charge Transfer (RCT) collisions are studied using Momentum Transfer Theory (MTT). Using the developed MTT we tested a previously available anisotropic set of cross-sections for Ar++Ar collisions bay making the comparisons with the available data for the transverse diffusion coefficient. We also developed an anisotropic set of Ne++Ne integral cross-sections based on the available data for mobility, longitudinal and transverse diffusion. Anisotropic sets of cross-sections are needed for Monte Carlo simulations of ion transport and plasma models. Application of Blanc's Law for drift velocities of electrons and ions in gas mixtures at arbitrary reduced electric field strengths E/n0 was studied theoretically and by numerical examples. Corrections for Blanc's Law that include effects of inelastic collisions were derived. In addition we have derived the common mean energy procedure that was proposed by Chiflikian in a general case both for ions and electrons. Both corrected common E/n0 and common mean energy procedures provide excellent results even for electrons at moderate E/n0 where application of Blanc's Law was regarded as impossible. In mixtures of two gases that have negative differential conductivity (NDC) even when neither of the two pure gases show NDC the Blanc's Law procedure was able to give excellent predictions.

  12. Ultrafast electron transport in graphene and magnetic nanostructures

    NASA Astrophysics Data System (ADS)

    Turchinovich, Dmitry

    2016-03-01

    Ultrafast terahertz spectroscopy is an ideal tool for observation of dynamics of charge, lattice and spin in solids on the most elementary timescale: in the regime ωτ ~ 1, where ω is the electromagnetic wave oscillation frequency, and τ is the characteristic timescale at which the fundamental phenomena in the three subsystems comprising the solid occur. In this paper two case studies will be discussed. (i) Ultrafast electron transport in graphene. We will show, that the free-carrier conductivity of graphene in arbitrary ultrafast, (sub-)picosecond electric fields is defined by the thermodynamic balance maintained within the electronic structure of graphene acting as thermalized electron gas. Within this simple thermodynamic picture, the electron gas quasi-instantaneously increases its temperature by absorbing the energy of driving ultrafast electric field, and at the same time cools down via a time-retarded, few picosecond-long process of phonon emission. The asymmetry in electron heating and cooling dynamics leads to heat accumulation in the electron population of graphene, concomitantly lowering the chemical potential for hotter electrons, and thereby reducing the intraband conductivity of graphene - an effect crucially important for understanding of ultrafast graphene transistors and photodetectors. (ii) We will also discuss the fundamental observation of spin-controlled electron conduction of Fermilevel electrons in ferromagnetic metals, and will directly quantify the Mott picture of conduction in ferromagnets - the effect directly employed in modern magnetic sensor technologies such as giant magnetoresistance.

  13. General theory of electronic transport in molecular crystals. I. Local linear electron-phonon coupling

    NASA Astrophysics Data System (ADS)

    Silbey, R.; Munn, R. W.

    1980-02-01

    An improved general theory of electronic transport in molecular crystals with local linear electron-phonon coupling is presented. It is valid for arbitrary electronic and phonon bandwidths and for arbitrary electron-phonon coupling strength, yielding small-polaron theory for narrow electronic bands and strong coupling, and semiconductor theory for wide electronic bands and weak coupling. Detailed results are derived for electronic excitations fully clothed with phonons and having a bandwidth no larger than the phonon frequency; the electronic and phonon densities of states are taken as Gaussian for simplicity. The dependence of the diffusion coefficient on temperature and on the other parameters is analyzed thoroughly. The calculated behavior provides a rational interpretation of observed trends in the magnitude and temperature dependence of charge-carrier drift mobilities in molecular crystals.

  14. Modeling High Altitude EMP using a Non-Equilibrium Electron Swarm Model to Monitor Conduction Electron Evolution (LA-UR-15-26151)

    NASA Astrophysics Data System (ADS)

    Pusateri, E. N.; Morris, H. E.; Nelson, E.; Ji, W.

    2015-12-01

    Electromagnetic pulse (EMP) events in the atmosphere are important physical phenomena that occur through both man-made and natural processes, such as lightning, and can be disruptive to surrounding electrical systems. Due to the disruptive nature of EMP, it is important to accurately predict EMP evolution and propagation with computational models. In EMP, low-energy conduction electrons are produced from Compton electron or photoelectron ionizations with air. These conduction electrons continue to interact with the surrounding air and alter the EMP waveform. Many EMP simulation codes use an equilibrium ohmic model for computing the conduction current. The equilibrium model works well when the equilibration time is short compared to the rise time or duration of the EMP. However, at high altitude, the conduction electron equilibration time can be comparable to or longer than the rise time or duration of the EMP. This matters, for example, when calculating the EMP propagating upward toward a satellite. In these scenarios, the equilibrium ionization rate becomes very large for even a modest electric field. The ohmic model produces an unphysically large number of conduction electrons that prematurely and abruptly short the EMP in the simulation code. An electron swarm model, which simulates the time evolution of conduction electrons, can be used to overcome the limitations exhibited by the equilibrium ohmic model. We have developed and validated an electron swarm model in an environment characterized by electric field and pressure previously in Pusateri et al. (2015). This swarm model has been integrated into CHAP-LA, a state-of-the-art EMP code developed by researchers at Los Alamos National Laboratory, which previously calculated conduction current using an ohmic model. We demonstrate the EMP damping behavior caused by the ohmic model at high altitudes and show improvements on high altitude EMP modeling obtained by employing the swarm model.

  15. Electron transport study of single wall nanotubes based on group 14 elements

    NASA Astrophysics Data System (ADS)

    Sivasathya, S.; Thiruvadigal, D. John

    2012-06-01

    By applying non-equilibrium Green's functions in combination with density functional theory, we investigate the transport behaviours of single wall nanotubes based on group14 elements. The transmission spectrum and density of states for single wall nanotubes such as Lead nanotube(PbNT), Germanium nanotube(GeNT), Silicon nanotube(SiNT), Tin nanotube(SnNT) and Carbon nanotube(CNT) are compared.

  16. Electronic transport in benzodifuran single-molecule transistors

    NASA Astrophysics Data System (ADS)

    Xiang, An; Li, Hui; Chen, Songjie; Liu, Shi-Xia; Decurtins, Silvio; Bai, Meilin; Hou, Shimin; Liao, Jianhui

    2015-04-01

    Benzodifuran (BDF) single-molecule transistors have been fabricated in electromigration break junctions for electronic measurements. The inelastic electron tunneling spectrum validates that the BDF molecule is the pathway of charge transport. The gating effect is analyzed in the framework of a single-level tunneling model combined with transition voltage spectroscopy (TVS). The analysis reveals that the highest occupied molecular orbital (HOMO) of the thiol-terminated BDF molecule dominates the charge transport through Au-BDF-Au junctions. Moreover, the energy shift of the HOMO caused by the gate voltage is the main reason for conductance modulation. In contrast, the electronic coupling between the BDF molecule and the gold electrodes, which significantly affects the low-bias junction conductance, is only influenced slightly by the applied gate voltage. These findings will help in the design of future molecular electronic devices.Benzodifuran (BDF) single-molecule transistors have been fabricated in electromigration break junctions for electronic measurements. The inelastic electron tunneling spectrum validates that the BDF molecule is the pathway of charge transport. The gating effect is analyzed in the framework of a single-level tunneling model combined with transition voltage spectroscopy (TVS). The analysis reveals that the highest occupied molecular orbital (HOMO) of the thiol-terminated BDF molecule dominates the charge transport through Au-BDF-Au junctions. Moreover, the energy shift of the HOMO caused by the gate voltage is the main reason for conductance modulation. In contrast, the electronic coupling between the BDF molecule and the gold electrodes, which significantly affects the low-bias junction conductance, is only influenced slightly by the applied gate voltage. These findings will help in the design of future molecular electronic devices. Electronic supplementary information (ESI) available: The fabrication procedure for BDF single

  17. Transport of the plasma sheet electrons to the geostationary distances

    NASA Astrophysics Data System (ADS)

    Ganushkina, N. Y.; Amariutei, O. A.; Shprits, Y. Y.; Liemohn, M. W.

    2013-01-01

    Abstract<p label="1">The <span class="hlt">transport</span> and acceleration of low-energy <span class="hlt">electrons</span> (50-250 keV) from the plasma sheet to the geostationary orbit were investigated. Two moderate storm events, which occurred on 6-7 November 1997 and 12-14 June 2005, were modeled using the Inner Magnetosphere Particle <span class="hlt">Transport</span> and Acceleration model (IMPTAM) with the boundary set at 10 RE in the plasma sheet. The output of the IMPTAM was compared to the observed <span class="hlt">electron</span> fluxes in four energy ranges (50-225 keV) measured by the Synchronous Orbit Particle Analyzer instrument onboard the Los Alamos National Laboratory spacecraft. It was found that the large-scale convection in combination with substorm-associated impulsive fields is the drivers of the <span class="hlt">transport</span> of plasma sheet <span class="hlt">electrons</span> from 10 RE to geostationary orbit at 6.6 RE during storm times. The addition of radial diffusion had no significant influence on the modeled <span class="hlt">electron</span> fluxes. At the same time, the modeled <span class="hlt">electron</span> fluxes are one (two) order(s) smaller than the observed ones for 50-150 keV (150-225 keV) <span class="hlt">electrons</span>, respectively, most likely due to inaccuracy of <span class="hlt">electron</span> boundary conditions. The loss processes due to wave-particle interactions were not considered. The choice of the large-scale convection electric field model used in simulations did not have a significant influence on the modeled <span class="hlt">electron</span> fluxes, since there is not much difference between the equipotential contours given by the Volland-Stern and the Boyle et al. (1997) models at distances from 10 to 6.6 RE in the plasma sheet. Using the TS05 model for the background magnetic field instead of the T96 model resulted in larger deviations of the modeled <span class="hlt">electron</span> fluxes from the observed ones due to specific features of the TS05 model. The increase in the modeled <span class="hlt">electron</span> fluxes can be as large as two orders of magnitude when substorm-associated electromagnetic fields were taken into account. The obtained model distribution of low-energy <span class="hlt">electron</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMSM44A..08G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMSM44A..08G"><span id="translatedtitle"><span class="hlt">Transport</span> of the plasma sheet <span class="hlt">electrons</span> to the geostationary distances</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ganushkina, N. Y.; Amariutei, O. A.; Shprits, Y.; Liemohn, M. W.</p> <p>2012-12-01</p> <p>The <span class="hlt">transport</span> and acceleration of low energy <span class="hlt">electrons</span> (10-250 keV) from the plasma sheet to the geostationary orbit were investigated. Two moderate storm events, which occurred on November 6-7, 1997 and June 12-14, 2005, were modeled using the Inner Magnetosphere Particle <span class="hlt">Transport</span> and Acceleration model (IMPTAM) with the boundary set at 10 RE in the plasma sheet. The output of the IMPTAM model was compared to the observed <span class="hlt">electron</span> fluxes in four energy ranges measured onboard the LANL spacecraft by the SOPA instrument. It was found that the large-scale convection in combination with substorm-associated impulsive fields are the drivers of the <span class="hlt">transport</span> of plasma sheet <span class="hlt">electrons</span> from 10 RE to geostationary orbit at 6.6 RE during storm times. The addition of radial diffusion had no significant influence on the modeled <span class="hlt">electron</span> fluxes. At the same time, comparison between the modeled <span class="hlt">electron</span> fluxes and observed ones showed two orders of difference most likely due to inaccuracy of <span class="hlt">electron</span> boundary conditions and omission of the important loss processes due to wave-particle interactions. This did not allow us to accuractly reproduce the dynamics of 150-225 keV <span class="hlt">electron</span> fluxes. The choice of the large-scale convection electric field model used in simulations did not significantly influence on the modeled <span class="hlt">electron</span> fluxes, since there is not much difference between the equipotential contours given by the Volland-Stern and Boyle et al. [1997] models at the distances from 10 to 6.6 RE in the plasma sheet. Using the TS05 model for the background magnetic field instead of the T96 model resulted in larger deviations of the modeled <span class="hlt">electron</span> fluxes from the observed ones due to specific features of the TS05 model. The increase in the modeled <span class="hlt">electron</span> fluxes can be as large as three orders of magnitude when substorm-associated electromagnetic fields were taken into account. The obtained model distribution of low energy <span class="hlt">electron</span> fluxes can be used as an input to the radiation</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1096488','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1096488"><span id="translatedtitle">LDRD project 151362 : low energy <span class="hlt">electron</span>-photon <span class="hlt">transport</span>.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kensek, Ronald Patrick; Hjalmarson, Harold Paul; Magyar, Rudolph J.; Bondi, Robert James; Crawford, Martin James</p> <p>2013-09-01</p> <p>At sufficiently high energies, the wavelengths of <span class="hlt">electrons</span> and photons are short enough to only interact with one atom at time, leading to the popular %E2%80%9Cindependent-atom approximation%E2%80%9D. We attempted to incorporate atomic structure in the generation of cross sections (which embody the modeled physics) to improve <span class="hlt">transport</span> at lower energies. We document our successes and failures. This was a three-year LDRD project. The core team consisted of a radiation-<span class="hlt">transport</span> expert, a solid-state physicist, and two DFT experts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.B54D..01N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.B54D..01N"><span id="translatedtitle">Extracellular <span class="hlt">Electron</span> <span class="hlt">Transport</span> (EET): Metal Cycling in Extreme Places</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nealson, K. H.</p> <p>2014-12-01</p> <p>Extracellular <span class="hlt">electron</span> <span class="hlt">transport</span>, or EET, is the process whereby bacteria either donate <span class="hlt">electrons</span> to an <span class="hlt">electron</span> acceptor (usually insoluble), or take up <span class="hlt">electrons</span> from and <span class="hlt">electron</span> donor (usually insoluble) that is located outside the cell. Iron cycling is inherently linked to EET, as both reduced iron (<span class="hlt">electron</span> donors), and oxidized iron (<span class="hlt">electron</span> acceptors) can be found as insoluble minerals, and require specialized molecular machines to accomplish these extracellular geobiological reactions. Bacteria in the group Shewanella are able to catalyze EET in both directions, and are involved with a number of different iron conversions, but are not good role models for extreme conditions - to our knowledge there are no shewanellae that are tolerant to extremes of temperature or pH, the two usual. This being said, when cells are energy starved via limitation for <span class="hlt">electron</span> acceptors, they respond by turning on the system(s) for EET. Thus, in this presentation the known mechanism(s) of EET will be discussed, along with recent findings and reports of EET-capable organisms from a variety of extreme environments. From these data, I put forward the hypothesis that there are many microbes (many of them from extreme environments) that will be resistant to cultivation by "standard microbiological methods", yet lend themselves well to cultivation via electrochemical methods.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Nanot..27m5302S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Nanot..27m5302S"><span id="translatedtitle">Geometric effects in the <span class="hlt">electronic</span> <span class="hlt">transport</span> of deformed nanotubes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Santos, Fernando; Fumeron, Sébastien; Berche, Bertrand; Moraes, Fernando</p> <p>2016-04-01</p> <p>Quasi-two-dimensional systems may exibit curvature, which adds three-dimensional influence to their internal properties. As shown by da Costa (1981 Phys. Rev. A 23 1982-7), charged particles moving on a curved surface experience a curvature-dependent potential which greatly influence their dynamics. In this paper, we study the <span class="hlt">electronic</span> ballistic <span class="hlt">transport</span> in deformed nanotubes. The one-<span class="hlt">electron</span> Schrödinger equation with open boundary conditions is solved numerically with a flexible MAPLE code made available as supplementary data. We find that the curvature of the deformations indeed has strong effects on the <span class="hlt">electron</span> dynamics, suggesting its use in the design of nanotube-based <span class="hlt">electronic</span> devices.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22051363','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22051363"><span id="translatedtitle">Spatially resolved study of primary <span class="hlt">electron</span> <span class="hlt">transport</span> in magnetic cusps</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hubble, Aimee A.; Foster, John E.</p> <p>2012-01-15</p> <p>Spatially resolved primary <span class="hlt">electron</span> current density profiles were measured using a planar Langmuir probe in the region above a magnetic cusp in a small ion thruster discharge chamber. The probe current maps obtained were used to study the <span class="hlt">electron</span> collection mechanics in the cusp region in the limit of zero gas flow and no plasma production, and they allowed for the visualization of primary <span class="hlt">electron</span> <span class="hlt">transport</span> through the cusp. Attenuation coefficients and loss widths were calculated as a function of probe distance above the anode at various operating conditions. Finally, the collection mechanics between two magnetic cusps were studied and compared. It was found that primary <span class="hlt">electron</span> collection was dominated by the upstream magnet ring.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/3847','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/3847"><span id="translatedtitle">The macro response Monte Carlo method for <span class="hlt">electron</span> <span class="hlt">transport</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Svatos, M M</p> <p>1998-09-01</p> <p>The main goal of this thesis was to prove the feasibility of basing <span class="hlt">electron</span> depth dose calculations in a phantom on first-principles single scatter physics, in an amount of time that is equal to or better than current <span class="hlt">electron</span> Monte Carlo methods. The Macro Response Monte Carlo (MRMC) method achieves run times that are on the order of conventional <span class="hlt">electron</span> <span class="hlt">transport</span> methods such as condensed history, with the potential to be much faster. This is possible because MRMC is a Local-to-Global method, meaning the problem is broken down into two separate <span class="hlt">transport</span> calculations. The first stage is a local, in this case, single scatter calculation, which generates probability distribution functions (PDFs) to describe the <span class="hlt">electron</span>'s energy, position and trajectory after leaving the local geometry, a small sphere or "kugel" A number of local kugel calculations were run for calcium and carbon, creating a library of kugel data sets over a range of incident energies (0.25 MeV - 8 MeV) and sizes (0.025 cm to 0.1 cm in radius). The second <span class="hlt">transport</span> stage is a global calculation, where steps that conform to the size of the kugels in the library are taken through the global geometry. For each step, the appropriate PDFs from the MRMC library are sampled to determine the <span class="hlt">electron</span>'s new energy, position and trajectory. The <span class="hlt">electron</span> is immediately advanced to the end of the step and then chooses another kugel to sample, which continues until <span class="hlt">transport</span> is completed. The MRMC global stepping code was benchmarked as a series of subroutines inside of the Peregrine Monte Carlo code. It was compared to Peregrine's class II condensed history <span class="hlt">electron</span> <span class="hlt">transport</span> package, EGS4, and MCNP for depth dose in simple phantoms having density inhomogeneities. Since the kugels completed in the library were of relatively small size, the zoning of the phantoms was scaled down from a clinical size, so that the energy deposition algorithms for spreading dose across 5-10 zones per kugel could be tested. Most</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/503467','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/503467"><span id="translatedtitle">Fabrication and <span class="hlt">electronic</span> <span class="hlt">transport</span> studies of single nanocrystal systems</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Klein, D L</p> <p>1997-05-01</p> <p>Semiconductor and metallic nanocrystals exhibit interesting <span class="hlt">electronic</span> <span class="hlt">transport</span> behavior as a result of electrostatic and quantum mechanical confinement effects. These effects can be studied to learn about the nature of <span class="hlt">electronic</span> states in these systems. This thesis describes several techniques for the <span class="hlt">electronic</span> study of nanocrystals. The primary focus is the development of novel methods to attach leads to prefabricated nanocrystals. This is because, while nanocrystals can be readily synthesized from a variety of materials with excellent size control, means to make electrical contact to these nanocrystals are limited. The first approach that will be described uses scanning probe microscopy to first image and then electrically probe surfaces. It is found that <span class="hlt">electronic</span> investigations of nanocrystals by this technique are complicated by tip-sample interactions and environmental factors such as salvation and capillary forces. Next, an atomic force microscope technique for the catalytic patterning of the surface of a self assembled monolayer is described. In principle, this nano-fabrication technique can be used to create <span class="hlt">electronic</span> devices which are based upon complex arrangements of nanocrystals. Finally, the fabrication and electrical characterization of a nanocrystal-based single <span class="hlt">electron</span> transistor is presented. This device is fabricated using a hybrid scheme which combines <span class="hlt">electron</span> beam lithography and wet chemistry to bind single nanocrystals in tunneling contact between closely spaced metallic leads. In these devices, both Au and CdSe nanocrystals show Coulomb blockade effects with characteristic energies of several tens of meV. Additional structure is seen the <span class="hlt">transport</span> behavior of CdSe nanocrystals as a result of its <span class="hlt">electronic</span> structure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22218426','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22218426"><span id="translatedtitle">Turbulent <span class="hlt">electron</span> <span class="hlt">transport</span> in edge pedestal by <span class="hlt">electron</span> temperature gradient turbulence</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Singh, R.; Jhang, Hogun; Diamond, P. H.</p> <p>2013-11-15</p> <p>We present a model for turbulent <span class="hlt">electron</span> thermal <span class="hlt">transport</span> at the edge pedestal in high (H)-mode plasmas based on <span class="hlt">electron</span> temperature gradient (ETG) turbulence. A quasi-linear analysis of electrostatic toroidal ETG modes shows that both turbulent <span class="hlt">electron</span> thermal diffusivity and hyper-resistivity exhibits the Ohkawa scaling in which the radial correlation length of turbulence becomes the order of <span class="hlt">electron</span> skin depth. Combination of the Ohkawa scales and the plasma current dependence results in a novel confinement scaling inside the pedestal region. It is also shown that ETG turbulence induces a thermoelectric pinch, which may accelerate the density pedestal formation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010cosp...38.2989R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010cosp...38.2989R"><span id="translatedtitle">Solar flare accelerated <span class="hlt">electron</span> <span class="hlt">transport</span> through the turbulent solar wind</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Reid, Hamish; Kontar, Eduard</p> <p></p> <p>Solar flare accelerated <span class="hlt">electron</span> beams can become unstable during <span class="hlt">transport</span> from the Sun to the Earth, producing plasma waves in the turbulent inner heliosphere. We simulate solar <span class="hlt">electron</span> beam propagation to the Earth in the weak turbulent regime taking into account the self-consistent generation of plasma waves. Induced plasma waves interact with the density fluctuations from low frequency MHD turbulence present in the background plasma. These fluctuations act to suppress the generation of waves, most acutely when fluctuations have large amplitudes or small wavelengths. The reduction of plasma wave generation alters the wave distribution which changes <span class="hlt">electron</span> beam <span class="hlt">transport</span>. Assuming an observed 5/3 Kolmogorov-type power density spectra of fluctuations, we investigate the energy spectra of the <span class="hlt">electron</span> beam near the Earth. We find the presence of turbulence in the background plasma alters the spectral index below the break energy of the double power-law formed at 1AU. From an initial single power-law <span class="hlt">electron</span> distribution, we find a range of spectra below the break energy, with higher levels of turbulence corresponding to a higher spectral index.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20860240','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20860240"><span id="translatedtitle">Nonlocal <span class="hlt">electron</span> <span class="hlt">transport</span> in magnetized plasmas with arbitrary atomic number</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bennaceur-Doumaz, D.; Bendib, A.</p> <p>2006-09-15</p> <p>The numerical solution of the steady-state <span class="hlt">electron</span> Fokker-Planck equation perturbed with respect to a global equilibrium is presented in magnetized plasmas with arbitrary atomic number Z. The magnetic field is assumed to be constant and the <span class="hlt">electron-electron</span> collisions are described by the Landau collision operator. The solution is derived in the Fourier space and in the framework of the diffusive approximation which captures the spatial nonlocal effects. The <span class="hlt">transport</span> coefficients are deduced and used to close a complete set of nonlocal <span class="hlt">electron</span> fluid equations. This work improves the results of A. Bendib et al. [Phys. Plasmas 9, 1555 (2002)] and of A. V. Brantov et al. [Phys. Plasmas 10, 4633 (2003)] restricted to the local and nonlocal high-Z plasma approximations, respectively. The influence of the magnetic field on the nonlocal effects is discussed. We propose also accurate numerical fits of the relevant <span class="hlt">transport</span> coefficients with respect to the collisionality parameter {lambda}{sub ei}/L and the atomic number Z, where L is the typical scale length and {lambda}{sub ei} is the <span class="hlt">electron</span>-ion mean-free-path.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007APS..MARL31012D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007APS..MARL31012D"><span id="translatedtitle"><span class="hlt">Electron</span> <span class="hlt">Transport</span> and Tunneling in Single Walled Carbon Nanotube Devices</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dirks, Travis; Mason, Nadya</p> <p>2007-03-01</p> <p>Carbon nanotubes remain a fertile ground for the exploration of interacting one-dimensional (1D) physics and Tomonaga-Luttinger liquid theory. Much is still unknown about the factors that influence the <span class="hlt">transport</span> and tunneling properties of interacting 1D systems such as nanotubes. We report on experiments that use techniques such as multiple contacts on long nanotubes and tunable tunnel barriers to determine how the manifestations of <span class="hlt">electron-electron</span> interactions, such as the zero-bias anomaly, depend on the length and defect strength in nanotubes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApPhL.108j3502C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApPhL.108j3502C"><span id="translatedtitle"><span class="hlt">Transport</span> in organic single-crystal microbelt for conformal <span class="hlt">electronics</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cui, Nan; Tong, Yanhong; Tang, Qingxin; Liu, Yichun</p> <p>2016-03-01</p> <p>We showed the advantages of flexible rubrene organic single-crystal microbelts in high-performance devices and circuits towards conformal <span class="hlt">electronics</span>. The anisotropic <span class="hlt">transport</span> based on the only one organic microbelt was studied by a "cross-channel" method, and the rubrene microbelt showed the highest mobility up to 26 cm2/V s in the length direction. Based on an individual rubrene microbelt, the organic single-crystal circuit with good adherence on a pearl ball and the gain as high as 18 was realized. These results present great potential for applications of organic single-crystal belts in the next-generation conformal <span class="hlt">electronics</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatCo...711381B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatCo...711381B"><span id="translatedtitle">Nanoscale <span class="hlt">electron</span> <span class="hlt">transport</span> at the surface of a topological insulator</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bauer, Sebastian; Bobisch, Christian A.</p> <p>2016-04-01</p> <p>The use of three-dimensional topological insulators for disruptive technologies critically depends on the dissipationless <span class="hlt">transport</span> of <span class="hlt">electrons</span> at the surface, because of the suppression of backscattering at defects. However, in real devices, defects are unavoidable and scattering at angles other than 180° is allowed for such materials. Until now, this has been studied indirectly by bulk measurements and by the analysis of the local density of states in close vicinity to defect sites. Here, we directly measure the nanoscale voltage drop caused by the scattering at step edges, which occurs if a lateral current flows along a three-dimensional topological insulator. The experiments were performed using scanning tunnelling potentiometry for thin Bi2Se3 films. So far, the observed voltage drops are small because of large contributions of the bulk to the <span class="hlt">electronic</span> <span class="hlt">transport</span>. However, for the use of ideal topological insulating thin films in devices, these contributions would play a significant role.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4844676','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4844676"><span id="translatedtitle">Nanoscale <span class="hlt">electron</span> <span class="hlt">transport</span> at the surface of a topological insulator</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Bauer, Sebastian; Bobisch, Christian A.</p> <p>2016-01-01</p> <p>The use of three-dimensional topological insulators for disruptive technologies critically depends on the dissipationless <span class="hlt">transport</span> of <span class="hlt">electrons</span> at the surface, because of the suppression of backscattering at defects. However, in real devices, defects are unavoidable and scattering at angles other than 180° is allowed for such materials. Until now, this has been studied indirectly by bulk measurements and by the analysis of the local density of states in close vicinity to defect sites. Here, we directly measure the nanoscale voltage drop caused by the scattering at step edges, which occurs if a lateral current flows along a three-dimensional topological insulator. The experiments were performed using scanning tunnelling potentiometry for thin Bi2Se3 films. So far, the observed voltage drops are small because of large contributions of the bulk to the <span class="hlt">electronic</span> <span class="hlt">transport</span>. However, for the use of ideal topological insulating thin films in devices, these contributions would play a significant role. PMID:27098939</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21537874','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21537874"><span id="translatedtitle"><span class="hlt">Electron</span> heat <span class="hlt">transport</span> from stochastic fields in gyrokinetic simulations</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wang, E.; Nevins, W. M.; Candy, J.; Hatch, D.; Terry, P.; Guttenfelder, W.</p> <p>2011-05-15</p> <p>GYRO is used to examine the perturbed magnetic field structure generated by electromagnetic gyrokinetic simulations of the CYCLONE base case as {beta}{sub e} is varied from 0.1% to 0.7%, as investigated by J. Candy [Phys. Plasmas 12, 072307 (2005)]. Poincare surface of section plots obtained from integrating the self-consistent magnetic field demonstrates widespread stochasticity for all nonzero values of {beta}{sub e}. Despite widespread stochasticity of the perturbed magnetic fields, no significant increase in <span class="hlt">electron</span> <span class="hlt">transport</span> is observed. The magnetic diffusion, d{sub m}[A. B. Rechester and M. N. Rosenbluth, Phys. Rev. Lett 40, 38 (1978)], is used to quantify the degree of stochasticity and related to the <span class="hlt">electron</span> heat <span class="hlt">transport</span> for hundreds of time slices in each simulation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5551451','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5551451"><span id="translatedtitle">Two-point model for <span class="hlt">electron</span> <span class="hlt">transport</span> in EBT</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Chiu, S.C.; Guest, G.E.</p> <p>1980-01-01</p> <p>The <span class="hlt">electron</span> <span class="hlt">transport</span> in EBT is simulated by a two-point model corresponding to the central plasma and the edge. The central plasma is assumed to obey neoclassical collisionless <span class="hlt">transport</span>. The edge plasma is assumed turbulent and modeled by Bohm diffusion. The steady-state temperatures and densities in both regions are obtained as functions of neutral influx and microwave power. It is found that as the neutral influx decreases and power increases, the edge density decreases while the core density increases. We conclude that if ring instability is responsible for the T-M mode transition, and if stability is correlated with cold <span class="hlt">electron</span> density at the edge, it will depend sensitively on ambient gas pressure and microwave power.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..MARA22005M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..MARA22005M"><span id="translatedtitle">Ab Initio <span class="hlt">Electronic</span> Relaxation Times and <span class="hlt">Transport</span> in Noble Metals</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mustafa, Jamal I.; Bernardi, Marco; Neaton, Jeffrey B.; Louie, Steven G.</p> <p></p> <p>Relaxation times employed to study <span class="hlt">electron</span> <span class="hlt">transport</span> in metals are typically assumed to be constants and obtained empirically using the Drude model. Here, we employ ab initio calculations to compute the <span class="hlt">electron</span>-phonon relaxation times of Cu, Ag, and Au, and find that they vary significantly on the Fermi surface, spanning ~15 -45 fs. We compute room temperature resistivities in excellent agreement with experiment by combining GW bandstructures, Wannier-interpolated band velocities, and ab initio relaxation times. Our calculations are compared to other approximations used for the relaxation times. Additionally, an importance sampling scheme is introduced to speed up the convergence of resistivity and <span class="hlt">transport</span> calculations by sampling directly points on the Fermi surface. This work was supported by NSF Grant No. DMR15-1508412 and U.S. DOE under Contract No. DE-AC02-05CH11231. Computational resources have been provided by DOE at LBNL's NERSC facility.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011PhPl...18e6111W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011PhPl...18e6111W"><span id="translatedtitle"><span class="hlt">Electron</span> heat <span class="hlt">transport</span> from stochastic fields in gyrokinetic simulationsa)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, E.; Nevins, W. M.; Candy, J.; Hatch, D.; Terry, P.; Guttenfelder, W.</p> <p>2011-05-01</p> <p>GYRO is used to examine the perturbed magnetic field structure generated by electromagnetic gyrokinetic simulations of the CYCLONE base case as βe is varied from 0.1% to 0.7%, as investigated by J. Candy [Phys. Plasmas 12, 072307 (2005)]. Poincare surface of section plots obtained from integrating the self-consistent magnetic field demonstrates widespread stochasticity for all nonzero values of βe. Despite widespread stochasticity of the perturbed magnetic fields, no significant increase in <span class="hlt">electron</span> <span class="hlt">transport</span> is observed. The magnetic diffusion, dm [A. B. Rechester and M. N. Rosenbluth, Phys. Rev. Lett 40, 38 (1978)], is used to quantify the degree of stochasticity and related to the <span class="hlt">electron</span> heat <span class="hlt">transport</span> for hundreds of time slices in each simulation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JAP...114f3304H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JAP...114f3304H"><span id="translatedtitle"><span class="hlt">Transport</span> of <span class="hlt">electron</span> beams with initial transverse-longitudinal correlation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Harris, J. R.; Lewellen, J. W.; Poole, B. R.</p> <p>2013-08-01</p> <p>When an <span class="hlt">electron</span> beam whose current varies in time is extracted from a DC gun, the competition between the time-dependent space charge force and the time-independent focusing force will cause a correlation between radius, divergence, current, and position along the beam. This correlation will determine the beam's configuration in trace space, and together with the design of the downstream <span class="hlt">transport</span> system, will determine the quality of the <span class="hlt">transport</span> solutions that can be obtained, including the amplitude of the mismatch oscillations occurring in each slice of the beam. Recent simulations of a simplified diode with Pierce-type focusing operating at nonrelativistic voltages indicated that the radius and divergence of beams extracted from such guns can be approximated to high accuracy as linear functions of current. Here, we consider the impact of this dependence on the beam configuration in trace space and investigate the implications for matching and <span class="hlt">transport</span> of such correlated beams in uniform linear focusing channels.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/532581','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/532581"><span id="translatedtitle">Status of <span class="hlt">electron</span> <span class="hlt">transport</span> in MCNP{trademark}</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hughes, H.G.</p> <p>1997-09-01</p> <p>The latest version of MCNP, the Los Alamos Monte Carlo <span class="hlt">transport</span> code, has now been officially released. MCNP4B has been sent to the Radiation Safety Information Computational Center (RSICC), in Oak Ridge, Tennessee, which is responsible for the further distribution of the code within the US. International distribution of MCNP is done by the Nuclear Energy Agency (ECD/NEA), in Paris, France. Readers with access to the World-Wide-Web should consult the MCNP distribution site http://www-xdiv.lanl.gov/XTM/mcnp/about.html for specific information about contacting RSICC and OECD/NEA. A variety of new features are available in MCNP4B. Among these are differential operator perturbations, cross-section plotting capabilities, enhanced diagnostics for <span class="hlt">transport</span> in repeated structures and lattices, improved efficiency in distributed-memory multiprocessing, corrected particle lifetime and lifespan estimators, and expanded software quality assurance procedures and testing, including testing of the multigroup Boltzmann-Fokker-Planck capability. New and improved cross section sets in the form of ENDF/B-VI evaluations have also been recently released and can be used in MCNP4B. Perhaps most significant for the interests of this special session, the <span class="hlt">electron</span> <span class="hlt">transport</span> algorithm has been improved, especially in the collisional energy-loss straggling and the angular-deflection treatments. In this paper, the author concentrates on a fairly complete documentation of the current status of the <span class="hlt">electron</span> <span class="hlt">transport</span> methods in MCNP.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22415564','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22415564"><span id="translatedtitle">The role of <span class="hlt">electron</span>-impact vibrational excitation in <span class="hlt">electron</span> <span class="hlt">transport</span> through gaseous tetrahydrofuran</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Duque, H. V.; Do, T. P. T.; Konovalov, D. A.; White, R. D.; Brunger, M. J. E-mail: darryl.jones@flinders.edu.au; Jones, D. B. E-mail: darryl.jones@flinders.edu.au</p> <p>2015-03-28</p> <p>In this paper, we report newly derived integral cross sections (ICSs) for <span class="hlt">electron</span> impact vibrational excitation of tetrahydrofuran (THF) at intermediate impact energies. These cross sections extend the currently available data from 20 to 50 eV. Further, they indicate that the previously recommended THF ICS set [Garland et al., Phys. Rev. A 88, 062712 (2013)] underestimated the strength of the <span class="hlt">electron</span>-impact vibrational excitation processes. Thus, that recommended vibrational cross section set is revised to address those deficiencies. <span class="hlt">Electron</span> swarm <span class="hlt">transport</span> properties were calculated with the amended vibrational cross section set, to quantify the role of <span class="hlt">electron</span>-driven vibrational excitation in describing the macroscopic swarm phenomena. Here, significant differences of up to 17% in the <span class="hlt">transport</span> coefficients were observed between the calculations performed using the original and revised cross section sets for vibrational excitation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007PhDT.......149T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007PhDT.......149T"><span id="translatedtitle">Charge <span class="hlt">transport</span> and injection in amorphous organic <span class="hlt">electronic</span> materials</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tse, Shing Chi</p> <p></p> <p>This thesis presents how we use various measuring techniques to study the charge <span class="hlt">transport</span> and injection in organic <span class="hlt">electronic</span> materials. Understanding charge <span class="hlt">transport</span> and injection properties in organic solids is of vital importance for improving performance characteristics of organic <span class="hlt">electronic</span> devices, including organic-light-emitting diodes (OLEDs), photovoltaic cells (OPVs), and field effect transistors (OFETs). The charge <span class="hlt">transport</span> properties of amorphous organic materials, commonly used in organic <span class="hlt">electronic</span> devices, are investigated by the means of carrier mobility measurements. Transient electroluminescence (EL) technique was used to evaluate the <span class="hlt">electron</span> mobility of an <span class="hlt">electron</span> <span class="hlt">transporting</span> material--- tris(8-hydroxyquinoline) aluminum (Alq3). The results are in excellent agreement with independent time-of-flight (TOF) measurements. Then, the effect of dopants on <span class="hlt">electron</span> <span class="hlt">transport</span> was also examined. TOF technique was also used to examine the effects of tertiary-butyl (t-Bu) substitutions on anthracene derivatives (ADN). All ADN compounds were found to be ambipolar. As the degree of t-Bu substitution increases, the carrier mobilities decrease progressively. The reduction of carrier mobilities with increasing t-butylation can be attributed to a decrease in the charge-transfer integral or the wavefunction overlap. In addition, from TOF measurements, two naphthylamine-based hole <span class="hlt">transporters</span>, namely, N,N'-diphenyl-N,N'-bis(1-naphthyl)(1,1'-biphenyl)-4,4'diamine (NPB) and 4,4',4"-tris(n-(2-naphthyl)-n-phenyl-amino)-triphenylamine (2TNATA) were found to possess <span class="hlt">electron-transporting</span> (ET) abilities. An organic light-emitting diode that employed NPB as the ET material was demonstrated. The <span class="hlt">electron</span> conducting mechanism of NPB and 2TNATA in relation to the hopping model will be discussed. Furthermore, the ET property of NPB applied in OLEDs will also be examined. Besides transient EL and TOF techniques, we also use dark-injection space-charge-limited current</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22486307','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22486307"><span id="translatedtitle"><span class="hlt">Electronic</span> <span class="hlt">transport</span> in VO{sub 2}—Experimentally calibrated Boltzmann <span class="hlt">transport</span> modeling</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kinaci, Alper; Rosenmann, Daniel; Chan, Maria K. Y. E-mail: mchan@anl.gov; Kado, Motohisa; Ling, Chen; Zhu, Gaohua; Banerjee, Debasish E-mail: mchan@anl.gov</p> <p>2015-12-28</p> <p>Materials that undergo metal-insulator transitions (MITs) are under intense study, because the transition is scientifically fascinating and technologically promising for various applications. Among these materials, VO{sub 2} has served as a prototype due to its favorable transition temperature. While the physical underpinnings of the transition have been heavily investigated experimentally and computationally, quantitative modeling of <span class="hlt">electronic</span> <span class="hlt">transport</span> in the two phases has yet to be undertaken. In this work, we establish a density-functional-theory (DFT)-based approach with Hubbard U correction (DFT + U) to model <span class="hlt">electronic</span> <span class="hlt">transport</span> properties in VO{sub 2} in the semiconducting and metallic regimes, focusing on band <span class="hlt">transport</span> using the Boltzmann <span class="hlt">transport</span> equations. We synthesized high quality VO{sub 2} films and measured the <span class="hlt">transport</span> quantities across the transition, in order to calibrate the free parameters in the model. We find that the experimental calibration of the Hubbard correction term can efficiently and adequately model the metallic and semiconducting phases, allowing for further computational design of MIT materials for desirable <span class="hlt">transport</span> properties.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27211110','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27211110"><span id="translatedtitle">Implementation of Outstanding <span class="hlt">Electronic</span> <span class="hlt">Transport</span> in Polar Covalent Boron Nitride Atomic Chains: another Extraordinary Odd-Even Behaviour.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Xu, Xiaodong; Li, Weiqi; Liu, Linhua; Feng, Jikang; Jiang, Yongyuan; Tian, Wei Quan</p> <p>2016-05-23</p> <p>A theoretical investigation of the unique <span class="hlt">electronic</span> <span class="hlt">transport</span> properties of the junctions composed of boron nitride atomic chains bridging symmetric graphene electrodes with point-contacts is executed through <span class="hlt">non-equilibrium</span> Green's function technique in combination with density functional theory. Compared with carbon atomic chains, the boron nitride atomic chains have an alternative arrangement of polar covalent B-N bonds and different contacts coupling electrodes, showing some unusual properties in functional atomic <span class="hlt">electronic</span> devices. Remarkably, they have an extraordinary odd-even behavior of conductivity with the length increase. The rectification character and negative differential resistance of nonlinear current-voltage characteristics can be achieved by manipulating the type of contacts between boron nitride atomic chains bridges and electrodes. The junctions with asymmetric contacts have an intrinsic rectification, caused by stronger coupling in the C-N contact than the C-B contact. On the other hand, for symmetric contact junctions, it is confirmed that the <span class="hlt">transport</span> properties of the junctions primarily depend on the nature of contacts. The junctions with symmetric C-N contacts have higher conductivity than their C-B contacts counterparts. Furthermore, the negative differential resistances of the junctions with only C-N contacts is very conspicuous and can be achieved at lower bias.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27211110','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27211110"><span id="translatedtitle">Implementation of Outstanding <span class="hlt">Electronic</span> <span class="hlt">Transport</span> in Polar Covalent Boron Nitride Atomic Chains: another Extraordinary Odd-Even Behaviour.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Xu, Xiaodong; Li, Weiqi; Liu, Linhua; Feng, Jikang; Jiang, Yongyuan; Tian, Wei Quan</p> <p>2016-01-01</p> <p>A theoretical investigation of the unique <span class="hlt">electronic</span> <span class="hlt">transport</span> properties of the junctions composed of boron nitride atomic chains bridging symmetric graphene electrodes with point-contacts is executed through <span class="hlt">non-equilibrium</span> Green's function technique in combination with density functional theory. Compared with carbon atomic chains, the boron nitride atomic chains have an alternative arrangement of polar covalent B-N bonds and different contacts coupling electrodes, showing some unusual properties in functional atomic <span class="hlt">electronic</span> devices. Remarkably, they have an extraordinary odd-even behavior of conductivity with the length increase. The rectification character and negative differential resistance of nonlinear current-voltage characteristics can be achieved by manipulating the type of contacts between boron nitride atomic chains bridges and electrodes. The junctions with asymmetric contacts have an intrinsic rectification, caused by stronger coupling in the C-N contact than the C-B contact. On the other hand, for symmetric contact junctions, it is confirmed that the <span class="hlt">transport</span> properties of the junctions primarily depend on the nature of contacts. The junctions with symmetric C-N contacts have higher conductivity than their C-B contacts counterparts. Furthermore, the negative differential resistances of the junctions with only C-N contacts is very conspicuous and can be achieved at lower bias. PMID:27211110</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4876473','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4876473"><span id="translatedtitle">Implementation of Outstanding <span class="hlt">Electronic</span> <span class="hlt">Transport</span> in Polar Covalent Boron Nitride Atomic Chains: another Extraordinary Odd-Even Behaviour</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Xu, Xiaodong; Li, Weiqi; Liu, Linhua; Feng, Jikang; Jiang, Yongyuan; Tian, Wei Quan</p> <p>2016-01-01</p> <p>A theoretical investigation of the unique <span class="hlt">electronic</span> <span class="hlt">transport</span> properties of the junctions composed of boron nitride atomic chains bridging symmetric graphene electrodes with point-contacts is executed through <span class="hlt">non-equilibrium</span> Green’s function technique in combination with density functional theory. Compared with carbon atomic chains, the boron nitride atomic chains have an alternative arrangement of polar covalent B-N bonds and different contacts coupling electrodes, showing some unusual properties in functional atomic <span class="hlt">electronic</span> devices. Remarkably, they have an extraordinary odd-even behavior of conductivity with the length increase. The rectification character and negative differential resistance of nonlinear current-voltage characteristics can be achieved by manipulating the type of contacts between boron nitride atomic chains bridges and electrodes. The junctions with asymmetric contacts have an intrinsic rectification, caused by stronger coupling in the C-N contact than the C-B contact. On the other hand, for symmetric contact junctions, it is confirmed that the <span class="hlt">transport</span> properties of the junctions primarily depend on the nature of contacts. The junctions with symmetric C-N contacts have higher conductivity than their C-B contacts counterparts. Furthermore, the negative differential resistances of the junctions with only C-N contacts is very conspicuous and can be achieved at lower bias. PMID:27211110</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016NatSR...626389X&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016NatSR...626389X&link_type=ABSTRACT"><span id="translatedtitle">Implementation of Outstanding <span class="hlt">Electronic</span> <span class="hlt">Transport</span> in Polar Covalent Boron Nitride Atomic Chains: another Extraordinary Odd-Even Behaviour</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xu, Xiaodong; Li, Weiqi; Liu, Linhua; Feng, Jikang; Jiang, Yongyuan; Tian, Wei Quan</p> <p>2016-05-01</p> <p>A theoretical investigation of the unique <span class="hlt">electronic</span> <span class="hlt">transport</span> properties of the junctions composed of boron nitride atomic chains bridging symmetric graphene electrodes with point-contacts is executed through <span class="hlt">non-equilibrium</span> Green’s function technique in combination with density functional theory. Compared with carbon atomic chains, the boron nitride atomic chains have an alternative arrangement of polar covalent B-N bonds and different contacts coupling electrodes, showing some unusual properties in functional atomic <span class="hlt">electronic</span> devices. Remarkably, they have an extraordinary odd-even behavior of conductivity with the length increase. The rectification character and negative differential resistance of nonlinear current-voltage characteristics can be achieved by manipulating the type of contacts between boron nitride atomic chains bridges and electrodes. The junctions with asymmetric contacts have an intrinsic rectification, caused by stronger coupling in the C-N contact than the C-B contact. On the other hand, for symmetric contact junctions, it is confirmed that the <span class="hlt">transport</span> properties of the junctions primarily depend on the nature of contacts. The junctions with symmetric C-N contacts have higher conductivity than their C-B contacts counterparts. Furthermore, the negative differential resistances of the junctions with only C-N contacts is very conspicuous and can be achieved at lower bias.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25909689','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25909689"><span id="translatedtitle">Theoretical investigations into the <span class="hlt">electronic</span> structures and <span class="hlt">electron</span> <span class="hlt">transport</span> properties of fluorine and carbonyl end-functionalized quarterthiophenes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Li, Qian; Duan, Yuai; Gao, Hong-Ze; Su, Zhong-Мin; Geng, Yun</p> <p>2015-06-01</p> <p>In this work, we concentrate on systematic investigation on the fluorination and carbonylation effect on <span class="hlt">electron</span> <span class="hlt">transport</span> properties of thiophene-based materials with the aim of seeking and designing <span class="hlt">electron</span> <span class="hlt">transport</span> materials. Some relative factors, namely, frontier molecular orbital (FMO), vertical <span class="hlt">electron</span> affinity (VEA), <span class="hlt">electron</span> reorganization energy (λele), <span class="hlt">electron</span> transfer integral (tele), <span class="hlt">electron</span> drift mobility (μele) and band structures have been calculated and discussed based on density functional theory. The results show that the introduction of fluorine atoms and carbonyl group especially for the latter could effectively increase EA and reduce λele, which is beneficial to the improvement of <span class="hlt">electron</span> <span class="hlt">transport</span> performance. Furthermore, these introductions could also affect the tele by changing molecular packing manner and distribution of FMO. Finally, according to our calculation, the 3d system is considered to be a promising <span class="hlt">electron</span> <span class="hlt">transport</span> material with small λele, high <span class="hlt">electron</span> <span class="hlt">transport</span> ability and good ambient stability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25909689','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25909689"><span id="translatedtitle">Theoretical investigations into the <span class="hlt">electronic</span> structures and <span class="hlt">electron</span> <span class="hlt">transport</span> properties of fluorine and carbonyl end-functionalized quarterthiophenes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Li, Qian; Duan, Yuai; Gao, Hong-Ze; Su, Zhong-Мin; Geng, Yun</p> <p>2015-06-01</p> <p>In this work, we concentrate on systematic investigation on the fluorination and carbonylation effect on <span class="hlt">electron</span> <span class="hlt">transport</span> properties of thiophene-based materials with the aim of seeking and designing <span class="hlt">electron</span> <span class="hlt">transport</span> materials. Some relative factors, namely, frontier molecular orbital (FMO), vertical <span class="hlt">electron</span> affinity (VEA), <span class="hlt">electron</span> reorganization energy (λele), <span class="hlt">electron</span> transfer integral (tele), <span class="hlt">electron</span> drift mobility (μele) and band structures have been calculated and discussed based on density functional theory. The results show that the introduction of fluorine atoms and carbonyl group especially for the latter could effectively increase EA and reduce λele, which is beneficial to the improvement of <span class="hlt">electron</span> <span class="hlt">transport</span> performance. Furthermore, these introductions could also affect the tele by changing molecular packing manner and distribution of FMO. Finally, according to our calculation, the 3d system is considered to be a promising <span class="hlt">electron</span> <span class="hlt">transport</span> material with small λele, high <span class="hlt">electron</span> <span class="hlt">transport</span> ability and good ambient stability. PMID:25909689</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014NatSR...4E5983J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014NatSR...4E5983J"><span id="translatedtitle">Energy level control: toward an efficient hot <span class="hlt">electron</span> <span class="hlt">transport</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jin, Xiao; Li, Qinghua; Li, Yue; Chen, Zihan; Wei, Tai-Huei; He, Xingdao; Sun, Weifu</p> <p>2014-08-01</p> <p>Highly efficient hot <span class="hlt">electron</span> <span class="hlt">transport</span> represents one of the most important properties required for applications in photovoltaic devices. Whereas the fabrication of efficient hot <span class="hlt">electron</span> capture and lost-cost devices remains a technological challenge, regulating the energy level of acceptor-donor system through the incorporation of foreign ions using the solution-processed technique is one of the most promising strategies to overcome this obstacle. Here we present a versatile acceptor-donor system by incorporating MoO3:Eu nanophosphors, which reduces both the `excess' energy offset between the conduction band of acceptor and the lowest unoccupied molecular orbital of donor, and that between the valence band and highest occupied molecular orbital. Strikingly, the hot <span class="hlt">electron</span> transfer time has been shortened. This work demonstrates that suitable energy level alignment can be tuned to gain the higher hot <span class="hlt">electron</span>/hole <span class="hlt">transport</span> efficiency in a simple approach without the need for complicated architectures. This work builds up the foundation of engineering building blocks for third-generation solar cells.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25099864','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25099864"><span id="translatedtitle">Energy level control: toward an efficient hot <span class="hlt">electron</span> <span class="hlt">transport</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Jin, Xiao; Li, Qinghua; Li, Yue; Chen, Zihan; Wei, Tai-Huei; He, Xingdao; Sun, Weifu</p> <p>2014-08-07</p> <p>Highly efficient hot <span class="hlt">electron</span> <span class="hlt">transport</span> represents one of the most important properties required for applications in photovoltaic devices. Whereas the fabrication of efficient hot <span class="hlt">electron</span> capture and lost-cost devices remains a technological challenge, regulating the energy level of acceptor-donor system through the incorporation of foreign ions using the solution-processed technique is one of the most promising strategies to overcome this obstacle. Here we present a versatile acceptor-donor system by incorporating MoO3:Eu nanophosphors, which reduces both the 'excess' energy offset between the conduction band of acceptor and the lowest unoccupied molecular orbital of donor, and that between the valence band and highest occupied molecular orbital. Strikingly, the hot <span class="hlt">electron</span> transfer time has been shortened. This work demonstrates that suitable energy level alignment can be tuned to gain the higher hot <span class="hlt">electron</span>/hole <span class="hlt">transport</span> efficiency in a simple approach without the need for complicated architectures. This work builds up the foundation of engineering building blocks for third-generation solar cells.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/527895','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/527895"><span id="translatedtitle">Multidimensional <span class="hlt">electron</span>-photon <span class="hlt">transport</span> with standard discrete ordinates codes</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Drumm, C.R.</p> <p>1997-04-01</p> <p>A method is described for generating <span class="hlt">electron</span> cross sections that are comparable with standard discrete ordinates codes without modification. There are many advantages of using an established discrete ordinates solver, e.g. immediately available adjoint capability. Coupled <span class="hlt">electron</span>-photon <span class="hlt">transport</span> capability is needed for many applications, including the modeling of the response of <span class="hlt">electronics</span> components to space and man-made radiation environments. The cross sections have been successfully used in the DORT, TWODANT and TORT discrete ordinates codes. The cross sections are shown to provide accurate and efficient solutions to certain multidimensional <span class="hlt">electron</span>-photon <span class="hlt">transport</span> problems. The key to the method is a simultaneous solution of the continuous-slowing-down (CSD) portion and elastic-scattering portion of the scattering source by the Goudsmit-Saunderson theory. The resulting multigroup-Legendre cross sections are much smaller than the true scattering cross sections that they represent. Under certain conditions, the cross sections are guaranteed positive and converge with a low-order Legendre expansion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/562079','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/562079"><span id="translatedtitle">Multidimensional <span class="hlt">electron</span>-photon <span class="hlt">transport</span> with standard discrete ordinates codes</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Drumm, C.R.</p> <p>1997-09-01</p> <p>A method is described for generating <span class="hlt">electron</span> cross sections that are compatible with standard discrete ordinates codes without modification. There are many advantages to using an established discrete ordinates solver, e.g., immediately available adjoint capability. Coupled <span class="hlt">electron</span>-photon <span class="hlt">transport</span> capability is needed for many applications, including the modeling of the response of <span class="hlt">electronics</span> components to space and synthetic radiation environments. The cross sections have been successfully used in the DORT, TWODANT, and TORT discrete ordinates codes. The cross sections are shown to provide accurate and efficient solutions to certain multidimensional <span class="hlt">electron</span>-photon <span class="hlt">transport</span> problems. The key to the method is a simultaneous solution of the continuous-slowing-down and elastic-scattering portions of the scattering source by the Goudsmit-Saunderson theory. The resulting multigroup-Legendre cross sections are much smaller than the true scattering cross sections that they represent. Under certain conditions, the cross sections are guaranteed positive and converge with a low-order Legendre expansion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24132041','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24132041"><span id="translatedtitle"><span class="hlt">Electron</span> <span class="hlt">transport</span> through a quantum dot assisted by cavity photons.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Abdullah, Nzar Rauf; Tang, Chi-Shung; Manolescu, Andrei; Gudmundsson, Vidar</p> <p>2013-11-20</p> <p>We investigate transient <span class="hlt">transport</span> of <span class="hlt">electrons</span> through a single quantum dot controlled by a plunger gate. The dot is embedded in a finite wire with length Lx assumed to lie along the x-direction with a parabolic confinement in the y-direction. The quantum wire, originally with hard-wall confinement at its ends, ±Lx/2, is weakly coupled at t = 0 to left and right leads acting as external <span class="hlt">electron</span> reservoirs. The central system, the dot and the finite wire, is strongly coupled to a single cavity photon mode. A non-Markovian density-matrix formalism is employed to take into account the full <span class="hlt">electron</span>-photon interaction in the transient regime. In the absence of a photon cavity, a resonant current peak can be found by tuning the plunger-gate voltage to lift a many-body state of the system into the source-drain bias window. In the presence of an x-polarized photon field, additional side peaks can be found due to photon-assisted <span class="hlt">transport</span>. By appropriately tuning the plunger-gate voltage, the <span class="hlt">electrons</span> in the left lead are allowed to undergo coherent inelastic scattering to a two-photon state above the bias window if initially one photon was present in the cavity. However, this photon-assisted feature is suppressed in the case of a y-polarized photon field due to the anisotropy of our system caused by its geometry. PMID:24132041</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JChPh.144l4105R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JChPh.144l4105R"><span id="translatedtitle">Distribution of tunnelling times for quantum <span class="hlt">electron</span> <span class="hlt">transport</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rudge, Samuel L.; Kosov, Daniel S.</p> <p>2016-03-01</p> <p>In <span class="hlt">electron</span> <span class="hlt">transport</span>, the tunnelling time is the time taken for an <span class="hlt">electron</span> to tunnel out of a system after it has tunnelled in. We define the tunnelling time distribution for quantum processes in a dissipative environment and develop a practical approach for calculating it, where the environment is described by the general Markovian master equation. We illustrate the theory by using the rate equation to compute the tunnelling time distribution for <span class="hlt">electron</span> <span class="hlt">transport</span> through a molecular junction. The tunnelling time distribution is exponential, which indicates that Markovian quantum tunnelling is a Poissonian statistical process. The tunnelling time distribution is used not only to study the quantum statistics of tunnelling along the average electric current but also to analyse extreme quantum events where an <span class="hlt">electron</span> jumps against the applied voltage bias. The average tunnelling time shows distinctly different temperature dependence for p- and n-type molecular junctions and therefore provides a sensitive tool to probe the alignment of molecular orbitals relative to the electrode Fermi energy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21544794','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21544794"><span id="translatedtitle"><span class="hlt">Electronic</span> <span class="hlt">transport</span> in oligo-para-phenylene junctions attached to carbon nanotube electrodes: Transition-voltage spectroscopy and chirality</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Brito Silva, C. A. Jr.; Silva, S. J. S. da; Leal, J. F. P.; Pinheiro, F. A.; Del Nero, J.</p> <p>2011-06-15</p> <p>We have investigated, by means of a <span class="hlt">nonequilibrium</span> Green's function method coupled to density functional theory, the <span class="hlt">electronic</span> <span class="hlt">transport</span> properties of molecular junctions composed of oligo-para-phenylene (with two, three, four, and five phenyl rings) covalently bridging the gap between metallic carbon nanotubes electrodes. We have found that the current is strongly correlated to a purely geometrical chiral parameter, both on-resonance and off-resonance. The Fowler-Nordheim plot exhibits minima, V{sub min}, that occur whenever the tail of a resonant transmission peak enters in the bias window. This result corroborates the scenario in which the coherent <span class="hlt">transport</span> model gives the correct interpretation to transition voltage spectroscopy (TVS). We have shown that V{sub min} corresponds to voltages where a negative differential resistance (NDR) occurs. The finding that V{sub min} corresponds to voltages that exhibit NDR, which can be explained only in single-molecule junctions within the coherent <span class="hlt">transport</span> model, further confirms the applicability of such models to adequately interpret TVS. The fact that the electrodes are organic is at the origin of differences in the behavior of V{sub min} if compared to the case of molecular junctions with nonorganic contacts treated so far.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26838371','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26838371"><span id="translatedtitle">Control of <span class="hlt">electronic</span> <span class="hlt">transport</span> in graphene by electromagnetic dressing.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kristinsson, K; Kibis, O V; Morina, S; Shelykh, I A</p> <p>2016-01-01</p> <p>We demonstrated theoretically that the renormalization of the <span class="hlt">electron</span> energy spectrum near the Dirac point of graphene by a strong high-frequency electromagnetic field (dressing field) drastically depends on polarization of the field. Namely, linear polarization results in an anisotropic gapless energy spectrum, whereas circular polarization leads to an isotropic gapped one. As a consequence, the stationary (dc) <span class="hlt">electronic</span> <span class="hlt">transport</span> in graphene strongly depends on parameters of the dressing field: A circularly polarized field monotonically decreases the isotropic conductivity of graphene, whereas a linearly polarized one results in both giant anisotropy of conductivity (which can reach thousands of percents) and the oscillating behavior of the conductivity as a function of the field intensity. Since the predicted phenomena can be observed in a graphene layer irradiated by a monochromatic electromagnetic wave, the elaborated theory opens a substantially new way to control <span class="hlt">electronic</span> properties of graphene with light. PMID:26838371</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4738282','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4738282"><span id="translatedtitle">Control of <span class="hlt">electronic</span> <span class="hlt">transport</span> in graphene by electromagnetic dressing</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kristinsson, K.; Kibis, O. V.; Morina, S.; Shelykh, I. A.</p> <p>2016-01-01</p> <p>We demonstrated theoretically that the renormalization of the <span class="hlt">electron</span> energy spectrum near the Dirac point of graphene by a strong high-frequency electromagnetic field (dressing field) drastically depends on polarization of the field. Namely, linear polarization results in an anisotropic gapless energy spectrum, whereas circular polarization leads to an isotropic gapped one. As a consequence, the stationary (dc) <span class="hlt">electronic</span> <span class="hlt">transport</span> in graphene strongly depends on parameters of the dressing field: A circularly polarized field monotonically decreases the isotropic conductivity of graphene, whereas a linearly polarized one results in both giant anisotropy of conductivity (which can reach thousands of percents) and the oscillating behavior of the conductivity as a function of the field intensity. Since the predicted phenomena can be observed in a graphene layer irradiated by a monochromatic electromagnetic wave, the elaborated theory opens a substantially new way to control <span class="hlt">electronic</span> properties of graphene with light. PMID:26838371</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009PPCF...51l4035P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009PPCF...51l4035P"><span id="translatedtitle">Fast-<span class="hlt">electron</span> <span class="hlt">transport</span> in cylindrically laser-compressed matter</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Perez, F.; Koenig, M.; Batani, D.; Baton, S. D.; Beg, F. N.; Benedetti, C.; Brambrink, E.; Chawla, S.; Dorchies, F.; Fourment, C.; Galimberti, M.; Gizzi, L. A.; Heathcote, R.; Higginson, D. P.; Hulin, S.; Jafer, R.; Koester, P.; Labate, L.; Lancaster, K.; Mac Kinnon, A. J.; McPhee, A. G.; Nazarov, W.; Nicolai, P.; Pasley, J.; Ravasio, A.; Richetta, M.; Santos, J. J.; Sgattoni, A.; Spindloe, C.; Vauzour, B.; Volpe, L.</p> <p>2009-12-01</p> <p>Experimental and theoretical results of relativistic <span class="hlt">electron</span> <span class="hlt">transport</span> in cylindrically compressed matter are presented. This experiment, which is a part of the HiPER roadmap, was achieved on the VULCAN laser facility (UK) using four long pulses beams (~4 × 50 J, 1 ns, at 0.53 µm) to compress a hollow plastic cylinder filled with plastic foam of three different densities (0.1, 0.3 and 1 g cm-3). 2D simulations predict a density of 2-5 g cm-3 and a plasma temperature up to 100 eV at maximum compression. A short pulse (10 ps, 160 J) beam generated fast <span class="hlt">electrons</span> that propagate through the compressed matter by irradiating a nickel foil at an intensity of 5 × 1018 W cm-2. X-ray spectrometer and imagers were implemented in order to estimate the compressed plasma conditions and to infer the hot <span class="hlt">electron</span> characteristics. Results are discussed and compared with simulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatSR...620082K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatSR...620082K"><span id="translatedtitle">Control of <span class="hlt">electronic</span> <span class="hlt">transport</span> in graphene by electromagnetic dressing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kristinsson, K.; Kibis, O. V.; Morina, S.; Shelykh, I. A.</p> <p>2016-02-01</p> <p>We demonstrated theoretically that the renormalization of the <span class="hlt">electron</span> energy spectrum near the Dirac point of graphene by a strong high-frequency electromagnetic field (dressing field) drastically depends on polarization of the field. Namely, linear polarization results in an anisotropic gapless energy spectrum, whereas circular polarization leads to an isotropic gapped one. As a consequence, the stationary (dc) <span class="hlt">electronic</span> <span class="hlt">transport</span> in graphene strongly depends on parameters of the dressing field: A circularly polarized field monotonically decreases the isotropic conductivity of graphene, whereas a linearly polarized one results in both giant anisotropy of conductivity (which can reach thousands of percents) and the oscillating behavior of the conductivity as a function of the field intensity. Since the predicted phenomena can be observed in a graphene layer irradiated by a monochromatic electromagnetic wave, the elaborated theory opens a substantially new way to control <span class="hlt">electronic</span> properties of graphene with light.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26838371','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26838371"><span id="translatedtitle">Control of <span class="hlt">electronic</span> <span class="hlt">transport</span> in graphene by electromagnetic dressing.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kristinsson, K; Kibis, O V; Morina, S; Shelykh, I A</p> <p>2016-02-03</p> <p>We demonstrated theoretically that the renormalization of the <span class="hlt">electron</span> energy spectrum near the Dirac point of graphene by a strong high-frequency electromagnetic field (dressing field) drastically depends on polarization of the field. Namely, linear polarization results in an anisotropic gapless energy spectrum, whereas circular polarization leads to an isotropic gapped one. As a consequence, the stationary (dc) <span class="hlt">electronic</span> <span class="hlt">transport</span> in graphene strongly depends on parameters of the dressing field: A circularly polarized field monotonically decreases the isotropic conductivity of graphene, whereas a linearly polarized one results in both giant anisotropy of conductivity (which can reach thousands of percents) and the oscillating behavior of the conductivity as a function of the field intensity. Since the predicted phenomena can be observed in a graphene layer irradiated by a monochromatic electromagnetic wave, the elaborated theory opens a substantially new way to control <span class="hlt">electronic</span> properties of graphene with light.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999PhDT.......165H&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999PhDT.......165H&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Electron</span> <span class="hlt">transport</span> and dephasing in semiconductor quantum dots</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huibers, Andrew Gerrit A.</p> <p></p> <p>At low temperatures, <span class="hlt">electrons</span> in semiconductors can be phase coherent over distances exceeding tens of microns and are sufficiently monochromatic that a variety of interesting quantum interference phenomena can be observed and manipulated. This work discusses <span class="hlt">electron</span> <span class="hlt">transport</span> measurements through cavities (quantum dots) formed by laterally confining <span class="hlt">electrons</span> in the two-dimensional sub-band of a GaAs/AlGaAs heterojunction. Metal gates fabricated using e-beam lithography enable fine control of the cavity shape as well as the leads which connect the dot cavity to source and drain reservoirs. Quantum dots can be modeled by treating the devices as chaotic scatterers. Predictions of this theoretical description are found to be in good quantitative agreement with experimental measurements of full conductance distributions at different temperatures. Weak localization, the suppression of conductance due to phase-coherent backscattering at zero magnetic field, is used to measure dephasing times in the system. Mechanisms responsible for dephasing, including <span class="hlt">electron-electron</span> scattering and Nyquist phase relaxation, are investigated by studying the loss of phase coherence as a function of temperature. Coupling of external microwave fields to the device is also studied to shed light on the unexpected saturation of dephasing that is observed below an <span class="hlt">electron</span> temperature of 100 mK. The effect of external fields in the present experiment is explained in terms of Joule heating from an ac bias.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21506911','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21506911"><span id="translatedtitle">Energetic <span class="hlt">Electron</span> <span class="hlt">Transport</span> In An Inhomogeneous Plasma Medium</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Das, Amita</p> <p>2010-11-23</p> <p>A review of the work carried out at IPR on energetic <span class="hlt">electron</span> <span class="hlt">transport</span> through an inhomogeneous plasma medium is presented in this article. A Generalized <span class="hlt">Electron</span> Magnetohydrodynamic (G-EMHD) fluid model has been developed and employed for such studies. Novel observations such as (i) the trapping of <span class="hlt">electron</span> current pulse structure in a high density plasma region, (ii) the formation of sharp magnetic field shock structures at the inhomogeneous plasma density layer (iii) and intense energy dissipation at the shock layer even in the collisionless limit are reported. The intense energy dissipation of the <span class="hlt">electron</span> current pulse at the shock layer provides a mechanism whereby highly energetic <span class="hlt">electrons</span> which are essentially collision-less can also successfully deposit their energy in a local region of the plasma. This is specially attractive as it opens up the possibility of heating a localized region of an overdense plasma (where lasers cannot penetrate) by highly energetic collision-less <span class="hlt">electrons</span>. A direct application of this mechanism to Fast Ignition (FT) experiments is discussed.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016APS..MARA23003N&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016APS..MARA23003N&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Non-equilibrium</span> hot carrier dynamics in plasmonic nanostructures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Narang, Prineha; Sundararaman, Ravishankar; Jermyn, Adam; Cortes, Emiliano; Maier, Stefan A.; Goddard, William A., III</p> <p></p> <p>Decay of surface plasmons to hot carriers is a new direction that has attracted considerable fundamental and application interest, yet a fundamental understanding of ultrafast plasmon decay processes and the underlying microscopic mechanisms remain incomplete. Ultrafast experiments provide insights into the relaxation of <span class="hlt">non-equilibrium</span> carriers at the tens and hundreds of femtoseconds time scales, but do not yet directly probe shorter times with nanometer spatial resolution. Here we report the first ab initio calculations of non equilibrium <span class="hlt">transport</span> of plasmonic hot carriers in metals and experimental observation of the injection of these carriers into molecules tethered to the metal surface. Specifically, metallic nanoantennas functionalized with a molecular monolayer allow for the direct probing of <span class="hlt">electron</span> injection via surface enhanced Raman spectroscopy of the original and reduced molecular species. We combine first principles calculations of <span class="hlt">electron-electron</span> and <span class="hlt">electron</span>-phonon scattering rates with Boltzmann <span class="hlt">transport</span> simulations to predict the ultrafast dynamics and <span class="hlt">transport</span> of carriers in real materials. We also predict and compare the evolution of <span class="hlt">electron</span> distributions in ultrafast experiments on noble metal nanoparticles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003APS..MARA22008B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003APS..MARA22008B"><span id="translatedtitle">Dissipative <span class="hlt">electronic</span> <span class="hlt">transport</span> through double quantum dots irradiated with microwaves</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brandes, Tobias; Aguado, Ramon; Platero, Gloria</p> <p>2003-03-01</p> <p>Double quantum dots in the strong Coulomb blockade regime are realizations of two-level systems defined from two tunnel--splitted ground states, which are separated by a large energy gap from the remaining many--particle states. The interactions between <span class="hlt">electrons</span> and bosonic degrees of freedom (photons, phonons) in these systems can be tested and manipulated in <span class="hlt">electronic</span> <span class="hlt">transport</span> experiments [1]. Monochromatic classical radiation (AC fields, microwaves) gives rise to various non-linear effects such as photo-sidebands or dynamical localization (coherent supression of tunneling) that show up in the time-averaged, stationary <span class="hlt">electronic</span> current [2]. On the other hand, quantum noise of a dissipative environment strongly influences the <span class="hlt">transport</span> properties of coupled quantum dots [3,4]. In this contribution, we quantitatively investigate the combined influence of a classical, monochromatic time-dependent AC field and a dissipative boson environment on the non-linear <span class="hlt">transport</span> through a double quantum dot. We develop a Floquet-like theory [5] that takes into account the effect of the <span class="hlt">electron</span> reservoirs (leads) and can be numerically evaluated for arbitrary strong AC fields and arbitrary boson environment. In limiting cases we reproduce previous analytical results (polaron tunneling, Tien-Gordon formula). [1] T. Fujisawa, T. H. Oosterkamp, W. G. van der Wiel, B. W. Broer, R. Aguado, S. Tarucha, and L. P. Kouwenhoven, Science 282, 932 (1998); R. H. Blick, D. Pfannkuche, R. J. Haug, K. v. Klitzing, and K. Eberl, Phys. Rev. Lett. 80, 4032 (1998). [2] T. H. Stoof, Yu. V. Nazarov, Phys. Rev. B 53, 1050 (1996). [3] T. Brandes, B. Kramer, Phys. Rev. Lett. 83, 3021 (1999); T. Brandes, F. Renzoni, R. H. Blick, Phys. Rev. B 64, 035319 (2001); T. Brandes, T. Vorrath, Phys. Rev. B 66, 075341 (2002). [4] R. Aguado and L. P. Kouwenhoven, Phys. Rev. Lett, 84, 1986 (2000). [5] M. Grifoni, P. Hänggi, Phys. Rep. 304, 229 (1998).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012asim.book..119Q','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012asim.book..119Q"><span id="translatedtitle">Probing <span class="hlt">Electronic</span> <span class="hlt">Transport</span> of Individual Nanostructures with Atomic Precision</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Qin, Shengyong; Li, An-Ping</p> <p></p> <p>Accessing individual nanostructures with atomic precision is an important process in the bottom-up fabrication and characterization of <span class="hlt">electronic</span> nanodevices. Local electrical contacts, namely nanoelectrodes, are often fabricated by using top-down lithography and chemical etching techniques. These processes however lack atomic precision and introduce the possibility of contamination. Here, we review recent reports on the application of a field-induced emission process in the fabrication of local contacts onto individual nanowires and nanotubes with atomic spatial precision. In this method, gold nanoislands are deposited onto nanostructures precisely by using a scanning tunneling microscope tip, which provides a clean and controllable process to ensure both electrically conductive and mechanically reliable contacts. The applicability of the technique has been demonstrated in a wide variety of nanostructures, including silicide atomic wires, carbon nanotubes, and copper nanowires. These local contacts bridge the nanostructures and the <span class="hlt">transport</span> probes, allowing for the measurements of both electrical <span class="hlt">transport</span> and scanning tunneling microscopy on the same nanostructures in situ. The direct correlation between <span class="hlt">electronic</span> and <span class="hlt">transport</span> properties and atomic structures can be explored on individual nanostructures at the unprecedented atomic level.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1040753','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1040753"><span id="translatedtitle">Probing <span class="hlt">electronic</span> <span class="hlt">transport</span> of individual nanostructures with atomic precision</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Qin, Shengyong; Li, An-Ping</p> <p>2012-01-01</p> <p>Accessing individual nanostructures with atomic precision is an important process in the bottom-up fabrication and characterization of <span class="hlt">electronic</span> nanodevices. Local electrical contacts, namely nanoelectrodes, are often fabricated by using top-down lithography and chemical etching techniques. These processes however lack atomic precision and introduce the possibility of contamination. Here, we review recent reports on the application of a field-induced emission process in the fabrication of local contacts onto individual nanowires and nanotubes with atomic spatial precision. In this method, gold nanoislands are deposited onto nanostructures precisely by using a scanning tunneling microscope tip, which provides a clean and controllable process to ensure both electrically conductive and mechanically reliable contacts. The applicability of the technique has been demonstrated in a wide variety of nanostructures, including silicide atomic wires, carbon nanotubes, and copper nanowires. These local contacts bridge the nanostructures and the <span class="hlt">transport</span> probes, allowing for the measurements of both electrical <span class="hlt">transport</span> and scanning tunneling microscopy on the same nanostructures in situ. The direct correlation between <span class="hlt">electronic</span> and <span class="hlt">transport</span> properties and atomic structures can be explored on individual nanostructures at the unprecedented atomic level.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/accomplishments/documents/fullText/ACC0141.pdf','DOE-RDACC'); return false;" href="http://www.osti.gov/accomplishments/documents/fullText/ACC0141.pdf"><span id="translatedtitle">Helium, Iron and <span class="hlt">Electron</span> Particle <span class="hlt">Transport</span> and Energy <span class="hlt">Transport</span> Studies on the TFTR Tokamak</span></a></p> <p><a target="_blank" href="http://www.osti.gov/accomplishments/fieldedsearch.html">DOE R&D Accomplishments Database</a></p> <p>Synakowski, E. J.; Efthimion, P. C.; Rewoldt, G.; Stratton, B. C.; Tang, W. M.; Grek, B.; Hill, K. W.; Hulse, R. A.; Johnson, D .W.; Mansfield, D. K.; McCune, D.; Mikkelsen, D. R.; Park, H. K.; Ramsey, A. T.; Redi, M. H.; Scott, S. D.; Taylor, G.; Timberlake, J.; Zarnstorff, M. C. (Princeton Univ., NJ (United States). Plasma Physics Lab.); Kissick, M. W. (Wisconsin Univ., Madison, WI (United States))</p> <p>1993-03-01</p> <p>Results from helium, iron, and <span class="hlt">electron</span> <span class="hlt">transport</span> on TFTR in L-mode and Supershot deuterium plasmas with the same toroidal field, plasma current, and neutral beam heating power are presented. They are compared to results from thermal <span class="hlt">transport</span> analysis based on power balance. Particle diffusivities and thermal conductivities are radially hollow and larger than neoclassical values, except possibly near the magnetic axis. The ion channel dominates over the <span class="hlt">electron</span> channel in both particle and thermal diffusion. A peaked helium profile, supported by inward convection that is stronger than predicted by neoclassical theory, is measured in the Supershot The helium profile shape is consistent with predictions from quasilinear electrostatic drift-wave theory. While the perturbative particle diffusion coefficients of all three species are similar in the Supershot, differences are found in the L-Mode. Quasilinear theory calculations of the ratios of impurity diffusivities are in good accord with measurements. Theory estimates indicate that the ion heat flux should be larger than the <span class="hlt">electron</span> heat flux, consistent with power balance analysis. However, theoretical values of the ratio of the ion to <span class="hlt">electron</span> heat flux can be more than a factor of three larger than experimental values. A correlation between helium diffusion and ion thermal <span class="hlt">transport</span> is observed and has favorable implications for sustained ignition of a tokamak fusion reactor.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10141674','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10141674"><span id="translatedtitle">Helium, iron and <span class="hlt">electron</span> particle <span class="hlt">transport</span> and energy <span class="hlt">transport</span> studies on the TFTR tokamak</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Synakowski, E.J.; Efthimion, P.C.; Rewoldt, G.; Stratton, B.C.; Tang, W.M.; Grek, B.; Hill, K.W.; Hulse, R.A.; Johnson, D.W.; Mansfield, D.K.; McCune, D.; Mikkelsen, D.R.; Park, H.K.; Ramsey, A.T.; Redi, M.H.; Scott, S.D.; Taylor, G.; Timberlake, J.; Zarnstorff, M.C.; Kissick, M.W.</p> <p>1993-03-01</p> <p>Results from helium, iron, and <span class="hlt">electron</span> <span class="hlt">transport</span> on TFTR in L-mode and Supershot deuterium plasmas with the same toroidal field, plasma current, and neutral beam heating power are presented. They are compared to results from thermal <span class="hlt">transport</span> analysis based on power balance. Particle diffusivities and thermal conductivities are radially hollow and larger than neoclassical values, except possibly near the magnetic axis. The ion channel dominates over the <span class="hlt">electron</span> channel in both particle and thermal diffusion. A peaked helium profile, supported by inward convection that is stronger than predicted by neoclassical theory, is measured in the Supershot The helium profile shape is consistent with predictions from quasilinear electrostatic drift-wave theory. While the perturbative particle diffusion coefficients of all three species are similar in the Supershot, differences are found in the L-Mode. Quasilinear theory calculations of the ratios of impurity diffusivities are in good accord with measurements. Theory estimates indicate that the ion heat flux should be larger than the <span class="hlt">electron</span> heat flux, consistent with power balance analysis. However, theoretical values of the ratio of the ion to <span class="hlt">electron</span> heat flux can be more than a factor of three larger than experimental values. A correlation between helium diffusion and ion thermal <span class="hlt">transport</span> is observed and has favorable implications for sustained ignition of a tokamak fusion reactor.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015PhDT........73D&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015PhDT........73D&link_type=ABSTRACT"><span id="translatedtitle">Understanding <span class="hlt">electronic</span> structure and <span class="hlt">transport</span> properties in nanoscale junctions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dhungana, Kamal B.</p> <p></p> <p>Understanding the <span class="hlt">electronic</span> structure and the <span class="hlt">transport</span> properties of nanoscale materials are pivotal for designing future nano-scale <span class="hlt">electronic</span> devices. Nanoscale materials could be individual or groups of molecules, nanotubes, semiconducting quantum dots, and biomolecules. Among these several alternatives, organic molecules are very promising and the field of molecular <span class="hlt">electronics</span> has progressed significantly over the past few decades. Despite these progresses, it has not yet been possible to achieve atomic level control at the metal-molecule interface during a conductance measurement, which hinders the progress in this field. The lack of atomic level information of the interface also makes it much harder for theorist to interpret the experimental results. To identify the junction configuration that possibly exists during the experimental measurement of conductance in molecular junction, we created an ensemble of Ruthanium-bis(terpyridine) molecular devices, and studied the <span class="hlt">transport</span> behavior in these molecular junctions. This helps us identifying the junction geometry that yields the experimentally measured current-voltage characteristics. Today's <span class="hlt">electronic</span> devices mostly ignore the spin effect of an <span class="hlt">electron</span>. The inclusion of spin effect of an <span class="hlt">electron</span> on solid-state transistor allows us to build more efficient <span class="hlt">electronic</span> devices; this also alleviates the problem of huge heat dissipation in the nanoscale <span class="hlt">electronic</span> devices. Different materials have been utilized to build three terminals spin transistor since its inception in 1950. In search of suitable candidates for the molecular spin transistor, we have recently designed a spin-valve transistor based on an organometallic molecule; a large amplification (320 %) in tunnel magneto-resistance (TMR) is found to occur at an experimentally accessible gate field. This suggests that the organic molecules can be utilized for making the next generation three terminal spintronic devices. Similarly, we have designed a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1985narn.rept.....P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1985narn.rept.....P"><span id="translatedtitle"><span class="hlt">Nonequilibrium</span> air radiation (Nequair) program: User's manual</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Park, C.</p> <p>1985-07-01</p> <p>A supplement to the data relating to the calculation of <span class="hlt">nonequilibrium</span> radiation in flight regimes of aeroassisted orbital transfer vehicles contains the listings of the computer code NEQAIR (<span class="hlt">Nonequilibrium</span> Air Radiation), its primary input data, and explanation of the user-supplied input variables. The user-supplied input variables are the thermodynamic variables of air at a given point, i.e., number densities of various chemical species, translational temperatures of heavy particles and <span class="hlt">electrons</span>, and vibrational temperature. These thermodynamic variables do not necessarily have to be in thermodynamic equilibrium. The code calculates emission and absorption characteristics of air under these given conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19850022467','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19850022467"><span id="translatedtitle"><span class="hlt">Nonequilibrium</span> air radiation (Nequair) program: User's manual</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Park, C.</p> <p>1985-01-01</p> <p>A supplement to the data relating to the calculation of <span class="hlt">nonequilibrium</span> radiation in flight regimes of aeroassisted orbital transfer vehicles contains the listings of the computer code NEQAIR (<span class="hlt">Nonequilibrium</span> Air Radiation), its primary input data, and explanation of the user-supplied input variables. The user-supplied input variables are the thermodynamic variables of air at a given point, i.e., number densities of various chemical species, translational temperatures of heavy particles and <span class="hlt">electrons</span>, and vibrational temperature. These thermodynamic variables do not necessarily have to be in thermodynamic equilibrium. The code calculates emission and absorption characteristics of air under these given conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22412974','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22412974"><span id="translatedtitle"><span class="hlt">Electron</span> and hole <span class="hlt">transport</span> in ambipolar, thin film pentacene transistors</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Saudari, Sangameshwar R.; Kagan, Cherie R.</p> <p>2015-01-21</p> <p>Solution-processed, ambipolar, thin-film pentacene field-effect transistors were employed to study both <span class="hlt">electron</span> and hole <span class="hlt">transport</span> simultaneously in a single, organic solid-state device. <span class="hlt">Electron</span> and hole mobilities were extracted from the respective unipolar saturation regimes and show thermally activated behavior and gate voltage dependence. We fit the gate voltage dependent saturation mobility to a power law to extract the characteristic Meyer-Neldel (MN) energy, a measure of the width of the exponential distribution of localized states extending into the energy gap of the organic semiconductor. The MN energy is ∼78 and ∼28 meV for <span class="hlt">electrons</span> and holes, respectively, which reflects a greater density of localized tail states for <span class="hlt">electrons</span> than holes. This is consistent with the lower measured <span class="hlt">electron</span> than hole mobility. For holes, the well-behaved linear regime allows for four-point probe measurement of the contact resistance independent mobility and separate characterization of the width of the localized density of states, yielding a consistent MN energy of 28 meV.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4791957','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4791957"><span id="translatedtitle">Nanoscale <span class="hlt">Electron</span> <span class="hlt">Transport</span> Measurements of Immobilized Cytochrome P450 Proteins</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Bostick, Christopher D.; Flora, Darcy R.; Gannett, Peter M.; Tracy, Timothy S.; Lederman, David</p> <p>2015-01-01</p> <p>Gold nanopillars, functionalized with an organic self-assembled monolayer, can be used to measure the electrical conductance properties of immobilized proteins without aggregation. Measurements of the conductance of nanopillars with cytochrome P450 2C9 (CYP2C9) proteins using conducting probe atomic force microscopy demonstrate that a correlation exists between the energy barrier height between hopping sites and CYP2C9 metabolic activity. Measurements performed as a function of tip force indicate that, when subjected to a large force, the protein is more stable in the presence of a substrate. This agrees with the hypothesis that substrate entry into the active site helps to stabilize the enzyme. The relative distance between hopping sites also increases with increasing force, possibly because protein functional groups responsible for <span class="hlt">electron</span> <span class="hlt">transport</span> depend on the structure of the protein. The inhibitor sulfaphenazole, in addition to the previously studied aniline, increased the barrier height for <span class="hlt">electron</span> transfer and thereby makes CYP2C9 reduction more difficult and inhibits metabolism. This suggests that P450 Type II binders may decrease the ease of <span class="hlt">electron</span> <span class="hlt">transport</span> processes in the enzyme, in addition to occupying the active site. PMID:25804257</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3552782','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3552782"><span id="translatedtitle"><span class="hlt">Electron</span> <span class="hlt">transport</span> in a GaPSb film</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p></p> <p>2012-01-01</p> <p>We have performed <span class="hlt">transport</span> measurements on a gallium phosphide antimonide (GaPSb) film grown on GaAs. At low temperatures (T), <span class="hlt">transport</span> is governed by three-dimensional Mott variable range hopping (VRH) due to strong localization. Therefore, electron–<span class="hlt">electron</span> interactions are not significant in GaPSb. With increasing T, the coexistence of VRH conduction and the activated behavior with a gap of 20 meV is found. The fact that the measured gap is comparable to the thermal broadening at room temperature (approximately 25 meV) demonstrates that <span class="hlt">electrons</span> can be thermally activated in an intrinsic GaPSb film. Moreover, the observed carrier density dependence on temperature also supports the coexistence of VRH and the activated behavior. It is shown that the carriers are delocalized either with increasing temperature or magnetic field in GaPSb. Our new experimental results provide important information regarding GaPSb which may well lay the foundation for possible GaPSb-based device applications such as in high-<span class="hlt">electron</span>-mobility transistor and heterojunction bipolar transistors. PMID:23173952</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2806741','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2806741"><span id="translatedtitle">Electrokinesis is a microbial behavior that requires extracellular <span class="hlt">electron</span> <span class="hlt">transport</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Harris, H. W.; El-Naggar, M. Y.; Bretschger, O.; Ward, M. J.; Romine, M. F.; Obraztsova, A. Y.; Nealson, K. H.</p> <p>2009-01-01</p> <p>We report a previously undescribed bacterial behavior termed electrokinesis. This behavior was initially observed as a dramatic increase in cell swimming speed during reduction of solid MnO2 particles by the dissimilatory metal-reducing bacterium Shewanella oneidensis MR-1. The same behavioral response was observed when cells were exposed to small positive applied potentials at the working electrode of a microelectrochemical cell and could be tuned by adjusting the potential on the working electrode. Electrokinesis was found to be different from both chemotaxis and galvanotaxis but was absent in mutants defective in <span class="hlt">electron</span> <span class="hlt">transport</span> to solid metal oxides. Using in situ video microscopy and cell tracking algorithms, we have quantified the response for different strains of Shewanella and shown that the response correlates with current-generating capacity in microbial fuel cells. The electrokinetic response was only exhibited by a subpopulation of cells closest to the MnO2 particles or electrodes. In contrast, the addition of 1 mM 9,10-anthraquinone-2,6-disulfonic acid, a soluble <span class="hlt">electron</span> shuttle, led to increases in motility in the entire population. Electrokinesis is defined as a behavioral response that requires functional extracellular <span class="hlt">electron</span> <span class="hlt">transport</span> and that is observed as an increase in cell swimming speeds and lengthened paths of motion that occur in the proximity of a redox active mineral surface or the working electrode of an electrochemical cell. PMID:20018675</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010APS..MART16001N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010APS..MART16001N"><span id="translatedtitle">Multiscale modelling of charge <span class="hlt">transport</span> in organic <span class="hlt">electronic</span> materials</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nelson, Jenny</p> <p>2010-03-01</p> <p>Charge <span class="hlt">transport</span> in disordered organic semiconductors is controlled by a complex combination of phenomena that span a range of length and time scales. As a result, it is difficult to rationalize charge <span class="hlt">transport</span> properties in terms of material parameters. Until now, efforts to improve charge mobilities in molecular semiconductors have proceeded largely by trial and error rather than through systematic design. However, recent developments have enabled the first predictive simulation studies of charge <span class="hlt">transport</span> in disordered organic semiconductors. In this presentation we will show how a set of computational methods, namely molecular modelling methods to simulate molecular packing, quantum chemical calculations of charge transfer rates, and Monte Carlo simulations of charge <span class="hlt">transport</span> can be used to reproduce experimental charge mobilities with few or no fitting parameters. Using case studies, we will show how such simulations can explain the relative values of <span class="hlt">electron</span> and hole mobility and the effects of grain size, side chains and polymer molecular weight on charge mobility. Although currently applied to material systems of relatively high symmetry or well defined structure, this approach can be developed to address more complex systems such as multicomponent solids and conjugated polymers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1036575','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1036575"><span id="translatedtitle">Contacting nanowires and nanotubes with atomic precision for <span class="hlt">electronic</span> <span class="hlt">transport</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Qin, Shengyong; Hellstrom, Sondra L; Bao, Zhenan; Boyanov, Boyan; Li, An-Ping</p> <p>2012-01-01</p> <p>Making contacts to nanostructures with atomic precision is an important process in the bottom-up fabrication and characterization of <span class="hlt">electronic</span> nanodevices. Existing contacting techniques use top-down lithography and chemical etching, but lack atomic precision and introduce the possibility of contamination. Here, we report that a field-induced emission process can be used to make local contacts onto individual nanowires and nanotubes with atomic spatial precision. The gold nano-islands are deposited onto nanostructures precisely by using a scanning tunneling microscope tip, which provides a clean and controllable method to ensure both electrically conductive and mechanically reliable contacts. To demonstrate the wide applicability of the technique, nano-contacts are fabricated on silicide atomic wires, carbon nanotubes, and copper nanowires. The electrical <span class="hlt">transport</span> measurements are performed in situ by utilizing the nanocontacts to bridge the nanostructures to the <span class="hlt">transport</span> probes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002JMMM..240..117F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002JMMM..240..117F"><span id="translatedtitle"><span class="hlt">Transport</span> properties and <span class="hlt">electronic</span> structure of epitaxial tunnel junctions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Freyss, M.; Papanikolaou, N.; Bellini, V.; Zeller, R.; Dederichs, P. H.; Turek, I.</p> <p>2002-02-01</p> <p>We present ab initio calculations for the <span class="hlt">electronic</span> ground-state and <span class="hlt">transport</span> properties of epitaxial Fe/semiconductor/Fe (0 0 1) tunnel junctions. The ground state properties are determined by the ab initio Screened KKR Green's function method and the <span class="hlt">transport</span> properties by a Green's function formulation of the Landauer-Büttiker formalism. We focus on tunnel junctions with a semiconducting ZnSe barrier and compare them to results for junctions with Si and GaAs barriers. We comment on the presence of metal-induced gap states (MIGS) in the semiconductor, the spin polarization of which strongly depends on the nature of the barrier. We investigate furthermore the influence of one atomic layer at the interface of a non-magnetic metal (Cu, Ag, Al) and of a magnetic 3d transition metal.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5197113','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5197113"><span id="translatedtitle">Conservative differencing of the <span class="hlt">electron</span> Fokker-Planck <span class="hlt">transport</span> equation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Langdon, A.B.</p> <p>1981-01-12</p> <p>We need to extend the applicability and improve the accuracy of kinetic <span class="hlt">electron</span> <span class="hlt">transport</span> codes. In this paper, special attention is given to modelling of e-e collisions, including the dominant contributions arising from anisotropy. The electric field and spatial gradient terms are also considered. I construct finite-difference analogues to the Fokker-Planck integral-differential collision operator, which conserve the particle number, momentum and energy integrals (sums) regardless of the coarseness of the velocity zoning. Such properties are usually desirable, but are especially useful, for example, when there are spatial regions and/or time intervals in which the plasma is cool, so that the collision operator acts rapidly and the velocity distribution is poorly resolved, yet it is crucial that gross conservation properties be respected in hydro-<span class="hlt">transport</span> applications, such as in the LASNEX code. Some points are raised concerning spatial differencing and time integration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPSJ...85j4715O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPSJ...85j4715O"><span id="translatedtitle">Schottky Junctions Studied Using Korringa-Kohn-Rostoker <span class="hlt">Nonequilibrium</span> Green's Function Method</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ogura, Masako; Akai, Hisazumi</p> <p>2016-10-01</p> <p>A scheme that combines the <span class="hlt">nonequilibrium</span> Green's function method with the Korringa-Kohn-Rostoker Green's function method is proposed. The method is applied to Schottky junctions composed of an Al/GaN/Al trilayer. The results show that a Schottky barrier is formed at an undoped GaN and Al interface. The <span class="hlt">transport</span> property of this system under various finite bias voltages is calculated. It is shown that the asymmetric behavior of <span class="hlt">electron</span> <span class="hlt">transport</span> against the direction of bias voltage occurs in this system, confirming the feature of rectification.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhDT........43H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhDT........43H"><span id="translatedtitle">An <span class="hlt">Electronic</span> Structure Approach to Charge Transfer and <span class="hlt">Transport</span> in Molecular Building Blocks for Organic Optoelectronics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hendrickson, Heidi Phillips</p> <p></p> <p> technological design and development. Time dependent perturbation theory, employed by <span class="hlt">non-equilibrium</span> Green's function formalism, is utilized to study the effect of quantum coherences on <span class="hlt">electron</span> <span class="hlt">transport</span> and the effect of symmetry breaking on the <span class="hlt">electronic</span> spectra of model molecular junctions. The fourth part of this thesis presents the design of a physical chemistry course based on a pedagogical approach called Writing-to-Teach. The nature of inaccuracies expressed in student-generated explanations of quantum chemistry topics, and the ability of a peer review process to engage these inaccuracies, is explored within this context.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/971443','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/971443"><span id="translatedtitle">Electrokinesis is a microbial behavior that requires extracellular <span class="hlt">electron</span> <span class="hlt">transport</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Harris, Howard W.; El-Naggar, Mohamed Y.; Bretschger, Orianna; Ward, Melissa J.; Romine, Margaret F.; Obraztsova, Anna; Nealson, Kenneth H.</p> <p>2010-01-05</p> <p>Shewanella species are widespread in nature, enjoying a cosmopolitan distribution in marine,freshwater, sedimentary and soil environments (1), and have attracted considerable attention in recent years because of their ability to reduce an extensive number of different <span class="hlt">electron</span> 3 acceptors, including the solid (oxy)hydroxides of iron and manganese, such as Fe(OH)3 and MnO2, using one or more proposed mechanisms of extracellular <span class="hlt">electron</span> <span class="hlt">transport</span> (EET) (2, 3). The EET ability of Shewanella species is consistent with their ability to generate electric current in microbial fuel cells in the absence of exogenous <span class="hlt">electron</span> shuttles (4). Various strategies of extracellular <span class="hlt">electron</span> transfer have been proposed in metal-reducing microbes, including naturally-occurring (2) or biogenic (5-7) soluble mediators that ‘shuttle’ <span class="hlt">electrons</span> from cells to acceptors, as well as direct transfer using multiheme cytochromes located on the cell exterior (8) and transfer via conductive nanowires (9-11). S. oneidensis MR-1 features several proteins that are involved with the <span class="hlt">transport</span> of <span class="hlt">electrons</span> to the exterior of the cell where they play an important role with regard to the reduction of solid <span class="hlt">electron</span> acceptors such as metal oxides. These include two outer-membrane decaheme c-type cytochromes (MtrC and OmcA), a membrane spanning protein (MtrB), and two periplasmic multi-heme c-type cytochromes (MtrA and CymA). Deletion of the genes encoding any of these proteins leads to phenotypes that are greatly inhibited with regard to metal-oxide reduction and current production in microbial fuel cells (MFCs) (12, 13). The mutation of genes that code for proteins involved in the movement of cytochromes to the outer membrane also results in loss of metal-reducing phenotypes (13). The shewanellae are highly motile, by virtue of a single polar flagellum, and individual S. oneidensis MR-1 cells have been tracked swimming at speeds of up to, and sometimes over, 100 μm/sec, although the average</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhDT.........6B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhDT.........6B"><span id="translatedtitle">Nanoscale <span class="hlt">transport</span> of <span class="hlt">electrons</span> and ions in water</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Boynton, Paul Christopher</p> <p></p> <p>The following dissertation discusses the theoretical study of water on the nanoscale, often involved with essential biological molecules such as DNA and proteins. First I introduce the study of water on the nanoscale and how experimentalists approach confinement with nanopores and nanogaps. Then I discuss the theoretical method we choose for understanding this important biological medium on the molecular level, namely classical molecular dynamics. This leads into <span class="hlt">transport</span> mechanisms that utilize water on the nanoscale, in our case <span class="hlt">electronic</span> and ionic <span class="hlt">transport</span>. On the scale of mere nanometers or less <span class="hlt">electronic</span> <span class="hlt">transport</span> in water enters the tunneling regime, requiring the use of a quantum treatment. In addition, I discuss the importance of water in ionic <span class="hlt">transport</span> and its known effects on biological phenomena such as ion selectivity. Water also has great influence over DNA and proteins, which are both introduced in the context of nanopore sequencing. Several techniques for nanopore sequencing are examined and the importance of protein sequencing is explained. In Chapter 2, we study the effect of volumetric constraints on the structure and <span class="hlt">electronic</span> <span class="hlt">transport</span> properties of distilled water in a nanopore with embedded electrodes. Combining classical molecular dynamics simulations with quantum scattering theory, we show that the structural motifs water assumes inside the pore can be probed directly by tunneling. In Chapter 3, we propose an improvement to the original sequencing by tunneling method, in which N pairs of electrodes are built in series along a synthetic nanochannel. Each current time series for each nucleobase is cross-correlated together, reducing noise in the signals. We show using random sampling of data from classical molecular dynamics, that indeed the sequencing error is significantly reduced as the number of pairs of electrodes, N, increases. In Chapter 4, we propose a new technique for de novo protein sequencing that involves translocating a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3986668','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3986668"><span id="translatedtitle">Inverted organic photovoltaic device with a new <span class="hlt">electron</span> <span class="hlt">transport</span> layer</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p></p> <p>2014-01-01</p> <p>We demonstrate that there is a new solution-processed <span class="hlt">electron</span> <span class="hlt">transport</span> layer, lithium-doped zinc oxide (LZO), with high-performance inverted organic photovoltaic device. The device exhibits a fill factor of 68.58%, an open circuit voltage of 0.86 V, a short-circuit current density of −9.35 cm/mA2 along with 5.49% power conversion efficiency. In addition, we studied the performance of blend ratio dependence on inverted organic photovoltaics. Our device also demonstrates a long stability shelf life over 4 weeks in air. PMID:24674457</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016APS..MARX23001T&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016APS..MARX23001T&link_type=ABSTRACT"><span id="translatedtitle">Thermal and <span class="hlt">Electronic</span> <span class="hlt">Transport</span> in Inorganic and Organic Thermoelectric Materials</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tian, Zhiting</p> <p></p> <p>In this talk, we will first talk about first-principles calculations of phonon and <span class="hlt">electron</span> <span class="hlt">transport</span> in inorganic thermoelectric materials. We will start with rocksalt PbTe and PbSe, and move on to wurtzite ZnO. We will emphasize the strategies to reduce the lattice thermal conductivity. Then we apply first-principles calculations to organic thermoelectric materials. The thermoelectric properties of doped polypyrrole (PPy) will be discussed. In addition, we will cover the chain confinement effects observed in amorphous polymer thin films using molecular dynamics simulations, which highlights the fundamental difference in heat conduction between crystalline polymers and amorphous polymers</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3896775','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3896775"><span id="translatedtitle">Orthogonally modulated molecular <span class="hlt">transport</span> junctions for resettable <span class="hlt">electronic</span> logic gates</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Meng, Fanben; Hervault, Yves-Marie; Shao, Qi; Hu, Benhui; Norel, Lucie; Rigaut, Stéphane; Chen, Xiaodong</p> <p>2014-01-01</p> <p>Individual molecules have been demonstrated to exhibit promising applications as functional components in the fabrication of computing nanocircuits. Based on their advantage in chemical tailorability, many molecular devices with advanced <span class="hlt">electronic</span> functions have been developed, which can be further modulated by the introduction of external stimuli. Here, orthogonally modulated molecular <span class="hlt">transport</span> junctions are achieved via chemically fabricated nanogaps functionalized with dithienylethene units bearing organometallic ruthenium fragments. The addressable and stepwise control of molecular isomerization can be repeatedly and reversibly completed with a judicious use of the orthogonal optical and electrochemical stimuli to reach the controllable switching of conductivity between two distinct states. These photo-/electro-cooperative nanodevices can be applied as resettable <span class="hlt">electronic</span> logic gates for Boolean computing, such as a two-input OR and a three-input AND-OR. The proof-of-concept of such logic gates demonstrates the possibility to develop multifunctional molecular devices by rational chemical design. PMID:24394717</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhyE...76...12F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhyE...76...12F"><span id="translatedtitle">Time dependent <span class="hlt">electronic</span> <span class="hlt">transport</span> in chiral edge channels</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fève, G.; Berroir, J.-M.; Plaçais, B.</p> <p>2016-02-01</p> <p>We study time dependent <span class="hlt">electronic</span> <span class="hlt">transport</span> along the chiral edge channels of the quantum Hall regime, focusing on the role of Coulomb interaction. In the low frequency regime, the a.c. conductance can be derived from a lumped element description of the circuit. At higher frequencies, the propagation equations of the Coulomb coupled edge channels need to be solved. As a consequence of the interchannel coupling, a charge pulse emitted in a given channel fractionalized in several pulses. In particular, Coulomb interaction between channels leads to the fractionalization of a charge pulse emitted in a given channel in several pulses. We finally study how the Coulomb interaction, and in particular the fractionalization process, affects the propagation of a single <span class="hlt">electron</span> in the circuit. All the above-mentioned topics are illustrated by experimental realizations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhyE...82..129F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhyE...82..129F"><span id="translatedtitle">Reprint of : Time dependent <span class="hlt">electronic</span> <span class="hlt">transport</span> in chiral edge channels</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fève, G.; Berroir, J.-M.; Plaçais, B.</p> <p>2016-08-01</p> <p>We study time dependent <span class="hlt">electronic</span> <span class="hlt">transport</span> along the chiral edge channels of the quantum Hall regime, focusing on the role of Coulomb interaction. In the low frequency regime, the a.c. conductance can be derived from a lumped element description of the circuit. At higher frequencies, the propagation equations of the Coulomb coupled edge channels need to be solved. As a consequence of the interchannel coupling, a charge pulse emitted in a given channel fractionalized in several pulses. In particular, Coulomb interaction between channels leads to the fractionalization of a charge pulse emitted in a given channel in several pulses. We finally study how the Coulomb interaction, and in particular the fractionalization process, affects the propagation of a single <span class="hlt">electron</span> in the circuit. All the above-mentioned topics are illustrated by experimental realizations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SeScT..31f5012Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SeScT..31f5012Y"><span id="translatedtitle">Analytical band Monte Carlo analysis of <span class="hlt">electron</span> <span class="hlt">transport</span> in silicene</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yeoh, K. H.; Ong, D. S.; Ooi, C. H. Raymond; Yong, T. K.; Lim, S. K.</p> <p>2016-06-01</p> <p>An analytical band Monte Carlo (AMC) with linear energy band dispersion has been developed to study the <span class="hlt">electron</span> <span class="hlt">transport</span> in suspended silicene and silicene on aluminium oxide (Al2O3) substrate. We have calibrated our model against the full band Monte Carlo (FMC) results by matching the velocity-field curve. Using this model, we discover that the collective effects of charge impurity scattering and surface optical phonon scattering can degrade the <span class="hlt">electron</span> mobility down to about 400 cm2 V-1 s-1 and thereafter it is less sensitive to the changes of charge impurity in the substrate and surface optical phonon. We also found that further reduction of mobility to ˜100 cm2 V-1 s-1 as experimentally demonstrated by Tao et al (2015 Nat. Nanotechnol. 10 227) can only be explained by the renormalization of Fermi velocity due to interaction with Al2O3 substrate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006JPhy4.133..405K&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006JPhy4.133..405K&link_type=ABSTRACT"><span id="translatedtitle">Behaviour of fast <span class="hlt">electron</span> <span class="hlt">transport</span> in solid targets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Koenig, M.; Baton, S. D.; Benuzzi-Mounaix, A.; Fuchs, J.; Loupias, B.; Guillou, P.; Batani, D.; Morace, A.; Piazza, D.; Kodama, R.; Norimatsu, T.; Nakatsutsumi, M.; Aglitskiy, Y.; Rousseaux, C.</p> <p>2006-06-01</p> <p>One of the main issues of the fast ignitor scheme is the role of fast <span class="hlt">electron</span> <span class="hlt">transport</span> in the solid fuel heating. Recent experiments used a new target scheme based on the use of cone to guide the PW laser and enhance the <span class="hlt">electron</span> production. In this context it is fundamental to understand the physics underlying this new target scheme. We report here recent and preliminary results of ultra-intense laser pulse interaction with three layer targets in presence of the cone or without. Experiments have been performed at LULI with the 100 TW laser facility, at intensities up to 3 1019 W/cm2. Several diagnostics have been implemented (2D Kα imaging, Kα spectroscopy and rear side imaging, protons emission) to quantify the cone effect.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25307017','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25307017"><span id="translatedtitle">Semiconducting black phosphorus: synthesis, <span class="hlt">transport</span> properties and <span class="hlt">electronic</span> applications.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Liu, Han; Du, Yuchen; Deng, Yexin; Ye, Peide D</p> <p>2015-05-01</p> <p>Phosphorus is one of the most abundant elements preserved in earth, and it comprises a fraction of ∼0.1% of the earth crust. In general, phosphorus has several allotropes, and the two most commonly seen allotropes, i.e. white and red phosphorus, are widely used in explosives and safety matches. In addition, black phosphorus, though rarely mentioned, is a layered semiconductor and has great potential in optical and <span class="hlt">electronic</span> applications. Remarkably, this layered material can be reduced to one single atomic layer in the vertical direction owing to the van der Waals structure, and is known as phosphorene, in which the physical properties can be tremendously different from its bulk counterpart. In this review article, we trace back to the research history on black phosphorus of over 100 years from the synthesis to material properties, and extend the topic from black phosphorus to phosphorene. The physical and <span class="hlt">transport</span> properties are highlighted for further applications in <span class="hlt">electronic</span> and optoelectronics devices.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22305687','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22305687"><span id="translatedtitle"><span class="hlt">Nonequilibrium</span> phonon effects in midinfrared quantum cascade lasers</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Shi, Y. B. Knezevic, I.</p> <p>2014-09-28</p> <p>We investigate the effects of <span class="hlt">nonequilibrium</span> phonon dynamics on the operation of a GaAs-based midinfrared quantum cascade laser over a range of temperatures (77–300 K) via a coupled ensemble Monte Carlo simulation of <span class="hlt">electron</span> and optical-phonon systems. <span class="hlt">Nonequilibrium</span> phonon effects are shown to be important below 200 K. At low temperatures, <span class="hlt">nonequilibrium</span> phonons enhance injection selectivity and efficiency by drastically increasing the rate of interstage <span class="hlt">electron</span> scattering from the lowest injector state to the next-stage upper lasing level via optical-phonon absorption. As a result, the current density and modal gain at a given field are higher and the threshold current density lower and considerably closer to experiment than results obtained with thermal phonons. By amplifying phonon absorption, <span class="hlt">nonequilibrium</span> phonons also hinder <span class="hlt">electron</span> energy relaxation and lead to elevated <span class="hlt">electronic</span> temperatures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPhCS.717a2043O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPhCS.717a2043O"><span id="translatedtitle"><span class="hlt">Electron</span> <span class="hlt">transport</span> estimated from <span class="hlt">electron</span> spectra using <span class="hlt">electron</span> spectrometer in LFEX laser target experiments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ozaki, T.; Hata, M.; Matsuo, K.; Kojima, S.; Arikawa, Y.; Fujioka, S.; Sakagami, H.; Sunahara, A.; Nagatomo, H.; Johzaki, T.; Yogo, A.; Morace, A.; Zhang, Z.; Shiraga, H.; Sakata, S.; Nagai, T.; Abe, Y.; Lee, S.; Nakai, M.; Nishimura, H.; Azechi, H.; FIREX Group; GXII-LFEX Group</p> <p>2016-05-01</p> <p>Hot <span class="hlt">electrons</span> which are generated from targets irradiated by a high-intense laser are measured by two <span class="hlt">electron</span> spectrometers (ESMs). However, total <span class="hlt">electron</span> energy observed by the ESM is only less than 1%. Hot <span class="hlt">electrons</span> are confined by self-fields due to the huge current. When an external magnetic field of several hundred Tesla is applied during the laser irradiation on targets, the ESM signals always increase. In the simulation, the same result can be obtained. The reason is that the Alfvén limit can be mitigated due to the external longitudinal magnetic field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1993PhDT........97G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1993PhDT........97G"><span id="translatedtitle">Long-Range Superexchange in <span class="hlt">Electron</span> <span class="hlt">Transport</span> Proteins</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gruschus, James Michael</p> <p></p> <p> cytochrome c, as well as plastocyanin, cytochrome b _5, and cytochrome c peroxidase. The surfaces reveal important clues as to which conformations of the <span class="hlt">electron</span> <span class="hlt">transport</span> protein complexes actually give rise to <span class="hlt">electron</span> transfer, a subject of broad biological interest.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6202181','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6202181"><span id="translatedtitle"><span class="hlt">Electron</span> heat <span class="hlt">transport</span> in a steep temperature gradient</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Rogers, J.H.; De Groot, J.S.; Abou-Assaleh, Z.; Matte, J.P.; Johnston, T.W.; Rosen, M.D.</p> <p>1989-04-01</p> <p>Temporal and spatial measurements of <span class="hlt">electron</span> heat <span class="hlt">transport</span> are made in the University of California Davis AURORA device (J. H. Rogers, Ph.D. dissertation, University of California, Davis, 1987). In AURORA, a microwave pulse heats a region of underdense, collisional, plasma (n/n/sub cr/ approx. <1, where n/sub cr/ = 1.8 x 10/sup 10/ cm/sup -3/ is the critical density, T/sub e//sub 0/ approx. =0.15 eV, and the <span class="hlt">electron</span> scattering mean free path lambda/sub perpendicular/approx. >2 cm). In this region, strong thermal heating (T/sub c/ approx. <0.7 eV) as well as suprathermal heating (T/sub h/approx. =3 eV) is observed. The strong heating results in a steep temperature gradient that violates the approximations of classical heat diffusion theory (L/sub T//lambda/sub perpendicular/approx. >3 for thermal <span class="hlt">electrons</span>, where L/sub T/ = T/sub c/(partialT/sub c//partialz)/sup -1/ is the cold <span class="hlt">electron</span> temperature scale length. The time evolution of the <span class="hlt">electron</span> temperature profile is measured using Langmuir probes. The measured relaxation of the temperature gradient after the microwave pulse is compared to calculations using the Fokker--Planck International code (Phys. Rev. Lett. 49, 1936 (1982)) and the multigroup, flux-limited, target design code LASNEX (Comm. Plasma Phys. 2, 51 (1975)). The <span class="hlt">electron</span> distribution function at the end of the microwave pulse is used as initial conditions for both codes. The Fokker--Planck calculations are found to agree very well with the measurements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/763897','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/763897"><span id="translatedtitle">Interfacial Charge <span class="hlt">Transport</span> in Organic <span class="hlt">Electronic</span> Materials: the Key to a New <span class="hlt">Electronics</span> Technology</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Smith, D.L.; Campbell, I.H.; Davids, P.S.; Heller, C.M.; Laurich, B.K.; Crone, B.K.; Saxena, A.; Bishop, A.R.; Ferraris, J.P.; Yu, Z.G.</p> <p>1999-06-04</p> <p>This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The primary aim of this project is to obtain a basic scientific understanding of electrical <span class="hlt">transport</span> processes at interfaces that contain an organic <span class="hlt">electronic</span> material. Because of their processing advantages and the tunability of their <span class="hlt">electronic</span> properties, organic <span class="hlt">electronic</span> materials are revolutionizing major technological areas such as information display. We completed an investigation of the fundamental <span class="hlt">electronic</span> excitation energies in the prototype conjugated polymer MEH-PPV. We completed a combined theoretical/experimental study of the energy relation between charged excitations in a conjugated polymer and the metal at a polymer/metal interface. We developed a theoretical model that explains injection currents at polymer/metal interfaces. We have made electrical measurements on devices fabricated using the conjugated polymer MEH-PPV a nd a series of metals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19730032179&hterms=density+chemistry&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Ddensity%2Bchemistry','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19730032179&hterms=density+chemistry&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Ddensity%2Bchemistry"><span id="translatedtitle">Effects of <span class="hlt">nonequilibrium</span> ablation chemistry on Viking radio blackout.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Evans, J. S.; Schexnayder, C. J., Jr.; Grose, W. L.</p> <p>1973-01-01</p> <p>The length of the entry blackout period during descent of the Viking Lander into the Mars atmosphere is predicted from calculated profiles of <span class="hlt">electron</span> density in the shock layer over the aeroshell. <span class="hlt">Nonequilibrium</span> chemistry plays a key role in the calculation, both in the inviscid flow and in the boundary layer. This is especially true in the boundary layer contaminated with ablation material, for which <span class="hlt">nonequilibrium</span> chemistry predicts <span class="hlt">electron</span> densities two decades lower than the same case calculated with equilibrium chemistry.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/477761','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/477761"><span id="translatedtitle"><span class="hlt">Electron</span> <span class="hlt">transport</span> in coupled double quantum wells and wires</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Harff, N.E.; Simmons, J.A.; Lyo, S.K.</p> <p>1997-04-01</p> <p>Due to inter-quantum well tunneling, coupled double quantum wells (DQWs) contain an extra degree of <span class="hlt">electronic</span> freedom in the growth direction, giving rise to new <span class="hlt">transport</span> phenomena not found in single <span class="hlt">electron</span> layers. This report describes work done on coupled DQWs subject to inplane magnetic fields B{sub {parallel}}, and is based on the lead author`s doctoral thesis, successfully defended at Oregon State University on March 4, 1997. First, the conductance of closely coupled DQWs in B{sub {parallel}} is studied. B{sub {parallel}}-induced distortions in the dispersion, the density of states, and the Fermi surface are described both theoretically and experimentally, with particular attention paid to the dispersion anticrossing and resulting partial energy gap. Measurements of giant distortions in the effective mass are found to agree with theoretical calculations. Second, the Landau level spectra of coupled DQWs in tilted magnetic fields is studied. The magnetoresistance oscillations show complex beating as Landau levels from the two Fermi surface components cross the Fermi level. A third set of oscillations resulting from magnetic breakdown is observed. A semiclassical calculation of the Landau level spectra is then performed, and shown to agree exceptionally well with the data. Finally, quantum wires and quantum point contacts formed in DQW structures are investigated. Anticrossings of the one-dimensional DQW dispersion curves are predicted to have interesting <span class="hlt">transport</span> effects in these devices. Difficulties in sample fabrication have to date prevented experimental verification. However, recently developed techniques to overcome these difficulties are described.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/787905','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/787905"><span id="translatedtitle">Simulations of <span class="hlt">Electron</span> <span class="hlt">Transport</span> in Laser Hot Spots</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>S. Brunner; E. Valeo</p> <p>2001-08-30</p> <p>Simulations of <span class="hlt">electron</span> <span class="hlt">transport</span> are carried out by solving the Fokker-Planck equation in the diffusive approximation. The system of a single laser hot spot, with open boundary conditions, is systematically studied by performing a scan over a wide range of the two relevant parameters: (1) Ratio of the stopping length over the width of the hot spot. (2) Relative importance of the heating through inverse Bremsstrahlung compared to the thermalization through self-collisions. As for uniform illumination [J.P. Matte et al., Plasma Phys. Controlled Fusion 30 (1988) 1665], the bulk of the velocity distribution functions (VDFs) present a super-Gaussian dependence. However, as a result of spatial <span class="hlt">transport</span>, the tails are observed to be well represented by a Maxwellian. A similar dependence of the distributions is also found for multiple hot spot systems. For its relevance with respect to stimulated Raman scattering, the linear Landau damping of the <span class="hlt">electron</span> plasma wave is estimated for such VD Fs. Finally, the nonlinear Fokker-Planck simulations of the single laser hot spot system are also compared to the results obtained with the linear non-local hydrodynamic approach [A.V. Brantov et al., Phys. Plasmas 5 (1998) 2742], thus providing a quantitative limit to the latter method: The hydrodynamic approach presents more than 10% inaccuracy in the presence of temperature variations of the order delta T/T greater than or equal to 1%, and similar levels of deformation of the Gaussian shape of the Maxwellian background.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JPCM...24p4209Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JPCM...24p4209Z"><span id="translatedtitle"><span class="hlt">Electron</span> <span class="hlt">transport</span> properties of single molecular junctions under mechanical modulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhou, Jianfeng; Guo, Cunlan; Xu, Bingqian</p> <p>2012-04-01</p> <p><span class="hlt">Electron</span> <span class="hlt">transport</span> behaviors of single molecular junctions are very sensitive to the atomic scale molecule-metal electrode contact interfaces, which have been difficult to control. We used a modified scanning probe microscope-break junction technique (SPM-BJT) to control the dynamics of the contacts and simultaneously monitor both the conductance and force. First, by fitting the measured data into a modified multiple tunneling barrier model, the static contact resistances, corresponding to the different contact conformations of single alkanedithiol and alkanediamine molecular junctions, were identified. Second, the changes of contact decay constant were measured under mechanical extensions of the molecular junctions, which helped to classify the different single molecular conductance sets into specific microscopic conformations of the molecule-electrode contacts. Third, by monitoring the changes of force and contact decay constant with the mechanical extensions, the changes of conductance were found to be caused by the changes of contact bond length and by the atomic reorganizations near the contact bond. This study provides a new insight into the understanding of the influences of contact conformations, especially the effect of changes of dynamic contact conformation on <span class="hlt">electron</span> <span class="hlt">transport</span> through single molecular junctions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1047362','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1047362"><span id="translatedtitle"><span class="hlt">Electron</span> <span class="hlt">Transport</span> Materials: Synthesis, Properties and Device Performance</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cosimbescu, Lelia; Wang, Liang; Helm, Monte L.; Polikarpov, Evgueni; Swensen, James S.; Padmaperuma, Asanga B.</p> <p>2012-06-01</p> <p>We report the design, synthesis and characterization, thermal and photophysical properties of two silane based <span class="hlt">electron</span> <span class="hlt">transport</span> materials, dibenzo[b,d]thiophen-2-yltriphenylsilane (Si{phi}87) and (dibenzo[b,d]thiophen-2-yl)diphenylsilane (Si{phi}88) and their performance in blue organic light emitting devices (OLEDs). The utility of these materials in blue OLEDs with iridium (III) bis[(4,6-difluorophenyl)-pyridinato-N,C']picolinate (Firpic) as the phosphorescent emitter was demonstrated. Using the silane Si{phi}87 as the <span class="hlt">electron</span> <span class="hlt">transport</span> material (ETm) an EQE of 18.2% was obtained, with a power efficiency of 24.3 lm/W (5.8V at 1mA/cm{sup 2}), in a heterostructure. When Si{phi}88 is used, the EQE is 18.5% with a power efficiency of 26.0 lm/W (5.5V at 1mA/cm{sup 2}).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22220220','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22220220"><span id="translatedtitle">Langmuir probe measurements in a time-fluctuating-highly ionized <span class="hlt">non-equilibrium</span> cutting arc: Analysis of the <span class="hlt">electron</span> retarding part of the time-averaged current-voltage characteristic of the probe</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Prevosto, L.; Mancinelli, B.; Kelly, H.</p> <p>2013-12-15</p> <p>This work describes the application of Langmuir probe diagnostics to the measurement of the <span class="hlt">electron</span> temperature in a time-fluctuating-highly ionized, <span class="hlt">non-equilibrium</span> cutting arc. The <span class="hlt">electron</span> retarding part of the time-averaged current-voltage characteristic of the probe was analysed, assuming that the standard exponential expression describing the <span class="hlt">electron</span> current to the probe in collision-free plasmas can be applied under the investigated conditions. A procedure is described which allows the determination of the errors introduced in time-averaged probe data due to small-amplitude plasma fluctuations. It was found that the experimental points can be gathered into two well defined groups allowing defining two quite different averaged <span class="hlt">electron</span> temperature values. In the low-current region the averaged characteristic was not significantly disturbed by the fluctuations and can reliably be used to obtain the actual value of the averaged <span class="hlt">electron</span> temperature. In particular, an averaged <span class="hlt">electron</span> temperature of 0.98 ± 0.07 eV (= 11400 ± 800 K) was found for the central core of the arc (30 A) at 3.5 mm downstream from the nozzle exit. This average included not only a time-average over the time fluctuations but also a spatial-average along the probe collecting length. The fitting of the high-current region of the characteristic using such <span class="hlt">electron</span> temperature value together with the corrections given by the fluctuation analysis showed a relevant departure of local thermal equilibrium in the arc core.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24387432','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24387432"><span id="translatedtitle">Langmuir probe measurements in a time-fluctuating-highly ionized <span class="hlt">non-equilibrium</span> cutting arc: analysis of the <span class="hlt">electron</span> retarding part of the time-averaged current-voltage characteristic of the probe.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Prevosto, L; Kelly, H; Mancinelli, B</p> <p>2013-12-01</p> <p>This work describes the application of Langmuir probe diagnostics to the measurement of the <span class="hlt">electron</span> temperature in a time-fluctuating-highly ionized, <span class="hlt">non-equilibrium</span> cutting arc. The <span class="hlt">electron</span> retarding part of the time-averaged current-voltage characteristic of the probe was analysed, assuming that the standard exponential expression describing the <span class="hlt">electron</span> current to the probe in collision-free plasmas can be applied under the investigated conditions. A procedure is described which allows the determination of the errors introduced in time-averaged probe data due to small-amplitude plasma fluctuations. It was found that the experimental points can be gathered into two well defined groups allowing defining two quite different averaged <span class="hlt">electron</span> temperature values. In the low-current region the averaged characteristic was not significantly disturbed by the fluctuations and can reliably be used to obtain the actual value of the averaged <span class="hlt">electron</span> temperature. In particular, an averaged <span class="hlt">electron</span> temperature of 0.98 ± 0.07 eV (= 11400 ± 800 K) was found for the central core of the arc (30 A) at 3.5 mm downstream from the nozzle exit. This average included not only a time-average over the time fluctuations but also a spatial-average along the probe collecting length. The fitting of the high-current region of the characteristic using such <span class="hlt">electron</span> temperature value together with the corrections given by the fluctuation analysis showed a relevant departure of local thermal equilibrium in the arc core.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..DMP.Q1094S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..DMP.Q1094S"><span id="translatedtitle">Computing Rydberg <span class="hlt">Electron</span> <span class="hlt">Transport</span> Rates via Classical Periodic Orbits</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sattari, Sulimon; Mitchell, Kevin</p> <p>2016-05-01</p> <p><span class="hlt">Electron</span> <span class="hlt">transport</span> properties of chaotic atomic systems may be computable from classical periodic orbits. This technique allows for replacing a Monte Carlo simulation launching millions of orbits with a sum over tens or hundreds of properly chosen periodic orbits. A firm grasp of the structure of the periodic orbits is required to obtain accurate <span class="hlt">transport</span> rates. We apply a technique called homotopic lobe dynamics (HLD) to understand the structure of periodic orbits to compute the ionization rate of a hydrogen atom in strong parallel electric and magnetic fields. HLD uses information encoded in the intersections of stable and unstable manifolds of a few orbits to compute all relevant periodic orbits in the system. The ionization rate computed from periodic orbits using HLD converges exponentially to the true value as a function of the highest period used. We then use periodic orbit continuation to accurately compute the ionization rate when the field strengths are varied. The ability to use periodic orbits in a mixed phase space could allow for studying <span class="hlt">transport</span> in even more complex few body systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24483414','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24483414"><span id="translatedtitle"><span class="hlt">Nonequilibrium</span> heat capacity.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mandal, Dibyendu</p> <p>2013-12-01</p> <p>Development of steady state thermodynamics and statistical mechanics depends crucially on our ability to extend the notions of equilibrium thermodynamics to <span class="hlt">nonequilibrium</span> steady states (NESS). The present paper considers the extension of heat capacity. A modified definition is proposed which continues to maintain the same relation to steady state Shannon entropy as in equilibrium, thus providing a thermodynamically consistent treatment of NESS heat capacity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21120514','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21120514"><span id="translatedtitle"><span class="hlt">Electron</span> thermal <span class="hlt">transport</span> analysis in Tokamak a Configuration Variable</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Asp, E.; Porte, L.; Alberti, S.; Karpushov, A.; Martin, Y.; Sauter, O.; Turri, G.; Kim, J.-H.; Horton, W.</p> <p>2008-08-15</p> <p>A Tokamak a Configuration Variable (TCV) [G. Tonetti, A. Heym, F. Hofmann et al., in Proceedings of the 16th Symposium on Fusion Technology, London, U.K., edited by R. Hemsworth (North-Holland, Amsterdam, 1991), p. 587] plasma with high power density (up to 8 MW/m{sup 3}) core deposited <span class="hlt">electron</span> cyclotron resonance heating at significant plasma densities ({<=}7x10{sup 19} m{sup -3}) is analyzed for the <span class="hlt">electron</span> thermal <span class="hlt">transport</span>. The discharge distinguishes itself as it has four distinct high confinement mode (H-mode) phases. An Ohmic H-mode with type III edge localized modes (ELMs), which turns into a type I ELMy H-mode when the ECRH is switched on. The ELMs then vanish, which gives rise to a quasistationary ELM-free H-mode. This ELM-free phase can be divided into two, one without magnetohydrodynamics (MHD) and one with. The MHD mode in the latter case causes the confinement to drop by {approx}15%. For all four phases both large-scale trapped <span class="hlt">electron</span> (TEM) and ion temperature gradient (ITG) modes and small-scale <span class="hlt">electron</span> temperature gradient (ETG) modes are analyzed. The analytical TEM formulas have difficulty in explaining both the magnitude and the radial profile of the <span class="hlt">electron</span> thermal flux. Collisionality governs the drive of the TEM, which for the discharge in question implies it can be driven by either the temperature or density gradient. The TEM response function is derived and it is shown to be relatively small and to have sharp resonances in its energy dependence. The ETG turbulence, predicted by the Institute for Fusion Studies <span class="hlt">electron</span> gyrofluid code, is on the other hand driven solely by the <span class="hlt">electron</span> temperature gradient. Both trapped and passing <span class="hlt">electrons</span> add to the ETG instability and turbulent thermal flux. For easy comparison of the results of the above approaches and also with the Weiland model, a dimensionless error measure, the so-called average relative variance is introduced. According to this method the ETG model explains 70% of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007PhDT.......202W&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007PhDT.......202W&link_type=ABSTRACT"><span id="translatedtitle">Spin-dependent <span class="hlt">electron</span> <span class="hlt">transport</span> in nanoscale samples</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wei, Yaguang</p> <p></p> <p>In this thesis, we describe the research in which we use metallic nanoparticles to explore spin-dependent <span class="hlt">electron</span> <span class="hlt">transport</span> at nanometer scale. Nanoscale samples were fabricated by using a state of the art <span class="hlt">electron</span> beam lithography and shadow evaporation technique. We have investigated spin relaxation and decoherence in metallic grains as a function of bias voltage and magnetic field at low temperatures (down to ˜30mK). At low temperatures, the discrete energy levels within a metallic nanoparticle provides a new means to study the physics of the spin-polarized <span class="hlt">electron</span> tunneling. We describe measurements of spin-polarized tunneling via discrete energy levels of single Aluminum grain. Spin polarized current saturates quickly as a function of bias voltage, which demonstrates that the ground state and the lowest excited states carry spin polarized current. The ratio of <span class="hlt">electron</span>-spin relaxation time (T1) to the <span class="hlt">electron</span>-phonon relaxation rate is in quantitative agreement with the Elliot-Yafet scaling, an evidence that spin-relaxation in Al grains is driven by the spin-orbit interaction. The spin-relaxation time of the low-lying excited states is T1 ≈ 0.7 mus and 0.1 mus in two samples, showing that <span class="hlt">electron</span> spin in a metallic grain could be a potential candidate for quantum information research. We also present measurements of mesoscopic resistance fluctuations in cobalt nanoparticles at low temperature and study how the fluctuations with bias voltage, bias fingerprints, respond to magnetization-reversal processes. Bias fingerprints rearrange when domains are nucleated or annihilated. The domain wall causes an <span class="hlt">electron</span> wave function-phase shift of ˜5 pi. The phase shift is not caused by the Aharonov-Bohm effect; we explain how it arises from the mistracking effect, where <span class="hlt">electron</span> spins lag in orientation with respect to the moments inside the domain wall. The dephasing length at low temperatures is only 30 nm, which is attributed to the large magnetocrystalline</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23385304','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23385304"><span id="translatedtitle">Nanogap structures: combining enhanced Raman spectroscopy and <span class="hlt">electronic</span> <span class="hlt">transport</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Natelson, Douglas; Li, Yajing; Herzog, Joseph B</p> <p>2013-04-21</p> <p>Surface-enhanced Raman spectroscopy (SERS) is an experimental tool for accessing vibrational and chemical information, down to the single molecule level. SERS typically relies on plasmon excitations in metal nanostructures to concentrate the incident radiation and to provide an enhanced photon density of states to couple emitted radiation to the far field. Many common SERS platforms involve metal nanoparticles to generate the required electromagnetic enhancements. Here we concentrate on an alternative approach, in which the relevant plasmon excitations are supported at a truly nanoscale gap between extended electrodes, rather than discrete subwavelength nanoparticles. The ability to fabricate precise gaps on demand, and in some cases to tune the gap size in situ, combined with the additional capability of simultaneous <span class="hlt">electronic</span> <span class="hlt">transport</span> measurements of the nanogap, provides access to information not previously available in standard SERS. We summarize the rich plasmonic physics at work in these extended systems and highlight the recent state of the art including tip-enhanced Raman spectroscopy (TERS) and the application of mechanical break junctions and electromigrated junctions. We describe in detail how we have performed in situ gap-enhanced Raman measurements of molecular-scale junctions while simultaneously subjecting these structures to <span class="hlt">electronic</span> <span class="hlt">transport</span>. These extended electrode structures allow us to study the pumping of vibrational modes by the flow of tunneling <span class="hlt">electrons</span>, as well as the shifting of vibrational energies due to the applied bias. These experiments extend SERS into a tool for examining fundamental processes of dissipation, and provide insight into the mechanisms behind SERS spectral diffusion. We conclude with a brief discussion of future directions. PMID:23385304</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22314296','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22314296"><span id="translatedtitle">First principles study on the <span class="hlt">electronic</span> <span class="hlt">transport</span> properties of C{sub 60} and B{sub 80} molecular bridges</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Zheng, X. H. Hao, H.; Lan, J.; Wang, X. L.; Shi, X. Q.; Zeng, Z.</p> <p>2014-08-21</p> <p>The <span class="hlt">electronic</span> <span class="hlt">transport</span> properties of molecular bridges constructed by C{sub 60} and B{sub 80} molecules which have the same symmetry are investigated by first principles calculations combined with a <span class="hlt">non-equilibrium</span> Green's function technique. It is found that, like C{sub 60}, monomer B{sub 80} is a good conductor arising from the charge transfer from the leads to the molecule, while the dimer (B{sub 80}){sub 2} and (C{sub 60}){sub 2} are both insulators due to the potential barrier formed at the molecule-molecule interface. Our further study shows that, although both the homogeneous dimer (B{sub 80}){sub 2} and (C{sub 60}){sub 2} display poor conductivity, the heterogeneous dimer B{sub 80}C{sub 60} shows a very high conductance as a result from the decreased HOMO-LUMO gap and the excess charge redistribution. Finally, we find that the conductivity of both (B{sub 80}){sub 2} and (C{sub 60}){sub 2} can be significantly improved by <span class="hlt">electron</span> doping, for example, by doping C in (B{sub 80}){sub 2} and doping N in (C{sub 60}){sub 2}.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhDT.......352S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhDT.......352S"><span id="translatedtitle"><span class="hlt">Electronic</span> structure and quantum <span class="hlt">transport</span> properties of metallic and semiconducting nanowires</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Simbeck, Adam J.</p> <p></p> <p>The future of the semiconductor industry hinges upon new developments to combat the scaling issues that currently afflict two main chip components: transistors and interconnects. For transistors this means investigating suitable materials to replace silicon for both the insulating gate and the semiconducting channel in order to maintain device performance with decreasing size. For interconnects this equates to overcoming the challenges associated with copper when the wire dimensions approach the confinement limit, as well as continuing to develop low-k dielectric materials that can assure minimal cross-talk between lines. In addition, such challenges make it increasingly clear that device design must move from a top-down to a bottom-up approach in which the desired <span class="hlt">electronic</span> characteristics are tailored from first-principles. It is with such fundamental hurdles in mind that ab initio calculations on the <span class="hlt">electronic</span> and quantum <span class="hlt">transport</span> properties of nanoscale metallic and semiconducting wires have been performed. More specifically, this study seeks to elaborate on the role played by confinement, contacts, dielectric environment, edge decoration, and defects in altering the <span class="hlt">electronic</span> and <span class="hlt">transport</span> characteristics of such systems. As experiments continue to achieve better control over the synthesis and design of nanowires, these results are expected to become increasingly more important for not only the interpretation of <span class="hlt">electronic</span> and <span class="hlt">transport</span> trends, but also in engineering the <span class="hlt">electronic</span> structure of nanowires for the needs of the devices of the future. For the metallic atomic wires, the quantum <span class="hlt">transport</span> properties are first investigated by considering finite, single-atom chains of aluminum, copper, gold, and silver sandwiched between gold contacts. <span class="hlt">Non-equilibrium</span> Green's function based <span class="hlt">transport</span> calculations reveal that even in the presence of the contact the conductivity of atomic-scale aluminum is greater than that of the other metals considered. This is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015SSCom.219...21Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015SSCom.219...21Z"><span id="translatedtitle"><span class="hlt">Electronic</span> <span class="hlt">transport</span> through a silicene-based zigzag and armchair junction</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zha, Dace; Chen, Changpeng; Wu, Jinping</p> <p>2015-10-01</p> <p>Using density functional theory and <span class="hlt">non-equilibrium</span> Green's function technique, we performed theoretical investigations on the <span class="hlt">transport</span> properties of several ZAZ SiNRs junctions (a similar kind of silicene molecules junction combined by zigzag and armchair silicene nanoribbons). It is found that the differential conductances of the three systems decrease with an order of 5-ZAZ>4-ZAZ>3-ZAZ. Particularly, the Negative differential resistance (NDR) can be observed within certain bias voltage range only in 3-ZAZ SiNRs. In order to elucidate the mechanism the NDR behavior, the transmission spectra and molecular projected self-consistent Hamiltonian (MPSH) states are discussed in details.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EL.....9935003N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EL.....9935003N"><span id="translatedtitle"><span class="hlt">Transport</span> of <span class="hlt">electrons</span> in Ar/H2 mixtures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nikitović, Ž.; Stojanović, V.; Petrović, Z. Lj.</p> <p>2012-08-01</p> <p>In this work we present <span class="hlt">transport</span> coefficients for <span class="hlt">electrons</span> in Ar/H2 mixtures for the conditions used in plasma-assisted technologies for semiconductor production, i.e., in moderate and very high E/N. We used a two-term numerical solution of the Boltzmann equation at the lowest E/N (E is the electric field; N is the gas density) and correspondingly at the lowest mean energies. We also use the Monte Carlo simulation technique at moderate and high E/N. We show that a good agreement with experimental data exists for low and moderate E/N and that based on the tests for pure H2 and Ar we can model properly the swarm properties at high E/N. For the conditions of very high electric fields runaway peaks develop in the <span class="hlt">electron</span> energy distribution function and appreciable contribution of backscattered high-energy <span class="hlt">electrons</span> produces additional emission of Hα emission close to the anode (made of stainless steel). Results are obtained for abundances of H2 from 1% to 30%, which are necessary in kinetic models for this mixture in a number of applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012APS..MARH13012H&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012APS..MARH13012H&link_type=ABSTRACT"><span id="translatedtitle">Hot <span class="hlt">electron</span> spin <span class="hlt">transport</span> in C60 fullerene</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hueso, Luis Eduardo; Gobbi, Marco; Bedoya-Pinto, Amilcar; Golmar, Federico; Llopis, Roger; Casanova, Felix</p> <p>2012-02-01</p> <p>Carbon-based molecular materials are interesting for spin <span class="hlt">transport</span> application mainly due to their small sources of spin relaxation [1]. However, spin coherence lengths reported in many molecular films do not exceed a few tens of nanometers [2]. In this work we will present results showing how hot spin-polarized <span class="hlt">electrons</span> injected well above the Fermi level in C60 fullerene films travel coherently for hundreds of nanometers. We fabricated hot-<span class="hlt">electron</span> vertical transistors, in which the current created across an Al/Al2O3 junction is polarized by a metallic Co/Cu/Py spin valve trilayer and subsequently injected in the molecular thin film. This geometry allows us to determine the energy level alignment at each interface between different materials. Moreover, the collector magnetocurrent excess 85%, even for C60 films thicknesses of 300 nm. We believe these results show the importance of hot spin-polarized <span class="hlt">electron</span> injection and propagation in molecular materials. [1] V. Dediu, L.E. Hueso, I. Bergenti, C. Taliani, Nature Mater. 8, 707 (2009) [2] M. Gobbi, F. Golmar, R. Llopis, F. Casanova, L.E. Hueso, Adv. Mater. 23, 1609 (2011)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22306196','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22306196"><span id="translatedtitle">Random paths and current fluctuations in <span class="hlt">nonequilibrium</span> statistical mechanics</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gaspard, Pierre</p> <p>2014-07-15</p> <p>An overview is given of recent advances in <span class="hlt">nonequilibrium</span> statistical mechanics about the statistics of random paths and current fluctuations. Although statistics is carried out in space for equilibrium statistical mechanics, statistics is considered in time or spacetime for <span class="hlt">nonequilibrium</span> systems. In this approach, relationships have been established between <span class="hlt">nonequilibrium</span> properties such as the <span class="hlt">transport</span> coefficients, the thermodynamic entropy production, or the affinities, and quantities characterizing the microscopic Hamiltonian dynamics and the chaos or fluctuations it may generate. This overview presents results for classical systems in the escape-rate formalism, stochastic processes, and open quantum systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22262617','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22262617"><span id="translatedtitle"><span class="hlt">Electron-electron</span> interaction, weak localization and spin valve effect in vertical-<span class="hlt">transport</span> graphene devices</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Long, Mingsheng; Gong, Youpin; Wei, Xiangfei; Zhu, Chao; Xu, Jianbao; Liu, Ping; Guo, Yufen; Li, Weiwei; Liu, Liwei; Liu, Guangtong</p> <p>2014-04-14</p> <p>We fabricated a vertical structure device, in which graphene is sandwiched between two asymmetric ferromagnetic electrodes. The measurements of <span class="hlt">electron</span> and spin <span class="hlt">transport</span> were performed across the combined channels containing the vertical and horizontal components. The presence of <span class="hlt">electron-electron</span> interaction (EEI) was found not only at low temperatures but also at moderate temperatures up to ∼120 K, and EEI dominates over weak localization (WL) with and without applying magnetic fields perpendicular to the sample plane. Moreover, spin valve effect was observed when magnetic filed is swept at the direction parallel to the sample surface. We attribute the EEI and WL surviving at a relatively high temperature to the effective suppress of phonon scattering in the vertical device structure. The findings open a way for studying quantum correlation at relatively high temperature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009JPhCS.162a1001P&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009JPhCS.162a1001P&link_type=ABSTRACT"><span id="translatedtitle">INTRODUCTION: <span class="hlt">Nonequilibrium</span> Processes in Plasmas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Petrović, Zoran; Marić, Dragana; Malović, Gordana</p> <p>2009-07-01</p> <p> cosmos collapsed from the uniform plasma stage into stars and empty space, practically nothing is in real equilibrium only in local equilibrium. How wrong we were. As our focus turned to anti particles, positrons and positronium, we realized that even in those early stages there was major <span class="hlt">non-equilibrium</span> between matter and anti matter originating from the earliest stages of the Big Bang. Thus it is safe to correct the famous quote by the renowned natural philosopher Sheldon Cooper into: 'If you know the laws of [<span class="hlt">non-equilibrium</span>] physics anything is possible'. From the matter-anti-matter ratio in the universe to life itself. But do we really need such farfetched introductory remarks to justify our scientific choices? It suffices to focus on <span class="hlt">non-equilibrium</span> plasmas and <span class="hlt">transport</span> of pollutants in the air and see how many new methods for diagnostics and treatment have been proposed for medicine in the past 10 years. So in addition to the past major achievements such as plasma etching for integrated circuit production, the field is full of possibilities and truly, almost anything is possible. We hope that some of the papers presented here summarize well how we learn about the laws of <span class="hlt">non-equilibrium</span> physics in the given context of plasmas and air pollution and how we open new possibilities for further understanding and further applications. A wide range of topics is covered in this volume. This time we start with elementary collisional processes and a review of the data for excitation of polyatomic molecules obtained by the binary collision experiments carried out at the Institute of Physics in Belgrade by the group of Bratislav Marinković. A wide range of activities on the foundation of gaseous positronics ranging from new measurements in the binary regime to the simulation of collective <span class="hlt">transport</span> in dense gases is presented by James Sullivan and coworkers. This work encompasses three continents, half a dozen groups and several lectures at the workshops while also covering</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ApPhL.107o3504B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ApPhL.107o3504B"><span id="translatedtitle">Density-dependent <span class="hlt">electron</span> <span class="hlt">transport</span> and precise modeling of GaN high <span class="hlt">electron</span> mobility transistors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bajaj, Sanyam; Shoron, Omor F.; Park, Pil Sung; Krishnamoorthy, Sriram; Akyol, Fatih; Hung, Ting-Hsiang; Reza, Shahed; Chumbes, Eduardo M.; Khurgin, Jacob; Rajan, Siddharth</p> <p>2015-10-01</p> <p>We report on the direct measurement of two-dimensional sheet charge density dependence of <span class="hlt">electron</span> <span class="hlt">transport</span> in AlGaN/GaN high <span class="hlt">electron</span> mobility transistors (HEMTs). Pulsed IV measurements established increasing <span class="hlt">electron</span> velocities with decreasing sheet charge densities, resulting in saturation velocity of 1.9 × 107 cm/s at a low sheet charge density of 7.8 × 1011 cm-2. An optical phonon emission-based <span class="hlt">electron</span> velocity model for GaN is also presented. It accommodates stimulated longitudinal optical (LO) phonon emission which clamps the <span class="hlt">electron</span> velocity with strong <span class="hlt">electron</span>-phonon interaction and long LO phonon lifetime in GaN. A comparison with the measured density-dependent saturation velocity shows that it captures the dependence rather well. Finally, the experimental result is applied in TCAD-based device simulator to predict DC and small signal characteristics of a reported GaN HEMT. Good agreement between the simulated and reported experimental results validated the measurement presented in this report and established accurate modeling of GaN HEMTs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22482256','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22482256"><span id="translatedtitle">Density-dependent <span class="hlt">electron</span> <span class="hlt">transport</span> and precise modeling of GaN high <span class="hlt">electron</span> mobility transistors</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bajaj, Sanyam Shoron, Omor F.; Park, Pil Sung; Krishnamoorthy, Sriram; Akyol, Fatih; Hung, Ting-Hsiang; Reza, Shahed; Chumbes, Eduardo M.; Khurgin, Jacob; Rajan, Siddharth</p> <p>2015-10-12</p> <p>We report on the direct measurement of two-dimensional sheet charge density dependence of <span class="hlt">electron</span> <span class="hlt">transport</span> in AlGaN/GaN high <span class="hlt">electron</span> mobility transistors (HEMTs). Pulsed IV measurements established increasing <span class="hlt">electron</span> velocities with decreasing sheet charge densities, resulting in saturation velocity of 1.9 × 10{sup 7 }cm/s at a low sheet charge density of 7.8 × 10{sup 11 }cm{sup −2}. An optical phonon emission-based <span class="hlt">electron</span> velocity model for GaN is also presented. It accommodates stimulated longitudinal optical (LO) phonon emission which clamps the <span class="hlt">electron</span> velocity with strong <span class="hlt">electron</span>-phonon interaction and long LO phonon lifetime in GaN. A comparison with the measured density-dependent saturation velocity shows that it captures the dependence rather well. Finally, the experimental result is applied in TCAD-based device simulator to predict DC and small signal characteristics of a reported GaN HEMT. Good agreement between the simulated and reported experimental results validated the measurement presented in this report and established accurate modeling of GaN HEMTs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12535543','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12535543"><span id="translatedtitle">On the application of quantum <span class="hlt">transport</span> theory to <span class="hlt">electron</span> sources.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Jensen, Kevin L</p> <p>2003-01-01</p> <p><span class="hlt">Electron</span> sources (e.g., field emitter arrays, wide band-gap (WBG) semiconductor materials and coatings, carbon nanotubes, etc.) seek to exploit ballistic <span class="hlt">transport</span> within the vacuum after emission from microfabricated structures. Regardless of kind, all sources strive to minimize the barrier to <span class="hlt">electron</span> emission by engineering material properties (work function/<span class="hlt">electron</span> affinity) or physical geometry (field enhancement) of the cathode. The unique capabilities of cold cathodes, such as instant ON/OFF performance, high brightness, high current density, large transconductance to capacitance ratio, cold emission, small size and/or low voltage operation characteristics, commend their use in several advanced devices when physical size, weight, power consumption, beam current, and pulse repletion frequency are important, e.g., RF power amplifier such as traveling wave tubes (TWTs) for radar and communications, electrodynamic tethers for satellite deboost/reboost, and electric propulsion systems such as Hall thrusters for small satellites. The theoretical program described herein is directed towards models to evaluate emission current from <span class="hlt">electron</span> sources (in particular, emission from WBG and Spindt-type field emitter) in order to assess their utility, capabilities and performance characteristics. Modeling efforts particularly include: band bending, non-linear and resonant (Poole-Frenkel) potentials, the extension of one-dimensional theory to multi-dimensional structures, and emission site statistics due to variations in geometry and the presence of adsorbates. Two particular methodologies, namely, the modified Airy approach and metal-semiconductor statistical hyperbolic/ellipsoidal model, are described in detail in their present stage of development.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AIPC.1728b0669B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AIPC.1728b0669B"><span id="translatedtitle">Effect of doping on the <span class="hlt">electron</span> <span class="hlt">transport</span> in polyfluorene</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bajpai, Manisha; Srivastava, Ritu; Dhar, Ravindra; Tiwari, R. S.</p> <p>2016-05-01</p> <p>In this paper, <span class="hlt">electron</span> <span class="hlt">transport</span> of pure and DMC doped polyfluorne (PF) films have been studied at various doping concentrations. Pure films show space charge limited conduction with field and temperature dependent mobility. The J-V characteristics of doped PF were ohmic at low voltages due to thermally released carriers from dopant states. At higher voltages the current density increases nonlinearly due to field dependent mobility and carrier concentration thereby filling of tail states of HOMO of the host. The conductivity of doped fims were analyzed using the Unified Gaussian Disorder Model (UGDM). The carrier concentration obtained from the fitting show a non-linear dependence on doping concentration which may be due to a combined effect of thermally activated carrier generation and increased carrier mobility.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..MARC26001B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..MARC26001B"><span id="translatedtitle"><span class="hlt">Electron</span> <span class="hlt">Transport</span> Simulations of 4-Terminal Crossed Graphene Nanoribbons Devices</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brandimarte, Pedro; Papior, Nick R.; Engelund, Mads; Garcia-Lekue, Aran; Frederiksen, Thomas; Sánchez-Portal, Daniel</p> <p></p> <p>Recently, it has been reported theoretically a current switching mechanism by voltage control in a system made by two perpendicular 14-armchair graphene nanoribbons (GNRs). In order to investigate the possibilities of using crossed GNRs as ON/OFF devices, we have studied their <span class="hlt">electronic</span> and <span class="hlt">transport</span> properties as function structural parameters determining the crossing. Our calculations were performed with TranSIESTA code, which has been recently generalized to consider N >= 1 arbitrarily distributed electrodes at finite bias. We find that the transmission along each individual GNR and among them strongly depends on the stacking. For a 60° rotation angle, the lattice matching in the crossing region provokes a strong scattering effect that translates into an increased interlayer transmission. FP7 FET-ICT PAMS-project (European Commission, contract 610446), MINECO (Grant MAT2013-46593-C6-2-P) and Basque Dep. de Educación, UPV/EHU (Grant IT-756-13).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22492133','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22492133"><span id="translatedtitle">Conformation dependent <span class="hlt">electronic</span> <span class="hlt">transport</span> in a DNA double-helix</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kundu, Sourav Karmakar, S. N.</p> <p>2015-10-15</p> <p>We present a tight-binding study of conformation dependent <span class="hlt">electronic</span> <span class="hlt">transport</span> properties of DNA double-helix including its helical symmetry. We have studied the changes in the localization properties of DNA as we alter the number of stacked bases within every pitch of the double-helix keeping fixed the total number of nitrogen bases within the DNA molecule. We take three DNA sequences, two of them are periodic and one is random and observe that in all the cases localization length increases as we increase the radius of DNA double-helix i.e., number of nucleobases within a pitch. We have also investigated the effect of backbone energetic on the I-V response of the system and found that in presence of helical symmetry, depending on the interplay of conformal variation and disorder, DNA can be found in either metallic, semiconducting and insulating phases, as observed experimentally.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005ApPhL..87w3509G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005ApPhL..87w3509G"><span id="translatedtitle">Device structure for <span class="hlt">electronic</span> <span class="hlt">transport</span> through individual molecules using nanoelectrodes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ghosh, Subhasis; Halimun, Henny; Mahapatro, Ajit Kumar; Choi, Jaewon; Lodha, Saurabh; Janes, David</p> <p>2005-12-01</p> <p>We present a simple and reliable method for making electrical contacts to small organic molecules with thiol endgroups. Nanometer-scale gaps between metallic electrodes have been fabricated by passing a large current through a lithographically-patterned Au-line with appropriate thickness. Under appropriate conditions, the passage of current breaks the Au-line, creating two opposite facing electrodes separated by a gap comparable to the length of small organic molecules. Current-voltage characteristics have been measured both before and after deposition of short organic molecules. The resistance of single 1,4-benzenedithiol and 1,4-bezenedimethanedithiol molecules were found to be 9MΩ and 26MΩ, respectively. The experimental results indicate strong <span class="hlt">electronic</span> coupling to the contacts and are discussed using a relatively simple model of mesoscopic <span class="hlt">transport</span>. The use of electrodes formed on an insulating surface by lithography and electromigration provides a stable structure suitable for integrated circuit applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1009202','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1009202"><span id="translatedtitle">Hot <span class="hlt">Electron</span> Generation and <span class="hlt">Transport</span> Using K(alpha) Emission</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Akli, K U; Stephens, R B; Key, M H; Bartal, T; Beg, F N; Chawla, S; Chen, C D; Fedosejevs, R; Freeman, R R; Friesen, H; Giraldez, E; Green, J S; Hey, D S; Higginson, D P; Hund, J; Jarrott, L C; Kemp, G E; King, J A; Kryger, A; Lancaster, K; LePape, S; Link, A; Ma, T; Mackinnon, A J; MacPhee, A G; McLean, H S; Murphy, C; Norreys, P A; Ovchinnikov, V; Patel, P K; Ping, Y; Sawada, H; Schumacher, D; Theobald, W; Tsui, Y Y; Van Woerkom, L D; Wei, M S; Westover, B; Yabuuchi, T</p> <p>2009-10-15</p> <p>We have conducted experiments on both the Vulcan and Titan laser facilities to study hot <span class="hlt">electron</span> generation and <span class="hlt">transport</span> in the context of fast ignition. Cu wires attached to Al cones were used to investigate the effect on coupling efficiency of plasma surround and the pre-formed plasma inside the cone. We found that with thin cones 15% of laser energy is coupled to the 40{micro}m diameter wire emulating a 40{micro}m fast ignition spot. Thick cone walls, simulating plasma in fast ignition, reduce coupling by x4. An increase of prepulse level inside the cone by a factor of 50 reduces coupling by a factor of 3.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..MAR.F5008Q','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..MAR.F5008Q"><span id="translatedtitle"><span class="hlt">Electronic</span> measurement of strain effects on spin <span class="hlt">transport</span> in silicon</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Qing, Lan; Tinkey, Holly; Appelbaum, Ian</p> <p></p> <p>Spin <span class="hlt">transport</span> in silicon is limited by the Elliott-Yafet spin relaxation mechanism, which is driven by scattering between degenerate conduction band valleys. Mechanical strain along a valley axis partially breaks this degeneracy, and will ultimately quench intervalley spin relaxation for transitions between states on orthogonal axes. Using a custom-designed and constructed strain probe, we study the effects of uniaxial compressive strain along the < 100 > direction on ballistic tunnel junction devices used to inject spin-polarized <span class="hlt">electrons</span> into silicon. The effects of strain-induced valley splitting will be presented and compared to our theoretical model. This work is supported by the Office of Naval Research under Contract No. N000141410317, the National Science Foundation under Contract No. ECCS-1231855, the Defense Threat Reduction Agency under Contract No. HDTRA1-13-1-0013, and the Maryland NanoCenter.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/984468','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/984468"><span id="translatedtitle">Anomalous <span class="hlt">Electron</span> <span class="hlt">Transport</span> Due to Multiple High Frequency Beam Ion Driven Alfven Eigenmode</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gorelenkov, N. N.; Stutman, D.; Tritz, K.; Boozer, A.; Delgardo-Aparicio, L.; Fredrickson, E.; Kaye, S.; White, R.</p> <p>2010-07-13</p> <p>We report on the simulations of recently observed correlations of the core <span class="hlt">electron</span> <span class="hlt">transport</span> with the sub-thermal ion cyclotron frequency instabilities in low aspect ratio plasmas of the National Spherical Torus Experiment (NSTX). In order to model the <span class="hlt">electron</span> <span class="hlt">transport</span> of the guiding center code ORBIT is employed. A spectrum of test functions of multiple core localized Global shear Alfven Eigenmode (GAE) instabilities based on a previously developed theory and experimental observations is used to examine the <span class="hlt">electron</span> <span class="hlt">transport</span> properties. The simulations exhibit thermal <span class="hlt">electron</span> <span class="hlt">transport</span> induced by <span class="hlt">electron</span> drift orbit stochasticity in the presence of multiple core localized GAE.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009PhDT.......167B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009PhDT.......167B"><span id="translatedtitle">Characterization of ionic <span class="hlt">transport</span> in polymer and <span class="hlt">electronic</span> <span class="hlt">transport</span> in disordered selenium and ceramic materials</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bandyopadhyay, Subhasish</p> <p></p> <p>In this thesis, the properties of <span class="hlt">electronic</span> conduction in vanadium (donor) and scandium (acceptor) doped Ba0.7Sr0.3TiO3 ceramics, amorphous Selenium and ionic conduction in polyester polyol based polyurethane have been investigated. The leakage current of bulk vanadium (donor) and scandium (acceptor) doped Ba0.7Sr0.3TiO3 ceramics structures measured using gold electrical contacts have been characterized and analyzed. Vanadium doping reduces the ohmic leakage current that dominates the <span class="hlt">transport</span> characteristics up to 5 kV/cm. The Arrhenius activation energy is 0.18, 0.20 and 0.23 eV for 1, 2 and 4 at % V-doped samples, respectively. Above this field, the current-voltage characteristics exhibit discontinuous current transitions associated with trap filling by <span class="hlt">electronic</span> carriers. At higher fields, trap controlled space charge limited conduction (SCLC) is observed with an effective mobility of 4+/-1x10-7 cm2/V s, characteristic of <span class="hlt">electronic</span> <span class="hlt">transport</span> process that involves quasi equilibrium between conduction in the band and trapping. In contrast, the leakage current of Sc-doped samples increases with impurity concentration and exhibits a 0.60 eV activation energy. In this case, the limiting current conduction mechanism is the <span class="hlt">transport</span> of holes over the electrostatic barrier at grain boundaries. Comparison of these results to those on similarly-doped homoepitaxial SrTiO3 thin-films deposited on single-crystal and bicrystal substrates helped to identify the characteristics of <span class="hlt">transport</span> in the bulk and across grain boundaries for this class of materials. Electrical, thermal and Li <span class="hlt">transport</span> properties have been measured for polyester polyol and isocyanate-based polyurethanes doped with Lithium trifluoromethanesulfonimide (LiTFSI) and Lithium perchlorate (LiClO4) Electrical conductivities are estimated at 10-5--10-6 S/cm near 300 K. The conductivities show Vogel-Tammann-Fulcher (VTF) behavior over a wide temperature ranges. Differential scanning calorimetry (DSC) shows</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PPCF...58e5002K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PPCF...58e5002K"><span id="translatedtitle">Simple predictive <span class="hlt">electron</span> <span class="hlt">transport</span> models applied to sawtoothing plasmas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kim, D.; Merle, A.; Sauter, O.; Goodman, T. P.</p> <p>2016-05-01</p> <p>In this work, we introduce two simple <span class="hlt">transport</span> models to evaluate the time evolution of <span class="hlt">electron</span> temperature and density profiles during sawtooth cycles (i.e. over a sawtooth period time-scale). Since the aim of these simulations is to estimate reliable profiles within a short calculation time, two simplified ad-hoc models have been developed. The goal for these models is to rely on a few easy-to-check free parameters, such as the confinement time scaling factor and the profiles’ averaged scale-lengths. Due to the simplicity and short calculation time of the models, it is expected that these models can also be applied to real-time <span class="hlt">transport</span> simulations. We show that it works well for Ohmic and EC heated L- and H-mode plasmas. The differences between these models are discussed and we show that their predictive capabilities are similar. Thus only one model is used to reproduce with simulations the results of sawtooth control experiments on the TCV tokamak. For the sawtooth pacing, the calculated time delays between the EC power off and sawtooth crash time agree well with the experimental results. The map of possible locking range is also well reproduced by the simulation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22493896','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22493896"><span id="translatedtitle"><span class="hlt">Electron</span> <span class="hlt">transport</span> in molecular junctions with graphene as protecting layer</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hüser, Falco; Solomon, Gemma C.</p> <p>2015-12-07</p> <p>We present ab initio <span class="hlt">transport</span> calculations for molecular junctions that include graphene as a protecting layer between a single molecule and gold electrodes. This vertical setup has recently gained significant interest in experiment for the design of particularly stable and reproducible devices. We observe that the signals from the molecule in the <span class="hlt">electronic</span> transmission are overlayed by the signatures of the graphene sheet, thus raising the need for a reinterpretation of the transmission. On the other hand, we see that our results are stable with respect to various defects in the graphene. For weakly physiosorbed molecules, no signs of interaction with the graphene are evident, so the <span class="hlt">transport</span> properties are determined by offresonant tunnelling between the gold leads across an extended structure that includes the molecule itself and the additional graphene layer. Compared with pure gold electrodes, calculated conductances are about one order of magnitude lower due to the increased tunnelling distance. Relative differences upon changing the end group and the length of the molecule on the other hand, are similar.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JChPh.143u4302H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JChPh.143u4302H"><span id="translatedtitle"><span class="hlt">Electron</span> <span class="hlt">transport</span> in molecular junctions with graphene as protecting layer</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hüser, Falco; Solomon, Gemma C.</p> <p>2015-12-01</p> <p>We present ab initio <span class="hlt">transport</span> calculations for molecular junctions that include graphene as a protecting layer between a single molecule and gold electrodes. This vertical setup has recently gained significant interest in experiment for the design of particularly stable and reproducible devices. We observe that the signals from the molecule in the <span class="hlt">electronic</span> transmission are overlayed by the signatures of the graphene sheet, thus raising the need for a reinterpretation of the transmission. On the other hand, we see that our results are stable with respect to various defects in the graphene. For weakly physiosorbed molecules, no signs of interaction with the graphene are evident, so the <span class="hlt">transport</span> properties are determined by offresonant tunnelling between the gold leads across an extended structure that includes the molecule itself and the additional graphene layer. Compared with pure gold electrodes, calculated conductances are about one order of magnitude lower due to the increased tunnelling distance. Relative differences upon changing the end group and the length of the molecule on the other hand, are similar.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..DPPJI3003N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..DPPJI3003N"><span id="translatedtitle"><span class="hlt">Non-equilibrium</span> Warm Dense Gold: Experiments and Simulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ng, Andrew</p> <p>2015-11-01</p> <p>This talk is an overview of a series of studies of <span class="hlt">non-equilibrium</span> Warm Dense Matter using a broad range of measured properties of a single material, namely Au, as comprehensive benchmarks for theory. The measurements are made in fs-laser pump-probe experiments. For understanding lattice stability, our investigation reveals a solid phase at high energy density. This leads to the calculation of lattice dynamics using MD simulations and phonon hardening in DFT-MD simulations. For understanding <span class="hlt">electron</span> <span class="hlt">transport</span> in two-temperature states, AC conductivity is used to evaluate DFT-MD and Kubo-Greenwood calculations while DC conductivity is used to test Ziman calculations in a DFT average atom model. The <span class="hlt">electron</span> density is also used to assess <span class="hlt">electronic</span> structure calculations in DFT simulations. In our latest study of <span class="hlt">electron</span> kinetics in states with a non-Fermi-Dirac distribution, three-body recombination is found to have a significant effect on <span class="hlt">electron</span> thermalizaiton time. This is driving an effort to develop <span class="hlt">electron</span> kinetics simulations using the Boltzmann equation method.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhPl...23g3512Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhPl...23g3512Z"><span id="translatedtitle">Analysis of <span class="hlt">non-equilibrium</span> phenomena in inductively coupled plasma generators</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, W.; Lani, A.; Panesi, M.</p> <p>2016-07-01</p> <p>This work addresses the modeling of <span class="hlt">non-equilibrium</span> phenomena in inductively coupled plasma discharges. In the proposed computational model, the electromagnetic induction equation is solved together with the set of Navier-Stokes equations in order to compute the electromagnetic and flow fields, accounting for their mutual interaction. Semi-classical statistical thermodynamics is used to determine the plasma thermodynamic properties, while <span class="hlt">transport</span> properties are obtained from kinetic principles, with the method of Chapman and Enskog. Particle ambipolar diffusive fluxes are found by solving the Stefan-Maxwell equations with a simple iterative method. Two physico-mathematical formulations are used to model the chemical reaction processes: (1) A Local Thermodynamics Equilibrium (LTE) formulation and (2) a thermo-chemical <span class="hlt">non-equilibrium</span> (TCNEQ) formulation. In the TCNEQ model, thermal <span class="hlt">non-equilibrium</span> between the translational energy mode of the gas and the vibrational energy mode of individual molecules is accounted for. The <span class="hlt">electronic</span> states of the chemical species are assumed in equilibrium with the vibrational temperature, whereas the rotational energy mode is assumed to be equilibrated with translation. Three different physical models are used to account for the coupling of chemistry and energy transfer processes. Numerical simulations obtained with the LTE and TCNEQ formulations are used to characterize the extent of <span class="hlt">non-equilibrium</span> of the flow inside the Plasmatron facility at the von Karman Institute. Each model was tested using different kinetic mechanisms to assess the sensitivity of the results to variations in the reaction parameters. A comparison of temperatures and composition profiles at the outlet of the torch demonstrates that the flow is in <span class="hlt">non-equilibrium</span> for operating conditions characterized by pressures below 30 000 Pa, frequency 0.37 MHz, input power 80 kW, and mass flow 8 g/s.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007ChPhL..24.1042O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007ChPhL..24.1042O"><span id="translatedtitle"><span class="hlt">Electronic</span> <span class="hlt">Transport</span> in Molecular Junction Based on C20 Cages</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ouyang, Fang-Ping; Xu, Hui</p> <p>2007-04-01</p> <p>Choosing closed-ended armchair (5, 5) single-wall carbon nanotubes (CCNTs) as electrodes, we investigate the <span class="hlt">electron</span> <span class="hlt">transport</span> properties across an all-carbon molecular junction consisting of C20 molecules suspended between two semi-infinite carbon nanotubes. It is shown that the conductances are quite sensitive to the number of C20 molecules between electrodes for both configuration CF1 and double-bonded models: the conductances of C20 dimers are markedly smaller than those of monomers. The physics is that incident <span class="hlt">electrons</span> easily pass the C20 molecules and are predominantly scattered at the C20-C20 junctions. Moreover, we study the doping effect of such molecular junction by doping nitrogen atoms substitutionally. The bonding property of the molecular junction with configuration CF1 has been analysed by calculating the Mulliken atomic charges. Our results have revealed that the C atoms in N-doped junctions are more ionic than those in pure-carbon ones, leading to the fact that N-doped junctions have relatively large conductance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/15328348','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/15328348"><span id="translatedtitle">Oxygen tolerance and coupling of mitochondrial <span class="hlt">electron</span> <span class="hlt">transport</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Campian, Jian Li; Qian, Mingwei; Gao, Xueshan; Eaton, John W</p> <p>2004-11-01</p> <p>Oxygen is critical to aerobic metabolism, but excessive oxygen (hyperoxia) causes cell injury and death. An oxygen-tolerant strain of HeLa cells, which proliferates even under 80% O2, termed "HeLa-80," was derived from wild-type HeLa cells ("HeLa-20") by selection for resistance to stepwise increases of oxygen partial pressure. Surprisingly, antioxidant defenses and susceptibility to oxidant-mediated killing do not differ between these two strains of HeLa cells. However, under both 20 and 80% O2, intracellular reactive oxygen species (ROS) production is significantly (approximately 2-fold) less in HeLa-80 cells. In both cell lines the source of ROS is evidently mitochondrial. Although HeLa-80 cells consume oxygen at the same rate as HeLa-20 cells, they consume less glucose and produce less lactic acid. Most importantly, the oxygen-tolerant HeLa-80 cells have significantly higher cytochrome c oxidase activity (approximately 2-fold), which may act to deplete upstream <span class="hlt">electron</span>-rich intermediates responsible for ROS generation. Indeed, preferential inhibition of cytochrome c oxidase by treatment with n-methyl protoporphyrin (which selectively diminishes synthesis of heme a in cytochrome c oxidase) enhances ROS production and abrogates the oxygen tolerance of the HeLa-80 cells. Thus, it appears that the remarkable oxygen tolerance of these cells derives from tighter coupling of the <span class="hlt">electron</span> <span class="hlt">transport</span> chain. PMID:15328348</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/100296','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/100296"><span id="translatedtitle">Multigroup Boltzmann Fokker Planck <span class="hlt">electron</span>-photon <span class="hlt">transport</span> capability in MCNP{sup trademark}</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Adams, K.J.; Hart, M.</p> <p>1995-07-01</p> <p>The MCNP code system has a robust multigroup <span class="hlt">transport</span> capability which includes a multigroup Boltzmann-Fokker-Planck (MGBFP) <span class="hlt">transport</span> algorithm to perform coupled <span class="hlt">electron</span>-photon or other coupled charged and neutral particle <span class="hlt">transport</span> in either a forward or adjoint mode. This paper will discuss this capability and compare code results with other <span class="hlt">transport</span> codes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5590089','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5590089"><span id="translatedtitle">Flash spectroscopic characterization of photosynthetic <span class="hlt">electron</span> <span class="hlt">transport</span> in isolated heterocysts</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Houchins, J.P.; Hind, G.</p> <p>1983-07-01</p> <p><span class="hlt">Electron</span> <span class="hlt">transport</span> was studied in heterocysts of the filamentous cyanobacterium Anabaena 7120 using spectral and kinetic analysis of absorbance transients elicited by single turnover flashes. Consistent photosynthetic turnovers were observed only in the presence of an exogenous source of reductant; therefore measurements were routinely made under a gas phase containing H2. Prominent absorbance changes corresponding to the oxidation of cytochrome c (554 nm) and the reduction of cytochrome b563 (563 nm) were observed. Under the most reducing conditions (99% H2/1% O2) cytochrome b563 was partially reduced between flashes in a slow, dark reaction. At 10-15% O2, the slow, dark reduction of cytochrome b563 was eliminated. Cytochrome turnover ceased entirely at high O2 concentrations (30%) but was restored by the addition of 25 microM KCN, demonstrating an interaction between the photosynthetic and respiratory <span class="hlt">electron</span> transfer chains. Strobilurin A slowed the re-reduction of cytochrome c and eliminated the appearance of reduced cytochrome b563 by blocking <span class="hlt">electron</span> transfer between reduced plastoquinone and the cytochrome b/f complex. Inhibition at a second site was apparent with 2-(n-heptyl)-4-hydroxyquinoline N-oxide, which blocked the reoxidation of cytochrome b563 but had little effect on cytochrome c relaxation. In uncoupled heterocysts, the rates of cytochrome c re-reduction and cytochrome b563 reduction were equal. Additional unassigned absorbance changes at 475 nm, 515 nm, and 572 nm were partially characterized. No absorbance change corresponding to an electrochromic shift was observed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PlPhR..42..713G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PlPhR..42..713G"><span id="translatedtitle">Simulation of <span class="hlt">electron</span> beam formation and <span class="hlt">transport</span> in a gas-filled <span class="hlt">electron</span>-optical system with a plasma emitter</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grishkov, A. A.; Kornilov, S. Yu.; Rempe, N. G.; Shidlovskiy, S. V.; Shklyaev, V. A.</p> <p>2016-07-01</p> <p>The results of computer simulations of the <span class="hlt">electron</span>-optical system of an <span class="hlt">electron</span> gun with a plasma emitter are presented. The simulations are performed using the KOBRA3-INP, XOOPIC, and ANSYS codes. The results describe the <span class="hlt">electron</span> beam formation and <span class="hlt">transport</span>. The <span class="hlt">electron</span> trajectories are analyzed. The mechanisms of gas influence on the energy inhomogeneity of the beam and its current in the regions of beam primary formation, acceleration, and <span class="hlt">transport</span> are described. Recommendations for optimizing the <span class="hlt">electron</span>-optical system with a plasma emitter are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25255961','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25255961"><span id="translatedtitle">Basic concepts of quantum interference and <span class="hlt">electron</span> <span class="hlt">transport</span> in single-molecule <span class="hlt">electronics</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lambert, C J</p> <p>2015-02-21</p> <p>This tutorial outlines the basic theoretical concepts and tools which underpin the fundamentals of phase-coherent <span class="hlt">electron</span> <span class="hlt">transport</span> through single molecules. The key quantity of interest is the transmission coefficient T(E), which yields the electrical conductance, current-voltage relations, the thermopower S and the thermoelectric figure of merit ZT of single-molecule devices. Since T(E) is strongly affected by quantum interference (QI), three manifestations of QI in single-molecules are discussed, namely Mach-Zehnder interferometry, Breit-Wigner resonances and Fano resonances. A simple MATLAB code is provided, which allows the novice reader to explore QI in multi-branched structures described by a tight-binding (Hückel) Hamiltonian. More generally, the strengths and limitations of materials-specific <span class="hlt">transport</span> modelling based on density functional theory are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApPhL.109o2904O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApPhL.109o2904O"><span id="translatedtitle"><span class="hlt">Electron</span> <span class="hlt">transport</span> and dielectric breakdown in silicon nitride using a charge <span class="hlt">transport</span> model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ogden, Sean P.; Lu, Toh-Ming; Plawsky, Joel L.</p> <p>2016-10-01</p> <p>Silicon nitride is an important material used in the <span class="hlt">electronics</span> industry. As such, the <span class="hlt">electronic</span> <span class="hlt">transport</span> and reliability of these materials are important to study and understand. We report on a charge <span class="hlt">transport</span> model to predict leakage current and failure trends based on previously published data for a stoichiometric silicon nitride dielectric. Failure occurs when the defect density increases to a critical value of approximately 6 × 1025 traps/m3. The model's parameters are determined using voltage ramp data only, and yet, the model is also able to predict constant voltage stress failure over a time scale ranging from minutes to months. The successful fit of the model to the experimental data validates our assumption that the dominant defect in the dielectric is the Si dangling bond, located approximately 2.2 eV below the conduction band. A comparison with previous SiCOH simulations shows SiN and SiCOH have similar defect-related material properties. It is also speculated that, based on the estimated parameter values of 2.75 eV for the defect formation activation energy, the materials' TDDB wear-out are caused by broken Si-H bonds, resulting in Si dangling bond defects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvB..94k5401A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvB..94k5401A"><span id="translatedtitle">Plasma wave instabilities in <span class="hlt">nonequilibrium</span> graphene</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aryal, Chinta M.; Hu, Ben Yu-Kuang; Jauho, Antti-Pekka</p> <p>2016-09-01</p> <p>We study two-stream instabilities in a <span class="hlt">nonequilibrium</span> system in which a stream of <span class="hlt">electrons</span> is injected into doped graphene. As with equivalent <span class="hlt">nonequilibrium</span> parabolic band systems, we find that the graphene systems can support unstable charge-density waves whose amplitudes grow with time. We determine the range of wave vectors q that are unstable, and their growth rates. We find no instability for waves with wave vectors parallel or perpendicular to the direction of the injected carriers. We find that, within the small-wave-vector approximation, the angle between q and the direction of the injected <span class="hlt">electrons</span> that maximizes the growth rate increases with increasing |q | . We compare the range and strength of the instability in graphene to that of two- and three-dimensional parabolic band systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ChPhL..31l7302T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ChPhL..31l7302T"><span id="translatedtitle"><span class="hlt">Electronic</span> <span class="hlt">Transport</span> of the Adsorbed Trigonal Graphene Flake: A First Principles Calculation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tan, Xun-Qiong</p> <p>2014-12-01</p> <p>Based on the <span class="hlt">non-equilibrium</span> Green's function method combined with the density functional theory, we investigate the <span class="hlt">transport</span> properties of a zigzag trigonal graphene flake (zTGF) adsorbed by a single atom (F or H) or a single group (OH or CH3) at the central site and connected to two symmetric Au electrodes by Au-S bonds. The results show that the OH adsorption can enhance the conductance, followed by the negative differential resistance effects, while the conductance for the zTGF adsorbed by H and CH3 is lowered obviously, and rectifying characteristics can be observed for the H-adsorbed system. The adsorbing action alters the molecular level position and the spatial distribution of the molecular orbital, leading to different <span class="hlt">transport</span> properties.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998JAP....83.3207B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998JAP....83.3207B"><span id="translatedtitle"><span class="hlt">Electron</span> <span class="hlt">transport</span> across metal/discotic liquid crystal interfaces</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Boden, N.; Bushby, R. J.; Clements, J.; Movaghar, B.</p> <p>1998-03-01</p> <p><span class="hlt">Electron</span> <span class="hlt">transport</span> across micron thick films of columnar hexagonal discotic liquid crystal phases homeotropically aligned between metal electrode surfaces has been studied both experimentally and theoretically. These molecules are unique in their combination of charge <span class="hlt">transport</span> along individual molecular columns with liquidlike self-organization. Typical of organic insulators, a high resistance Ohmic regime is evident at fields of less than 0.05 MV cm-1, due to a low concentration of chemical impurities (n<109cm-3), and a space-charge injection regime at higher fields. Breakdown fields are reasonably high: in hexakis(hexyloxy)triphenylene they reach ˜5 MV cm-1 at room temperature. Our results show that triphenylene-based discotics form an excellent class of highly ordered optically transparent insulators. At high temperatures and high fields the current is injection controlled and exhibits typical tunneling and space charge limited, nonlinear I-V characteristics. Dramatic jumps in injection currents are observed at phase transitions. The change at the crystalline to liquid crystalline phase transition is mainly due to more efficient "wetting" of the electrode surface in the liquid crystalline phase, whilst at the liquid crystalline to isotropic phase transition it arises from the enhancement in the molecular mobility. The concepts of semiconducting gaps, band mobilities, and carrier injection rates are extended to these new materials. The experimental observations are interpreted in a framework which takes into account the important role played by liquidlike dynamics in establishing the microscopic structural order in, what is, otherwise a highly anisotropic and weakly bonded "molecular crystal."</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002PhDT........72B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002PhDT........72B"><span id="translatedtitle">Nonlinear quantum <span class="hlt">transport</span> in low-dimensional <span class="hlt">electronic</span> devices</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barrios, Andres Javier</p> <p></p> <p>The study of <span class="hlt">transport</span> processes in low-dimensional semiconductors requires a rigorous quantum mechanical treatment. However, a full-fledged quantum <span class="hlt">transport</span> theory of <span class="hlt">electrons</span> (or holes) in semiconductors of small scale, applicable in the presence of external fields of arbitrary strength, is still not available. In the literature, different approaches have been proposed, including: (a) the semiclassical Boltzmann equation, (b) perturbation theory based on Keldysh's Green functions, and (c) the Quantum Boltzmann Equation (QBE), previously derived by Van Vliet and coworkers, applicable in the realm of Kubo's Linear Response Theory (LRT). In the present work, we follow the method originally proposed by Van Wet in LRT. The Hamiltonian in this approach is of the form: H = H 0(E, B) + lambdaV, where H0 contains the externally applied fields, and lambdaV includes many-body interactions. This Hamiltonian differs from the LRT Hamiltonian, H = H0 - AF(t) + lambdaV, which contains the external field in the field-response part, -AF(t). For the nonlinear problem, the eigenfunctions of the system Hamiltonian, H0(E, B), include the external fields without any limitation on strength. In Part A of this dissertation, both the diagonal and nondiagonal Master equations are obtained after applying projection operators to the von Neumann equation for the density operator in the interaction picture, and taking the Van Hove limit, (lambda → 0, t → infinity, so that (lambda2 t)n remains finite). Similarly, the many-body current operator J is obtained from the Heisenberg equation of motion. In Part B, the Quantum Boltzmann Equation is obtained in the occupation-number representation for an <span class="hlt">electron</span> gas, interacting with phonons or impurities. On the one-body level, the current operator obtained in Part A leads to the Generalized Calecki current for electric and magnetic fields of arbitrary strength. Furthermore, in this part, the LRT results for the current and conductance are</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016Nanot..27H5503P&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016Nanot..27H5503P&link_type=ABSTRACT"><span id="translatedtitle">Surface trap mediated <span class="hlt">electronic</span> <span class="hlt">transport</span> in biofunctionalized silicon nanowires</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Puppo, F.; Traversa, F. L.; Di Ventra, M.; De Micheli, G.; Carrara, S.</p> <p>2016-08-01</p> <p>Silicon nanowires (SiNWs), fabricated via a top-down approach and then functionalized with biological probes, are used for electrically-based sensing of breast tumor markers. The SiNWs, featuring memristive-like behavior in bare conditions, show, in the presence of biomarkers, modified hysteresis and, more importantly, a voltage memory component, namely a voltage gap. The voltage gap is demonstrated to be a novel and powerful parameter of detection thanks to its high-resolution dependence on charges in proximity of the wire. This unique approach of sensing has never been studied and adopted before. Here, we propose a physical model of the surface <span class="hlt">electronic</span> <span class="hlt">transport</span> in Schottky barrier SiNW biosensors, aiming at reproducing and understanding the voltage gap based behavior. The implemented model describes well the experimental I–V characteristics of the device. It also links the modification of the voltage gap to the changing concentration of antigens by showing the decrease of this parameter in response to increasing concentrations of the molecules that are detected with femtomolar resolution in real human samples. Both experiments and simulations highlight the predominant role of the dynamic recombination of the nanowire surface states, with the incoming external charges from bio-species, in the appearance and modification of the voltage gap. Finally, thanks to its compactness, and strict correlation with the physics of the nanodevice, this model can be used to describe and predict the I–V characteristics in other nanostructured devices, for different than antibody-based sensing as well as <span class="hlt">electronic</span> applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27418560','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27418560"><span id="translatedtitle">Surface trap mediated <span class="hlt">electronic</span> <span class="hlt">transport</span> in biofunctionalized silicon nanowires.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Puppo, F; Traversa, F L; Ventra, M Di; Micheli, G De; Carrara, S</p> <p>2016-08-26</p> <p>Silicon nanowires (SiNWs), fabricated via a top-down approach and then functionalized with biological probes, are used for electrically-based sensing of breast tumor markers. The SiNWs, featuring memristive-like behavior in bare conditions, show, in the presence of biomarkers, modified hysteresis and, more importantly, a voltage memory component, namely a voltage gap. The voltage gap is demonstrated to be a novel and powerful parameter of detection thanks to its high-resolution dependence on charges in proximity of the wire. This unique approach of sensing has never been studied and adopted before. Here, we propose a physical model of the surface <span class="hlt">electronic</span> <span class="hlt">transport</span> in Schottky barrier SiNW biosensors, aiming at reproducing and understanding the voltage gap based behavior. The implemented model describes well the experimental I-V characteristics of the device. It also links the modification of the voltage gap to the changing concentration of antigens by showing the decrease of this parameter in response to increasing concentrations of the molecules that are detected with femtomolar resolution in real human samples. Both experiments and simulations highlight the predominant role of the dynamic recombination of the nanowire surface states, with the incoming external charges from bio-species, in the appearance and modification of the voltage gap. Finally, thanks to its compactness, and strict correlation with the physics of the nanodevice, this model can be used to describe and predict the I-V characteristics in other nanostructured devices, for different than antibody-based sensing as well as <span class="hlt">electronic</span> applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Nanot..27H5503P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Nanot..27H5503P"><span id="translatedtitle">Surface trap mediated <span class="hlt">electronic</span> <span class="hlt">transport</span> in biofunctionalized silicon nanowires</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Puppo, F.; Traversa, F. L.; Di Ventra, M.; De Micheli, G.; Carrara, S.</p> <p>2016-08-01</p> <p>Silicon nanowires (SiNWs), fabricated via a top-down approach and then functionalized with biological probes, are used for electrically-based sensing of breast tumor markers. The SiNWs, featuring memristive-like behavior in bare conditions, show, in the presence of biomarkers, modified hysteresis and, more importantly, a voltage memory component, namely a voltage gap. The voltage gap is demonstrated to be a novel and powerful parameter of detection thanks to its high-resolution dependence on charges in proximity of the wire. This unique approach of sensing has never been studied and adopted before. Here, we propose a physical model of the surface <span class="hlt">electronic</span> <span class="hlt">transport</span> in Schottky barrier SiNW biosensors, aiming at reproducing and understanding the voltage gap based behavior. The implemented model describes well the experimental I-V characteristics of the device. It also links the modification of the voltage gap to the changing concentration of antigens by showing the decrease of this parameter in response to increasing concentrations of the molecules that are detected with femtomolar resolution in real human samples. Both experiments and simulations highlight the predominant role of the dynamic recombination of the nanowire surface states, with the incoming external charges from bio-species, in the appearance and modification of the voltage gap. Finally, thanks to its compactness, and strict correlation with the physics of the nanodevice, this model can be used to describe and predict the I-V characteristics in other nanostructured devices, for different than antibody-based sensing as well as <span class="hlt">electronic</span> applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22341856','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22341856"><span id="translatedtitle">Study of <span class="hlt">electronic</span> <span class="hlt">transport</span> in gamma ray exposed nanowires</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gehlawat, Devender Chauhan, R.P.</p> <p>2014-01-01</p> <p>Graphical abstract: A sharp decline in the I–V characteristics of Cu (and Cd) nanowires was experimentally observed after the gamma ray exposure of nanowires. Irradiation induced transformations in the granular properties and the resonance state of electron–phonon coupling beyond a particular value of external field may be accountable for observed shape of I–V characteristics in gamma ray exposed nanowires. - Highlights: • Cu and Cd nanowires were synthesized by technique of electrodeposition in templates. • The nanowires were exposed to different doses of gamma ray photons. • A sharp decline in the current in I–V characteristics (IVC) was observed. • Structural deviation in terms of granular orientations was also analysed. • The electron–phonon coupling may be responsible for observed sharp decline in IVC. - Abstract: One dimensional nanostructures provide the most restricted and narrow channel for the <span class="hlt">transport</span> of charge carriers and therefore 1D structures preserve their significance from the viewpoint of <span class="hlt">electronic</span> devices. The net radiation effect on nanomaterials is expected to be more (due to their increased reactivity and lesser bulk volume) than their bulk counterparts. Radiation often modifies the structure and simultaneously the other physical properties of materials. In this manner, the irradiation phenomenon could be counted as a strong criterion to induce changes in the structural and electrical properties of nanowires. We have studied the effect of gamma rays on the <span class="hlt">electronic</span> flow through Cu and Cd nanowires by plotting their I–V characteristics (IVC). The IVC of gamma ray exposed nanowires was found to be a combination of the linear and nonlinear regions and a decreasing pattern in the electrical conductivity (calculated from the linear portion of IVC) was observed as we increased the dose of gamma rays.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27418560','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27418560"><span id="translatedtitle">Surface trap mediated <span class="hlt">electronic</span> <span class="hlt">transport</span> in biofunctionalized silicon nanowires.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Puppo, F; Traversa, F L; Ventra, M Di; Micheli, G De; Carrara, S</p> <p>2016-08-26</p> <p>Silicon nanowires (SiNWs), fabricated via a top-down approach and then functionalized with biological probes, are used for electrically-based sensing of breast tumor markers. The SiNWs, featuring memristive-like behavior in bare conditions, show, in the presence of biomarkers, modified hysteresis and, more importantly, a voltage memory component, namely a voltage gap. The voltage gap is demonstrated to be a novel and powerful parameter of detection thanks to its high-resolution dependence on charges in proximity of the wire. This unique approach of sensing has never been studied and adopted before. Here, we propose a physical model of the surface <span class="hlt">electronic</span> <span class="hlt">transport</span> in Schottky barrier SiNW biosensors, aiming at reproducing and understanding the voltage gap based behavior. The implemented model describes well the experimental I-V characteristics of the device. It also links the modification of the voltage gap to the changing concentration of antigens by showing the decrease of this parameter in response to increasing concentrations of the molecules that are detected with femtomolar resolution in real human samples. Both experiments and simulations highlight the predominant role of the dynamic recombination of the nanowire surface states, with the incoming external charges from bio-species, in the appearance and modification of the voltage gap. Finally, thanks to its compactness, and strict correlation with the physics of the nanodevice, this model can be used to describe and predict the I-V characteristics in other nanostructured devices, for different than antibody-based sensing as well as <span class="hlt">electronic</span> applications. PMID:27418560</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20366621','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20366621"><span id="translatedtitle">Reversal of nonlocal vortex motion in the regime of strong <span class="hlt">nonequilibrium</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Otto, Florian; Bilusić, Ante; Babić, Dinko; Vodolazov, Denis Yu; Sürgers, Christoph; Strunk, Christoph</p> <p>2010-01-15</p> <p>We investigate nonlocal vortex motion in weakly pinning a-NbGe nanostructures, which is driven by a <span class="hlt">transport</span> current I and remotely detected as a nonlocal voltage V{nl}. At a high I of a given polarity, V{nl} changes sign dramatically. This is followed by V{nl} becoming even in I, with the opposite sign at low and high temperatures T. These findings can be explained by a Nernst-like effect resulting from local <span class="hlt">electron</span> overheating (low T), and a magnetization enhancement due to a <span class="hlt">nonequilibrium</span> quasiparticle distribution that leads to a gap enhancement near the vortex core (high T).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012Nanos...4.5490Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012Nanos...4.5490Z"><span id="translatedtitle"><span class="hlt">Electronic</span> structure and quantum <span class="hlt">transport</span> properties of trilayers formed from graphene and boron nitride</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhong, Xiaoliang; Amorim, Rodrigo G.; Scheicher, Ralph H.; Pandey, Ravindra; Karna, Shashi P.</p> <p>2012-08-01</p> <p>We report the results of a theoretical study of graphene/BN/graphene and BN/graphene/BN trilayers using the van-der-Waals-corrected density functional theory in conjunction with the <span class="hlt">non-equilibrium</span> Green's Function method. These trilayer systems formed from graphene and BN exhibit distinct stacking-dependent features in their ground state <span class="hlt">electronic</span> structure and response to an applied electric field perpendicular to the trilayer planes. The graphene/BN/graphene system shows a negligible gap in the <span class="hlt">electronic</span> band structure that increases for the AAA and ABA stackings under an external electric field, while the zero-field band gap of BN/graphene/BN remains unaffected by the electric field. When both types of trilayer systems are contacted with gold electrodes, a metal-like conduction is predicted in the low-field regime, which changes to a p-type conduction with an increase in the applied perpendicular bias field.We report the results of a theoretical study of graphene/BN/graphene and BN/graphene/BN trilayers using the van-der-Waals-corrected density functional theory in conjunction with the <span class="hlt">non-equilibrium</span> Green's Function method. These trilayer systems formed from graphene and BN exhibit distinct stacking-dependent features in their ground state <span class="hlt">electronic</span> structure and response to an applied electric field perpendicular to the trilayer planes. The graphene/BN/graphene system shows a negligible gap in the <span class="hlt">electronic</span> band structure that increases for the AAA and ABA stackings under an external electric field, while the zero-field band gap of BN/graphene/BN remains unaffected by the electric field. When both types of trilayer systems are contacted with gold electrodes, a metal-like conduction is predicted in the low-field regime, which changes to a p-type conduction with an increase in the applied perpendicular bias field. <span class="hlt">Electronic</span> supplementary information (ESI) available. See DOI: 10.1039/c2nr31310c</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6067021','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6067021"><span id="translatedtitle">Considerations of beta and <span class="hlt">electron</span> <span class="hlt">transport</span> in internal dose calculations</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bolch, W.E.; Poston, J.W. Sr. . Dept. of Nuclear Engineering)</p> <p>1990-12-01</p> <p>Ionizing radiation has broad uses in modern science and medicine. These uses often require the calculation of energy deposition in the irradiated media and, usually, the medium of interest is the human body. Energy deposition from radioactive sources within the human body and the effects of such deposition are considered in the field of internal dosimetry. In July of 1988, a three-year research project was initiated by the Nuclear Engineering Department at Texas A M University under the sponsorship of the US Department of Energy. The main thrust of the research was to consider, for the first time, the detailed spatial <span class="hlt">transport</span> of <span class="hlt">electron</span> and beta particles in the estimation of average organ doses under the Medical Internal Radiation Dose (MIRD) schema. At the present time (December of 1990), research activities are continuing within five areas. Several are new initiatives begun within the second or third year of the current contract period. They include: (1) development of small-scale dosimetry; (2) development of a differential volume phantom; (3) development of a dosimetric bone model; (4) assessment of the new ICRP lung model; and (5) studies into the mechanisms of DNA damage. A progress report is given for each of these tasks within the Comprehensive Report. In each use, preliminary results are very encouraging and plans for further research are detailed within this document. 22 refs., 13 figs., 1 tab.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/pages/biblio/1200859-electronic-transport-two-dimensional-high-dielectric-constant-nanosystems','SCIGOV-DOEP'); return false;" href="http://www.osti.gov/pages/biblio/1200859-electronic-transport-two-dimensional-high-dielectric-constant-nanosystems"><span id="translatedtitle"><span class="hlt">Electronic</span> <span class="hlt">transport</span> in two-dimensional high dielectric constant nanosystems</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGESBeta</a></p> <p>Ortuño, M.; Somoza, A. M.; Vinokur, V. M.; Baturina, T. I.</p> <p>2015-04-10</p> <p>There has been remarkable recent progress in engineering high-dielectric constant two dimensional (2D) materials, which are being actively pursued for applications in nanoelectronics in capacitor and memory devices, energy storage, and high-frequency modulation in communication devices. Yet many of the unique properties of these systems are poorly understood and remain unexplored. Here we report a numerical study of hopping conductivity of the lateral network of capacitors, which models two-dimensional insulators, and demonstrate that 2D long-range Coulomb interactions lead to peculiar size effects. We find that the characteristic energy governing <span class="hlt">electronic</span> <span class="hlt">transport</span> scales logarithmically with either system size or electrostatic screeningmore » length depending on which one is shorter. Our results are relevant well beyond their immediate context, explaining, for example, recent experimental observations of logarithmic size dependence of electric conductivity of thin superconducting films in the critical vicinity of superconductor-insulator transition where a giant dielectric constant develops. Our findings mark a radical departure from the orthodox view of conductivity in 2D systems as a local characteristic of materials and establish its macroscopic global character as a generic property of high-dielectric constant 2D nanomaterials.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005PhDT........42Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005PhDT........42Y"><span id="translatedtitle"><span class="hlt">Electronic</span> <span class="hlt">transport</span> of N-type semiconductor nanocrystalline solids</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yu, Dong</p> <p>2005-07-01</p> <p>A bottleneck limiting the widespread applications of semiconductor nanocrystalline solids on optoelectronic devices such as photovoltaic cells, light emitting devices and quantum dots lasers is their poor conductivity. In this thesis, we show that the conductivity of thin films of CdSe nanocrystals is increased by many orders of magnitude when n-doped either by potassium or electrochemistry. Around half-filling of the first <span class="hlt">electronic</span> shell, a peak in the conductivity is observed indicating shell to shell <span class="hlt">transport</span>. Introducing conjugated ligands between nanocrystals increases the conductivities to ˜10-2 S cm. NaOH treatment of the thin films leads to a large carrier mobility and a semiconductor nanocrystals field effect transistor is produced. The temperature and electrical field dependent conductivity of n-type CdSe nanocrystal thin films is then investigated. The low field conductivity follows exp(-(T*/T)-1/2 ) and high field conductivity follows exp(-(E*/ E)-1/2). The complete behavior is very well described by the variable range hopping theory with a Coulomb gap. Finally, n-type colloidal CdSe nanocrystalline solids show large positive magnetoresistance at low temperatures (0.3K--4K). We attempted to dope Manganese (II) ions in nanocrystals, which might show interesting negative magnetoresistance. However, they still show similar positive magnetoresistance probably due to the difficulty of Mn doping. At ˜0.3K the resistance is increased by ˜150% at 10 Tesla.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6067078','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6067078"><span id="translatedtitle">Considerations of beta and <span class="hlt">electron</span> <span class="hlt">transport</span> in internal dose calculations</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bolch, W.E.; Poston, J.W. Sr.</p> <p>1990-12-01</p> <p>Ionizing radiation has broad uses in modern science and medicine. These uses often require the calculation of energy deposition in the irradiated media and, usually, the medium of interest is the human body. Energy deposition from radioactive sources within the human body and the effects of such deposition are considered in the field of internal dosimetry. In July of 1988, a three-year research project was initiated by the Nuclear Engineering Department at Texas A M University under the sponsorship of the US Department of Energy. The main thrust of the research was to consider, for the first time, the detailed spatial <span class="hlt">transport</span> of <span class="hlt">electron</span> and beta particles in the estimation of average organ doses under the Medical Internal Radiation Dose (MIRD) schema. At the present time (December of 1990), research activities are continuing within five areas. Several are new initiatives begun within the second or third year of the current contract period. They include: (1) development of small-scale dosimetry; (2) development of a differential volume phantom; (3) development of a dosimetric bone model; (4) assessment of the new ICRP lung model; and (5) studies into the mechanisms of DNA damage. A progress report is given for each of these tasks within the Comprehensive Report. In each case, preliminary results are very encouraging and plans for further research are detailed within this document.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NatSR...5E9667O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NatSR...5E9667O"><span id="translatedtitle"><span class="hlt">Electronic</span> <span class="hlt">transport</span> in two-dimensional high dielectric constant nanosystems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ortuño, M.; Somoza, A. M.; Vinokur, V. M.; Baturina, T. I.</p> <p>2015-04-01</p> <p>There has been remarkable recent progress in engineering high-dielectric constant two dimensional (2D) materials, which are being actively pursued for applications in nanoelectronics in capacitor and memory devices, energy storage, and high-frequency modulation in communication devices. Yet many of the unique properties of these systems are poorly understood and remain unexplored. Here we report a numerical study of hopping conductivity of the lateral network of capacitors, which models two-dimensional insulators, and demonstrate that 2D long-range Coulomb interactions lead to peculiar size effects. We find that the characteristic energy governing <span class="hlt">electronic</span> <span class="hlt">transport</span> scales logarithmically with either system size or electrostatic screening length depending on which one is shorter. Our results are relevant well beyond their immediate context, explaining, for example, recent experimental observations of logarithmic size dependence of electric conductivity of thin superconducting films in the critical vicinity of superconductor-insulator transition where a giant dielectric constant develops. Our findings mark a radical departure from the orthodox view of conductivity in 2D systems as a local characteristic of materials and establish its macroscopic global character as a generic property of high-dielectric constant 2D nanomaterials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1200859','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1200859"><span id="translatedtitle"><span class="hlt">Electronic</span> <span class="hlt">transport</span> in two-dimensional high dielectric constant nanosystems</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ortuño, M.; Somoza, A. M.; Vinokur, V. M.; Baturina, T. I.</p> <p>2015-04-10</p> <p>There has been remarkable recent progress in engineering high-dielectric constant two dimensional (2D) materials, which are being actively pursued for applications in nanoelectronics in capacitor and memory devices, energy storage, and high-frequency modulation in communication devices. Yet many of the unique properties of these systems are poorly understood and remain unexplored. Here we report a numerical study of hopping conductivity of the lateral network of capacitors, which models two-dimensional insulators, and demonstrate that 2D long-range Coulomb interactions lead to peculiar size effects. We find that the characteristic energy governing <span class="hlt">electronic</span> <span class="hlt">transport</span> scales logarithmically with either system size or electrostatic screening length depending on which one is shorter. Our results are relevant well beyond their immediate context, explaining, for example, recent experimental observations of logarithmic size dependence of electric conductivity of thin superconducting films in the critical vicinity of superconductor-insulator transition where a giant dielectric constant develops. Our findings mark a radical departure from the orthodox view of conductivity in 2D systems as a local characteristic of materials and establish its macroscopic global character as a generic property of high-dielectric constant 2D nanomaterials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19990071231','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19990071231"><span id="translatedtitle">Inner Magnetospheric Superthermal <span class="hlt">Electron</span> <span class="hlt">Transport</span>: Photoelectron and Plasma Sheet <span class="hlt">Electron</span> Sources</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Khazanov, G. V.; Liemohn, M. W.; Kozyra, J. U.; Moore, T. E.</p> <p>1998-01-01</p> <p>Two time-dependent kinetic models of superthermal <span class="hlt">electron</span> <span class="hlt">transport</span> are combined to conduct global calculations of the nonthermal <span class="hlt">electron</span> distribution function throughout the inner magnetosphere. It is shown that the energy range of validity for this combined model extends down to the superthermal-thermal intersection at a few eV, allowing for the calculation of the en- tire distribution function and thus an accurate heating rate to the thermal plasma. Because of the linearity of the formulas, the source terms are separated to calculate the distributions from the various populations, namely photoelectrons (PEs) and plasma sheet <span class="hlt">electrons</span> (PSEs). These distributions are discussed in detail, examining the processes responsible for their formation in the various regions of the inner magnetosphere. It is shown that convection, corotation, and Coulomb collisions are the dominant processes in the formation of the PE distribution function and that PSEs are dominated by the interplay between the drift terms. Of note is that the PEs propagate around the nightside in a narrow channel at the edge of the plasmasphere as Coulomb collisions reduce the fluxes inside of this and convection compresses the flux tubes inward. These distributions are then recombined to show the development of the total superthermal <span class="hlt">electron</span> distribution function in the inner magnetosphere and their influence on the thermal plasma. PEs usually dominate the dayside heating, with integral energy fluxes to the ionosphere reaching 10(exp 10) eV/sq cm/s in the plasmasphere, while heating from the PSEs typically does not exceed 10(exp 8) eV/sq cm/s. On the nightside, the inner plasmasphere is usually unheated by superthermal <span class="hlt">electrons</span>. A feature of these combined spectra is that the distribution often has upward slopes with energy, particularly at the crossover from PE to PSE dominance, indicating that instabilities are possible.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/319673','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/319673"><span id="translatedtitle"><span class="hlt">Electron</span> heat <span class="hlt">transport</span> in improved confinement discharges in DIII-D</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Stallard, B.W.; Greenfield, C.M.; Staebler, G.M.</p> <p>1999-01-01</p> <p>In DIII-D tokamak plasmas with an internal <span class="hlt">transport</span> barrier (ITB), the comparison of gyrokinetic linear stability (GKS) predictions with experiments in both low and strong negative magnetic shear plasmas provide improved understanding for <span class="hlt">electron</span> thermal <span class="hlt">transport</span> within the plasma. Within a limited region just inside the ITB, the <span class="hlt">electron</span> temperature gradient (ETG) modes appear to control the <span class="hlt">electron</span> temperature gradient and, consequently, the <span class="hlt">electron</span> thermal <span class="hlt">transport</span>. The increase in the <span class="hlt">electron</span> temperature gradient with more strongly negative magnetic shear is consistent with the increase in the ETG mode marginal gradient. Closer to the magnetic axis the T{sub e} profile flattens and the ETG modes are predicted to be stable. With additional core <span class="hlt">electron</span> heating, FIR scattering measurements near the axis show the presence of high k fluctuations (12 cm{sup {minus}1}), rotating in the <span class="hlt">electron</span> diamagnetic drift direction. This turbulence could impact <span class="hlt">electron</span> <span class="hlt">transport</span> and possibly also ion <span class="hlt">transport</span>. Thermal diffusivities for <span class="hlt">electrons</span>, and to a lesser degree ions, increase. The ETG mode can exist at this wavenumber, but it is computed to be robustly stable near the axis. Consequently, in the plasmas the authors have examined, calculations of drift wave linear stability do not explain the observed <span class="hlt">transport</span> near the axis in plasmas with or without additional <span class="hlt">electron</span> heating, and there are probably other processes controlling <span class="hlt">transport</span> in this region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22854975','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22854975"><span id="translatedtitle"><span class="hlt">Electronic</span> structure and quantum <span class="hlt">transport</span> properties of trilayers formed from graphene and boron nitride.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhong, Xiaoliang; Amorim, Rodrigo G; Scheicher, Ralph H; Pandey, Ravindra; Karna, Shashi P</p> <p>2012-09-01</p> <p>We report the results of a theoretical study of graphene/BN/graphene and BN/graphene/BN trilayers using the van-der-Waals-corrected density functional theory in conjunction with the <span class="hlt">non-equilibrium</span> Green's Function method. These trilayer systems formed from graphene and BN exhibit distinct stacking-dependent features in their ground state <span class="hlt">electronic</span> structure and response to an applied electric field perpendicular to the trilayer planes. The graphene/BN/graphene system shows a negligible gap in the <span class="hlt">electronic</span> band structure that increases for the AAA and ABA stackings under an external electric field, while the zero-field band gap of BN/graphene/BN remains unaffected by the electric field. When both types of trilayer systems are contacted with gold electrodes, a metal-like conduction is predicted in the low-field regime, which changes to a p-type conduction with an increase in the applied perpendicular bias field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=adobe&pg=3&id=EJ1068668','ERIC'); return false;" href="http://eric.ed.gov/?q=adobe&pg=3&id=EJ1068668"><span id="translatedtitle">Using Adobe Flash Animations of <span class="hlt">Electron</span> <span class="hlt">Transport</span> Chain to Teach and Learn Biochemistry</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Teplá, Milada; Klímová, Helena</p> <p>2015-01-01</p> <p>Teaching the subject of the <span class="hlt">electron</span> <span class="hlt">transport</span> chain is one of the most challenging aspects of the chemistry curriculum at the high school level. This article presents an educational program called "<span class="hlt">Electron</span> <span class="hlt">Transport</span> Chain" which consists of 14 visual animations including a biochemistry quiz. The program was created in the Adobe Flash…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19900018657','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19900018657"><span id="translatedtitle"><span class="hlt">Nonequilibrium</span> radiation and chemistry models for aerocapture vehicle flowfields</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Carlson, Leland A.</p> <p>1990-01-01</p> <p>The primary tasks during January 1990 to June 1990 have been the development and evaluation of various <span class="hlt">electron</span> and <span class="hlt">electron-electronic</span> energy equation models, the continued development of improved <span class="hlt">nonequilibrium</span> radiation models for molecules and atoms, and the continued development and investigation of precursor models and their effects. In addition, work was initiated to develop a vibrational model for the viscous shock layer (VSL) <span class="hlt">nonequilibrium</span> chemistry blunt body engineering code. Also, an effort was started associated with the effects of including carbon species, say from an ablator, in the flowfield.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997MPLB...11...35C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997MPLB...11...35C"><span id="translatedtitle">Landauer Approach to Time-Dependent <span class="hlt">Transport</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, L. Y.; Nash, P. L.</p> <p></p> <p>Based upon the <span class="hlt">nonequilibrium</span> Green's function formalism, we present a time-dependent Landauer approach to <span class="hlt">transport</span> through a mesoscopic system under an ac bias voltage. The system is modeled as an elastic scatterer coupled to large <span class="hlt">electron</span> reservoirs through perfect conducting wires (leads). The chemical potentials of the reservoirs are driven apart by the bias and, consequently, current flows through the leads from one reservoir to another. We examine the <span class="hlt">nonequilibrium</span> statistical processes of <span class="hlt">electrons</span> in the leads. The <span class="hlt">electronic</span> waves are quantized on the basis of orthonormal wave packets moving along the leads, scattered by the scatterer, and coupled to the reservoirs. The time for an <span class="hlt">electron</span> to traverse the leads between the source and the drain reservoirs plus the phase delay time caused by the scatterer is found to be the relevant time scale in the time-dependent <span class="hlt">transport</span>. The frequency dependence of the admittance is fully investigated.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_24 --> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2010-title41-vol3/pdf/CFR-2010-title41-vol3-sec102-118-65.pdf','CFR'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2010-title41-vol3/pdf/CFR-2010-title41-vol3-sec102-118-65.pdf"><span id="translatedtitle">41 CFR 102-118.65 - Can my agency receive <span class="hlt">electronic</span> billing for payment of <span class="hlt">transportation</span> services?</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2010&page.go=Go">Code of Federal Regulations, 2010 CFR</a></p> <p></p> <p>2010-07-01</p> <p>... <span class="hlt">electronic</span> billing for payment of <span class="hlt">transportation</span> services? 102-118.65 Section 102-118.65 Public Contracts and... <span class="hlt">Transportation</span> Services § 102-118.65 Can my agency receive <span class="hlt">electronic</span> billing for payment of <span class="hlt">transportation</span>... to use <span class="hlt">electronic</span> billing for the procurement and billing of <span class="hlt">transportation</span> services....</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/411733','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/411733"><span id="translatedtitle">Multigroup Boltzmann-Fokker-Planck <span class="hlt">electron</span>-photon <span class="hlt">transport</span> capability in MCNP</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Adams, K.J.; Hart, M.</p> <p>1995-12-31</p> <p>The MCNP code system has a robust multigroup <span class="hlt">transport</span> capability that includes a Boltzmann-Fokker-Planck (MGBFP) <span class="hlt">transport</span> algorithm to perform coupled <span class="hlt">electron</span>-photon or other coupled charged and neutral particle <span class="hlt">transport</span> in either a forward or adjoint mode. This paper discusses this capability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014NJPh...16g3014T&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014NJPh...16g3014T&link_type=ABSTRACT"><span id="translatedtitle">A reduced model for relativistic <span class="hlt">electron</span> beam <span class="hlt">transport</span> in solids and dense plasmas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Touati, M.; Feugeas, J.-L.; Nicolaï, Ph; Santos, J. J.; Gremillet, L.; Tikhonchuk, V. T.</p> <p>2014-07-01</p> <p>A hybrid reduced model for relativistic <span class="hlt">electron</span> beam <span class="hlt">transport</span> based on the angular moments of the relativistic kinetic equation with a special closure is presented. It takes into account collective effects with the self-generated electromagnetic fields as well as collisional effects with the slowing down of the relativistic <span class="hlt">electrons</span> by plasmons, bound and free <span class="hlt">electrons</span> and their angular scattering on both ions and <span class="hlt">electrons</span>. This model allows for fast computations of relativistic <span class="hlt">electron</span> beam <span class="hlt">transport</span> while describing their energy distribution evolution. Despite the loss of information concerning the angular distribution of the <span class="hlt">electron</span> beam, the model reproduces analytical estimates in the academic case of a monodirectional and monoenergetic <span class="hlt">electron</span> beam propagating through a warm and dense plasma and hybrid particle-in-cell simulation results in a realistic laser-generated <span class="hlt">electron</span> beam <span class="hlt">transport</span> case.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3572443','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3572443"><span id="translatedtitle">Hot <span class="hlt">electron</span> <span class="hlt">transport</span> in a strongly correlated transition-metal oxide</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Rana, Kumari Gaurav; Yajima, Takeaki; Parui, Subir; Kemper, Alexander F.; Devereaux, Thomas P.; Hikita, Yasuyuki; Hwang, Harold Y.; Banerjee, Tamalika</p> <p>2013-01-01</p> <p>Oxide heterointerfaces are ideal for investigating strong correlation effects to <span class="hlt">electron</span> <span class="hlt">transport</span>, relevant for oxide-<span class="hlt">electronics</span>. Using hot-<span class="hlt">electrons</span>, we probe <span class="hlt">electron</span> <span class="hlt">transport</span> perpendicular to the La0.7Sr0.3MnO3 (LSMO)- Nb-doped SrTiO3 (Nb:STO) interface and find the characteristic hot-<span class="hlt">electron</span> attenuation length in LSMO to be 1.48 ± 0.10 unit cells (u.c.) at −1.9 V, increasing to 2.02 ± 0.16 u.c. at −1.3 V at room temperature. Theoretical analysis of this energy dispersion reveals the dominance of <span class="hlt">electron-electron</span> and polaron scattering. Direct visualization of the local <span class="hlt">electron</span> <span class="hlt">transport</span> shows different transmission at the terraces and at the step-edges. PMID:23429420</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1096262','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1096262"><span id="translatedtitle">Modeling <span class="hlt">electron</span> <span class="hlt">transport</span> in the presence of electric and magnetic fields.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Fan, Wesley C.; Drumm, Clifton Russell; Pautz, Shawn D.; Turner, C. David</p> <p>2013-09-01</p> <p>This report describes the theoretical background on modeling <span class="hlt">electron</span> <span class="hlt">transport</span> in the presence of electric and magnetic fields by incorporating the effects of the Lorentz force on <span class="hlt">electron</span> motion into the Boltzmann <span class="hlt">transport</span> equation. Electromagnetic fields alter the <span class="hlt">electron</span> energy and trajectory continuously, and these effects can be characterized mathematically by differential operators in terms of <span class="hlt">electron</span> energy and direction. Numerical solution techniques, based on the discrete-ordinates and finite-element methods, are developed and implemented in an existing radiation <span class="hlt">transport</span> code, SCEPTRE.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23698325','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23698325"><span id="translatedtitle">Stepping stones in the <span class="hlt">electron</span> <span class="hlt">transport</span> from cells to electrodes in Geobacter sulfurreducens biofilms.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bonanni, Pablo Sebastián; Massazza, Diego; Busalmen, Juan Pablo</p> <p>2013-07-01</p> <p>Geobacter sulfurreducens bacteria grow on biofilms and have the particular ability of using polarized electrodes as the final <span class="hlt">electron</span> acceptor of their respiratory chain. In these biofilms, <span class="hlt">electrons</span> are <span class="hlt">transported</span> through distances of more than 50 μm before reaching the electrode. The way in which <span class="hlt">electrons</span> are <span class="hlt">transported</span> across the biofilm matrix through such large distances remains under intense discussion. None of the two mechanisms proposed for explaining the process, <span class="hlt">electron</span> hopping through outer membrane cytochromes and metallic like conduction through conductive PilA filaments, can account for all the experimental evidence collected so far. Aiming at providing new elements for understanding the basis for <span class="hlt">electron</span> <span class="hlt">transport</span>, in this perspective article we present a modelled structure of Geobacter pilus. Its analysis in combination with already existing experimental evidence gives support to the proposal of the "stepping stone" mechanism, in which the combined action of pili and cytochromes allows long range <span class="hlt">electron</span> <span class="hlt">transport</span> through the biofilm. PMID:23698325</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19940023568','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19940023568"><span id="translatedtitle"><span class="hlt">Nonequilibrium</span> radiation and chemistry models for aerocapture vehicle flowfields</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Carlson, Leland A.</p> <p>1994-01-01</p> <p>The primary accomplishments of the project were as follows: (1) From an overall standpoint, the primary accomplishment of this research was the development of a complete gasdynamic-radiatively coupled <span class="hlt">nonequilibrium</span> viscous shock layer solution method for axisymmetric blunt bodies. This method can be used for rapid engineering modeling of <span class="hlt">nonequilibrium</span> re-entry flowfields over a wide range of conditions. (2) Another significant accomplishment was the development of an air radiation model that included local thermodynamic <span class="hlt">nonequilibrium</span> (LTNE) phenomena. (3) As part of this research, three <span class="hlt">electron-electronic</span> energy models were developed. The first was a quasi-equilibrium <span class="hlt">electron</span> (QEE) model which determined an effective free <span class="hlt">electron</span> temperature and assumed that the <span class="hlt">electronic</span> states were in equilibrium with the free <span class="hlt">electrons</span>. The second was a quasi-equilibrium <span class="hlt">electron-electronic</span> (QEEE) model which computed an effective <span class="hlt">electron-electronic</span> temperature. The third model was a full <span class="hlt">electron-electronic</span> (FEE) differential equation model which included convective, collisional, viscous, conductive, vibrational coupling, and chemical effects on <span class="hlt">electron-electronic</span> energy. (4) Since vibration-dissociation coupling phenomena as well as vibrational thermal <span class="hlt">nonequilibrium</span> phenomena are important in the <span class="hlt">nonequilibrium</span> zone behind a shock front, a vibrational energy and vibration-dissociation coupling model was developed and included in the flowfield model. This model was a modified coupled vibrational dissociation vibrational (MCVDV) model and also included <span class="hlt">electron</span>-vibrational coupling. (5) Another accomplishment of the project was the usage of the developed models to investigate radiative heating. (6) A multi-component diffusion model which properly models the multi-component nature of diffusion in complex gas mixtures such as air, was developed and incorporated into the blunt body model. (7) A model was developed to predict the magnitude and characteristics of the shock</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19960022306','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19960022306"><span id="translatedtitle">Turbulence modeling for <span class="hlt">non-equilibrium</span> flow</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Durbin, P. A.</p> <p>1995-01-01</p> <p>The work performed during this year has involved further assessment and extension of the k-epsilon-v(exp 2) model, and initiation of work on scalar <span class="hlt">transport</span>. The latter is introduced by the contribution of Y. Shabany to this volume. Flexible, computationally tractable models are needed for engineering CFD. As computational technology has progressed, the ability and need to use elaborate turbulence closure models has increased. The objective of our work is to explore and develop new analytical frameworks that might extend the applicability of the modeling techniques. In past years the development of a method for near-wall modeling was described. The method has been implemented into a CFD code and its viability has been demonstrated by various test cases. Further tests are reported herein. <span class="hlt">Non-equilibrium</span> near-wall models are needed for some heat transfer applications. Scalar <span class="hlt">transport</span> seems generally to be more sensitive to <span class="hlt">non-equilibrium</span> effects than is momentum <span class="hlt">transport</span>. For some applications turbulence anisotropy plays a role and an estimate of the full Reynolds stress tensor is needed. We have begun work on scalar <span class="hlt">transport</span> per se, but in this brief I will only report on an extension of the k-epsilon-v(exp 2) model to predict the Reynolds stress tensor.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19930055896&hterms=OSL&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DOSL','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19930055896&hterms=OSL&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DOSL"><span id="translatedtitle">On non-local <span class="hlt">transport</span> processes in the solar atmosphere</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Macneice, P.</p> <p>1992-01-01</p> <p>We review two mechanisms which can lend a non-local character to energy <span class="hlt">transport</span> in the solar atmosphere, heat flux propagating in the form of collisionless <span class="hlt">electrons</span>, and <span class="hlt">non-equilibrium</span> ionization of hydrogen driven by ambipolar diffusion. Application of these processes to modelling of the lower transition region and upper chromosphere is considered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/7252688','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/7252688"><span id="translatedtitle">Nonlocal <span class="hlt">electron</span> <span class="hlt">transport</span> in the presence of high-intensity laser irradiation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Epperlein, E.M.; Short, R.W. )</p> <p>1994-08-01</p> <p>We investigate <span class="hlt">electron</span> <span class="hlt">transport</span> in a plasma heated by spatially modulated laser irradiation. When the heating rate is greater than the <span class="hlt">electron-electron</span> collision rate, the thermal conductivity is reduced by a factor of 3 to 4 from the Spitzer-Haerm [Phys. Rev. 89, 977 (1953)] value for [ital K][lambda][sub [ital e</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27420809','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27420809"><span id="translatedtitle">Competition of static magnetic and dynamic photon forces in <span class="hlt">electronic</span> <span class="hlt">transport</span> through a quantum dot.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rauf Abdullah, Nzar; Tang, Chi-Shung; Manolescu, Andrei; Gudmundsson, Vidar</p> <p>2016-09-21</p> <p>We investigate theoretically the balance of the static magnetic and the dynamical photon forces in the <span class="hlt">electron</span> <span class="hlt">transport</span> through a quantum dot in a photon cavity with a single photon mode. The quantum dot system is connected to external leads and the total system is exposed to a static perpendicular magnetic field. We explore the <span class="hlt">transport</span> characteristics through the system by tuning the ratio, [Formula: see text], between the photon energy, [Formula: see text], and the cyclotron energy, [Formula: see text]. Enhancement in the <span class="hlt">electron</span> <span class="hlt">transport</span> with increasing <span class="hlt">electron</span>-photon coupling is observed when [Formula: see text]. In this case the photon field dominates and stretches the <span class="hlt">electron</span> charge distribution in the quantum dot, extending it towards the contact area for the leads. Suppression in the <span class="hlt">electron</span> <span class="hlt">transport</span> is found when [Formula: see text], as the external magnetic field causes circular confinement of the charge density around the dot.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25680580','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25680580"><span id="translatedtitle">Induction events and short-term regulation of <span class="hlt">electron</span> <span class="hlt">transport</span> in chloroplasts: an overview.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tikhonov, Alexander N</p> <p>2015-08-01</p> <p>Regulation of photosynthetic <span class="hlt">electron</span> <span class="hlt">transport</span> at different levels of structural and functional organization of photosynthetic apparatus provides efficient performance of oxygenic photosynthesis in plants. This review begins with a brief overview of the chloroplast <span class="hlt">electron</span> <span class="hlt">transport</span> chain. Then two noninvasive biophysical methods (measurements of slow induction of chlorophyll a fluorescence and EPR signals of oxidized P700 centers) are exemplified to illustrate the possibility of monitoring induction events in chloroplasts in vivo and in situ. Induction events in chloroplasts are considered and briefly discussed in the context of short-term mechanisms of the following regulatory processes: (i) pH-dependent control of the intersystem <span class="hlt">electron</span> <span class="hlt">transport</span>; (ii) the light-induced activation of the Calvin-Benson cycle; (iii) optimization of <span class="hlt">electron</span> <span class="hlt">transport</span> due to fitting alternative pathways of <span class="hlt">electron</span> flow and partitioning light energy between photosystems I and II; and (iv) the light-induced remodeling of photosynthetic apparatus and thylakoid membranes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27420809','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27420809"><span id="translatedtitle">Competition of static magnetic and dynamic photon forces in <span class="hlt">electronic</span> <span class="hlt">transport</span> through a quantum dot.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rauf Abdullah, Nzar; Tang, Chi-Shung; Manolescu, Andrei; Gudmundsson, Vidar</p> <p>2016-09-21</p> <p>We investigate theoretically the balance of the static magnetic and the dynamical photon forces in the <span class="hlt">electron</span> <span class="hlt">transport</span> through a quantum dot in a photon cavity with a single photon mode. The quantum dot system is connected to external leads and the total system is exposed to a static perpendicular magnetic field. We explore the <span class="hlt">transport</span> characteristics through the system by tuning the ratio, [Formula: see text], between the photon energy, [Formula: see text], and the cyclotron energy, [Formula: see text]. Enhancement in the <span class="hlt">electron</span> <span class="hlt">transport</span> with increasing <span class="hlt">electron</span>-photon coupling is observed when [Formula: see text]. In this case the photon field dominates and stretches the <span class="hlt">electron</span> charge distribution in the quantum dot, extending it towards the contact area for the leads. Suppression in the <span class="hlt">electron</span> <span class="hlt">transport</span> is found when [Formula: see text], as the external magnetic field causes circular confinement of the charge density around the dot. PMID:27420809</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26896971','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26896971"><span id="translatedtitle">Reconciling perturbative approaches in phonon-assisted <span class="hlt">transport</span> junctions.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Agarwalla, Bijay Kumar; Segal, Dvira</p> <p>2016-02-21</p> <p>We present consistent results for molecular conduction using two central-complementary approaches: the <span class="hlt">non-equilibrium</span> Green's function technique and the quantum master equation method. Our model describes <span class="hlt">electronic</span> conduction in a donor-acceptor junction in which <span class="hlt">electron</span> transfer is coupled to nuclear motion, modeled by a harmonic vibrational mode. This primary mode is further coupled to secondary phonon modes, a thermal bath. Assuming weak <span class="hlt">electron</span>-phonon coupling but an arbitrary large molecule-metal hybridization, we compute several <span class="hlt">non-equilibrium</span> <span class="hlt">transport</span> quantities: the mean phonon number of the primary mode, charge current statistics. We further present scaling relations for the cumulants valid in the large voltage regime. Our analysis illustrates that the <span class="hlt">non-equilibrium</span> Green's function technique and the quantum master equation method can be worked out consistently, when taking into account corresponding scattering processes. PMID:26896971</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/211608','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/211608"><span id="translatedtitle">Conceptual study of <span class="hlt">electron</span> ripple injection for tokamak <span class="hlt">transport</span> control</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Choe, W.; Ono, M.; Chang, C.S.</p> <p>1995-08-01</p> <p>A non-intrusive method for inducing radial electric field based on <span class="hlt">electron</span> ripple injection is under development by the Princeton CDX-U group. The radial electric field is known to play an important role in the L-H and H-VH mode transition according to the recent theoretical and experimental research. It is therefore important to develop a non-intrusive tool to control the radial electric field profile in tokamak plasmas. The present technique utilizes externally-applied local magnetic ripple fields to trap <span class="hlt">electrons</span> at the edge, allowing them to penetrate towards the plasma center via {gradient}B and curvature drifts, causing the flux surfaces to charge up negatively. <span class="hlt">Electron</span> cyclotron resonance heating is utilized to increase the trapped population and the <span class="hlt">electron</span> drift velocity by raising the perpendicular energy of trapped <span class="hlt">electrons</span>. In order to quantify the effects of cyclotron resonance heating on <span class="hlt">electrons</span>, the temperature anisotropy of resonant <span class="hlt">electrons</span> in a tokamak plasma is calculated. For the calculation of anisotropic temperatures, energy moments of the bounce-averaged Fokker-Planck equation with a bi-Maxwellian distribution function for heated <span class="hlt">electrons</span> are solved, assuming a moderate wave power and a constant quasilinear diffusion coefficient. Simulation using a guiding-center orbit model have been performed to understand the behavior of suprathermal <span class="hlt">electrons</span> in the presence of ripple fields. Examples for CDX-U and ITER parameters are given.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SeScT..31k5004B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SeScT..31k5004B"><span id="translatedtitle">Monte Carlo study of <span class="hlt">electron</span> <span class="hlt">transport</span> in monolayer silicene</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Borowik, Piotr; Thobel, Jean-Luc; Adamowicz, Leszek</p> <p>2016-11-01</p> <p><span class="hlt">Electron</span> mobility and diffusion coefficients in monolayer silicene are calculated by Monte Carlo simulations using simplified band structure with linear energy bands. Results demonstrate reasonable agreement with the full-band Monte Carlo method in low applied electric field conditions. Negative differential resistivity is observed and an explanation of the origin of this effect is proposed. <span class="hlt">Electron</span> mobility and diffusion coefficients are studied in low applied electric field conditions. We demonstrate that a comparison of these parameter values can provide a good check that the calculation is correct. Low-field mobility in silicene exhibits {T}-3 temperature dependence for nondegenerate <span class="hlt">electron</span> gas conditions and {T}-1 for higher <span class="hlt">electron</span> concentrations, when degenerate conditions are imposed. It is demonstrated that to explain the relation between mobility and temperature in nondegenerate <span class="hlt">electron</span> gas the linearity of the band structure has to be taken into account. It is also found that <span class="hlt">electron-electron</span> scattering only slightly modifies low-field <span class="hlt">electron</span> mobility in degenerate <span class="hlt">electron</span> gas conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19960021284&hterms=Energy+Solar+Wind&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DEnergy%2B%252B%2BSolar%2B%252B%2BWind','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19960021284&hterms=Energy+Solar+Wind&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DEnergy%2B%252B%2BSolar%2B%252B%2BWind"><span id="translatedtitle"><span class="hlt">Electron</span> energy <span class="hlt">transport</span> in the solar wind: Ulysses observations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Scime, Earl; Gary, S. Peter; Phillips, J. L.; Corniileau-Wehrlin, N.; Solomon, J.</p> <p>1995-01-01</p> <p>The <span class="hlt">electron</span> heat flux in the solar wind has been measured by the Ulysses solar wind plasma experiment in the ecliptic from 1 to 5 AU and out of the ecliptic during the recently completed pass over the solar south pole and the ongoing pass over the solar north pole. Although the <span class="hlt">electron</span> heat flux contains only a fraction of the kinetic energy of the solar wind. the available energy is sufficient to account for the non-adiabatic expansion of the solar wind <span class="hlt">electrons</span>. The Ulysses measurements indicate that the <span class="hlt">electron</span> heat flux is actively dissipated in the solar wind. The exact mechanism or mechanisms is unknown. but a model based on the whistler heat flux instability predicts radial gradients for the <span class="hlt">electron</span> heat flux in good agreement with the data. We will present measurements of the correlation between wave activity measured by the unified radio and plasma experiment (URAP) and the <span class="hlt">electron</span> heat flux throughout the Ulysses mission. The goal is to determine if whistler waves are a good candidate for the observed <span class="hlt">electron</span> heat flux dissipation. The latitudinal gradients of the <span class="hlt">electron</span> heat flux. wave activity. and <span class="hlt">electron</span> pressure will be discussed in light of the changes in the magnetic field geometry from equator to poles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001JaJAP..40.7072F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001JaJAP..40.7072F"><span id="translatedtitle"><span class="hlt">Electron</span> <span class="hlt">Transport</span> across Magnetic Filter in Negative Hydrogen Ion Source</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fukano, Azusa; Ogasawara, Masatada</p> <p>2001-12-01</p> <p>Profiles of <span class="hlt">electron</span> temperature and number density in a negative-ion source are investigated theoretically. Spatial dependence over the magnetic filter region is obtained using the equations of <span class="hlt">electron</span> flux and <span class="hlt">electron</span> heat flux that include the effect of interference of forces by the density gradient and temperature gradient. Due to the effect of the magnetic filter, temperature and density of the <span class="hlt">electron</span> decrease from the source chamber to the extraction chamber, and the decrease depends on the magnitude of the magnetic flux. The effect of the magnetic filter on the production and destruction rates of the negative hydrogen ion is examined. The reaction rate for the dissociative attachment reaction which produces the negative hydrogen ion increases with the decrease of the <span class="hlt">electron</span> temperature. However, the production rate per one vibrationally excited hydrogen molecule decreases with the decrease of <span class="hlt">electron</span> density. On the other hand, the destruction probability of the negative ion by the <span class="hlt">electron</span> detachment reaction decreases significantly by the decrease of the <span class="hlt">electron</span> density and temperature. The magnetic filter does not enhance the production of the negative hydrogen ion, but it reduces the destruction of the negative ion because of the decrease of the <span class="hlt">electron</span> density.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ApPhL.103d1603W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ApPhL.103d1603W"><span id="translatedtitle">The effect of <span class="hlt">electron</span> induced hydrogenation of graphene on its electrical <span class="hlt">transport</span> properties</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Woo, Sung Oh; Teizer, Winfried</p> <p>2013-07-01</p> <p>We report a deterioration of the electrical <span class="hlt">transport</span> properties of a graphene field effect transistor due to energetic <span class="hlt">electron</span> irradiation on a stack of Poly Methyl Methacrylate (PMMA) on graphene (PMMA/graphene bilayer). Prior to <span class="hlt">electron</span> irradiation, we observed that the PMMA layer on graphene does not deteriorate the carrier <span class="hlt">transport</span> of graphene but improves its electrical properties instead. As a result of the <span class="hlt">electron</span> irradiation on the PMMA/graphene bilayer, the Raman "D" band appears after removal of PMMA. We argue that the degradation of the <span class="hlt">transport</span> behavior originates from the binding of hydrogen generated during the PMMA backbone secession process.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013MPLB...2750175L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013MPLB...2750175L"><span id="translatedtitle">The <span class="hlt">Electron</span> <span class="hlt">Transport</span> in a Nanostructure Modulated by the Magnetic Field and the δ-DOPING</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lu, Jian-Duo; Xu, Bin; Zheng, Wei</p> <p>2013-09-01</p> <p>We theoretically investigate the effect of the δ-doping on the <span class="hlt">electron</span> <span class="hlt">transport</span> in a magnetic nanostructure, which can be experimentally realized by depositing one ferromagnetic stripe on the top of a semiconductor heterostructure. We find that the position and the strength of the δ-doping as well as the distance between the two magnetic fields play an important role on the <span class="hlt">electron</span> <span class="hlt">transport</span> properties such as the transmission probability, the conductance and the spin polarization. These interesting results may be very helpful for analyzing the spin-dependent <span class="hlt">transport</span> mechanism of the <span class="hlt">electron</span> and making the new types of the spintronic devices.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_25 --> <center> <div class="footer-extlink text-muted"><small>Some links on this page may take you to non-federal websites. 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