Sample records for charge carrier transport

  1. Microstructure and charge carrier transport in phthalocyanine based semiconductor blends

    E-print Network

    Schreiber, Frank

    comprises ambipolar field-effect transistors as well as organic photovoltaic cells. Structural, optical the field of organic photovoltaics: Yu et al. reported a polymeric solar cell with an interpenetrating donor conductive materials are widely used for ambipolar charge carrier transport and photovoltaic cells

  2. Charge Carrier Injection and Transport in PPV Light Emitting Devices

    Microsoft Academic Search

    W. Brütting; E. Buchwald; G. Egerer; M. Meier; K. Zuleeg; M. Schwoerer

    1997-01-01

    Charge carrier injection and transport in light emitting devices based on poly-phenylene-vinylene are investigated by internal photoemission and thermally stimulated currents. The barrier heights for electron injection depend very weakly on the metal work function, indicating a significant influence of surface states or interfacial layers. Trap states in PPV are detected with trap energies ranging from 0.1eV in fresh samples

  3. Dispersive transport of charge carriers in disordered nanostructured materials

    NASA Astrophysics Data System (ADS)

    Sibatov, R. T.; Uchaikin, V. V.

    2015-07-01

    Dispersive transport of charge carriers in disordered nanostructured semiconductors is described in terms of integral diffusion equations nonlocal in time. Transient photocurrent kinetics is analyzed for different situations. Relation to the fractional differential approach is demonstrated. Using this relation provides specifications in interpretation of the time-of-flight data. Joint influence of morphology and energy distribution of localized states is described in frames of the trap-limited advection-diffusion on a comb structure modeling a percolation cluster.

  4. Charge carrier transport properties in layer structured hexagonal boron nitride

    SciTech Connect

    Doan, T. C.; Li, J.; Lin, J. Y.; Jiang, H. X., E-mail: hx.jiang@ttu.edu [Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas 79409 (United States)

    2014-10-15

    Due to its large in-plane thermal conductivity, high temperature and chemical stability, large energy band gap (~ 6.4 eV), hexagonal boron nitride (hBN) has emerged as an important material for applications in deep ultraviolet photonic devices. Among the members of the III-nitride material system, hBN is the least studied and understood. The study of the electrical transport properties of hBN is of utmost importance with a view to realizing practical device applications. Wafer-scale hBN epilayers have been successfully synthesized by metal organic chemical deposition and their electrical transport properties have been probed by variable temperature Hall effect measurements. The results demonstrate that undoped hBN is a semiconductor exhibiting weak p-type at high temperatures (> 700?°K). The measured acceptor energy level is about 0.68 eV above the valence band. In contrast to the electrical transport properties of traditional III-nitride wide bandgap semiconductors, the temperature dependence of the hole mobility in hBN can be described by the form of ? ? (T/T{sub 0}){sup ??} with ? = 3.02, satisfying the two-dimensional (2D) carrier transport limit dominated by the polar optical phonon scattering. This behavior is a direct consequence of the fact that hBN is a layer structured material. The optical phonon energy deduced from the temperature dependence of the hole mobility is ?? = 192 meV (or 1546 cm{sup -1}), which is consistent with values previously obtained using other techniques. The present results extend our understanding of the charge carrier transport properties beyond the traditional III-nitride semiconductors.

  5. Charge carrier transport properties in layer structured hexagonal boron nitride

    NASA Astrophysics Data System (ADS)

    Doan, T. C.; Li, J.; Lin, J. Y.; Jiang, H. X.

    2014-10-01

    Due to its large in-plane thermal conductivity, high temperature and chemical stability, large energy band gap (˜ 6.4 eV), hexagonal boron nitride (hBN) has emerged as an important material for applications in deep ultraviolet photonic devices. Among the members of the III-nitride material system, hBN is the least studied and understood. The study of the electrical transport properties of hBN is of utmost importance with a view to realizing practical device applications. Wafer-scale hBN epilayers have been successfully synthesized by metal organic chemical deposition and their electrical transport properties have been probed by variable temperature Hall effect measurements. The results demonstrate that undoped hBN is a semiconductor exhibiting weak p-type at high temperatures (> 700 °K). The measured acceptor energy level is about 0.68 eV above the valence band. In contrast to the electrical transport properties of traditional III-nitride wide bandgap semiconductors, the temperature dependence of the hole mobility in hBN can be described by the form of ? ? (T/T0)-? with ? = 3.02, satisfying the two-dimensional (2D) carrier transport limit dominated by the polar optical phonon scattering. This behavior is a direct consequence of the fact that hBN is a layer structured material. The optical phonon energy deduced from the temperature dependence of the hole mobility is ?? = 192 meV (or 1546 cm-1), which is consistent with values previously obtained using other techniques. The present results extend our understanding of the charge carrier transport properties beyond the traditional III-nitride semiconductors.

  6. Optical Profile and Nanostructure Effects in the Charge Carrier Transport and Performance of Photovoltaic Devices

    NASA Astrophysics Data System (ADS)

    Liu, Yingchi

    Charge carrier plays a significant role in energy harvesting in photovoltaic devices. Due to recombination, the inadequate charge carrier transport length prevents the devices from achieving efficient absorption by increasing active layer thickness. Fundamental research on the charge transport is important as it is a critical factor to determine the optimal device structures. In this thesis, the charge carrier transport process is studied in photovoltaic devices by linking local characteristic light absorption profiles to photocurrent measurements. Local light absorption profile can be approximated as the free charge generation profile, which determines the average charge transport distance. Together with incident light wavelength, illumination direction effectively controls the generation profile and hence the charge transport distance. And this charge transport distance is demonstrated to relate to recombination that can be measured from photocurrent. Therefore, the charge carrier transport length can be estimated. On the other hand, the potential of the nanostructured solar cells as a key to solve the problem lies between adequate light absorption and efficient charge carrier collection. In this thesis, the discussion focuses on the nanostructured bulk heterojunction (BHJ) organic photovoltaics (OPVs). As photonic crystal nanostructures have been proposed to increase the light trapping effects without increasing the volumes of the active materials, intuitively, it is believed that the nanostructure will affect only the optical absorption. However, in this thesis it is demonstrated that there is a tradeoff between light trapping enhancement and charge carrier collection deterioration due to the nanopatterning effects. Furthermore, the nanopatterning process is shown to affect the material composition in BHJ OPVs as well. Improvement of BHJ OPVs' performance by nanostructures is not a simple task of increasing light absorption. Comprehensive considerations are demonstrated necessary for design of optimal device structures.

  7. Exciton harvesting, charge transfer, and charge-carrier transport in amorphous-silicon nanopillar/polymer hybrid solar cells

    E-print Network

    McGehee, Michael

    Exciton harvesting, charge transfer, and charge-carrier transport in amorphous-silicon nanopillar/polymer hybrid solar cells Vignesh Gowrishankar,1,a Shawn R. Scully,1 Albert T. Chan,1 Michael D. McGehee,1,b Qi report on the device physics of nanostructured amorphous-silicon a-Si:H /polymer hybrid solar cells

  8. Determination of charge carrier transport in radio frequency plasma polymerized aniline thin films

    NASA Astrophysics Data System (ADS)

    Sivaraman, Sajeev; Anantharaman, M. R.

    2010-02-01

    The carrier transport mechanism of polyaniline (PA) thin films prepared by radio frequency plasma polymerization is described in this paper. The mechanism of electrical conduction and carrier mobility of PA thin films for different temperatures were examined using the aluminium-PA-aluminium (Al-PA-Al) structure. It is found that the mechanism of carrier transport in these thin films is space charge limited conduction. J-V studies on an asymmetric electrode configuration using indium tin oxide (ITO) as the base electrode and Al as the upper electrode (ITO-PA-Al structure) show a diode-like behaviour with a considerable rectification ratio.

  9. Hydrodynamical Modeling of Charge Carrier Transport in Semiconductors

    Microsoft Academic Search

    ANGELO MARCELLO ANILE; VITTORIO ROMANO

    2000-01-01

    Enhanced functional integration in modern electron devices requires an accurate modeling of energy transport in semiconductors in order to describe high-field phenomena such as hot electron propagation, impact ionization and heat generation in the bulk material. The standard drift-diffusion models cannot cope with high- field phenomena because they do not comprise energy as a dynamical variable. Furthermore for many applications

  10. Charge carrier transport in molecularly doped polycarbonate as a test case for the dipolar glass model

    NASA Astrophysics Data System (ADS)

    Novikov, S. V.; Tyutnev, A. P.

    2013-03-01

    We present the results of Monte Carlo simulations of the charge carrier transport in a disordered molecular system containing spatial and energetic disorders using the dipolar glass model. Model parameters of the material were chosen to fit a typical polar organic photoconductor polycarbonate doped with 30% of aromatic hydrazone, whose transport properties are well documented in literature. Simulated carrier mobility demonstrates a usual Poole-Frenkel field dependence and its slope is very close to the experimental value without using any adjustable parameter. At room temperature transients are universal with respect to the electric field and transport layer thickness. At the same time, carrier mobility does not depend on the layer thickness and transients develop a well-defined plateau where the current does not depend on time, thus demonstrating a non-dispersive transport regime. Tails of the transients decay as power law with the exponent close to -2. This particular feature indicates that transients are close to the boundary between dispersive and non-dispersive transport regimes. Shapes of the simulated transients are in very good agreement with the experimental ones. In summary, we provide a first verification of a self-consistency of the dipolar glass transport model, where major transport parameters, extracted from the experimental transport data, are then used in the transport simulation, and the resulting mobility field dependence and transients are in very good agreement with the initial experimental data.

  11. Charge carrier injection and transport in polymer blend films

    Microsoft Academic Search

    Shan Yu Quan; Feng Teng; Dongdong Wang; Deang Liu; Zheng Xu; Yongsheng Wang; Xurong Xu

    2005-01-01

    The steady current–voltage characteristics of single layer organic devices based on MEH-PPV and N,N?-diphenyl-N,N?-bis(4?-[N,N-bis(naphth-1-yl)-amino]-biphenyl-4-yl)-benzidine (TPTE) blend with different TPTE concentrations was investigated. The thickness dependence of the current–voltage relationship clearly demonstrates that the current at low voltage and at high voltage are all space charge limited. The current density–electric field characteristic proves the blend polymer LEDs to operate in the

  12. Charge-carrier transport and recombination in thin insulating films studied via extraction of injected plasma

    Microsoft Academic Search

    G. Juska; G. Sliauzys; K. Genevicius; K. Arlauskas; A. Pivrikas; M. Scharber; G. Dennler; N. S. Sariciftci; R. Österbacka

    2006-01-01

    We show how charge-carrier transport and recombination in thin insulator films are directly measured using the technique of extraction of injected plasma. This technically simple technique is complementary to the well-known time-of-flight technique. We use this technique on bulk-heterojunction solar cells, where the double-injection current into an insulator is found, and we show how to use the extraction of the

  13. A charge carrier transport model for donor-acceptor blend layers

    NASA Astrophysics Data System (ADS)

    Fischer, Janine; Widmer, Johannes; Kleemann, Hans; Tress, Wolfgang; Koerner, Christian; Riede, Moritz; Vandewal, Koen; Leo, Karl

    2015-01-01

    Highly efficient organic solar cells typically comprise donor-acceptor blend layers facilitating effective splitting of excitons. However, the charge carrier mobility in the blends can be substantially smaller than in neat materials, hampering the device performance. Currently, available mobility models do not describe the transport in blend layers entirely. Here, we investigate hole transport in a model blend system consisting of the small molecule donor zinc phthalocyanine (ZnPc) and the acceptor fullerene C60 in different mixing ratios. The blend layer is sandwiched between p-doped organic injection layers, which prevent minority charge carrier injection and enable exploiting diffusion currents for the characterization of exponential tail states from a thickness variation of the blend layer using numerical drift-diffusion simulations. Trap-assisted recombination must be considered to correctly model the conductivity behavior of the devices, which are influenced by local electron currents in the active layer, even though the active layer is sandwiched in between p-doped contacts. We find that the density of deep tail states is largest in the devices with 1:1 mixing ratio (Et = 0.14 eV, Nt = 1.2 × 1018 cm-3) directing towards lattice disorder as the transport limiting process. A combined field and charge carrier density dependent mobility model are developed for this blend layer.

  14. Charge Carrier Transport and Photogeneration in P3HT:PCBM Photovoltaic Blends.

    PubMed

    Laquai, Frédéric; Andrienko, Denis; Mauer, Ralf; Blom, Paul W M

    2015-06-01

    This article reviews the charge transport and photogeneration in bulk-heterojunction solar cells made from blend films of regioregular poly(3-hexylthiophene) (RR-P3HT) and methano-fullerene (PCBM). The charge transport, specifically the hole mobility in the RR-P3HT phase of the polymer:fullerene photovoltaic blend, is dramatically affected by thermal annealing. The hole mobility increases more than three orders of magnitude and reaches a value of up to 2 × 10(-4) cm(2) V(-1) s(-1) after the thermal annealing process as a result of an improved semi-crystallinity of the film. This significant increase of the hole mobility balances the electron and hole mobilities in a photovoltaic blend in turn reducing space-charge formation, and this is the most important factor for the strong enhancement of the photovoltaic efficiency compared to an as cast, that is, non-annealed device. In fact, the balanced charge carrier mobility in RR-P3HT:PCBM blends in combination with a field- and temperature-independent charge carrier generation and greatly reduced non-geminate recombination explains the large quantum efficiencies mea-sured in P3HT:PCBM photovoltaic devices. PMID:25940132

  15. Fundamentals of Carrier Transport

    NASA Astrophysics Data System (ADS)

    Lundstrom, Mark

    2000-11-01

    Fundamentals of Carrier Transport explores the behavior of charged carriers in semiconductors and semiconductor devices for readers without an extensive background in quantum mechanics and solid-state physics. This second edition contains many new and updated sections, including a completely new chapter on transport in ultrasmall devices and coverage of "full band" transport. Lundstrom also covers both low- and high-field transport, scattering, transport in devices, and transport in mesoscopic systems. He explains in detail the use of Monte Carlo simulation methods and provides many homework exercises along with a variety of worked examples. What makes this book unique is its broad theoretical treatment of transport for advanced students and researchers engaged in experimental semiconductor device research and development.

  16. Distribution of charge carrier transport properties in organic semiconductors with Gaussian disorder

    NASA Astrophysics Data System (ADS)

    Lorrmann, Jens; Ruf, Manuel; Vocke, David; Dyakonov, Vladimir; Deibel, Carsten

    2014-05-01

    The charge carrier drift mobility in disordered semiconductors is commonly graphically extracted from time-of-flight (TOF) photocurrent transients yielding a single transit time. However, the term transit time is ambiguously defined and fails to deliver a mobility in terms of a statistical average. Here, we introduce an advanced computational procedure to evaluate TOF transients, which allows to extract the whole distribution of transit times and mobilities from the photocurrent transient, instead of a single value. This method, extending the work of Scott et al. (Phys. Rev. B 46, 8603 (1992)), is applicable to disordered systems with a Gaussian density of states and its accuracy is validated using one-dimensional Monte Carlo simulations. We demonstrate the superiority of this new approach by comparing it to the common geometrical analysis of hole TOF transients measured on poly(3-hexyl thiophene-2,5-diyl). The extracted distributions provide access to a very detailed and accurate analysis of the charge carrier transport. For instance, not only the mobility given by the mean transit time but also the mean mobility can be calculated. Whereas the latter determines the macroscopic photocurrent, the former is relevant for an accurate determination of the energetic disorder parameter ? within the Gaussian disorder model. ? derived by using the common geometrical method is, as we show, underestimated instead.

  17. A new approach to calculate charge carrier transport mobility in organic molecular crystals from imaginary time path integral simulations

    NASA Astrophysics Data System (ADS)

    Song, Linze; Shi, Qiang

    2015-05-01

    We present a new non-perturbative method to calculate the charge carrier mobility using the imaginary time path integral approach, which is based on the Kubo formula for the conductivity, and a saddle point approximation to perform the analytic continuation. The new method is first tested using a benchmark calculation from the numerical exact hierarchical equations of motion method. Imaginary time path integral Monte Carlo simulations are then performed to explore the temperature dependence of charge carrier delocalization and mobility in organic molecular crystals (OMCs) within the Holstein and Holstein-Peierls models. The effects of nonlocal electron-phonon interaction on mobility in different charge transport regimes are also investigated.

  18. Insights from transport modeling of unusual charge carrier behavior of PDTSiTzTz:PC71BM bulk heterojunction materials

    NASA Astrophysics Data System (ADS)

    Slobodyan, Oleksiy; Moench, Sarah; Liang, Kelly; Danielson, Eric; Holliday, Bradley; Dodabalapur, Ananth

    2015-03-01

    Development of hole-transporting copolymers for use in bulk heterojunctions (BHJs) has significantly improved organic solar cell performance. Despite advances on the materials side, the physics of charge carrier transport remains unsettled. Intrigued by its ability to maintain high fill factors in thick active layers, we studied the copolymer poly[2-(5-(4,4-dioctyl-4H-silolo[3,2-b:4,5-b’]dithiophen-2-yl)-3-tetradecylthiophen-2-yl)- 5-(3-tetradecylthiophen-2-yl)thiazolo[5,4-d]thiazole] (PDTSiTzTz) blended with PC71BM. Results show mobilities which are carrier-concentration-dependent and characterized by a negative Poole-Frenkel effect. Such behavior is not described by current carrier transport models. Established transport mechanisms like multiple-trap-and-release or variable range hopping yield dependence of mobility on carrier concentration. However, a more basic model like Gaussian distribution model (GDM) is needed to produce the negative Poole-Frenkel effect, though GDM cannot describe carrier-concentration-dependent mobility. We have combined key aspects of existing models to create a unified transport model capable of describing phenomena observed in PDTSiTzTz:PC71BM. This model can be used to address open questions about transport physics of organic BHJ materials. U.S. Department of Energy, Award Number DE-SC0001091.

  19. A new approach to calculate charge carrier transport mobility in organic molecular crystals from imaginary time path integral simulations.

    PubMed

    Song, Linze; Shi, Qiang

    2015-05-01

    We present a new non-perturbative method to calculate the charge carrier mobility using the imaginary time path integral approach, which is based on the Kubo formula for the conductivity, and a saddle point approximation to perform the analytic continuation. The new method is first tested using a benchmark calculation from the numerical exact hierarchical equations of motion method. Imaginary time path integral Monte Carlo simulations are then performed to explore the temperature dependence of charge carrier delocalization and mobility in organic molecular crystals (OMCs) within the Holstein and Holstein-Peierls models. The effects of nonlocal electron-phonon interaction on mobility in different charge transport regimes are also investigated. PMID:25956086

  20. Charge carrier injection and ambipolar transport in C60\\/CuPc organic semiconductor blends

    Microsoft Academic Search

    Andreas Opitz; Markus Bronner; W. Brütting

    2008-01-01

    Ambipolar organic field-effect transistors with a mixed active layer of n-conducting fullerene and p-conducting copper-phthalocyanine were prepared. The influence of the mixing ratio and the preparation conditions on the mobilities and the threshold voltages was determined for both charge carrier types. Hole accumulation in the phthalocyanine at the fullerene\\/phthalocyanine interface is observed. A strong correlation between contact resistance and mobility

  1. Charge Carrier Transport Properties of Semiconductor Materials Suitable for Nuclear Radiation Detectors

    Microsoft Academic Search

    G. Ottaviani; C. Canali; A. Alberigi Quaranta

    1975-01-01

    Charge carrier drift velocities in semiconductor materials suitable for solid state detectors has been reviewed. Si, Ge, CdTe and GaAs are considered. New data for HgI2 recently obtained are also reported. The data cover a large range of temperatures (6-430 K) and electric fields up to 50 KV\\/cm. An anisotropy effect in the drift velocity obtained by applying the electric

  2. Morphological reasoning for the enhanced charge carrier mobility of a hole transport molecule in polystyrene

    Microsoft Academic Search

    Ferdous Khan; Ah-Mee Hor; P. R. Sundararajan

    2004-01-01

    Pai and coworkers have reported that the charge carrier mobility of the hole trans- port molecule N,N'-diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine (TPD) is higher with polystyrene (PS) as the host polymer, in comparison to bisphenol A polycar- bonate (PC) as the binder. It was proposed that the enhanced interaction of TPD with PC and the effect of the carbonyl dipole are responsible for such

  3. Structural Phase Transition and Photo-Charge Carrier Transport in SrTiO3

    Microsoft Academic Search

    P. Galinetto; F. Rossella; G. Samoggia; V. Trepakov; E. Kotomin; E. Heifets; P. Markovin; L. Jastrabik

    2006-01-01

    The effect of the antiferrodistorsive phase transition observed at ? 105 K on the photo-carriers transport and band structure of nominally pure SrTiO3 single crystals was investigated. Simultaneously the ab-initio analysis based on the DFT-HF hybrid approach was performed in order to elucidate the atomic and electronic structure changes. It was found that the structural transition play a minor role

  4. A planarized triphenylborane mesogen: discotic liquid crystals with ambipolar charge-carrier transport properties.

    PubMed

    Kushida, Tomokatsu; Shuto, Ayumi; Yoshio, Masafumi; Kato, Takashi; Yamaguchi, Shigehiro

    2015-06-01

    A discotic liquid-crystalline (LC) material, consisting of a planarized triphenylborane mesogen, was synthesized. X-ray diffraction analysis confirmed that this compound forms a hexagonal columnar LC phase with an interfacial distance of 3.57?Å between the discs. At ambient temperature, this boron-centered discotic liquid crystal exhibited ambipolar carrier transport properties with electron and hole mobility values of approximately 10(-3) and 3×10(-5) ?cm(2) ?V(-1) ?s(-1) , respectively. PMID:25907576

  5. A quantitative model for charge carrier transport, trapping and recombination in nanocrystal-based solar cells

    PubMed Central

    Bozyigit, Deniz; Lin, Weyde M. M.; Yazdani, Nuri; Yarema, Olesya; Wood, Vanessa

    2015-01-01

    Improving devices incorporating solution-processed nanocrystal-based semiconductors requires a better understanding of charge transport in these complex, inorganic–organic materials. Here we perform a systematic study on PbS nanocrystal-based diodes using temperature-dependent current–voltage characterization and thermal admittance spectroscopy to develop a model for charge transport that is applicable to different nanocrystal-solids and device architectures. Our analysis confirms that charge transport occurs in states that derive from the quantum-confined electronic levels of the individual nanocrystals and is governed by diffusion-controlled trap-assisted recombination. The current is limited not by the Schottky effect, but by Fermi-level pinning because of trap states that is independent of the electrode–nanocrystal interface. Our model successfully explains the non-trivial trends in charge transport as a function of nanocrystal size and the origins of the trade-offs facing the optimization of nanocrystal-based solar cells. We use the insights from our charge transport model to formulate design guidelines for engineering higher-performance nanocrystal-based devices. PMID:25625647

  6. Charge carrier transport properties in thallium bromide crystals used as radiation detectors

    Microsoft Academic Search

    F. Olschner; M. Toledo-Quinones; K. S. Shah; J. C. Lund

    1990-01-01

    The authors report on measurements of the two most important transport parameters, the mobility ? and the mean trapping time ? for electrons and holes, in TlBr crystals prepared in the laboratory. The results using the transient charge technique are presented along with the data obtained by the pulse height spectrum analysis. The values of (??)e and (??)h measured for

  7. Charge carrier transport in Ge{sub 20}As{sub 20}S{sub 60} chalcogenide semiconductor films

    SciTech Connect

    Kazakova, L. P., E-mail: Kazakova@mail.ioffe.ru; Tsendin, K. D.; Lebedev, E. A. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation); Arsova, D. [Bulgarian Academy of Sciences, Institute of Solid State Physics (Bulgaria); Obukhova, I. A. [St. Petersburg State Forest Technical Academy (Russian Federation)

    2010-01-15

    Charge-carrier transport in Ge{sub 20}As{sub 20}S{sub 60} films has been studied using the transit time method under low-injection conditions at room temperature. It was found that drift mobilities of electrons and holes in Ge{sub 20}As{sub 20}S{sub 60} films are close to each other, i.e., {mu}{sub e} {approx} {mu}{sub h} {approx} 2 x 10{sup -3} cm{sup 2} V{sup -1} s{sup -1} at T = 295 K and F = 5 x 10{sup 4} V/cm. It was shown that the time dependence of the photocurrent during carrier drift and the voltage dependence of the drift mobility allowed the use of the concept of anomalous dispersive transport. Experimental data were explained using the model of transport controlled by carrier trapping by localized states with energy distribution near conduction and valence band edges described by the exponential law with a characteristic energy of {approx}0.05 eV.

  8. Effects of doped dye on the charge carrier injection, transport, and electroluminescent performance in polymeric light-emitting diodes

    Microsoft Academic Search

    Zhenyu Chen; Dongge Ma

    2007-01-01

    The effects of doped fluorescent dye 4-(dicyanomethylene)-2-i-propyl-6-(1, 1, 7, 7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTI) on the charge carrier injection, transport and electroluminescence (EL) performance in polyfluorene (PFO)-based polymer light-emitting diodes (PLEDs) were investigated by steady-state current-voltage (I-V) characteristics and transient EL measurements. A red EL from DCJTI was observed and the EL performance depended strongly on the DCJTI concentration. The analysis of the

  9. The Effect of Dynamical Image Forces on The Transport Properties of Charge Carriers and Excitons in Metal-Semiconductor Nanostructures

    NASA Astrophysics Data System (ADS)

    Cherqui, Charles

    We examine coupled metal nanoparticle/semiconductor hybrid nano-stuctures and analyze the effect that the surface response metal nanoparticles (MNP) has on the transport properties of the system. This analysis is accomplished by treating surface plasmons as quantum oscillators. We find that charge carriers traveling in the nearby semiconductors experience a repulsion due to the ground state energy of the quantum SP (QSP). This effect is shown to be the quantum analogue of the ponderomotive effect found in plasma physics. We then extend the theory to examine the transport properties of carbon nano-tube excitons in the presence of localized SPs and show that this system maps onto a Fano-Anderson Hamiltonian. Through numerical simulation, we show that the emission patterns of the system are severely modified by the presence of localized surface plasmons.

  10. Thermal influence on charge carrier transport in solar cells based on GaAs PN junctions

    SciTech Connect

    Osses-Márquez, Juan; Calderón-Muñoz, Williams R., E-mail: wicalder@ing.uchile.cl [Department of Mechanical Engineering, University of Chile, Beauchef 850, Santiago (Chile)

    2014-10-21

    The electron and hole one-dimensional transport in a solar cell based on a Gallium Arsenide (GaAs) PN junction and its dependency with electron and lattice temperatures are studied here. Electrons and heat transport are treated on an equal footing, and a cell operating at high temperatures using concentrators is considered. The equations of a two-temperature hydrodynamic model are written in terms of asymptotic expansions for the dependent variables with the electron Reynolds number as a perturbation parameter. The dependency of the electron and hole densities through the junction with the temperature is analyzed solving the steady-state model at low Reynolds numbers. Lattice temperature distribution throughout the device is obtained considering the change of kinetic energy of electrons due to interactions with the lattice and heat absorbed from sunlight. In terms of performance, higher values of power output are obtained with low lattice temperature and hot energy carriers. This modeling contributes to improve the design of heat exchange devices and thermal management strategies in photovoltaic technologies.

  11. Charge-carrier transport and recombination in heteroepitaxial CdTe

    NASA Astrophysics Data System (ADS)

    Kuciauskas, Darius; Farrell, Stuart; Dippo, Pat; Moseley, John; Moutinho, Helio; Li, Jian V.; Allende Motz, A. M.; Kanevce, Ana; Zaunbrecher, Katherine; Gessert, Timothy A.; Levi, Dean H.; Metzger, Wyatt K.; Colegrove, Eric; Sivananthan, S.

    2014-09-01

    We analyze charge-carrier dynamics using time-resolved spectroscopy and varying epitaxial CdTe thickness in undoped heteroepitaxial CdTe/ZnTe/Si. By employing one-photon and nonlinear two-photon excitation, we assess surface, interface, and bulk recombination. Two-photon excitation with a focused laser beam enables characterization of recombination velocity at the buried epilayer/substrate interface, 17.5 ?m from the sample surface. Measurements with a focused two-photon excitation beam also indicate a fast diffusion component, from which we estimate an electron mobility of 650 cm2 (Vs)-1 and diffusion coefficient D of 17 cm2 s-1. We find limiting recombination at the epitaxial film surface (surface recombination velocity Ssurface = (2.8 ± 0.3) × 105 cm s-1) and at the heteroepitaxial interface (interface recombination velocity Sinterface = (4.8 ± 0.5) × 105 cm s-1). The results demonstrate that reducing surface and interface recombination velocity is critical for photovoltaic solar cells and electronic devices that employ epitaxial CdTe.

  12. Charge-carrier transport and recombination in heteroepitaxial CdTe

    SciTech Connect

    Kuciauskas, Darius, E-mail: Darius.Kuciauskas@nrel.gov; Farrell, Stuart; Dippo, Pat; Moseley, John; Moutinho, Helio; Li, Jian V.; Allende Motz, A. M.; Kanevce, Ana; Zaunbrecher, Katherine; Gessert, Timothy A.; Levi, Dean H.; Metzger, Wyatt K. [National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401-3305 (United States); Colegrove, Eric; Sivananthan, S. [Microphysics Laboratory, Physics Department, University of Illinois at Chicago, Chicago, Illinois 60612 (United States)

    2014-09-28

    We analyze charge-carrier dynamics using time-resolved spectroscopy and varying epitaxial CdTe thickness in undoped heteroepitaxial CdTe/ZnTe/Si. By employing one-photon and nonlinear two-photon excitation, we assess surface, interface, and bulk recombination. Two-photon excitation with a focused laser beam enables characterization of recombination velocity at the buried epilayer/substrate interface, 17.5 ?m from the sample surface. Measurements with a focused two-photon excitation beam also indicate a fast diffusion component, from which we estimate an electron mobility of 650 cm² (Vs)?¹ and diffusion coefficient D of 17 cm² s?¹. We find limiting recombination at the epitaxial film surface (surface recombination velocity Ssurface = (2.8 ± 0.3) × 10?cm s ?¹) and at the heteroepitaxial interface (interface recombination velocity Sinterface = (4.8 ± 0.5) × 10? cm s?¹). The results demonstrate that reducing surface and interface recombination velocity is critical for photovoltaic solar cells and electronic devices that employ epitaxial CdTe.

  13. Charge carrier transport mechanisms in perovskite CdTiO3 fibers

    NASA Astrophysics Data System (ADS)

    Imran, Z.; Rafiq, M. A.; Hasan, M. M.

    2014-06-01

    Electrical transport properties of electrospun cadmium titanate (CdTiO3) fibers have been investigated using ac and dc measurements. Air annealing of as spun fibers at 1000 °C yielded the single phase perovskite fibers having diameter ˜600 nm - 800 nm. Both the ac and dc electrical measurements were carried out at temperatures from 200 K - 420 K. The complex impedance plane plots revealed a single semicircular arc which indicates the interfacial effect due to grain boundaries of fibers. The dielectric properties obey the Maxwell-Wagner theory of interfacial polarization. In dc transport study at low voltages, data show Ohmic like behavior followed by space charge limited current (SCLC) with traps at higher voltages at all temperatures (200 K - 420 K). Trap density in our fibers system is Nt = 6.27 × 1017 /cm3. Conduction mechanism in the sample is governed by 3-D variable range hopping (VRH) from 200 K - 300 K. The localized density of states were found to be N(EF) = 5.51 × 1021 eV-1 cm-3 at 2 V. Other VRH parameters such as hopping distance (Rhop) and hopping energy (Whop) were also calculated. In the high temperature range of 320 K - 420 K, conductivity follows the Arrhenius law. The activation energy found at 2 V is 0.10 eV. Temperature dependent and higher values of dielectric constant make the perovskite CdTiO3 fibers efficient material for capacitive energy storage devices.

  14. Improvement in performance of organic light-emitting diodes by adjusting charge-carrier mobility in organic\\/inorganic hybrid hole transporting layer

    Microsoft Academic Search

    Fushan Li; Zhijian Chen; Chunling Liu; Qihuang Gong

    2005-01-01

    The charge-carrier transportation in an organic\\/inorganic (triphenylamine\\/SiO2) hybrid film was studied using time-of-flight photocurrent measurement. The hole-mobility increases with triphenylamine concentration and hole transportation in this film corresponds to hopping model. The organic light-emitting diodes (OLEDs) based the organic\\/inorganic hybrid film as hole-transporting layer were fabricated and electroluminescent characteristics were investigated. The experiments demonstrated that emitting efficiency reached a max

  15. Perforating gun charge carrier improvements

    SciTech Connect

    Vann, R.R.; Colle, E.A. Jr.

    1986-07-08

    This patent describes a perforating gun for perforating a casing located downhole in a cased borehole, the gun having a housing, shaped charges in the housing spaced from one another and connected to a detonation means, each shaped charge having a flange means on one end of a body portion, the other end of the body portion being the detonator end, the combination with the housing, charges, and detonation means of a charge carrier assembly. The charge carrier assembly comprises charge holders connected together along the longitudinal axis of the gun; each charge holder describes a polyhedron, each polyhedron being described by relatively thin wall surfaces joined together by lateral edges which extend parallel to the axial centerline of the gun and provide opposed fasteners for the shaped charge. Each charge holder has lateral faces, one of the faces is apertured to telescopingly receive a shaped charge therewithin, adjacent charge holders have means for orienting the shaped charges of alternate charge holders in different radial directions; and means for capturing a shaped charge within an aperture of a charge holder. The body portion of the shaped charge is received within the aperture of the charge holder with the flange means of the shaped charge abutting a lateral of the charge holder, and having the opposed fasteners extending towards an opposed fastener located on an alternate charge holder to capture the flange between two opposed fasteners and the lateral face of the charge holder so that the inner detonator end of the charge is positioned near the geometrical center of the charge holder.

  16. Charge carrier injection and transport in PVK : Alq3 blend films

    Microsoft Academic Search

    Yanguang Zhang; Yufeng Hu; Jiangshan Chen; Quanguo Zhou; Dongge Ma

    2003-01-01

    We have investigated the current-voltage and electroluminescent (EL) characteristics of single-layer organic devices based on poly(9-vinylcarbazole) (PVK) and tris(8-hydroxyquinoline)aluminium (Alq3) blend with different PVK : Alq3 concentrations. The experimental results from the observed thickness and temperature dependence clearly demonstrate that the current at low voltage is due to the holes injected at the anode and is space-charge limited, whereas the

  17. Transport of the charge carriers in SiC-detector structures after extreme radiation fluences

    Microsoft Academic Search

    N. B. Strokan; A. M. Ivanov; A. A. Lebedev

    2006-01-01

    The charge collection efficiency (CCE) of SiC-detectors preliminarily irradiated with 8 MeV protons at a fluence of 1014 cm-2 was investigated. Nuclear spectrometric techniques were employed, with 5.4 MeV alpha particles used to test the detectors. A concentration of primarily created defects of 4×1016 cm-3 was estimated and deep compensation of SiC conductivity was observed. In order to obtain a

  18. Transport of the charge carriers in SiC-detector structures after extreme radiation fluences

    Microsoft Academic Search

    N. B. Strokan; A. M. Ivanov; A. A. Lebedev

    2006-01-01

    The charge collection efficiency (CCE) of SiC-detectors preliminarily irradiated with 8MeV protons at a fluence of 1014cm?2 was investigated. Nuclear spectrometric techniques were employed, with 5.4MeV alpha particles used to test the detectors.A concentration of primarily created defects of 4×1016cm?3 was estimated and deep compensation of SiC conductivity was observed. In order to obtain a more uniform electric field distribution

  19. Low-field charge-carrier hopping transport in energetically and positionally disordered organic materials

    NASA Astrophysics Data System (ADS)

    Fishchuk, I. I.; Kadashchuk, A.; Bässler, H.; Abkowitz, M.

    2004-12-01

    The influence of superimposed energetic and positional disorder on the field dependence of drift mobility in disordered organic solids is considered for the first time analytically by an effective medium theory using jump rate expressions based either on Miller-Abrahams or Marcus models. We find that the negative field dependence of drift mobility at low fields is a genuine property of the hopping transport in disordered solids rather than an artifact and it can be theoretically reproduced for certain parameters of the investigated material and specific measurement conditions. We demonstrate that the recently suggested influence of the diffusion-controlled transport at low fields on the measured time-of-flight mobility plays no role in explaining the observed phenomena. Furthermore the frequently used practice of extrapolating field dependence of mobility to zero field has no theoretical justification. The results of the calculations are found to be in good agreement with both appropriate computer simulations and experimental results.

  20. Mean carrier transport properties and charge collection dynamics of single-crystal, natural type IIa diamonds from ion-induced conductivity measurements

    SciTech Connect

    Han, S.S.

    1993-09-01

    Ion-induced conductivity has been used to investigate the detector characteristics of diamond detectors. Both integrated-charge, and time-resolved current measurements were performed to examine the mean carrier transport properties of diamond and the dynamics of charge collection under highly-localized and high-density excitation conditions. The integrated-charge measurements were conducted with a standard pulse-counting system with {sup 241}Am radioactivity as the excitation source for the detectors. The time-resolved current measurements were performed using a 70 GHz random sampling oscilloscope with the detectors incorporated into high-speed microstrip transmission lines and the excitation source for these measurements was an ion beam of either 5-MeV He{sup +} or 10-MeV Si{sup 3+}. The detectors used in both experiments can be described as metal-semiconductor-metal (MSM) devices where a volume of the detector material is sandwiched between two metal plates. A charge collection model was developed to interpret the integrated-charge measurements which enabled estimation of the energy required to produce an electron-hole pair ({epsilon}{sub di}) and the mean carrier transport properties in diamond, such as carrier mobility and lifetime, and the behavior of the electrical contacts to diamond.

  1. Charge carrier injection and transport associated with thermally generated cracks in a 6,13-bis(triisopropylsilylethynyl) pentacene thin-film transistor

    Microsoft Academic Search

    Jin-Hyuk Bae; Hyeok Kim; Gilles Horowitz; Sin-Doo Lee

    2011-01-01

    We describe how the charge carrier injection and transport are influenced by thermal cracks in a 6,13-bis(triisopropylsilylethynyl) (TIPS) pentacene film in terms of the contact resistance and the channel resistance in a TIPS pentacene thin-film transistor (TFT). Through a post-thermal annealing (PTA) process at a certain temperature Ta, the high structural order of TIPS-pentacene molecules is produced without thermal cracks,

  2. Measurement of charge carrier's transportation in a large size self-standing CVD single crystal diamond film fabricated using lift-off method

    Microsoft Academic Search

    F. Fujita; A. Kakimoto; J. H. Kaneko; N. Tsubouchi; Y. Mokuno; A. Chayahara; K. Sato; Y. Konno; A. Homma; S. Shikata; M. Furusaka

    2010-01-01

    Using lift-off method, we synthesized large self-standing plasma CVD diamond films on various substrates. Charge carrier transportation in diamond was measured using ? particle measurements and TOF methods with a short-pulsed UV laser. The high-quality films were synthesized rapidly. We observed the maximum transit time of holes and electrons shorter than 5ns. The lift-off method is useful to fabricate the

  3. Photocurrent spectroscopy for the investigation of charge carrier generation and transport mechanisms in organic p\\/n-junction solar cells

    Microsoft Academic Search

    Jörn Rostalski; Dieter Meissner

    2000-01-01

    The photovoltaic behavior in a perylene\\/phthalocyanine hetero-p\\/n-junction solar cell was investigated using intensity-dependent I\\/V-characteristics and short circuit photocurrent spectroscopy. It is concluded that the charge carrier generation occurs only in a very thin active region at the contact. By optimizing the light trapping, a maximum solar AM 1.5 efficiency of about 2% can be obtained. A further increase requires better

  4. Generation-dependent charge carrier transport in Cu(In,Ga)Se2/CdS/ZnO thin-film solar-cells

    NASA Astrophysics Data System (ADS)

    Nichterwitz, Melanie; Caballero, Raquel; Kaufmann, Christian A.; Schock, Hans-Werner; Unold, Thomas

    2013-01-01

    Cross section electron-beam induced current (EBIC) and illumination-dependent current voltage (IV) measurements show that charge carrier transport in Cu(In,Ga)Se2 (CIGSe)/CdS/ZnO solar-cells is generation-dependent. We perform a detailed analysis of CIGSe solar cells with different CdS layer thicknesses and varying Ga-content in the absorber layer. In conjunction with numerical simulations, EBIC and IV data are used to develop a consistent model for charge and defect distributions with a focus on the heterojunction region. The best model to explain our experimental data is based on a p+ layer at the CIGSe/CdS interface leading to generation-dependent transport in EBIC at room temperature. Acceptor-type defect states at the CdS/ZnO interface cause a significant reduction of the photocurrent in the red-light illuminated IV characteristics at low temperatures (red kink effect). Shallow donor-type defect states at the p+ layer/CdS interface of some grains of the absorber layer are responsible for grain specific, i.e., spatially inhomogeneous, charge carrier transport observed in EBIC.

  5. Optimization of charge carrier transport balance for performance improvement of PDPP3T-based polymer solar cells prepared using a hot solution.

    PubMed

    Wang, Jian; Zhang, Fujun; Zhang, Miao; Wang, Wenbin; An, Qiaoshi; Li, Lingliang; Sun, Qianqian; Tang, Weihua; Zhang, Jian

    2015-04-21

    Polymer solar cells (PSCs), with poly(diketopyrrolopyrrole-terthiophene) (PDPP3T):[6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as the active layers, were fabricated using solutions of different temperatures. The best power conversion efficiency (PCE) of the PSCs prepared using a hot solution was about 6.22%, which is better than 5.54% for PSCs prepared using cool (room temperature) solutions and 5.85% for PSCs prepared using cool solutions with a 1,8-diiodooctane (DIO) solvent additive. The underlying reasons for the improved PCE of the PSCs prepared using a hot solution could be attributed to the more dispersive donor and acceptor distribution in the active layer, resulting in a better bi-continuous interpenetrating network for exciton dissociation and charge carrier transport. An enhanced and more balanced charge carrier transport in the active layer is obtained for the PSCs prepared using a hot solution, which can be determined from the J-V curves of the related hole-only and electron-only devices. PMID:25777139

  6. CARRIER MEDIATED LIPID TRANSPORT

    Microsoft Academic Search

    Scott D. Covey

    2003-01-01

    Lipids are essential molecules for cellular function; they are required for energy production, membrane structure, and can serve as signaling molecules. Normal metabolism requires cellular uptake and efflux as well as intercellular transport of lipids. Disruption of these events can lead to pathological processes like obesity and atherosclerosis. Transport of lipids between tissues involves moving hydrophobic species through a polar

  7. Screening-induced carrier transport in silicene

    NASA Astrophysics Data System (ADS)

    Hu, Bo

    2015-06-01

    Based on the Boltzmann transport equation in the MRT approximation, we present a theory to investigate low-field carrier transport in dual-gated silicene FETs by taking into account screened charged impurity scattering, which is the most likely scattering mechanism limiting the conductivity. Static RPA dielectric screening is also included in the conductivity calculation to study temperature-dependent silicene transport. It is found that both calculated conductivity and band gap not only depend strongly on carrier sheet density, but also depend strongly on effective offset density. More importantly, screening-induced metal-insulator-transition phenomena in buckled silicene can be observed theoretically, which is similar to that obtained in monolayer graphene.

  8. Screening-induced carrier transport in silicene.

    PubMed

    Hu, Bo

    2015-06-24

    Based on the Boltzmann transport equation in the MRT approximation, we present a theory to investigate low-field carrier transport in dual-gated silicene FETs by taking into account screened charged impurity scattering, which is the most likely scattering mechanism limiting the conductivity. Static RPA dielectric screening is also included in the conductivity calculation to study temperature-dependent silicene transport. It is found that both calculated conductivity and band gap not only depend strongly on carrier sheet density, but also depend strongly on effective offset density. More importantly, screening-induced metal-insulator-transition phenomena in buckled silicene can be observed theoretically, which is similar to that obtained in monolayer graphene. PMID:26030373

  9. Dynamics of spin charge carriers in polyaniline

    NASA Astrophysics Data System (ADS)

    Krinichnyi, V. I.

    2014-06-01

    The review summarizes the results of the study of emeraldine forms of polyaniline by multifrequency (9.7-140 GHz, 3-cm and 2-mm) wavebands Electron Paramagnetic Resonance (EPR) spectroscopy combined with the spin label and probe, steady-state saturation of spin-packets, and saturation transfer methods. Spin excitations formed in emeraldine form of polyaniline govern structure, magnetic resonance, and electronic properties of the polymer. Conductivity in neutral or weakly doped samples is defined mainly by interchain charge tunneling in the frames of the Kivelson theory. As the doping level increases, this process is replaced by a charge thermal activation transport by molecular-lattice polarons. In heavily doped polyaniline, the dominating is the Mott charge hopping between well-conducting crystalline ravels embedded into amorphous polymer matrix. The main properties of polyaniline are described in the first part. The theoretical background of the magnetic, relaxation, and dynamics study of nonlinear spin carriers transferring a charge in polyaniline is briefly explicated in the second part. An original data obtained in the EPR study of the nature, relaxation, and dynamics of polarons as well as the mechanism of their transfer in polyaniline chemically modified by sulfuric, hydrochloric, camphorsulfonic, 2-acrylamido-2-methyl-1-propanesulfonic, and para-toluenesulfonic acids up to different doping levels are analyzed in the third part. Some examples of utilization of polyaniline in molecular electronics and spintronics are described.

  10. Bipolar charge-carrier injection in semiconductor\\/insulator\\/conductor heterostructures: Self-consistent consideration

    Microsoft Academic Search

    S. V. Yampolskii; Yu. A. Genenko; C. Melzer; K. Stegmaier; H. von Seggern

    2008-01-01

    A self-consistent model of bipolar charge-carrier injection and transport processes in a semiconductor\\/insulator\\/conductor system is developed, which incorporates space-charge effects in the description of the injection process. The amount of charge carriers injected is strongly determined by the energy barrier emerging at the contact, but at the same time the electrostatic potential generated by the injected charge carriers modifies the

  11. Injection-level dependence of charge carrier mobility in high-injection plasma

    Microsoft Academic Search

    D. Reznik; W Gerlach

    1997-01-01

    The contradictions between results of commonly used charge carrier transport equations resulting from electron-hole scattering on the one hand and experimental data concerning transport coefficients in an electron-hole plasma on the other are pointed out. To resolve them, the influence of the injection level on the transfer of charge carrier momentum to the phonon system is investigated. The effective momentum

  12. Delayed emission of surface-generated trapped carriers in transient charge transport of single-crystal and polycrystalline HgI2

    NASA Astrophysics Data System (ADS)

    Zuck, Asaf; Schieber, Michael M.; Khakhan, Oleg; Burshtein, Zeev

    2003-01-01

    Transient charge transport (TCT) measurements were used to evaluate the electrical conduction properties of HgI2 single crystals. Some comparative preliminary results for polycrystalline mercuric iodide (poly-HgI2) thick-film X-ray detectors are also reported. The latter were prepared by physical vapor deposition (PVD). The mobility , trapping time 2, and surface recombination velocity s of electrons or holes were determined by analyses of transient voltages developed across the sample in response to a drift of the corresponding charge carriers created by alpha particle absorption near one of the electrodes. Electron-, and hole mobilities of single crystal HgI2 were n = 80 cm2/V•s and p = 4.8 cm2/V•s, respectively. Trapping times were 2n ? 22 V and 2p ? 8 V, and surface recombination velocities sn ? 1.1 ×105 cm/s and sp ? 3.6 ×103 cm/s . Those of the polycrystalline material depend on the deposition technology, and vary between 65 and 88 cm2/V•s for electrons, and between 4.3 and 4.1 cm2/V•s for holes. Bulk trapping-times and surface recombination velocities appear of the same order of magnitude as in the single crystal. An effect of carriers being first generated in near-surface traps and then gradually released is observed for both the single crystal and the polycrystalline material. It is stronger for electrons as compared to holes, and stronger in the polycrystalline material as compared to the single crystal.

  13. Saturation of charge carrier velocity with increasing electric fields: Theoretical investigations for pure organic crystals

    E-print Network

    Kenkre, V.M.

    injected charge carrier velocities to saturate as the applied electric field is increased simply becauseSaturation of charge carrier velocity with increasing electric fields: Theoretical investigations: NEED FOR CLARIFICATION Recent transport experiments on injected charges in ultra- pure organic solids

  14. Carrier facilitated transport through membranes

    SciTech Connect

    Kaper, H.G.; Leaf, G.K.; Matkowsky, B.J.

    1980-06-01

    Facilitated transport is a process whereby the diffusion of a solute across a membrane is chemically enhanced. In this report an analysis is given of a facilitated transport system involving a volatile species A which reacts with a nonvolatile carrier species B to form the nonvolatile product AB. The species A is transported across the membrane by ordinary diffusion, as well as by the diffusion of the product AB. It is assumed that the reaction rates are large, so the reactions are confined mostly to thin boundary layers near the surfaces of the membrane. The method of matched asymptotic expansions is used to derive the asymptotic solution of the nonlinear boundary value problem governing equilibrium. The effect of various parameters on the facilitation factor is analyzed in detail.

  15. The Impact of the Dielectric/Semiconductor Interface on Microstructure and Charge Carrier Transport in High-Performance Polythiophene Transistors

    SciTech Connect

    Jung, Y.; Kline, R; Lin, E; Fischer, D; Toney, M; Heeney, M; McCulloch, I; DeLongchamp, D

    2008-01-01

    The performance of organic field-effect transistors (OFETs) significantly depends on the properties of the interface between the semiconductor and gate dielectric. Here, we study the impact of chemically modified and morphologically controlled dielectrics on the performance of poly(2,5-bis(3-alkylthiophen-2-yl)thieno[3,2-b]thiophene) (pBTTT) semiconductors. We find that the molecular packing, domain size, and carrier mobility of pBTTT are highly sensitive to dielectric chemistry and dielectric roughness. The large and well-oriented terraced domains that are the origin of pBTTT's high performance can develop well on certain dielectrics, but can be disrupted on others.

  16. Terahertz microscopy of charge carriers in semiconductors

    NASA Astrophysics Data System (ADS)

    Buersgens, F.; Kersting, R.; Chen, H.-T.

    2006-03-01

    We report on the application of apertureless THz near-field microscopy for sensing charge carriers in semiconductors. This technique allows for contactless probing of electron concentrations on a micrometer scale. Experimental data and model calculations indicate that as few as about 5000 electrons can be detected in a GaAs structure.

  17. Charge carrier kinetics in MnOx, Mn2O3 and Mn3O4 films for water oxidation

    NASA Astrophysics Data System (ADS)

    Ramírez, A.; Friedrich, D.; Kunst, M.; Fiechter, S.

    2013-05-01

    Manganese oxide films on conductive substrates were prepared by electrochemical deposition. Charge carrier kinetics in these films was studied by contactless transient photoconductivity measurements. These measurements revealed the generation of mobile charge carriers with a nonneglectable lifetime. The transport from charge carriers generated in the oxides to the substrate was observed.

  18. Dynamic Charge Carrier Trapping in Quantum Dot Field Effect Transistors.

    PubMed

    Zhang, Yingjie; Chen, Qian; Alivisatos, A Paul; Salmeron, Miquel

    2015-07-01

    Noncrystalline semiconductor materials often exhibit hysteresis in charge transport measurements whose mechanism is largely unknown. Here we study the dynamics of charge injection and transport in PbS quantum dot (QD) monolayers in a field effect transistor (FET). Using Kelvin probe force microscopy, we measured the temporal response of the QDs as the channel material in a FET following step function changes of gate bias. The measurements reveal an exponential decay of mobile carrier density with time constants of 3-5 s for holes and ?10 s for electrons. An Ohmic behavior, with uniform carrier density, was observed along the channel during the injection and transport processes. These slow, uniform carrier trapping processes are reversible, with time constants that depend critically on the gas environment. We propose that the underlying mechanism is some reversible electrochemical process involving dissociation and diffusion of water and/or oxygen related species. These trapping processes are dynamically activated by the injected charges, in contrast with static electronic traps whose presence is independent of the charge state. Understanding and controlling these processes is important for improving the performance of electronic, optoelectronic, and memory devices based on disordered semiconductors. PMID:26099508

  19. Electroluminescence from both a light-emitting layer and hole transport layer: spectral evidence for charge carrier tunneling injection

    Microsoft Academic Search

    Xi-Cun Gao; Hong Cao; Chun-Hui Huang; Biao-Guo Li; K. Ibrahim; Feng-Qin Liu; Shigeo Umitani

    1998-01-01

    We investigate the electroluminescence spectra of a series of double- and triple-layered devices based on a rare-earth complex PTT, tris-(1-phenyl-3-methyl-4-isobutyryl-5-pyrozolone)-bis(triphenyl phosphine oxide) terbium. In triple-layer devices, besides green electroluminescence from the light-emitting layer PTT, blue emission from the hole transport layer TPD (N,N?-bis (3-methylphenyl)-N,N?-diphenyl-benzidine) occurs at high electric field strength (EFS) and its peak intensity increases with EFS. This indicates

  20. Selective modulation of charge-carrier transport of a photoanode in a photoelectrochemical cell by a graphitized fullerene interfacial layer.

    PubMed

    Park, Sun-Young; Lim, Dong Chan; Hong, Eun Mi; Lee, Joo-Yeoul; Heo, Jinhee; Lim, Jae Hong; Lee, Chang-Lyoul; Kim, Young Dok; Mul, Guido

    2015-01-01

    We show that a graphitic carbon interfacial layer, derived from C70 by annealing at 500?°C, results in a significant increase in the attainable photocurrent of a photoelectrochemical cell that contains a WO3 -functionalized fluorine-doped tin oxide (FTO) photoanode. Time-resolved photoluminescence spectroscopy, photoconductive atomic force microscopy, Hall measurements, and electrochemical impedance spectroscopy show that the increase in photocurrent is the result of fast and selective electron transport from optically excited WO3 through the graphitic carbon interfacial layer to the FTO-coated glass electrode. Thus the energy efficiency of perspective solar-to-fuel devices can be improved by modification of the interface of semiconductors and conducting substrate electrodes by using graphitized fullerene derivatives. PMID:25410298

  1. 47 CFR 69.153 - Presubscribed interexchange carrier charge (PICC).

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...CONTINUED) ACCESS CHARGES Computation of Charges for Price Cap Local Exchange Carriers § 69.153 Presubscribed interexchange...interexchange carrier to recover revenues totaling Average Price Cap CMT Revenues per Line month times the number of base...

  2. The impact of hot charge carrier mobility on photocurrent losses in polymer-based solar cells

    PubMed Central

    Philippa, Bronson; Stolterfoht, Martin; Burn, Paul L.; Juška, Gytis; Meredith, Paul; White, Ronald D.; Pivrikas, Almantas

    2014-01-01

    A typical signature of charge extraction in disordered organic systems is dispersive transport, which implies a distribution of charge carrier mobilities that negatively impact on device performance. Dispersive transport has been commonly understood to originate from a time-dependent mobility of hot charge carriers that reduces as excess energy is lost during relaxation in the density of states. In contrast, we show via photon energy, electric field and film thickness independence of carrier mobilities that the dispersive photocurrent in organic solar cells originates not from the loss of excess energy during hot carrier thermalization, but rather from the loss of carrier density to trap states during transport. Our results emphasize that further efforts should be directed to minimizing the density of trap states, rather than controlling energetic relaxation of hot carriers within the density of states. PMID:25047086

  3. Non-contact, non-destructive, quantitative probing of interfacial trap sites for charge carrier transport at semiconductor-insulator boundary

    SciTech Connect

    Choi, Wookjin; Miyakai, Tomoyo; Sakurai, Tsuneaki; Saeki, Akinori [Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita 565-0871 (Japan); Yokoyama, Masaaki [Kaneka Fundamental Technology Research Alliance Laboratories, Graduate School of Engineering, Osaka University, Suita 565-0871 (Japan); Seki, Shu, E-mail: seki@chem.eng.osaka-u.ac.jp [Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita 565-0871 (Japan); Kaneka Fundamental Technology Research Alliance Laboratories, Graduate School of Engineering, Osaka University, Suita 565-0871 (Japan)

    2014-07-21

    The density of traps at semiconductor–insulator interfaces was successfully estimated using microwave dielectric loss spectroscopy with model thin-film organic field-effect transistors. The non-contact, non-destructive analysis technique is referred to as field-induced time-resolved microwave conductivity (FI-TRMC) at interfaces. Kinetic traces of FI-TRMC transients clearly distinguished the mobile charge carriers at the interfaces from the immobile charges trapped at defects, allowing both the mobility of charge carriers and the number density of trap sites to be determined at the semiconductor-insulator interfaces. The number density of defects at the interface between evaporated pentacene on a poly(methylmethacrylate) insulating layer was determined to be 10{sup 12?}cm{sup ?2}, and the hole mobility was up to 6.5?cm{sup 2} V{sup ?1} s{sup ?1} after filling the defects with trapped carriers. The FI-TRMC at interfaces technique has the potential to provide rapid screening for the assessment of interfacial electronic states in a variety of semiconductor devices.

  4. Hopping charge transport in organic materials

    E-print Network

    Novikov, S V

    2013-01-01

    General properties of the transport of charge carriers (electrons and holes) in disordered organic materials are discussed. It was demonstrated that the dominant part of the total energetic disorder in organic material is usually provided by the electrostatic disorder, generated by randomly located and oriented dipoles and quadrupoles. For this reason this disorder is strongly spatially correlated. Spatial correlation directly governs the field dependence of the carrier drift mobility. Shape of the current transients, which is of primary importance for a correct determination of the carrier mobility, is considered. A notable feature of the electrostatic disorder is its modification in the vicinity of the electrode, and this modification takes place without modification of the structure of the material. It is shown how this phenomenon affects characteristics of the charge injection. We consider also effect of inter-charge interaction on charge transport.

  5. Electronic transport in normal-conductor/graphene/normal-conductor junctions and conditions for insulating behavior at a finite charge-carrier density

    NASA Astrophysics Data System (ADS)

    Robinson, John P.; Schomerus, Henning

    2007-09-01

    We investigate the conductance of normal-conductor/graphene/normal-conductor (NGN) junctions for arbitrary on-site potentials in the normal and graphitic parts of the system. We find that a ballistic NGN junction can display insulating behavior even when the charge-carrier density in the graphene part is finite. This effect originates in the different k intervals supporting propagating modes in graphene and a normal conductor, and persists for moderate levels of bulk, edge, or interface disorder. The ensuing conductance thresholds could be used as an electronic tool to map out details of the graphene band structure in absolute k space.

  6. Carrier transport and collection in fully depleted semiconductors by a combined action of the space charge field and the field due to electrode voltages

    DOEpatents

    Rehak, P.; Gatti, E.

    1984-02-24

    A semiconductor charge transport device and method for making same, characterized by providing a thin semiconductor wafer having rectifying functions on its opposing major surfaces and including a small capacitance ohmic contact, in combination with bias voltage means and associated circuit means for applying a predetermined voltage to effectively deplete the wafer in regions thereof between the rectifying junctions and the ohmic contact. A charge transport device of the invention is usable as a drift chamber, a low capacitance detector, or a charge coupled device each constructed according to the methods of the invention for making such devices. Detectors constructed according to the principles of the invention are characterized by having significantly higher particle position indicating resolution than is attainable with prior art detectors, while at the same time requiring substantially fewer readout channels to realize such high resolution.

  7. Carrier transport and collection in fully depleted semiconductors by a combined action of the space charge field and the field due to electrode voltages

    DOEpatents

    Rehak, P.; Gatti, E.

    1987-08-18

    A semiconductor charge transport device and method for making same are disclosed, characterized by providing a thin semiconductor wafer having rectifying junctions on its opposing major surfaces and including a small capacitance ohmic contact, in combination with bias voltage means and associated circuit means for applying a predetermined voltage to effectively deplete the wafer in regions thereof between the rectifying junctions and the ohmic contact. A charge transport device of the invention is usable as a drift chamber, a low capacitance detector, or a charge coupled device each constructed according to the methods of the invention for making such devices. Detectors constructed according to the principles of the invention are characterized by having significantly higher particle position indicating resolution than is attainable with prior art detectors, while at the same time requiring substantially fewer readout channels to realize such high resolution. 16 figs.

  8. 47 CFR 69.154 - Per-minute carrier common line charge.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES (CONTINUED) ACCESS CHARGES Computation of Charges for Price Cap Local Exchange Carriers § 69.154 Per-minute carrier common line charge. (a) Local exchange carriers may...

  9. Molecular length dictates the nature of charge carriers in single-molecule junctions of oxidized oligothiophenes

    NASA Astrophysics Data System (ADS)

    Dell, Emma J.; Capozzi, Brian; Xia, Jianlong; Venkataraman, Latha; Campos, Luis M.

    2015-03-01

    To develop advanced materials for electronic devices, it is of utmost importance to design organic building blocks with tunable functionality and to study their properties at the molecular level. For organic electronic and photovoltaic applications, the ability to vary the nature of charge carriers and so create either electron donors or acceptors is critical. Here we demonstrate that charge carriers in single-molecule junctions can be tuned within a family of molecules that contain electron-deficient thiophene-1,1-dioxide (TDO) building blocks. Oligomers of TDO were designed to increase electron affinity and maintain delocalized frontier orbitals while significantly decreasing the transport gap. Through thermopower measurements we show that the dominant charge carriers change from holes to electrons as the number of TDO units is increased. This results in a unique system in which the charge carrier depends on the backbone length, and provides a new means to tune p- and n-type transport in organic materials.

  10. Electric Field Dependence of the Probability of Charge Carriers Recombination

    Microsoft Academic Search

    M. Obarowska; J. Godlewski

    2008-01-01

    The influence of an external electric field on the probability of charge carriers recombination in molecular solid state was investigated. From analytical approximations, the probability of charge carriers recombination is found to decrease with increasing electric field. The results could be useful to explain the decrease of electroluminescence efficiency in single layer organic light emitting diodes (OLEDs) at high electric

  11. Charge Carrier Energy Disorder in Polar Amorphous Organic Thin Films Conor Madigan and Vladimir Bulovic*

    E-print Network

    charge transport in such materials [5­7]. As a result, the calculation of this DOS has received consider is the dielectric constant of the material. Implicit in this approach is the assumption that one can replaceCharge Carrier Energy Disorder in Polar Amorphous Organic Thin Films Conor Madigan and Vladimir

  12. Forth-back oscillated charge carrier motion in dynamically disordered hexathienocoronene molecules: a theoretical study.

    PubMed

    Navamani, K; Senthilkumar, K

    2015-07-21

    Electronic structure calculations were performed to investigate the charge transport properties of hexathienocoronene (HTC) based molecules. The effective displacement of the charge carrier along the ?-orbital of nearby molecules is calculated by monitoring the forth and back oscillations of the charge carrier through kinetic Monte Carlo simulation. The charge transport parameters such as charge transfer rate, mobility, hopping conductivity, localized charge density, time average effective mass and degeneracy pressure are calculated and used to study the charge transport mechanism in the studied molecules. The existence of degeneracy levels facilitates the charge transfer and is analyzed through degeneracy pressure. Theoretical results show that the site energy difference in the dynamically disordered system controls the forth-back oscillation of charge carrier and facilitates the unidirectional charge transport mechanism along the sequential localized sites. The ethyl substituted HTC has good hole and electron hopping conductivity of 415 and 894 S cm(-1), respectively, whereas unsubstituted HTC has the small hole mobility of 0.06 cm(2) V(-1) s(-1) which is due to large average effective mass of 1.42 × 10(-28) kg. PMID:26080732

  13. Charge carrier mobility and transmission across the liquid-vapor interface for the dielectric liquid hydrogen

    Microsoft Academic Search

    G. E. Grimm

    1979-01-01

    A radioactive source is used to inject positive and negative charge carriers into the dielectric fluid, liquid hydrogen. The mobility of positive and negative charge carriers is measured. The negative charge carrier mobility is found to be greater than that of the positive charge carrier. Both mobilities are found to be temperature dependent. The radius of the charge carriers is

  14. Low-field carrier transport properties in biased bilayer graphene

    NASA Astrophysics Data System (ADS)

    Hu, Bo

    2014-07-01

    Based on a semiclassical Boltzmann transport equation in random phase approximation, we develop a theoretical model to understand low-field carrier transport in biased bilayer graphene, which takes into account the charged impurity scattering, acoustic phonon scattering, and surface polar phonon scattering as three main scattering mechanisms. The surface polar optical phonon scattering of carriers in supported bilayer graphene is thoroughly studied using the Rode iteration method. By considering the metal-BLG contact resistance as the only one free fitting parameter, we find that the carrier density dependence of the calculated total conductivity agrees well with that observed in experiment under different temperatures. The conductivity results also suggest that in high carrier density range, the metal-BLG contact resistance can be a significant factor in determining the BLG conductivity at low temperature, and both acoustic phonon scattering and surface polar phonon scattering play important roles at higher temperature, especially for BLG samples with a low doping concentration, which can compete with charged impurity scattering.

  15. Effect of charge carrier relaxation during hopping process on electroluminescence in organic solids

    E-print Network

    Arunandan Kumar; Priyanka Tyagi; Ritu Srivastava; M. N. Kamalasanan

    2014-10-03

    Energetic disorder in disordered organic solids has been found to alter their physical parameters. Here, we have demonstrated, by means of Monte-Carlo simulation and experiments, that the electroluminescence (EL) spectrum is dependent on energetic disorder. This dependence has been attributed to the charge carrier relaxation during hopping process. The dependence of EL spectrum on energetic disorder makes it temperature dependent and temperature dependence has been found to vary with energetic disorder in a variety of materials. The simulation has been performed by taking the relaxation of charge carriers via transport energy in the Gaussian density of states. An analytical equation was established for spectral shift as a function of transport energy.

  16. Anomalous Charge Transport in Disordered Organic Semiconductors

    SciTech Connect

    Muniandy, S. V.; Woon, K. L. [Department of Physics, University of Malaya, 50603 Kuala Lumpur (Malaysia); Choo, K. Y. [Faculty of Engineering, Multimedia University, 63100 Cyberjaya, Selangor (Malaysia)

    2011-03-30

    Anomalous charge carrier transport in disordered organic semiconductors is studied using fractional differential equations. The connection between index of fractional derivative and dispersion exponent is examined from the perspective of fractional Fokker-Planck equation and its link to the continuous time random walk formalism. The fractional model is used to describe the bi-scaling power-laws observed in the time-of flight photo-current transient data for two different types of organic semiconductors.

  17. A review of some charge transport properties of silicon

    Microsoft Academic Search

    C. Jacoboni; C. Canali; G. Ottaviani; A. Alberigi Quaranta

    1977-01-01

    Basic bulk transport properties of charge carriers in silicon are reviewed, with particular reference to their use in designing solid-state components. The current theoretical model for transport in silicon is outlined, along with experimental techniques for determining most important transport parameters such as the drift velocity and diffusion coefficient. Phenomenological expressions are presented, which are in good agreement with experimental

  18. Ambipolar charge injection and transport in a single pentacene monolayer island

    E-print Network

    Paris-Sud XI, Université de

    . Charge carriers were locally injected by the apex of an #12;3 atomic force microscope tip, and that both charge carriers are delocalized over the whole island. On the contrary, charges injected1 Ambipolar charge injection and transport in a single pentacene monolayer island T. HEIM, K

  19. On the role of local charge carrier mobility in the charge separation mechanism of organic photovoltaics.

    PubMed

    Yoshikawa, Saya; Saeki, Akinori; Saito, Masahiko; Osaka, Itaru; Seki, Shu

    2015-07-01

    Although the charge separation (CS) and transport processes that compete with geminate and non-geminate recombination are commonly regarded as the governing factors of organic photovoltaic (OPV) efficiency, the details of the CS mechanism remain largely unexplored. Here we provide a systematic investigation on the role of local charge carrier mobility in bulk heterojunction films of ten different low-bandgap polymers and polythiophene analogues blended with methanofullerene (PCBM). By correlating with the OPV performances, we demonstrated that the local mobility of the blend measured by time-resolved microwave conductivity is more important for the OPV output than those of the pure polymers. Furthermore, the results revealed two separate trends for crystalline and semi-crystalline polymers. This work offers guidance in the design of high-performance organic solar cells. PMID:26084482

  20. Essential physics of carrier transport in nanoscale MOSFETs

    Microsoft Academic Search

    Mark Lundstrom; Zhibin Ren; Supriyo Datta

    2000-01-01

    A simple, physical view of carrier transport in nanoscale MOSFETs is presented. The role of ballistic transport, scattering and off-transport, equilibrium transport, and quantum transport are illustrated by numerical simulation, and the limitations of common approaches used for device TCAD are examined

  1. Nanoscale Charge Transport in Excitonic Solar Cells

    SciTech Connect

    Venkat Bommisetty, South Dakota State University

    2011-06-23

    Excitonic solar cells, including all-organic, hybrid organic-inorganic and dye-sensitized solar cells (DSSCs), offer strong potential for inexpensive and large-area solar energy conversion. Unlike traditional inorganic semiconductor solar cells, where all the charge generation and collection processes are well understood, these excitonic solar cells contain extremely disordered structures with complex interfaces which results in large variations in nanoscale electronic properties and has a strong influence on carrier generation, transport, dissociation and collection. Detailed understanding of these processes is important for fabrication of highly efficient solar cells. Efforts to improve efficiency are underway at a large number of research groups throughout the world focused on inorganic and organic semiconductors, photonics, photophysics, charge transport, nanoscience, ultrafast spectroscopy, photonics, semiconductor processing, device physics, device structures, interface structure etc. Rapid progress in this multidisciplinary area requires strong synergetic efforts among researchers from diverse backgrounds. Such effort can lead to novel methods for development of new materials with improved photon harvesting and interfacial treatments for improved carrier transport, process optimization to yield ordered nanoscale morphologies with well defined electronic structures.

  2. Anisotropic dynamics of charge carriers in graphene

    NASA Astrophysics Data System (ADS)

    Márk, Géza I.; Vancsó, Péter; Hwang, Chanyong; Lambin, Philippe; Biró, László P.

    2012-03-01

    Computer simulation by numerically solving the time-dependent Schrödinger equation was used to investigate the spreading of electronic wave packets on the graphene surface injected from a local probe. The simulations show a highly anisotropic in-plane dynamics following a 60? angular periodicity even near the Fermi energy. The wave packet first tunnels onto the small graphene clusters below the tip and the electronic states of these clusters govern the further spreading of the electron on the graphene surface. It was found that in the vicinity of the injection point the molecular physical behavior dominates, but at larger distances the wave propagation is governed by solid-state physical rules. The calculations show complex charge-spreading phenomena at graphene grain boundaries. Our results reveal a new picture of charge propagation in graphene, which has important consequences for nanoelectronic applications.

  3. Balanced ambipolar charge carrier mobility in mixed layers for application in hybrid white organic light-emitting diodes

    Microsoft Academic Search

    Gregor Schwartz; Tung-Huei Ke; Chung-Chih Wu; Karsten Walzer; Karl Leo

    2008-01-01

    We investigate the electron and hole mobility in mixed layers of N,N'-di(naphthalen-1-yl)-N,N'-diphenyl-benzidine and bis(2-methyl-8-quinolinato)-4-phenylphenolate aluminum with different mix ratios, using both space-charge limited currents of single-carrier devices with electrically doped charge transport layers and time-of-flight measurements. Both experimental methods yield consistent results. The 1:1 blend shows balanced ambipolar charge carrier transport, which is advantageous for the application as exciton blocking

  4. Behavior of Charge Carriers in Organic Insulating Materials

    Microsoft Academic Search

    Teruyoshi Mizutani

    2006-01-01

    Organic insulating materials have been widely used in electrical and electronic equipments and a large number of papers have been published for the past several decades. However, the behavior of charge carriers in organic insulating polymers is not well understood yet because insulating polymers have complicated physical\\/chemical structure and also various additives and impurities which strongly affect the behavior of

  5. Charge Carrier Lifetime and Recombination in Bulk Heterojunction Solar Cells

    Microsoft Academic Search

    Almantas Pivrikas; Helmut Neugebauer; Niyazi Serdar Sariciftci

    2010-01-01

    In this paper, the main photocurrent density and power conversion efficiency limiting mechanisms in bulk heterojunction solar cells are discussed with the emphasis on recombination processes. Charge extraction by linearly increasing voltage, time of flight, and other methods that allow the carrier lifetime and recombination to be studied experimentally in operating solar cells are discussed. It is shown that non-Langevin

  6. Combined Charge Carrier Transport and Photoelectrochemical Characterization of BiVO4 Single Crystals: Intrinsic Behavior of a Complex Metal Oxide

    SciTech Connect

    Rettie, Alexander J.; Lee, Heung Chan; Marshall, Luke G.; Lin, Jung-Fu; Capen, Cigdem; Lindemuth, Jeffrey; McCloy, John S.; Zhou, Jianshi; Bard, Allen J.; Mullins, C. Buddie

    2013-07-08

    ABSTRACT: Bismuth vanadate (BiVO4) is a promising photoelectrode material for the oxidation of water, but fundamental studies of this material are lacking. To address this, we report electrical and photoelectrochemical (PEC) properties of BiVO4 single crystals (undoped, 0.6% Mo and 0.3% W:BiVO4) grown using the floating zone technique. We demonstrate that a small polaron hopping conduction mechanism dominates from 250-400 K, transitioning to a variable range hopping mechanism at lower temperatures. An anisotropy ratio of ~3 was observed along the c-axis, attributed to the layered structure of BiVO4. Measurements of the AC field Hall effect yielded an electron mobility of ~0.2 cm2 V-1 s-1 for Mo and W:BiVO4 at 300 K. By application of the Gärtner model, a hole diffusion length of ~140 nm was estimated. As a result of low carrier mobility, attempts to measure the DC Hall effect were unsuccessful. Analyses of the Raman spectra showed that Mo and W substituted for V and acted as donor impurities. Mott-Schottky analysis of electrodes with the (001) face exposed yielded a flat band potential of 0.03-0.08 V vs. RHE, while incident photon conversion efficiency tests showed that the dark coloration of the doped single crystals did not result in additional photocurrent. Comparison of these intrinsic properties to other metal oxides for PEC applications gives valuable insight into this material as a photoanode.

  7. CHARGE TRANSPORT IN CONJUGATED POLYMERS

    E-print Network

    Tessler, Nir

    Peer, that each in his turn contributed for the design and fabrication of the polymer field effect this "long distance run" with a smile on my face (besides, it is always nice to have a physicist in the house.1.2 Transport Green function - mobility and diffusion ...........................10 1.1.3 Anomalous charge

  8. Acoustic charge transport signal processors

    NASA Astrophysics Data System (ADS)

    Kansy, R. J.; Hoskins, M. J.; Fleisch, D. A.; Hunsinger, B. J.

    1988-11-01

    The fundamentals of the technology of acoustic charge transport (ACT) devices are reviewed. Devices capable of perfoming functions such as programmable delay, memory, and transversal filtering have been demonstrated, and application-specific processors based on ACT are currently under development.

  9. Band filling with free charge carriers in organometal halide perovskites

    NASA Astrophysics Data System (ADS)

    Manser, Joseph S.; Kamat, Prashant V.

    2014-09-01

    The unique and promising properties of semiconducting organometal halide perovskites have brought these materials to the forefront of solar energy research. Here, we present new insights into the excited-state properties of CH3NH3PbI3 thin films through femtosecond transient absorption spectroscopy measurements. The photoinduced bleach recovery at 760?nm reveals that band-edge recombination follows second-order kinetics, indicating that the dominant relaxation pathway is via recombination of free electrons and holes. Additionally, charge accumulation in the perovskite films leads to an increase in the intrinsic bandgap that follows the Burstein-Moss band filling model. Both the recombination mechanism and the band-edge shift are studied as a function of the photogenerated carrier density and serve to elucidate the behaviour of charge carriers in hybrid perovskites. These results offer insights into the intrinsic photophysics of semiconducting organometal halide perovskites with direct implications for photovoltaic and optoelectronic applications.

  10. Exciton-charge carrier interactions in the electroluminescence of crystalline anthracene

    Microsoft Academic Search

    M. Wittmer; I. Zschokke-Gränacher

    1975-01-01

    The interactions of triplet excitons with trapped charge carriers are studied in anthracene single crystals. The triplet excitons are generated by the recombination of charge carriers through double injection. The lifetime of the triplet excitons is studied from the decay of the phosphorescence intensity in a transient measurement. The interaction rate constant for the trapped charge carriers is of the

  11. Characterization of charge-carrier dynamics in thin oxide layers on silicon by second harmonic generation

    E-print Network

    Pantelides, Sokrates T.

    Characterization of charge-carrier dynamics in thin oxide layers on silicon by second harmonic and nonlin- ear optics have opened up new venues for fundamental stud- ies of carrier injection dynamics electric field arising from charge separation depends strongly on the dynamics of the charge carriers

  12. Mobility of Charge Carriers in Polymer and Mica Electrets

    NASA Astrophysics Data System (ADS)

    Novikov, G. K.; Fedchishin, V. V.

    2015-04-01

    Ionizing radiation of an electric corona gas discharge (ECGD) and electric barrier gas discharge (EBGD) creates a radiation thickness gradient of recombination center concentration N rec = f(h) near the surface of polymer and mica electrets. The mobility of charge carriers in polymer and mica electrets and the stability of the electret potential difference U el = f(t) are obtained by the method of experimental measurements of the x-ray radiation half-absorption depth ? 1/2ECGD, EBGD .

  13. Charge carrier separation in modulation doped coaxial semiconductor nanowires.

    PubMed

    Nduwimana, A; Wang, Xiao-Qian

    2009-01-01

    Complementary doped donor and acceptor dipoles effectively generate confinement potentials for carriers across a p-type/intrinsic/n-type coaxial nanowire due to the lineup of charge neutrality level. In order to verify this physical picture, we employ first-principles density functional theory to study the confinement of electrons and holes in complementary boron (p-type) and phosphorus (n-type) doped coaxial silicon nanowires. An analysis of the charge density distributions reveals that the electrons and holes are spatially separated in core and outer shell regions, respectively, in conformity with a type-II lineup of band structures. PMID:19143504

  14. Charge Transport in one dimension

    E-print Network

    Holcombe, S R

    2010-01-01

    We consider charge transport in nanopores where the dielectric constant inside the nanopore is much greater than in the surrounding material, so that the flux of the electric fields due to the charges is almost entirely confined to the nanopore. That means that we may model the electric fields due to charge densities in the nanopore in terms of average properties across the nanopore as solutions of one dimensional Poisson equations. We develop basic equations for an M component system using equations of continuity to relate concentrations to currents, and flux equations relating currents to concentration gradients and conductivities. We then derive simplified scaled versions of the equations. We develop exact solutions for the one component case in a variety of boundary conditions using a Hopf-Cole transformation, Fourier series, and periodic solutions of the Burgers equation. These are compared with a simpler model in which the scaled diffusivity is zero so that all charge motion is driven by the electric fi...

  15. Energy Carrier Transport In Surface-Modified Carbon Nanotubes

    E-print Network

    Ryu, Yeontack

    2012-11-30

    of organic molecules or inorganic nanoparticles, debundling of nanotubes by dispersing agents, and microwave irradiation. Because carbon nanotubes have unique carrier transport characteristics along a sheet of graphite in a cylindrical shape, the properties...

  16. High speed quantum-well lasers and carrier transport effects

    Microsoft Academic Search

    Radhakrishnan Nagarajan; Masayuki Ishikawa; Toru Fukushima; Randall S. Geels; John E. Bowers

    1992-01-01

    Carrier transport can significantly affect the high-speed properties of quantum-well lasers. The authors have developed a model and derived analytical expressions for the modulation response, resonance frequency, damping rate, and K factor to include these effects. They show theoretically and experimentally that carrier transport can lead to significant low-frequency parasitic-like rolloff that reduces the modulation response by as much as

  17. Quantitative characterization of carrier transport in nanowire photodetectors

    Microsoft Academic Search

    Y. Gu; J. P. Romankiewicz; L. J. Lauhon

    2007-01-01

    Scanning photocurrent microscopy was used to study carrier transport processes in semiconductor nanowire photodetectors. Under high-level local carrier injection in CdS nanowire devices, spatially non-uniform photocurrent distributions were observed and explained in terms of bipolar transport with spatially separated electrons and holes. The mobility-lifetime product, (µt)*, for both electrons and holes was determined in intrinsic CdS nanowire photodetectors under high-level

  18. Effect of 2-D Delocalization on Charge Transport and Recombination in Bulk-Heterojunction Solar Cells

    Microsoft Academic Search

    Ronald Osterbacka; Almantas Pivrikas; Gytis Juska; Andrius Poskus; Harri Aarnio; Gytis Sliauzys; Kristijonas Genevicius; Kestutis Arlauskas; Niyazi Serdar Sariciftci

    2010-01-01

    Charge-carrier transport and recombination in thermally treated and untreated films of poly(3-hexylthiophene) (P3HT) and 1-(3-methoxycarbonyl)propyl-l-phenyl-[6,6]-methanofullerene (PCBM) bulk-heterojunction solar cells (BHSCs) have been measured using various electrooptical techniques. The formation of lamellar structure in P3HT has a large effect on the efficiency, carrier transport, and recombination of photogenerated charge carriers. Treated P3HT\\/PCBM solar cells show greatly reduced carrier recombination compared to

  19. Scaling properties of charge transport in polycrystalline graphene.

    PubMed

    Van Tuan, Dinh; Kotakoski, Jani; Louvet, Thibaud; Ortmann, Frank; Meyer, Jannik C; Roche, Stephan

    2013-04-10

    Polycrystalline graphene is a patchwork of coalescing graphene grains of varying lattice orientations and size, resulting from the chemical vapor deposition (CVD) growth at random nucleation sites on metallic substrates. The morphology of grain boundaries has become an important topic given its fundamental role in limiting the mobility of charge carriers in polycrystalline graphene, as compared to mechanically exfoliated samples. Here we report new insights to the current understanding of charge transport in polycrystalline geometries. We created realistic models of large CVD-grown graphene samples and then computed the corresponding charge carrier mobilities as a function of the average grain size and the coalescence quality between the grains. Our results reveal a remarkably simple scaling law for the mean free path and conductivity, correlated to atomic-scale charge density fluctuations along grain boundaries. PMID:23448361

  20. Carrier transport and viscosity of discotic liquid-crystalline photoconductor hexaoctylthio-triphenylene

    NASA Astrophysics Data System (ADS)

    Monobe, Hirosato; Shimizu, Yo

    2014-01-01

    In this study, the electronic and ionic carrier transports and viscosity of 2,3,6,7,10,11-hexaoctylthio-triphenylene (C8STP) were studied by a time-of-flight method and using a rotational viscometer. Ambipolar charge carrier transport was investigated in the isotropic liquid (Iso) phase of C8STP, similarly to the columnar hexagonal mesophase, and the activation energies were estimated to be 0.1 eV for one positive and one negative, and 0.4 eV for the other negative charge carrier mobility in Iso. The viscosity of C8STP was investigated using a rotation viscometer, and relative viscosity was measured by a capillary method in the isotropic phase, and the activation energy of viscosity was 0.4 eV. The Stokes radii of ionic carriers were experimentally estimated using Walden’s rule. The existence of ionic and electronic (hopping) carrier transports in Iso was implied for the discotic liquid crystalline photoconductor.

  1. TRAPPING-RELATED RECOMBINATION OF CHARGE CARRIERS IN SILICON , N.-P. Harder

    E-print Network

    TRAPPING-RELATED RECOMBINATION OF CHARGE CARRIERS IN SILICON R. Gogolin 1 , N.-P. Harder 1,2 , R if these trap states only capture minority charge carriers and therefore do not contribute to recombination injection levels. EXPERIMENTS We investigate the carrier lifetime in p-type multicrystalline (mc) silicon

  2. Low temperature carrier transport properties in isotopically controlled germanium

    SciTech Connect

    Itoh, K.

    1994-12-01

    Investigations of electronic and optical properties of semiconductors often require specimens with extremely homogeneous dopant distributions and precisely controlled net-carrier concentrations and compensation ratios. The previous difficulties in fabricating such samples are overcome as reported in this thesis by growing high-purity Ge single crystals of controlled {sup 75}Ge and {sup 70}Ge isotopic compositions, and doping these crystals by the neutron transmutation doping (NTD) technique. The resulting net-impurity concentrations and the compensation ratios are precisely determined by the thermal neutron fluence and the [{sup 74}Ge]/[{sup 70}Ge] ratios of the starting Ge materials, respectively. This method also guarantees unprecedented doping uniformity. Using such samples the authors have conducted four types of electron (hole) transport studies probing the nature of (1) free carrier scattering by neutral impurities, (2) free carrier scattering by ionized impurities, (3) low temperature hopping conduction, and (4) free carrier transport in samples close to the metal-insulator transition.

  3. Spin-dependent transport of carriers in semiconductors

    Microsoft Academic Search

    R. Winkler

    2006-01-01

    This article reviews spin-dependent transport of carriers in homogenous three-dimensional and two-dimensional semiconductors. We begin with a discussion of optical orientation of electron spins, which allows both the creation and detection of spin-polarized carriers in semiconductors. Then we review non-equilibrium spin flow including spin drift and diffusion caused by electric fields and concentration gradients. A controlled spin precession is possible

  4. Structural influences on charge carrier dynamics for small-molecule organic photovoltaics

    SciTech Connect

    Wang, Zhiping, E-mail: wang-zhiping@aist.go.jp; Shibata, Yosei; Yamanari, Toshihiro; Matsubara, Koji; Yoshida, Yuji [Research Center for Photovoltaic Technologies, National Institute of Advanced Industrial Science and Technology (AIST), AIST Tsukuba Central 5, 1-1-1 Higashi, 305-8565 Tsukuba (Japan); Miyadera, Tetsuhiko, E-mail: tetsuhiko-miyadera@aist.go.jp [Research Center for Photovoltaic Technologies, National Institute of Advanced Industrial Science and Technology (AIST), AIST Tsukuba Central 5, 1-1-1 Higashi, 305-8565 Tsukuba (Japan); JST-PRESTO, Japan Science and Technology Agency (JST), 4-1-8 Honcho Kawaguchi, 332-0012 Saitama (Japan); Saeki, Akinori; Seki, Shu [Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, 565-0871 Suita, Osaka (Japan); Zhou, Ying [Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), AIST Tsukuba Central 5, 1-1-1 Higashi, 305-8565 Tsukuba (Japan)

    2014-07-07

    We investigated the structural influences on the charge carrier dynamics in zinc phthalocyanine/fullerene (ZnPc/C{sub 60}) photovoltaic cells by introducing poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) and 2,5-bis(4-biphenylyl)-bithiophene (BP2T) between indium tin oxide and ZnPc layers. ZnPc films can be tuned to be round, long fiber-like, and short fiber-like structure, respectively. Time-resolved microwave conductivity measurements reveal that charge carrier lifetime in ZnPc/C{sub 60} bilayer films is considerably affected by the intra-grain properties. Transient photocurrent of ZnPc single films indicated that the charge carriers can transport for a longer distance in the long fiber-like grains than that in the round grains, due to the greatly lessened grain boundaries. By carefully controlling the structure of ZnPc films, the short-circuit current and fill factor of a ZnPc/C{sub 60} heterojunction solar cell with BP2T are significantly improved and the power conversion efficiency is increased to 2.6%, which is 120% larger than the conventional cell without BP2T.

  5. Charge-carrier effects on the optical properties of poly(p-phenylene vinylene)

    Microsoft Academic Search

    I. H. Campbell; D. L. Smith; C. J. Neef; J. P. Ferraris

    2001-01-01

    We present measurements of the effects of electrically injected charge carriers on the optical properties of a soluble, poly(p-phenylene vinylene) derivative. Pulsed electrical excitation was used to acquire the modulated optical characteristics of single-carrier polymer diodes for photon energies from 0.5 to 3.1 eV and for average injected charge-carrier densities up to about 1×1018 cm-3. For injected carrier densities below

  6. Charge transport in lightly reduced graphene oxide: A transport energy perspective

    NASA Astrophysics Data System (ADS)

    Kajen, R. S.; Chandrasekhar, N.; Pey, K. L.; Vijila, C.; Jaiswal, M.; Saravanan, S.; Ng, Andrew M. H.; Wong, C. P.; Loh, K. P.

    2013-02-01

    Significant variation in the charge transport behaviour in graphene oxide (GO) ranging from Schottky to Poole-Frenkel and to space charge limited transport exists. These have been extensively reported in the literature. However, the validity of such conventional charge transport models meant for delocalized carriers, to study charge transport through localised states in GO, a disordered semiconductor is open to question. In this work, we use the concept of transport energy (TE) to model charge transport in lightly reduced GO (RGO) and demonstrate that the TE calculations match well with temperature dependent experimental I-V data on RGO. We report on a temperature dependent TE ranging from a few 10 meV to 0.1 eV in slightly reduced GO. Last, we point out that, despite the success of several delocalised charge transport models in estimating barrier heights that resemble the TE level, they remain largely accidental and lack the insight in which the TE concept provides in understanding charge transport in RGO.

  7. Correlated charge transport in bilinear tunnel junction arrays

    NASA Astrophysics Data System (ADS)

    Walker, Kelly A.; Cole, Jared H.

    2013-12-01

    We study theoretically the nature of correlations in space and time of the current in a one-dimensional bilinear array of tunnel junctions in the normal conduction limit, using the kinetic Monte Carlo method. The bilinear array consists of two parallel rows of tunnel junctions, capacitively coupled in a ladder configuration. The electrostatic potential landscape and the charge-charge interaction length both depend on the circuit capacitances, which in turn influence transport and charge correlations in the array. We observe the formation of stationary charge states when only one rail is voltage biased. When a symmetric bias is applied to both rails, the site at which the positive and negative charge carriers recombine can drift throughout the array. We also calculate charge densities and auto- and cross-correlation functions.

  8. Carrier dynamics and photodetection in charge injection transistors Michael Y. Frankel

    E-print Network

    Carrier dynamics and photodetection in charge injection transistors Michael Y. Frankel CODE 5670, charge injection transistors CHINTs are based on the RST of hot carriers and were originally proposed induced by 200 fs 1.55 m optical pulses in charge injection transistor structures. We propose

  9. Modelling of Charge Carrier Mobility Effect on Organic Bulk Heterojunction Solar Cells

    Microsoft Academic Search

    Wenbin Guo; Liang Shen; Caixia Liu; Shengping Ruan; Weiyou Chen

    2012-01-01

    In this article, we did some simulations of organic bulk heterojunction solar cells according to the Koster model. The study shows that bimolecular recombination and a temperature- and field dependence generation mechanism of free charges incorporation. The charge carrier is one of most important factors that have influence on the devices’ power conversion efficiency (PCE), because the charge carrier mobility

  10. Charge transport in nanoscale junctions.

    PubMed

    Albrecht, Tim; Kornyshev, Alexei; Bjørnholm, Thomas

    2008-09-01

    Understanding the fundamentals of nanoscale charge transfer is pivotal for designing future nano-electronic devices. Such devices could be based on individual or groups of molecular bridges, nanotubes, nanoparticles, biomolecules and other 'active' components, mimicking wire, diode and transistor functions. These have operated in various environments including vacuum, air and condensed matter, in two- or three-electrode configurations, at ultra-low and room temperatures. Interest in charge transport in ultra-small device components has a long history and can be dated back to Aviram and Ratner's letter in 1974 (Chem. Phys. Lett. 29 277-83). So why is there a necessity for a special issue on this subject? The area has reached some degree of maturity, and even subtle geometric effects in the nanojunction and noise features can now be resolved and rationalized based on existing theoretical concepts. One purpose of this special issue is thus to showcase various aspects of nanoscale and single-molecule charge transport from experimental and theoretical perspectives. The main principles have 'crystallized' in our minds, but there is still a long way to go before true single-molecule electronics can be implemented. Major obstacles include the stability of electronic nanojunctions, reliable operation at room temperature, speed of operation and, last but not least, integration into large networks. A gradual transition from traditional silicon-based electronics to devices involving a single (or a few) molecule(s) therefore appears to be more viable from technologic and economic perspectives than a 'quantum leap'. As research in this area progresses, new applications emerge, e.g. with a view to characterizing interfacial charge transfer at the single-molecule level in general. For example, electrochemical experiments with individual enzyme molecules demonstrate that catalytic processes can be studied with nanometre resolution, offering a route towards optimizing biosensors at the molecular level. Nanoscale charge transport experiments in ionic liquids extend the field to high temperatures and to systems with intriguing interfacial potential distributions. Other directions may include dye-sensitized solar cells, new sensor applications and diagnostic tools for the study of surface-bound single molecules. Another motivation for this special issue is thus to highlight activities across different research communities with nanoscale charge transport as a common denominator. This special issue gathers 27 articles by scientists from the United States, Germany, the UK, Denmark, Russia, France, Israel, Canada, Australia, Sweden, Switzerland, the Netherlands, Belgium and Singapore; it gives us a flavour of the current state-of-the-art of this diverse research area. While based on contributions from many renowned groups and institutions, it obviously cannot claim to represent all groups active in this very broad area. Moreover, a number of world-leading groups were unable to take part in this project within the allocated time limit. Nevertheless, we regard the current selection of papers to be representative enough for the reader to draw their own conclusions about the current status of the field. Each paper is original and has its own merit, as all papers in Journal of Physics: Condensed Matter special issues are subjected to the same scrutiny as regular contributions. The Guest Editors have deliberately not defined the specific subjects covered in this issue. These came out logically from the development of this area, for example: 'Traditional' solid state nanojunctions based on adsorbed layers, oxide films or nanowires sandwiched between two electrodes: effects of molecular structure (aromaticity, anchoring groups), symmetry, orientation, dynamics (noise patterns) and current-induced heating. Various 'physical effects': inelastic tunnelling and Coulomb blockade, polaron effects, switching modes, and negative differential resistance; the role of many particle excitations, new surface states in semiconductor electrodes, various mechanisms for

  11. Charge transport through thin films made of colloidal CuInS2 nanocrystals

    NASA Astrophysics Data System (ADS)

    Miranti, R.; Krause, C.; Parisi, J.; Borchert, H.

    2015-06-01

    CuInS2 nanocrystals (CIS NCs) are prospective materials for solar cells with solution-producible absorber layers. However, the charge transport through the film of nanoparticles has not been investigated in detail yet. In this paper we report the charge transport characteristics in thin films of CIS NCs investigated in single carrier device structures, namely hole-only and electron-only devices. The current density–voltage (J–V) characteristics showed that the charge carrier transport in thin CIS NC films is hole dominated. Both, Mott Gurney’s and Murgatroyd’s model were applied for better understanding.

  12. Relaxation of photoexited charge carrier concentration and mobility in ?c-Si:H

    Microsoft Academic Search

    G. Juška; N. Nekrašas; K. Genevi?ius; J. Stuchlik; J. Ko?ka

    2004-01-01

    In ?c-Si:H layers deposited on substrates at various temperatures, the relaxation of the mobility, density of the equilibrium, photogenerated and injected charge carriers using extraction by linearly increasing voltage method has been investigated. We found that in ?c-Si:H layers, especially those deposited at low temperature, charge carrier mobility decreases with time, the charge carrier density relaxation is much slower, and

  13. Ballistic charge carrier transmission through graphene multi-barrier structures in uniform magnetic field

    NASA Astrophysics Data System (ADS)

    Zubarev, A.; Dragoman, D.

    2014-10-01

    We investigate charge carrier transport in graphene multi-barrier structures placed in a uniform magnetic field. The transmission coefficient is found analytically by generalizing the transfer matrix method for the case of graphene regions subjected to a uniform magnetic field. The transmission coefficient through the structure can be modulated by varying the gate voltages, the magnetic field and/or the width of the gated regions. Such a configuration could be used in multiple-valued logic circuits, since it has several output states with discrete and easily selectable transmission/current values.

  14. Top-gate dielectric induced doping and scattering of charge carriers in epitaxial graphene

    NASA Astrophysics Data System (ADS)

    Puls, Conor P.; Staley, Neal E.; Moon, Jeong-Sun; Robinson, Joshua A.; Campbell, Paul M.; Tedesco, Joseph L.; Myers-Ward, Rachael L.; Eddy, Charles R.; Gaskill, D. Kurt; Liu, Ying

    2011-07-01

    We show that an e-gun deposited dielectric impose severe limits on epitaxial graphene-based device performance based on Raman spectroscopy and low-temperature transport measurements. Specifically, we show from studies of epitaxial graphene Hall bars covered by SiO2 that the measured carrier density is strongly inhomogenous and predominantly induced by charged impurities at the grapheme/dielectric interface that limit mobility via Coulomb interactions. Our work emphasizes that material integration of epitaxial graphene and a gate dielectric is the next major road block towards the realization of graphene-based electronics.

  15. Proton-irradiation effects on the charge transport in highly oriented pyrolytic graphite

    NASA Astrophysics Data System (ADS)

    Kim, Jinsoo; Kim, Dowan; Lee, Kyu Won; Choi, E. H.; Noh, S. J.; Kim, H. S.; Lee, Cheol Eui

    2014-05-01

    We have investigated the proton-irradiation effects on the electrical resistivity and magnetoresistance of highly oriented pyrolytic graphite (HOPG). The temperature- and magnetic field-dependent measurements indicate that the carrier mobility rather than the carrier density dictates the charge transport in the HOPG systems.

  16. Charge carrier trapping into mobile, ionic defects in nanoporous ultra-low-k dielectric materials

    NASA Astrophysics Data System (ADS)

    Plawsky, Joel; Borja, Juan; Lu, Toh-Ming; Gill, William

    2014-03-01

    Reliability and robustness of low-k materials for advanced interconnects has become a major challenge for the continuous down-scaling of silicon semiconductor devices. Metal catalyzed time dependent breakdown (TDDB) is a major force preventing the integration of sub-32nm process technology nodes. We investigate how ionic species can become trapping centers (mobile defects) for charge carriers. A mechanism for describing and quantifying the trapping of charge carriers into mobile ions under bias and temperature stress is presented and experimentally investigated. The dynamics of trapping into ionic centers are severely impacted by temperature and species mass transport. After extended bias and temperature stress, the magnitude of charge trapping into ionic centers decreases asymptotically. Various processes such as the reduction of ionic species, moisture outgassing, and the inhibition of ionic drift via the distortion of local fields were investigated as possible cause for the reduction in charge trapping. Simulations suggest that built-in fields reduce the effect of an externally applied field in directing ionic drift, which can lead to the inhibition of the trapping mechanism. In addition, conduction mechanisms are investigated for reactive and inert electrodes. Seimconductor Research Corporation.

  17. Charge Transport across DNA-Based Three-Way Junctions.

    PubMed

    Young, Ryan M; Singh, Arunoday P N; K Thazhathveetil, Arun; Cho, Vincent Y; Zhang, Yuqi; Renaud, Nicolas; Grozema, Ferdinand C; Beratan, David N; Ratner, Mark A; Schatz, George C; Berlin, Yuri A; Lewis, Frederick D; Wasielewski, Michael R

    2015-04-22

    DNA-based molecular electronics will require charges to be transported from one site within a 2D or 3D architecture to another. While this has been shown previously in linear, ?-stacked DNA sequences, the dynamics and efficiency of charge transport across DNA three-way junction (3WJ) have yet to be determined. Here, we present an investigation of hole transport and trapping across a DNA-based three-way junction systems by a combination of femtosecond transient absorption spectroscopy and molecular dynamics simulations. Hole transport across the junction is proposed to be gated by conformational fluctuations in the ground state which bring the transiently populated hole carrier nucleobases into better aligned geometries on the nanosecond time scale, thus modulating the ?-? electronic coupling along the base pair sequence. PMID:25822073

  18. Fractal spectrum of charge carriers in quasiperiodic graphene structures

    NASA Astrophysics Data System (ADS)

    Sena, S. H. R.; Pereira, J. M., Jr.; Farias, G. A.; Vasconcelos, M. S.; Albuquerque, E. L.

    2010-11-01

    In this work we investigate the interaction of charge carriers in graphene with a series of p-n-p junctions arranged according to a deterministic quasiperiodic substitutional Fibonacci sequence. The junctions create a potential landscape with quantum wells and barriers of different widths, allowing the existence of quasi-confined states. Spectra of quasi-confined states are calculated for several generations of the Fibonacci sequence as a function of the wavevector component parallel to the barrier interfaces. The results show that, as the Fibonacci generation is increased, the dispersion branches form energy bands distributed as a Cantor-like set. Besides, for a quasiperiodic set of potential barriers, we obtain the electronic tunneling probability as a function of energy, which shows a striking self-similar behavior for different generation numbers.

  19. Fractal spectrum of charge carriers in quasiperiodic graphene structures.

    PubMed

    Sena, S H R; Pereira, J M; Farias, G A; Vasconcelos, M S; Albuquerque, E L

    2010-11-24

    In this work we investigate the interaction of charge carriers in graphene with a series of p-n-p junctions arranged according to a deterministic quasiperiodic substitutional Fibonacci sequence. The junctions create a potential landscape with quantum wells and barriers of different widths, allowing the existence of quasi-confined states. Spectra of quasi-confined states are calculated for several generations of the Fibonacci sequence as a function of the wavevector component parallel to the barrier interfaces. The results show that, as the Fibonacci generation is increased, the dispersion branches form energy bands distributed as a Cantor-like set. Besides, for a quasiperiodic set of potential barriers, we obtain the electronic tunneling probability as a function of energy, which shows a striking self-similar behavior for different generation numbers. PMID:21403366

  20. 49 CFR 385.13 - Unsatisfactory rated motor carriers; prohibition on transportation; ineligibility for Federal...

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...TRANSPORTATION FEDERAL MOTOR CARRIER SAFETY REGULATIONS SAFETY FITNESS PROCEDURES General § 385.13 Unsatisfactory rated...carrier is making a good-faith effort to improve its safety fitness, FMCSA may allow the motor carrier to operate for up to...

  1. 49 CFR 385.13 - Unsatisfactory rated motor carriers; prohibition on transportation; ineligibility for Federal...

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...TRANSPORTATION FEDERAL MOTOR CARRIER SAFETY REGULATIONS SAFETY FITNESS PROCEDURES General § 385.13 Unsatisfactory rated...carrier is making a good-faith effort to improve its safety fitness, FMCSA may allow the motor carrier to operate for up to...

  2. 49 CFR 385.13 - Unsatisfactory rated motor carriers; prohibition on transportation; ineligibility for Federal...

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...TRANSPORTATION FEDERAL MOTOR CARRIER SAFETY REGULATIONS SAFETY FITNESS PROCEDURES General § 385.13 Unsatisfactory rated...carrier is making a good-faith effort to improve its safety fitness, FMCSA may allow the motor carrier to operate for up to...

  3. BALLISTIC CARRIER TRANSPORT IN SEMICONDUCTORS STUDIED BY ULTRAFAST LASER TECHNIQUES

    E-print Network

    Werake, Lalani Kumari

    2011-08-31

    2007; Huang 2007; Jonker 2007) Spin-polarized electrons were injected electrically from an Iron (Fe) contact through an Al2O3 tunneling barrier into Si and circular polarization of the electroluminescence was observed which indicates a net spin...: Introduction .……………………………………..………………………… 1 1.1 Spintronics ………………………………………………………….…….. 1 1.2 Semiconductor spintronics …………………………….…………………. 3 1.3 Spin transport ………………………………………….………………… 4 Chapter 2: Carrier transport in semiconductors...

  4. Energy resolution and related charge carrier mobility in LaBr{sub 3}:Ce scintillators

    SciTech Connect

    Khodyuk, I. V.; Quarati, F. G. A.; Alekhin, M. S.; Dorenbos, P. [Luminescence Materials Research Group, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, Delft, 2629JB (Netherlands)] [Luminescence Materials Research Group, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, Delft, 2629JB (Netherlands)

    2013-09-28

    The scintillation response of LaBr{sub 3}:Ce scintillation crystals was studied as function of temperature and Ce concentration with synchrotron X-rays between 9 keV and 100 keV. The results were analyzed using the theory of carrier transport in wide band gap semiconductors to gain new insights into charge carrier generation, diffusion, and capture mechanisms. Their influence on the efficiency of energy transfer and conversion from X-ray or ?-ray photon to optical photons and therefore on the energy resolution of lanthanum halide scintillators was studied. From this, we will propose that scattering of carriers by both the lattice phonons and by ionized impurities are key processes determining the temperature dependence of carrier mobility and ultimately the scintillation efficiency and energy resolution. When assuming about 100 ppm ionized impurity concentration in 0.2% Ce{sup 3+} doped LaBr{sub 3,} mobilities are such that we can reproduce the observed temperature dependence of the energy resolution, and in particular, the minimum in resolution near room temperature is reproduced.

  5. Extended Hydrodynamical Model of Carrier Transport in Semiconductors

    Microsoft Academic Search

    Angelo Marcello Anile; Giovanni Russo; Vittorio Romano

    2000-01-01

    A hydrodynamical model based on the theory of extended thermodynamics is pre- sented for carrier transport in semiconductors. Closure relations for fluxes are obtained by employing the maximum entropy principle. The production terms are modeled by fitting the Monte Carlo data for homogeneously doped semiconductors. The mathematical properties of the model are studied. A suitable numerical method, which is a

  6. Airline Transport Pilot-Airplane (Air Carrier) Written Test Guide.

    ERIC Educational Resources Information Center

    Federal Aviation Administration (DOT), Washington, DC. Flight Standards Service.

    Presented is information useful to applicants who are preparing for the Airline Transport Pilot-Airplane (Air Carrier) Written Test. The guide describes the basic aeronautical knowledge and associated requirements for certification, as well as information on source material, instructions for taking the official test, and questions that are…

  7. Bridging carrier transport and amorphous dynamics in phase change materials

    Microsoft Academic Search

    Andrea L. Lacaita; Daniele Ielmini

    Physics of amorphous chalcogenides sets the scaling potentials of PCM elements and their perspectives in multi-bit storage. Carrier transport, threshold switching, structural relaxation and crystallization processes have key importance from the application standpoint. They also represent peculiar effects which have always attracted interest and speculations by decades. The paper reviews experimental and modeling analysis of threshold voltage and resistance transients

  8. Behavior of charge carriers and excitons in multilayer organic light-emitting diodes made from a polysilane polymer as monitored with electroluminescence

    Microsoft Academic Search

    Hiroyuki Suzuki; Satoshi Hoshino

    1996-01-01

    Using electroluminescence (EL) as a monitor, we have investigated the behavior of charge carriers injected from electrodes and excitons generated by the recombination of charge carriers in multilayer organic light-emitting diodes (LEDs) using poly(methylphenylsilane) (PMPS) as a hole transporting material. Our multilayer LEDs have two or three functional organic layers including Coumarin 6 [3-(2?-benzothiazolyl)-7-diethylaminocoumarin, abbreviated as C6] and\\/or tris-(8-hydroxyquinoline) aluminum

  9. Carrier Transport and Related Effects in Detectors of the Cryogenic Dark Matter Search

    NASA Astrophysics Data System (ADS)

    Sundqvist, Kyle Michael

    The Cryogenic Dark Matter Search (CDMS) is searching for weakly-interacting massive particles (WIMPS), which could explain the dark matter problem in cosmology and particle physics. By simultaneously measuring signals from deposited charge and the energy in non-equilibrium phonons created by particle interactions in intrinsic germanium crystals at a temperature of 40 mK, a signature response for each event is produced. This response, combined with phonon pulse-shape information, allows CDMS to actively discriminate candidate WIMP interactions with nuclei from electromagnetic radioactive background which interacts with electrons. The challenges associated with these techniques are unique. Carrier scattering is dominated by the spontaneous emission of Luke-Neganov phonons due to zero-point fluctuations of the lattice ions. Drift fields are maintained at only a few V/cm, else these emitted phonons would dominate the phonons of the original interaction. The dominant systematic issues with CDMS detectors are due to the effects of space charge accumulation. It has been an open question how space charge accrues, and by which of several potential recombination and ionization processes. In this work, we have simulated the transport of electrons and holes in germanium under CDMS conditions. We have implemented both a traditional Monte Carlo technique based on carrier energy, followed later by a novel Monte Carlo algorithm with scattering rates defined and sampled by vector momentum. This vector-based method provides for a full anisotropic simulation of carrier transport including free-flight acceleration with an anisotropic mass, and anisotropic scattering rates. With knowledge of steady state carrier dynamics as a function of applied field, the results of our Monte Carlo simulations allow us to make a wide variety of predictions for energy dependent processes for both electrons and holes. Such processes include carrier capture by charged impurities, neutral impurities, static dipoles, and capture forming “anion” ( D-/A+) states. We also generate predictions for impact ionization of shallow impurities and of impact “neutralization” of D- /A+ states. We use measurements of carrier capture performed on CDMS detectors to validate a plausible model for electron and hole capture due to neutral shallow impurities and their charged D-/A + states. This model, along with carrier drift and diffusion parameters from Monte Carlo simulation, can be used as the foundation for simulations of space charge evolution in CDMS detectors, simultaneously solving continuity equations with Poisson's equation.

  10. The effect of carrier gas contaminants on the charging probability of aerosols under bipolar charging conditions

    PubMed Central

    Steiner, Gerhard; Reischl, Georg P.

    2012-01-01

    This work concentrates on the experimental determination of the properties of ionic molecular clusters that are produced in the bipolar ionic atmosphere of a radioactivity based 241Am charger. The main scope of this study was to investigate the dependency of the ions' properties on carrier gas contaminants caused by the evaporation of trace gases from different kinds of frequently encountered tubing materials. A recently developed high resolution mobility spectrometer allows the precise determination of the ions' electrical mobility; an empirical mass-mobility relationship was used to approximate the corresponding ion masses. It was found that impurities in the carrier gas dramatically change the pattern of the ion mobility/size distribution, resulting in very different ion properties that strongly depend on the carrier gas composition. Since the ion properties control the charging process of aerosols, it was further investigated how the different ion properties affect the calculation of the charging probabilities of aerosols. The results show that despite large variations of the ions' properties, only a minor effect on the calculated charging probabilities can be found. PMID:23209330

  11. Effect of majority carrier space charges on minority carrier injection in dye doped polymer light-emitting devices

    Microsoft Academic Search

    S. Berleb; W. Brütting; M. Schwoerer; R. Wehrmann; A. Elschner

    1998-01-01

    By blending suitable dyes into poly(N-vinylcarbazole) we have fabricated devices which emit light in the whole visible spectrum. Their current-voltage characteristics can be described by space-charge limited currents with effective trapping of the charge carriers by the dye molecules, while the light intensity shows a Fowler-Nordheim-like behavior as a function of the external electric field. However, the anodic space charge

  12. CCM-a new low-noise charge carrier multiplier suitable for detection of charge in small pixel CCD image sensors

    Microsoft Academic Search

    J. Hynecek; A. Hangleiter; M. H. Pilkuhn; K. Wandel; U. Kunze; W. Kowalsky; J. Appl

    1992-01-01

    A new charge detection concept, useful for small pixel CCD image sensors, where the collected signal carriers are first multiplied before charge is converted into an output voltage is described. The carrier multiplication is performed in a low-noise charge carrier multiplier (CCM) which is located in a CCD channel. The multiplication occurs during the charge transfer process and is externally

  13. Onset of electroluminescence from bilayer light emitting diodes under space charge limited majority carrier injection

    Microsoft Academic Search

    V. R. Nikitenko

    2000-01-01

    An analytic theory has been developed to analyze the rise of electroluminescence from bilayer light emitting diodes upon applying a rectangular voltage pulse if the current of majority carriers is space charge limited while minority carrier injection is electrode limited. The onset of electroluminescence is governed by the growth of the interfacial charge densities rather than by the transit time.

  14. Mobilities of negative and positive charge carriers injected from metal electrodes into liquid benzene

    Microsoft Academic Search

    G. Kleinheins

    1970-01-01

    The influence of dissolved water on the electric current between metal electrodes in liquid benzene can be interpreted by assuming an injection of charge carriers, the mobility of which depends linearly on water content. This injection can be demonstrated by a drift method, which allows the determination of the mobility and polarity of the charge carriers in question. It will

  15. Localized Excited Charge Carriers Generate Ultrafast Inhomogeneous Strain in the Multiferroic BiFeO3

    E-print Network

    Evans, Paul G.

    to monitor the lattice dynamics in a thin film of multiferroic BiFeO3 after above-band-gap photoexcitationLocalized Excited Charge Carriers Generate Ultrafast Inhomogeneous Strain in the Multiferroic BiFeO of existing models of photogenerated stresses in BiFeO3: the relevant excited charge carriers must remain

  16. Impuritiy diffusion and flicker fluctuations in charge-carrier mobility in semiconductors

    SciTech Connect

    Orlov, V.B.; Yakimov, A.V.

    1985-06-01

    The authors consider fluctuations in charge-carrier mobility due to diffusion of contaminating impurities and defects within a semiconductor volume. It is shown that this mechanism can lead to flicker fluctuations in charge-carrier concentration. It becomes possible to interpret the empirical Hooge-Kleinpenning-Vandamme relationship and certain other well known experimental data on the basis of the analysis performed.

  17. Minority-charge-carrier mobility at low injection level in semiconductors

    Microsoft Academic Search

    L. I. Pomortseva

    2011-01-01

    From the kinetic equations, the distribution functions for majority and minority charge carriers are obtained at a low injection\\u000a level. For describing the electron-hole collisions, the Landau collision integral is used. The carrier scattering at ionized\\u000a or neutral impurity and at acoustic phonons is taken into account. The majority-carrier distribution function is presented\\u000a in the analytical form. The minority-carrier mobility

  18. Influence of ionizing dopants on charge transport in organic semiconductors.

    PubMed

    Abate, Antonio; Staff, Daniel R; Hollman, Derek J; Snaith, Henry J; Walker, Alison B

    2014-01-21

    Ionizing chemical dopants are widely used in organic semiconductors to enhance the charge transport properties by increasing the number of mobile charge carriers. However, together with mobile charges, chemical doping produces anion-cation pairs in the organic matrix. In this work we use experimental and computational analysis to study the influence of these ionic species on the charge transport. We show that the anion-cation pairs introduced upon doping have a detrimental, doping-level dependent effect on charge mobility. For doping levels of 0.02-0.05% molar ratio with respect to the molecular organic semiconductor, the increase in conductivity from the extra mobile charges is partially cancelled by a reduction in charge mobility from traps introduced by the anion-cation pairs. As the doping concentration increases, anion-cation pairs start to overlap, resulting in a comparatively smoother potential landscape, which increases the charge mobility to values closer to the undoped semiconductor. This result has a significant, practical impact, as it shows the need to dope at or slightly above a threshold level, which depends on the specific host-dopant combination. PMID:24287888

  19. Investigation of the charge transport through disordered organic molecular heterojunctions

    NASA Astrophysics Data System (ADS)

    Houili, H.; Tutiš, E.; Batisti?, I.; Zuppiroli, L.

    2006-08-01

    We present a three-dimensional multiparticle Monte Carlo (3DMPMC) simulation of hopping transport in disordered organic molecular media. We used this approach in order to study the charge transport across an energetically disordered organic molecular heterojunction which is known to strongly influence the characteristics of the multilayer devices based on thin organic films. The role of the energetic disorder and its spatial correlations, which govern the transport in the bulk, are examined here for the bilayer homopolar system where the heterojunction represents the bottleneck for the transport. We study the effects of disorder on both sides of the heterojunction, including the effects of the spatial correlation within each material and among the layers. The 3DMPMC approach allowed us to correctly tackle the effects of the Coulomb interaction among carriers in the region where the charge accumulation in the device is particularly important and the Coulomb interaction most pronounced. The Coulomb interaction enhances the current by increasing the electric field at the heterojunction as well as by affecting the thermalization of the carriers in front of the barrier. In order to build a rather comprehensive picture of the hopping transport over the homopolar heterojunction, we supplemented the MC simulations by a master equation (ME) calculation.

  20. Charge transport in Weyl semimetals

    NASA Astrophysics Data System (ADS)

    Hosur, Pavan; Parameswaran, Siddharth; Vishwanath, Ashvin

    2012-02-01

    Weyl semimetals are three-dimensional phases with band touchings, whose low-energy excitations are governed by the Weyl equation. They can be thought of as higher dimensional cousins of graphene. Recent theoretical work predicted certain pyrochlore iridates such as Y2Ir2O7 to be in this phase. We study charge transport in Weyl semimetals in the presence of Coulomb interactions or disorder at temperature T and compare our results to existing data on Y2Ir2O7 and Eu2Ir2O7. In the interacting clean limit, we determine the conductivity by solving a quantum Boltzmann equation within a ``leading log'' approximation and find it to be proportional to T, upto logarithmic factors arising from the flow of couplings. In the noninteracting disordered case, we compute the finite-frequency Kubo conductivity and show that it exhibits distinct behaviors for low and high frequencies compared to T. The behavior of Weyl semimetals in a magnetic field will also be briefly discussed.

  1. Electric Properties of Obsidian: Evidence for Positive Hole Charge Carriers

    NASA Astrophysics Data System (ADS)

    Nordvik, R.; Freund, F. T.

    2012-12-01

    The blackness of obsidian is due to the presence of oxygen anions in the valence state 1-, creating broad energy levels at the upper edge of the valence band, which absorb visible light over a wide spectral range. These energy states are associated with defect electrons in the oxygen anion sublattice, well-known from "smoky quartz", where Al substituting for Si captures a defect electron in the oxygen anion sublattice for charge compensation [1]. Such defect electrons, also known as positive holes, are responsible for the increase in electrical conductivity in igneous rocks when uniaxial stresses are applied, causing the break-up of pre-existing peroxy defects, Si-OO-Si [2]. Peroxy defects in obsidian cannot be so easily activated by mechanical stress because the glassy matrix will break before sufficiently high stress levels can be reached. If peroxy defects do exist, however, they can be studied by activating them thermally [3]. We describe experiments with rectangular slabs of obsidian with Au electrodes at both ends. Upon heating one end, we observe (i) a thermopotential and (ii) a thermocurrent developing at distinct temperatures around 250°C and 450°C, marking the 2-step break-up of peroxy bonds. [1] Schnadt, R., and Schneider, J.: The electronic structure of the trapped-hole center in smoky quartz, Zeitschrift Physik B Condensed Matter 11, 19-42, 1970. [2] Freund, F. T., Takeuchi, A., and Lau, B. W.: Electric currents streaming out of stressed igneous rocks - A step towards understanding pre-earthquake low frequency EM emissions, Physics and Chemistry of the Earth, 31, 389-396, 2006. [3] Freund, F., and Masuda, M. M.: Highly mobile oxygen hole-type charge carriers in fused silica, Journal Material Research, 8, 1619-1622, 1991.

  2. Ambipolar charge transport in microcrystalline silicon thin-film transistors

    SciTech Connect

    Knipp, Dietmar; Marinkovic, M. [Electronic Devices and Nanophotonics Laboratory, Jacobs University Bremen, 28759 Bremen (Germany); Chan, Kah-Yoong [IEF5-Photovoltaics, Research Center Juelich, 52425 Juelich (Germany); Faculty of Engineering, Multimedia University, Cyberjaya, 63100 Selangor (Malaysia); Gordijn, Aad [IEF5-Photovoltaics, Research Center Juelich, 52425 Juelich (Germany); Stiebig, Helmut [IEF5-Photovoltaics, Research Center Juelich, 52425 Juelich (Germany); Malibu Solar GmbH and Co. KG, 33609 Bielefeld (Germany)

    2011-01-15

    Hydrogenated microcrystalline silicon ({mu}c-Si:H) is a promising candidate for thin-film transistors (TFTs) in large-area electronics due to high electron and hole charge carrier mobilities. We report on ambipolar TFTs based on {mu}c-Si:H prepared by plasma-enhanced chemical vapor deposition at temperatures compatible with flexible substrates. Electrons and holes are directly injected into the {mu}c-Si:H channel via chromium drain and source contacts. The TFTs exhibit electron and hole charge carrier mobilities of 30-50 cm{sup 2}/V s and 10-15 cm{sup 2}/V s, respectively. In this work, the electrical characteristics of the ambipolar {mu}c-Si:H TFTs are described by a simple analytical model that takes the ambipolar charge transport into account. The analytical expressions are used to model the transfer curves, the potential and the net surface charge along the channel of the TFTs. The electrical model provides insights into the electronic transport of ambipolar {mu}c-Si:H TFTs.

  3. Polymer electrolyte-gated organic field-effect transistors: low-voltage, high-current switches for organic electronics and testbeds for probing electrical transport at high charge carrier density.

    PubMed

    Panzer, Matthew J; Frisbie, C Daniel

    2007-05-23

    We report the fabrication and extensive characterization of solid polymer electrolyte-gated organic field-effect transistors (PEG-FETs) in which a polyethylene oxide (PEO) film containing a dissolved Li salt is used to modulate the hole conductivity of a polymer semiconductor. The large capacitance (approximately 10 microF/cm2) of the solution-processed polymer electrolyte gate dielectric facilitates polymer semiconductor conductivities on the order of 103 S/cm at low gate voltages (<3 V). In PEG-FETs based on regioregular poly(3-hexylthiophene), gate-induced hole densities were 2 x 10(14) charges/cm2 with mobilities >3 cm2/V.s. PEG-FETs fabricated with gate electrodes either aligned or intentionally nonaligned to the channel exhibited dramatically different electrical behavior when tested in vacuum or in air. Large differences in ionic diffusivity can explain the dominance of either electrostatic charging (in vacuum) or bulk electrochemical doping (in air) as the device operational mechanism. The use of a larger anion in the polymer electrolyte, bis(trifluoromethanesulfonyl)imide (TFSI-), yielded transistors that showed clear current saturation and square law behavior in the output characteristics, which also points to electrostatic (field-effect) charging. In addition, negative transconductances were observed using the PEO/LiTFSI electrolyte for all three polymer semiconductors at gate voltages larger than -3 V. Bias stress measurements performed with PEO/LiTFSI-gated bottom contact PEG-FETs showed that polymer semiconductors can sustain high ON currents for greater than 10 min without large losses in conductance. Collectively, the results indicate that PEG-FETs may serve as useful devices for high-current/low-voltage applications and as testbeds for probing electrical transport in polymer semiconductors at high charge density. PMID:17472381

  4. Charge carrier mobility and electronic properties of Al(Op)3: impact of excimer formation

    PubMed Central

    Friederich, Pascal; Schäfer, Bernhard; Fattori, Valeria; Sun, Xiangnan; Strunk, Timo; Meded, Velimir; Hueso, Luis E; Wenzel, Wolfgang; Ruben, Mario

    2015-01-01

    Summary We have studied the electronic properties and the charge carrier mobility of the organic semiconductor tris(1-oxo-1H-phenalen-9-olate)aluminium(III) (Al(Op)3) both experimentally and theoretically. We experimentally estimated the HOMO and LUMO energy levels to be ?5.93 and ?3.26 eV, respectively, which were close to the corresponding calculated values. Al(Op)3 was successfully evaporated onto quartz substrates and was clearly identified in the absorption spectra of both the solution and the thin film. A structured steady state fluorescence emission was detected in solution, whereas a broad, red-shifted emission was observed in the thin film. This indicates the formation of excimers in the solid state, which is crucial for the transport properties. The incorporation of Al(Op)3 into organic thin film transistors (TFTs) was performed in order to measure the charge carrier mobility. The experimental setup detected no electron mobility, while a hole mobility between 0.6 × 10?6 and 2.1 × 10?6 cm2·V?1·s?1 was measured. Theoretical simulations, on the other hand, predicted an electron mobility of 9.5 × 10?6 cm2·V?1·s?1 and a hole mobility of 1.4 × 10?4 cm2·V?1·s?1. The theoretical simulation for the hole mobility predicted an approximately one order of magnitude higher hole mobility than was observed in the experiment, which is considered to be in good agreement. The result for the electron mobility was, on the other hand, unexpected, as both the calculated electron mobility and chemical common sense (based on the capability of extended aromatic structures to efficiently accept and delocalize additional electrons) suggest more robust electron charge transport properties. This discrepancy is explained by the excimer formation, whose inclusion in the multiscale simulation workflow is expected to bring the theoretical simulation and experiment into agreement. PMID:26171287

  5. Molecular modeling and ligand docking for Solute Carrier (SLC) transporters

    PubMed Central

    Schlessinger, Avner; Khuri, Natalia; Giacomini, Kathleen M.; Sali, Andrej

    2014-01-01

    Solute Carrier (SLC) transporters are membrane proteins that transport solutes, such as ions, metabolites, peptides, and drugs, across biological membranes, using diverse energy coupling mechanisms. In human, there are 386 SLC transporters, many of which contribute to the absorption, distribution, metabolism, and excretion of drugs and/or can be targeted directly by therapeutics. Recent atomic structures of SLC transporters determined by X-ray crystallography and NMR spectroscopy have significantly expanded the applicability of structure-based prediction of SLC transporter ligands, by enabling both comparative modeling of additional SLC transporters and virtual screening of small molecules libraries against experimental structures as well as comparative models. In this review, we begin by describing computational tools, including sequence analysis, comparative modeling, and virtual screening, that are used to predict the structures and functions of membrane proteins such as SLC transporters. We then illustrate the applications of these tools to predicting ligand specificities of select SLC transporters, followed by experimental validation using uptake kinetic measurements and other assays. We conclude by discussing future directions in the discovery of the SLC transporter ligands. PMID:23578028

  6. Diffusive charge transport in graphene

    Microsoft Academic Search

    Jianhao Chen

    2009-01-01

    The physical mechanisms limiting the mobility of graphene on SiO 2 are studied and printed graphene devices on a flexible substrate are realized. Intentional addition of charged scattering impurities is used to study the effects of charged impurities. Atomic-scale defects are created by noble-gas ions irradiation to study the effect of unitary scatterers. The results show that charged impurities and

  7. Light-emitting quantum dot transistors: emission at high charge carrier densities.

    PubMed

    Schornbaum, Julia; Zakharko, Yuriy; Held, Martin; Thiemann, Stefan; Gannott, Florentina; Zaumseil, Jana

    2015-03-11

    For the application of colloidal semiconductor quantum dots in optoelectronic devices, for example, solar cells and light-emitting diodes, it is crucial to understand and control their charge transport and recombination dynamics at high carrier densities. Both can be studied in ambipolar, light-emitting field-effect transistors (LEFETs). Here, we report the first quantum dot light-emitting transistor. Electrolyte-gated PbS quantum dot LEFETs exhibit near-infrared electroluminescence from a confined region within the channel, which proves true ambipolar transport in ligand-exchanged quantum dot solids. Unexpectedly, the external quantum efficiencies improve significantly with current density. This effect correlates with the unusual increase of photoluminescence quantum yield and longer average lifetimes at higher electron and hole concentrations in PbS quantum dot thin films. We attribute the initially low emission efficiencies to nonradiative losses through trap states. At higher carrier densities, these trap states are deactivated and emission is dominated by trions. PMID:25652433

  8. Light-Emitting Quantum Dot Transistors: Emission at High Charge Carrier Densities

    PubMed Central

    2015-01-01

    For the application of colloidal semiconductor quantum dots in optoelectronic devices, for example, solar cells and light-emitting diodes, it is crucial to understand and control their charge transport and recombination dynamics at high carrier densities. Both can be studied in ambipolar, light-emitting field-effect transistors (LEFETs). Here, we report the first quantum dot light-emitting transistor. Electrolyte-gated PbS quantum dot LEFETs exhibit near-infrared electroluminescence from a confined region within the channel, which proves true ambipolar transport in ligand-exchanged quantum dot solids. Unexpectedly, the external quantum efficiencies improve significantly with current density. This effect correlates with the unusual increase of photoluminescence quantum yield and longer average lifetimes at higher electron and hole concentrations in PbS quantum dot thin films. We attribute the initially low emission efficiencies to nonradiative losses through trap states. At higher carrier densities, these trap states are deactivated and emission is dominated by trions. PMID:25652433

  9. Investigation of the effect of band-edge nonparabolicity on the carrier transport in ITO thin films

    NASA Astrophysics Data System (ADS)

    Ziabari, Ali Abdolahzadeh; Rozati, S. M.

    2014-08-01

    The impact of band-edge nonparabolicity on the charge carrier transport in degenerate n-type indium-tin-oxide (ITO) thin films has been investigated theoretically in order to understand the fundamental concepts of electron scattering in such materials regardless of the precise details of the preparation procedure. The Fermi energy level and the scattering parameter of the ITO thin films have been calculated as functions of the carrier concentration. The results indicate that the nonparabolicity has a drastic effect on the total mobility of carriers in the films. We have also discussed the role of grain boundaries in carrier transport. Additionally, to survey the dominant scattering mechanism in the grain bulk of ITO films, we have calculated the scattering parameter. The evaluated values lie near the trend expected for ionized impurity scattering.

  10. Charge carrier injection into insulating media: Singleparticle versus mean-field approach

    Microsoft Academic Search

    Yu. A. Genenko; S. V. Yampolskii; C. Melzer; K. Stegmaier; H. von Seggern

    2010-01-01

    Self-consistent, mean-field description of charge injection into a dielectric medium is modified to account for discreteness of charge carriers. The improved scheme includes both the Schottky barrier lowering due to the individual image charge and the barrier change due to the field penetration into the injecting electrode that ensures validity of the model at both high and low injection rates

  11. Carrier transport at the metal-MoS2 interface

    NASA Astrophysics Data System (ADS)

    Ahmed, Faisal; Choi, Min Sup; Liu, Xiaochi; Yoo, Won Jong

    2015-05-01

    This study illustrates the nature of electronic transport and its transition from one mechanism to another between a metal electrode and MoS2 channel interface in a field effect transistor (FET) device. Interestingly, measurements of the contact resistance (Rc) as a function of temperature indicate a transition in the carrier transport across the energy barrier from thermionic emission at a high temperature to tunneling at a low temperature. Furthermore, at a low temperature, the nature of the tunneling behavior is ascertained by the current-voltage dependency that helps us feature direct tunneling at a low bias and Fowler-Nordheim tunneling at a high bias for a Pd-MoS2 contact due to the effective barrier shape modulation by biasing. In contrast, only direct tunneling is observed for a Cr-MoS2 contact over the entire applied bias range. In addition, simple analytical calculations were carried out to extract Rc at the gating range, and the results are consistent with the experimental data. Our results describe the transition in carrier transport mechanisms across a metal-MoS2 interface, and this information provides guidance for the design of future flexible, transparent electronic devices based on 2-dimensional materials.This study illustrates the nature of electronic transport and its transition from one mechanism to another between a metal electrode and MoS2 channel interface in a field effect transistor (FET) device. Interestingly, measurements of the contact resistance (Rc) as a function of temperature indicate a transition in the carrier transport across the energy barrier from thermionic emission at a high temperature to tunneling at a low temperature. Furthermore, at a low temperature, the nature of the tunneling behavior is ascertained by the current-voltage dependency that helps us feature direct tunneling at a low bias and Fowler-Nordheim tunneling at a high bias for a Pd-MoS2 contact due to the effective barrier shape modulation by biasing. In contrast, only direct tunneling is observed for a Cr-MoS2 contact over the entire applied bias range. In addition, simple analytical calculations were carried out to extract Rc at the gating range, and the results are consistent with the experimental data. Our results describe the transition in carrier transport mechanisms across a metal-MoS2 interface, and this information provides guidance for the design of future flexible, transparent electronic devices based on 2-dimensional materials. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr01044f

  12. Minority-charge-carrier mobility at low injection level in semiconductors

    SciTech Connect

    Pomortseva, L. I., E-mail: lipom@list.ru [All-Russia Electrotechnical Institute Federal State Unitary Enterprise (Russian Federation)

    2011-04-15

    From the kinetic equations, the distribution functions for majority and minority charge carriers are obtained at a low injection level. For describing the electron-hole collisions, the Landau collision integral is used. The carrier scattering at ionized or neutral impurity and at acoustic phonons is taken into account. The majority-carrier distribution function is presented in the analytical form. The minority-carrier mobility is calculated and analyzed, and the features of its behavior at low temperatures are revealed. It follows from the developed theory that the hole mobility in an n-type material increases with doping and neutral-impurity concentration. This effect is attributed to mutual charge-carrier collisions and different effective masses of different-sign carriers.

  13. Suppressing the process of charge carrier delocalization in high-power pulse-pumped semiconductor lasers

    NASA Astrophysics Data System (ADS)

    Veselov, D. A.; Shakshin, I. S.; Pikhtin, N. A.; Slipchenko, S. O.; Sokolova, Z. N.; Tarasov, I. S.

    2015-03-01

    The process of charge carrier delocalization in high-power semiconductor lasers is examined under high current, pulse-pumped operation conditions. It is established that the carrier delocalization process is mostly determined by the injection of electrons (rather than holes) into the waveguide. Two methods of suppression of carrier delocalization are experimentally demonstrated, which are based on increasing the waveguide bandgap width and on using the waveguide containing a potential energy barrier for electrons in the p-region.

  14. 75 FR 48409 - Establishment of the Toxic by Inhalation Hazard Common Carrier Transportation Advisory Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-10

    ...Docket No. EP 698] Establishment of the Toxic by Inhalation Hazard Common Carrier Transportation...ACTION: Notice of establishment of the Toxic by Inhalation Hazard Common Carrier Transportation...Administration, the Board will create the Toxic by Inhalation Hazard Common Carrier...

  15. Dielectric relaxation of free charge carriers in some fluorite-type solid solutions

    NASA Astrophysics Data System (ADS)

    Hairetdinov, E. F.; Uvarov, N. F.; Reau, J.-M.; Hagenmuller, P.

    1998-01-01

    Low-frequency dielectric relaxation was observed in solid solutions Ba 1 - xTh xF 2 + x and Cd 1 - xEr xF 2 + x of fluorite type. The relaxation can be satisfactorily described by the Havriliak-Negami formula: ? ?( f) - ? ? = ??/ {1 + [ if/f r] 1 - ?} 1 - ?. The activation energy for relaxation turned to be equal to that for DC-conductivity in the system under study. This suggests that the relaxation is closely related to the ion transport and agrees with the model of a dipole-like behavior of free charge carriers. The relaxation is of strongly non-Debye type and contributes to the high frequency conductivity in the form: ? = ?DC[1 + ( f/ fh) ?] with ? = ? + ? - ??.

  16. Temperature dependence of exciton and charge carrier dynamics in organic thin films

    NASA Astrophysics Data System (ADS)

    Platt, A. D.; Kendrick, M. J.; Loth, M.; Anthony, J. E.; Ostroverkhova, O.

    2011-12-01

    We report on physical mechanisms behind the temperature-dependent optical absorption, photoluminescence (PL), and photoconductivity in spin-coated films of a functionalized anthradithiophene (ADT) derivative, ADT-triethylsilylethynyl (TES)-F, and its composites with C60 and another ADT derivative, ADT-TIPS-CN. Measurements of absorption and PL spectra, PL lifetimes, and transient photocurrent were performed at temperatures between 98 and 300 K as a function of applied electric field. In pristine ADT-TES-F films, absorptive and emissive species were identified to be disordered H aggregates whose properties are affected by static and dynamic disorder. The exciton bandwidths were ?0.06 and ˜0.115 eV for absorptive and emissive aggregates, respectively, indicative of higher disorder in the emissive species. The exciton in the latter was found to be delocalized over approximately four to five molecules. The PL properties were significantly modified upon adding a guest molecule to the ADT-TES-F host. In ADT-TES-F/C60 composites, the PL was considerably quenched due to photoinduced electron transfer from ADT-TES-F to C60, while in ADT-TES-F/ADT-TIPS-CN blends, the PL was dominated by emission from an exciplex formed between ADT-TES-F and ADT-TIPS-CN molecules. In all materials, the PL quantum yield dramatically decreased as the temperature increased due to thermally activated nonradiative recombination. Considerable electric-field-induced PL quenching was observed at low temperatures at electric fields above ˜105 V/cm due to tunneling into dark states. No significant contribution of ADT-TES-F emissive exciton dissociation to transient photocurrent was observed. In all materials, charge carriers were photogenerated at sub-500-ps time scales, limited by the laser pulse width, with temperature- and electric-field-independent photogeneration efficiency. In ADT-TES-F/C60 (2%) composites, the photogeneration efficiency was a factor of 2-3 higher than that in pristine ADT-TES-F films. In ADT-TES-F/ADT-TIPS-CN (2%) blends, an additional charge carrier photogeneration component was observed at room temperature at time scales of ˜20 ns due to exciplex dissociation. At ˜0.5-5 ns after photoexcitation, the carriers propagated via thermally and electric-field-activated hopping with an activation energy of ˜0.025 eV. At time scales longer than ˜5 ns, charge transport of carriers that are not frozen in traps proceeded through tunneling via isoenergetic sites.

  17. Nanocone Tip-Film Solar Cells with Efficient Charge Transport

    SciTech Connect

    Lee, Sang Hyun [ORNL; Zhang, Xiaoguang [ORNL; Parish, Chad M [ORNL; Smith, Barton [ORNL; Xu, Jun [ORNL; Lee, Ho Nyung [ORNL

    2011-01-01

    Nanojunctions promise to provide higher charge transport efficiencies and less costly solar cell fabrication methods. We report a three-dimensional (3D) solar cell structure based on interdigitated nanojunctions formed with the tips of n-type ZnO nanocones embedded in a p-type polycrystalline (PX) CdTe film. This 3D nanocone tip-film cell, without optimization, enabled 3.2% power conversion efficiency, higher than that produced by a planar solar cell fabricated using the same materials. Reducing CdTe grain size and enriching the grain boundaries with chlorine improved the conversion efficiency for the tip-film structure. This higher conversion efficiency is attributable to improved charge transport in the nanojunction due to a combination of the high electric field generated in the CdTe and the utilization of the small junction area. The high field facilitates the extraction of minority carriers from the photoactive layer to the small junction region, while the use of the small junction area reduces the total electron recombination loss. The improved carrier transport in the nanocone tip-film junction implies that nanocone-based photovoltaic solar cells are capable of tolerating the imperfect materials produced using low-cost fabrication methods.

  18. Charge-Carrier Injection and the Pre-exponential Factor in Semiconducting Organic Substances

    Microsoft Academic Search

    M. E. Green

    1969-01-01

    A charge-carrier injection model is shown to lead to an approximately linear dependence of the preexponential factor on activation energy for small organic semiconductors, without assuming a linear temperature dependence for the activation energy.

  19. Quantum dynamics in condensed phases : charge carrier mobility, decoherence, and excitation energy transfer

    E-print Network

    Cheng, Yuan-Chung, Ph. D. Massachusetts Institute of Technology

    2006-01-01

    In this thesis, we develop analytical models for quantum systems and perform theoretical investigations on several dynamical processes in condensed phases. First, we study charge-carrier mobilities in organic molecular ...

  20. High energetic excitons in carbon nanotubes directly probe charge-carriers.

    PubMed

    Soavi, Giancarlo; Scotognella, Francesco; Viola, Daniele; Hefner, Timo; Hertel, Tobias; Cerullo, Giulio; Lanzani, Guglielmo

    2015-01-01

    Theory predicts peculiar features for excited-state dynamics in one dimension (1D) that are difficult to be observed experimentally. Single-walled carbon nanotubes (SWNTs) are an excellent approximation to 1D quantum confinement, due to their very high aspect ratio and low density of defects. Here we use ultrafast optical spectroscopy to probe photogenerated charge-carriers in (6,5) semiconducting SWNTs. We identify the transient energy shift of the highly polarizable S33 transition as a sensitive fingerprint of charge-carriers in SWNTs. By measuring the coherent phonon amplitude profile we obtain a precise estimate of the Stark-shift and discuss the binding energy of the S33 excitonic transition. From this, we infer that charge-carriers are formed instantaneously (<50 fs) even upon pumping the first exciton, S11. The decay of the photogenerated charge-carrier population is well described by a model for geminate recombination in 1D. PMID:25959462

  1. Determination of charge carriers in superconducting La-Ba-Cu-O by thermoelectric measurements

    SciTech Connect

    Chen, J.T.; McEwan, C.J.; Wenger, L.E.; Logothetis, E.M.

    1987-05-01

    Majority-charge carriers in high-T/sub c/ superconducting La-Ba-Cu-O are shown to be positive (holelike) carriers as determined by thermoelectric measurements in the temperature range of 300 to 28 K, the superconducting transition temperature.

  2. From charge transport parameters to charge mobility in organic semiconductors through multiscale simulation.

    PubMed

    Shuai, Zhigang; Geng, Hua; Xu, Wei; Liao, Yi; André, Jean-Marie

    2014-04-21

    This review introduces the development and application of a multiscale approach to assess the charge mobility for organic semiconductors, which combines quantum chemistry, Kinetic Monte Carlo (KMC), and molecular dynamics (MD) simulations. This approach is especially applicable in describing a large class of organic semiconductors with intermolecular electronic coupling (V) much less than intramolecular charge reorganization energy (?), a situation where the band description fails obviously. The charge transport is modeled as successive charge hopping from one molecule to another. We highlight the quantum nuclear tunneling effect in the charge transfer, beyond the semiclassical Marcus theory. Such an effect is essential for interpreting the "paradoxical" experimental finding that optical measurement indicated "local charge" while electrical measurement indicated "bandlike". Coupled MD and KMC simulations demonstrated that the dynamic disorder caused by intermolecular vibration has negligible effect on the carrier mobility. We further apply the approach for molecular design of n-type materials and for rationalization of experimental results. The charge reorganization energy is analyzed through decomposition into internal coordinates relaxation, so that chemical structure contributions to the intramolecular electron-phonon interaction are revealed and give helpful indication to reduce the charge reorganization energy. PMID:24394992

  3. Charge-carrier injection into CuPc thin films: a scanning tunneling microscopy study

    Microsoft Academic Search

    S. F. Alvarado; L. Rossi; P. Müller; W. Rieß

    2001-01-01

    Injection of charge carriers into the LUMO and HOMO levels of copper phthalocyanine (CuPc) is investigated by scanning tunneling microscopy (STM) and spectroscopy. The threshold for injection of charge carriers emitted by the tip of the STM allows us to determine the so-called single-particle band gap (Egsp) of CuPc polymorphs as well as the band edge alignment with respect to

  4. Ab initio description and visualization of charge transport in durene crystals

    NASA Astrophysics Data System (ADS)

    Ortmann, Frank; Hannewald, Karsten; Bechstedt, Friedhelm

    2008-12-01

    We study the charge transport through crystalline durene which exhibits large hole mobilities. By means of ab initio calculations, we determine the temperature-dependent polaron bandwidth and the mobility tensor of the charge carriers. The origin of the bandlike mobility curves is discussed, and the strong anisotropy of the mobility is analyzed in detail. We put a special focus on the relationship between crystal packing geometry, molecular wave function overlap, and charge transport properties. The results include a visualization of the transport channels in durene which can be regarded as a prototypical herringbone-stacked crystal.

  5. Charge fluctuations in nonlinear heat transport

    NASA Astrophysics Data System (ADS)

    Gergs, Niklas M.; Hörig, Christoph B. M.; Wegewijs, Maarten R.; Schuricht, Dirk

    2015-05-01

    We show that charge fluctuation processes are crucial for the nonlinear heat conductance through an interacting nanostructure, even far from a resonance. We illustrate this for an Anderson quantum dot accounting for the first two leading orders of the tunneling in a master equation. The often made assumption that off-resonant transport proceeds entirely by virtual occupation of charge states, underlying exchange-scattering models, can fail dramatically for heat transport. The identified energy-transport resonances in the Coulomb blockade regime provide qualitative information about relaxation processes, for instance, by a strong negative differential heat conductance relative to the heat current. These can go unnoticed in the charge current, making nonlinear heat-transport spectroscopy with energy-level control a promising experimental tool.

  6. 47 CFR 69.153 - Presubscribed interexchange carrier charge (PICC).

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...69.153 Section 69.153 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES (CONTINUED...calculated under paragraph (a) of this section for Primary Rate Interface ISDN service. (e) The maximum monthly PICC for...

  7. 14 CFR 234.13 - Reports by air carriers on incidents involving animals during air transport.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...incidents involving animals during air transport. 234.13 Section 234.13...incidents involving animals during air transport. (a) Any air carrier that...or death of an animal during air transport provided by the air...

  8. 14 CFR 234.13 - Reports by air carriers on incidents involving animals during air transport.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...incidents involving animals during air transport. 234.13 Section 234.13...incidents involving animals during air transport. (a) Any air carrier that...or death of an animal during air transport provided by the air...

  9. 14 CFR 234.13 - Reports by air carriers on incidents involving animals during air transport.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...incidents involving animals during air transport. 234.13 Section 234.13...incidents involving animals during air transport. (a) Any air carrier that...or death of an animal during air transport provided by the air...

  10. 14 CFR 234.13 - Reports by air carriers on incidents involving animals during air transport.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...incidents involving animals during air transport. 234.13 Section 234.13...incidents involving animals during air transport. (a) Any air carrier that...or death of an animal during air transport provided by the air...

  11. 14 CFR 234.13 - Reports by air carriers on incidents involving animals during air transport.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...incidents involving animals during air transport. 234.13 Section 234.13...incidents involving animals during air transport. (a) Any air carrier that...or death of an animal during air transport provided by the air...

  12. 29 CFR 780.155 - Delivery “to carriers for transportation to market.”

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...transportation to market” includes taking agricultural or horticultural commodities, dairy products, livestock, bees or their honey, fur-bearing animals or their pelts, and poultry to any carrier (including carriers by truck,...

  13. 29 CFR 780.155 - Delivery “to carriers for transportation to market.”

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...transportation to market” includes taking agricultural or horticultural commodities, dairy products, livestock, bees or their honey, fur-bearing animals or their pelts, and poultry to any carrier (including carriers by truck,...

  14. Carrier Transport Properties of the Field Effect Transistors with Graphene Channel Prepared by Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Negishi, Ryota; Ohno, Yasuhide; Maehashi, Kenzo; Matsumoto, Kazuhiko; Kobayashi, Yoshihiro

    2012-06-01

    We investigate the carrier transport properties of multilayer graphene with a turbostratic structure grown by chemical vapor deposition (CVD). The observed sheet resistivity of field effect transistors using the grown multilayer graphene (GG-FETs) with a turbostratic structure as a channel is almost constant at any temperature. The feature is virtually identical to that of FET using monolayer graphene rather than to that of FET using mechanically exfoliated multilayer graphene with well-ordered stacking. This indicates that the electronic band of the grown multilayer graphene with a turbostratic structure has a linear dispersion around the Dirac point similarity to that of a monolayer graphene. The mobility of the GG-FETs is low (300-400 cm2 V-1 s-1) in comparison with that of the FETs using mechanically exfoliated graphene. From structural analysis using Raman spectroscopy, we find that the low carrier mobility can be explained by the existence of a charged impurity at the grown graphene layers.

  15. Ultrafast charge carrier relaxation and charge transfer processes in CdS/CdTe thin films.

    PubMed

    Pandit, Bill; Dharmadasa, Ruvini; Dharmadasa, I M; Druffel, Thad; Liu, Jinjun

    2015-06-24

    Ultrafast transient absorption pump-probe spectroscopy (TAPPS) has been employed to investigate charge carrier relaxation in cadmium sulfide/cadmium telluride (CdS/CdTe) nanoparticle (NP)-based thin films and electron transfer (ET) processes between CdTe and CdS. Effects of post-growth annealing treatments to ET processes have been investigated by carrying out TAPPS experiments on three CdS/CdTe samples: as deposited, heat treated, and CdCl2 treated. Clear evidence of ET process in the treated thin films has been observed by comparing transient absorption (TA) spectra of CdS/CdTe thin films to those of CdS and CdTe. Quantitative comparison between ultrafast kinetics at different probe wavelengths unravels the ET processes and enables determination of its rate constants. Implication of the photoinduced dynamics to photovoltaic devices is discussed. PMID:26033446

  16. Charge transfer and charge transport on the double helix

    NASA Astrophysics Data System (ADS)

    Armitage, N. P.; Briman, M.; Grüner, G.

    2004-01-01

    We present a short review of various experiments that measure charge transfer and charge transport in DNA. Some general comments are made on the possible connection between various chemistry-style charge transfer experiments that probe fluorescence quenching and remote oxidative damage and physics-style measurements that measure transport properties as defined typically in the solid-state. We then describe measurements performed by our group on the millimeter wave response of DNA. By measuring over a wide range of humidity conditions and comparing the response of single strand DNA and double strand DNA, we show that the appreciable AC conductivity of DNA is not due to photon assisted hopping between localized states, but instead due to dissipation from dipole motion in the surrounding water helix.

  17. Raman scattering studies and charge transport in polyfluorenes

    NASA Astrophysics Data System (ADS)

    Arif, Mohammad Ali Iftekhar

    Organic semiconductors, such as short-chain oligomers and long-chain polymers, are now a core constituent in numerous organic and organic-inorganic hybrid technologies. Blue-emitting polyfluorenes (PFs) have emerged as especially attractive pi conjugated polymers (CP) due to their high luminescence efficiency and excellent electronic properties and thus great prospects for device applications. The performance of devices based on these polymers depends on side chain conformations, overall crystalline structure, and charge transport processes at the microscopic level. This project entails detailed Raman scattering studies and charge transport properties of two side chain substituted PFs: Poly(2,7-[9,9'-bis(2-ethylhexyl)] fluorene) (PF2/6) and Poly(9,9-(di-n,n-octyl) fluorene) (PF8). The structural properties of PFs are extremely sensitive to the choice of functionalizing side chains. PF8 adopts metastable structures that depend upon the thermal history and choice of solvents used in film forming conditions. Raman scattering techniques as a function of thermal cycling are used to monitor the changes in the backbone and side chain morphology of PF8. These studies establish a correlation between the conformational isomers and the side and main chain morphology. Theoretical modeling of the vibrational spectra of single chain oligomers in conjunction with the experimental results demonstrate the incompatibility of the beta phase, a low energy emitting chromophore, with the overall crystalline phase in PF8. Further, electroluminescence and photoluminescence measurements from PF-based light-emitting diodes (LEDs) are presented and discussed in terms of the crystalline phases and chain morphologies in the PFs. Charge carrier injection and transport properties of PF-based LEDs are presented using current-voltage (I--V) characteristic which is modeled by a space-charge-limited conduction (SCLC) for discrete and continuous traps. PF2/6 with a high level of molecular disorder is an exemplary system for the SCLC model with discrete single level shallow traps. Charge transport as a function of sample thickness uncovers the origin of these traps. The thickness dependent SCLC measurements show the influence of both surface and bulk traps on charge transport. Temperature dependence of I--V and dc conductivity measurements suggest thermal assisted variable-range hopping transport instead of band transport in these materials. Charge carrier injection and doping in CPs induce structural deformation with the formation of self-localized excitation states, such as polarons or bipolarons inside the band gap. Raman scattering studies of PF2/6-based LEDs with doping and in the presence of injected and photo-generated charge carriers show increasing backgrounds with asymmetric Briet-Wigner Fano (BWF) line shapes, indicating strong electron-phonon interactions.

  18. Strong Asymmetric Charge Carrier Dependence in Inelastic Electron Tunneling Spectroscopy of Graphene Phonons

    NASA Astrophysics Data System (ADS)

    Natterer, Fabian D.; Zhao, Yue; Wyrick, Jonathan; Chan, Yang-Hao; Ruan, Wen-Ying; Chou, Mei-Yin; Watanabe, Kenji; Taniguchi, Takashi; Zhitenev, Nikolai B.; Stroscio, Joseph A.

    2015-06-01

    The observation of phonons in graphene by inelastic electron tunneling spectroscopy has been met with limited success in previous measurements arising from weak signals and other spectral features which inhibit a clear distinction between phonons and miscellaneous excitations. Utilizing a back-gated graphene device that allows adjusting the global charge carrier density, we introduce an averaging method where individual tunneling spectra at varying charge carrier density are combined into one representative spectrum. This method improves the signal for inelastic transitions while it suppresses dispersive spectral features. We thereby map the total graphene phonon density of states, in good agreement with density functional calculations. Unexpectedly, an abrupt change in the phonon intensity is observed when the graphene charge carrier type is switched through a variation of the back-gate electrode potential. This sudden variation in phonon intensity is asymmetric in the carrier type, depending on the sign of the tunneling bias.

  19. Charge Transport in Weyl Semimetals

    Microsoft Academic Search

    Pavan Hosur; S. A. Parameswaran; Ashvin Vishwanath

    2011-01-01

    We study transport in three dimensional Weyl semimetals with N isotropic Weyl nodes in the presence of Coulomb interactions or disorder at temperature T. In the interacting clean limit, we determine the conductivity by solving a quantum Boltzmann equation within a `leading log' approximation and find it to be proportional to T, upto logarithmic factors arising from the flow of

  20. Theoretical and experimental study of charge carrier kinetics in crystalline silicon

    Microsoft Academic Search

    Olaf Hahneiser; Marinus Kunst

    1999-01-01

    A model simulating excess charge carrier kinetics in Si wafers was developed taking into account space charge fields and surface recombination. This model was applied to experimental data obtained by contactless transient and frequency resolved photoconductivity measurements of silicon wafers with accumulation or depletion layers at the surface. It is shown that a surface accumulation layer has only a minor

  1. Channeling of charge carrier plasmons in carbon nanotubes C. Kramberger,1

    E-print Network

    Maruyama, Shigeo

    of them [5­7] may be envisaged as a nano-meshed meta-material. In dielectric meta-materials the plasmon plasmon. The elec- tron density and hence the frequency of the charge car- rier plasmon in freestandingChanneling of charge carrier plasmons in carbon nanotubes C. Kramberger,1 F. Roth,2 R. Schuster,2 R

  2. Macroscopic acoustoelectric charge transport in graphene

    NASA Astrophysics Data System (ADS)

    Bandhu, L.; Lawton, L. M.; Nash, G. R.

    2013-09-01

    We demonstrate macroscopic acoustoelectric transport in graphene, transferred onto piezoelectric lithium niobate substrates, between electrodes up to 500 ?m apart. Using double finger interdigital transducers we have characterised the acoustoelectric current as a function of both surface acoustic wave intensity and frequency. The results are consistent with a relatively simple classical relaxation model, in which the acoustoelectric current is proportional to both the surface acoustic wave intensity and the attenuation of the wave caused by the charge transport.

  3. High-temperature thermoelectric transport at small scales: Thermal generation, transport and recombination of minority carriers

    PubMed Central

    Bakan, Gokhan; Khan, Niaz; Silva, Helena; Gokirmak, Ali

    2013-01-01

    Thermoelectric transport in semiconductors is usually considered under small thermal gradients and when it is dominated by the role of the majority carriers. Not much is known about effects that arise under the large thermal gradients that can be established in high-temperature, small-scale electronic devices. Here, we report a surprisingly large asymmetry in self-heating of symmetric highly doped silicon microwires with the hottest region shifted along the direction of minority carrier flow. We show that at sufficiently high temperatures and strong thermal gradients (~1?K/nm), energy transport by generation, transport and recombination of minority carriers along these structures becomes very significant and overcomes convective energy transport by majority carriers in the opposite direction. These results are important for high-temperature nanoelectronics such as emerging phase-change memory devices which also employ highly doped semiconducting materials and in which local temperatures reach ~1000?K and thermal gradients reach ~10–100?K/nm. PMID:24056703

  4. High-temperature thermoelectric transport at small scales: thermal generation, transport and recombination of minority carriers.

    PubMed

    Bakan, Gokhan; Khan, Niaz; Silva, Helena; Gokirmak, Ali

    2013-01-01

    Thermoelectric transport in semiconductors is usually considered under small thermal gradients and when it is dominated by the role of the majority carriers. Not much is known about effects that arise under the large thermal gradients that can be established in high-temperature, small-scale electronic devices. Here, we report a surprisingly large asymmetry in self-heating of symmetric highly doped silicon microwires with the hottest region shifted along the direction of minority carrier flow. We show that at sufficiently high temperatures and strong thermal gradients (~1 K/nm), energy transport by generation, transport and recombination of minority carriers along these structures becomes very significant and overcomes convective energy transport by majority carriers in the opposite direction. These results are important for high-temperature nanoelectronics such as emerging phase-change memory devices which also employ highly doped semiconducting materials and in which local temperatures reach ~1000 K and thermal gradients reach ~10-100 K/nm. PMID:24056703

  5. Photothermal radiometry analysis of charge transport

    NASA Astrophysics Data System (ADS)

    Zambrano-Arjona, M. A.; Smit, M. A.; Alvarado-Gil, Juan J.

    2005-02-01

    Photothermal techniques have been applied successfully in the study of the charge transport process in inorganic semiconductors in crystalline and polycrystalline form. Photothermal radiometry is a non-contact technique that could provide not only the thermal properties but also parameters related with recombination of charge. In this work the potential of photothermal radiometry in the study of charge recombination in organic polymeric semiconductors is explored. It has been shown that conjugated polymers are especially interesting for its charge transport properties. In this work, polyaniline samples grown on stainless steel by electrochemical methods are studied. Photothermal radiometry profiles were obtained by illuminating the sample with modulated light of an ion Argon laser and detecting the changes of temperature with an IR detector. The profiles show marked differences depending on the conditions of preparation. In order to determine the effects of charge recombination, and at the same time to eliminate the influence of the roughness of the different samples, a normalization procedure was devised. This procedure consisted in dividing the signal of the sample with charge recombination effects by the signal of the sample that would not present charge recombination. Our results are discussed and compared with an inorganic semiconductor.

  6. Theory of radiation-induced and carrier-enhanced conductivity: Space charge and contact effects. [Kapton

    SciTech Connect

    Parker, L.W.; Meulenberg, A.

    1984-12-01

    Numerous experiments to determine conductivity in dielectrics are reported. It is often necessary to use a theoretical model to correctly interpret them. A carrier model is described here, based on steady-state solutions of general kinetic equations for electrons and holes. An assumption is made that the holes are instantaneously trapped into deep traps, while the electrons hop from shallow trap to shallow trap and are described as quasi-free with a lowered ''trap-modulated'' effective mobility. This simplifies the description of the system to the Poisson equation plus a single transport equation for the electrons. Parameters required by the model include mobility, recombination rate, pair generation rate, and excess charge deposition rate. Raw data on a 6.4-..mu..m biased sample of Kapton, penetrated by a 28-keV incident electron beam, are considered for interpretation. A number of solutions yielding valuable insights are discussed. Current measurements at zero bias can be interpreted in terms of the shape of the excess-charge deposition profile. Measurements at high bias are matched by the model with an appropriate choice for the trap-modulated electron mobility (about 7 x 10/sup -15/ m/sup 2//V-s), provided injection is assumed to occur at the cathode contact.

  7. Charge Transport in Weyl Semimetals

    NASA Astrophysics Data System (ADS)

    Hosur, Pavan; Parameswaran, S. A.; Vishwanath, Ashvin

    2012-01-01

    We study transport in Weyl semimetals with N isotropic Weyl nodes in the presence of Coulomb interactions or disorder at temperature T. In the interacting clean limit, we determine the conductivity ?(?,T) by solving a quantum Boltzmann equation within a “leading log” approximation and find it to be proportional to T, up to logarithmic factors arising from the flow of couplings. In the noninteracting disordered case, we compute the Kubo conductivity and show that it behaves differently for ??T and ??T: in the former regime we recover a previous result, of a finite dc conductivity and a Drude width vanishing as NT2; in the latter, we find that ?(?,T) vanishes linearly with ? with a leading term as T?0 equal to the clean, free-fermion result: ?0(N)(?,T=0)=N(e2)/(12h)(|?|)/(vF). We compare our results to transport data on Y2Ir2O7 and comment on the possible relevance to recent experiments on Eu2Ir2O7.

  8. Stochastic resonance of charge carriers diffusing in a nonhomogeneous medium with nonhomogeneous temperature

    NASA Astrophysics Data System (ADS)

    Aragie, Berhanu; Tatek, Yergou B.; Bekele, Mulugeta

    2014-05-01

    We investigate the dynamics of charge carriers hopping from one trap to the other trap along an n-type semiconductor layer consisting of a spatially nonhomogeneous trap distribution of depth ? assisted by thermal noise. The trap profile is denser at the center and decays as one moves outward. In presence of a uniform background temperature, the charge carriers tend to accumulate around the center. Moreover, applying a nonhomogeneous temperature which is hot at the location of the maximum of trap density, results in a new redistribution of charge carriers which pile up around two points symmetrically positioned with respect to the center of the semiconductor layer making the system to behave like a bistable potential. The thermally activated rate of hopping of charge carriers as a function of the model parameters is studied in the high barrier limit. Using the two-state approximation, the stochastic resonance (SR) of the charge carriers dynamics in the presence of time varying external signal is also investigated.

  9. An angular multigrid method for modeling charged-particle transport

    E-print Network

    MacLachlan, Scott

    -particle transport in Flatland- p.2 #12;Constrained Optimization Problem In general, the radiation dose planningAn angular multigrid method for modeling charged-particle transport in Flatland Scott Mac method for modeling charged-particle transport in Flatland- p.1 #12;Charged-Particle Transport Interest

  10. Temperature-dependent carrier-transport and light-emission processes in a phosphorescent organic light-emitting device

    Microsoft Academic Search

    Isao Tanaka; Shizuo Tokito

    2005-01-01

    We report on carrier-transport, electroluminescence, and photoluminescence processes in a phosphorescent organic light-emitting device based on fac tris(2-phenylpyridine) iridium doped 4,4'-N,N'-dicarbazole-biphenyl over a wide temperature range from 5 to 295 K. The current flow could be described in terms of a space-charge-limited current with an exponential trap distribution at temperatures above 150 K. The electroluminescence intensity gradually decreased with decreasing

  11. Dependence of the carrier mobility and trapped charge limited conduction on silver nanoparticles embedment in doped polypyrrole nanostructures

    NASA Astrophysics Data System (ADS)

    Biswas, Swarup; Dutta, Bula; Bhattacharya, Subhratanu

    2013-10-01

    The present article demonstrates an intensive study upon the temperature dependent current density (J)-voltage (V) characteristics of moderately doped polypyrrole nanostructure and its silver nanoparticles incorporated nanocomposites. Analysis of the measured J-V characteristics of different synthesized nano-structured samples within a wide temperature range revealed that the electrical conduction behavior followed a trapped charge-limited conduction and a transition of charge transport mechanism from deep exponential trap limited conduction to shallow traps limited conduction had been occurred due to the incorporation of silver nanoparticles within the polypyrrole matrix. A direct evaluation of carrier mobility as a function of electric field and temperature from the measured J-V characteristics illustrates that the incorporation of silver nanoparticles within the polypyrrole matrix enhances the carrier mobility at a large extent by reducing the concentration of traps within the polypyrrole matrix. The calculated mobility is consistent with the Poole-Frenkel form for the electrical field up to a certain temperature range. The nonlinear low temperature dependency of mobility of all the nanostructured samples was explained by Mott variable range hopping conduction mechanisms. Quantitative information regarding the charge transport parameters obtained from the above study would help to extend optimization strategies for the fabrication of new organic semiconducting nano-structured devices.

  12. High-frequency acoustic charge transport in GaAs nanowires.

    PubMed

    Büyükköse, S; Hernández-Mínguez, A; Vratzov, B; Somaschini, C; Geelhaar, L; Riechert, H; van der Wiel, W G; Santos, P V

    2014-04-01

    The oscillating piezoelectric fields accompanying surface acoustic waves are able to transport charge carriers in semiconductor heterostructures. Here, we demonstrate high-frequency (above 1 GHz) acoustic charge transport in GaAs-based nanowires deposited on a piezoelectric substrate. The short wavelength of the acoustic modulation, smaller than the length of the nanowire, allows the trapping of photo-generated electrons and holes at the spatially separated energy minima and maxima of conduction and valence bands, respectively, and their transport along the nanowire with a well defined acoustic velocity towards indium-doped recombination centers. PMID:24595075

  13. Tuning the polarity of charge transport in InSb nanowires via heat treatment

    NASA Astrophysics Data System (ADS)

    Hnida, Katarzyna E.; Bä?ler, Svenja; Akinsinde, Lewis; Gooth, Johannes; Nielsch, Kornelius; Socha, Robert P.; ?aszcz, Adam; Czerwinski, Andrzej; Sulka, Grzegorz D.

    2015-07-01

    InSb nanowire (NW) arrays were prepared by pulsed electrodeposition combined with a porous template technique. The resulting polycrystalline material has a stoichiometric composition (In:Sb = 1:1) and a high length-to-diameter ratio. Based on a combination of Fourier transform infrared spectroscopy (FTIR) analysis and field-effect measurements, the band gap, the charge carrier polarity, the carrier concentration, the mobility and the effective mass for the InSb NWs was investigated. In this preliminary work, a transition from p-type to n-type charge transport was observed when the InSb NWs were subjected to annealing.

  14. Tuning the polarity of charge transport in InSb nanowires via heat treatment.

    PubMed

    Hnida, Katarzyna E; Bä?ler, Svenja; Akinsinde, Lewis; Gooth, Johannes; Nielsch, Kornelius; Socha, Robert P; ?aszcz, Adam; Czerwinski, Andrzej; Sulka, Grzegorz D

    2015-07-17

    InSb nanowire (NW) arrays were prepared by pulsed electrodeposition combined with a porous template technique. The resulting polycrystalline material has a stoichiometric composition (In:Sb = 1:1) and a high length-to-diameter ratio. Based on a combination of Fourier transform infrared spectroscopy (FTIR) analysis and field-effect measurements, the band gap, the charge carrier polarity, the carrier concentration, the mobility and the effective mass for the InSb NWs was investigated. In this preliminary work, a transition from p-type to n-type charge transport was observed when the InSb NWs were subjected to annealing. PMID:26112309

  15. The mitochondrial dicarboxylate and 2-oxoglutarate carriers do not transport glutathione.

    PubMed

    Booty, Lee M; King, Martin S; Thangaratnarajah, Chancievan; Majd, Homa; James, Andrew M; Kunji, Edmund R S; Murphy, Michael P

    2015-02-27

    Glutathione carries out vital protective roles within mitochondria, but is synthesised in the cytosol. Previous studies have suggested that the mitochondrial dicarboxylate and 2-oxoglutarate carriers were responsible for glutathione uptake. We set out to characterise the putative glutathione transport by using fused membrane vesicles of Lactococcus lactis overexpressing the dicarboxylate and 2-oxoglutarate carriers. Although transport of the canonical substrates could be measured readily, an excess of glutathione did not compete for substrate uptake nor could transport of glutathione be measured directly. Thus these mitochondrial carriers do not transport glutathione and the identity of the mitochondrial glutathione transporter remains unknown. PMID:25637873

  16. Impedance spectroscopy of organic hetero-layer OLEDs as a probe for charge carrier injection and device degradation

    Microsoft Academic Search

    Stefan Nowy; Wei Ren; Julia Wagner; Josef A. Weber; Wolfgang Brütting

    2009-01-01

    Impedance spectroscopy (IS) is a powerful method for characterizing the electrical properties of materials and their interfaces. In this study we use IS to investigate the charge carrier injection properties of different anodes and anode treatments in bottom-emitting organic light-emitting diodes (OLEDs). These are ITO-based (indium tin oxide) hetero-layer devices with TPD (N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4-diamine) as hole transporting layer (HTL) and Alq3

  17. The Impact of Donor-Acceptor Phase Separation on the Charge Carrier Dynamics in pBTTT:PCBM Photovoltaic Blends.

    PubMed

    Gehrig, Dominik W; Howard, Ian A; Sweetnam, Sean; Burke, Timothy M; McGehee, Michael D; Laquai, Frédéric

    2015-06-01

    The effect of donor-acceptor phase separation, controlled by the donor-acceptor mixing ratio, on the charge generation and recombination dynamics in pBTTT-C14:PC70 BM bulk heterojunction photovoltaic blends is presented. Transient absorption (TA) spectroscopy spanning the dynamic range from pico- to microseconds in the visible and near-infrared spectral regions reveals that in a 1:1 blend exciton dissociation is ultrafast; however, charges cannot entirely escape their mutual Coulomb attraction and thus predominantly recombine geminately on a sub-ns timescale. In contrast, a polymer:fullerene mixing ratio of 1:4 facilitates the formation of spatially separated, that is free, charges and reduces substantially the fraction of geminate charge recombination, in turn leading to much more efficient photovoltaic devices. This illustrates that spatially extended donor or acceptor domains are required for the separation of charges on an ultrafast timescale (<100 fs), indicating that they are not only important for efficient charge transport and extraction, but also critically influence the initial stages of free charge carrier formation. PMID:25857289

  18. Extraction of carrier transport parameters from hydrogenated amorphous and nanocrystalline silicon solar cells

    Microsoft Academic Search

    Baojie Yan; Guozhen Yue; Laura Sivec; Jeffrey Yang; Subhendu Guha

    2009-01-01

    Transport properties are very important for solar cells. The efficiency of solar cells is determined by the competition of carrier collection and recombination. The most important parameter is the carrier mobility-lifetime product. However, methods commonly used for measuring transport parameters require specially designed samples. The results are often not easily correlated to solar cell performance. In this paper, we present

  19. Coupling of carriers injection and charges distribution in Schottky barrier charge-trapping memories using source-side electrons programming

    NASA Astrophysics Data System (ADS)

    Luo, Yan-Xiang; Shih, Chun-Hsing

    2014-11-01

    This study elucidates the coupling of Schottky barriers and trapped charges involved in the source-side electrons programming and two-bit/cell reading of the Schottky barrier charge-trapping cells. Two-dimensional numerical iterations were employed to examine the distribution of electron injections and trapped charges, and to discuss the differences of physical mechanisms between the Schottky barrier and conventional cells. In the Schottky barrier cells, both the conduction and injection of electron carriers depend on the Schottky source barrier lowering. The source-side trapped charges alter the source-side lateral field distribution, reducing the maximum of the lateral electric field, and moving the subsequent injections away from the source edge. The distribution of total trapped-charges is considerably wider than that of the initial injection. However, because of source-side conduction, the excellent screening of second-bit effect is beneficial to operate the NOR-type multibit/cell charge-trapping memories.

  20. Critical Slowing Down of the Charge Carrier Dynamics at the Mott Metal-Insulator Transition

    NASA Astrophysics Data System (ADS)

    Hartmann, Benedikt; Zielke, David; Polzin, Jana; Sasaki, Takahiko; Müller, Jens

    2015-05-01

    We report on the dramatic slowing down of the charge carrier dynamics in a quasi-two-dimensional organic conductor, which can be reversibly tuned through the Mott metal-insulator transition (MIT). At the finite-temperature critical end point, we observe a divergent increase of the resistance fluctuations accompanied by a drastic shift of spectral weight to low frequencies, demonstrating the critical slowing down of the order parameter (doublon density) fluctuations. The slow dynamics is accompanied by non-Gaussian fluctuations, indicative of correlated charge carrier dynamics. A possible explanation is a glassy freezing of the electronic system as a precursor of the Mott MIT.

  1. Characterization of charge carrier lateral conduction in irradiated dielectric materials

    NASA Astrophysics Data System (ADS)

    Hanna, R.; Paulmier, T.; Belhaj, M.; Molinie, P.; Dirassen, B.; Payan, D.; Balcon, N.

    2011-11-01

    A characterization method for surface charging analysis on insulators submitted to electron irradiation has been developed. This method, based on the use of two Kelvin probes (KPs), provides details on the transit time motion for injection of both holes and electrons. It can also be used to assess the isotropy of lateral electrical conduction on the sample. The feasibility of this method was tested on fluorinated ethylene propylene (Teflon® FEP) samples. It was found that central electron injection induces rapid surface charge spreading, in contrast to injection of holes. An electrical anisotropic behaviour of the sample was also detected.

  2. Charge Transport and Glassy Dynamics in Ionic Liquids

    SciTech Connect

    Sangoro, Joshua R [ORNL; Kremer, Friedrich [University of Leipzig

    2012-01-01

    Ionic liquids (ILs) exhibit unique features such as low melting points, low vapor pressures, wide liquidus temperature ranges, high thermal stability, high ionic conductivity, and wide electrochemical windows. As a result, they show promise for use in variety of applications: as reaction media, in batteries and supercapacitors, in solar and fuel cells, for electrochemical deposition of metals and semiconductors, for protein extraction and crystallization, and many others. Because of the ease with which they can be supercooled, ionic liquids offer new opportunities to investigate long-standing questions regarding the nature of the dynamic glass transition and its possible link to charge transport. Despite the significant steps achieved from experimental and theoretical studies, no generally accepted quantitative theory of dynamic glass transition to date has been capable of reproducing all the experimentally observed features. In this Account, we discuss recent studies of the interplay between charge transport and glassy dynamics in ionic liquids as investigated by a combination of several experimental techniques including broadband dielectric spectroscopy, pulsed field gradient nuclear magnetic resonance, dynamic mechanical spectroscopy, and differential scanning calorimetry. Based on EinsteinSmoluchowski relations, we use dielectric spectra of ionic liquids to determine diffusion coefficients in quantitative agreement with independent pulsed field gradient nuclear magnetic resonance measurements, but spanning a broader range of more than 10 orders of magnitude. This approach provides a novel opportunity to determine the electrical mobility and effective number density of charge carriers as well as their types of thermal activation from the measured dc conductivity separately. We also unravel the origin of the remarkable universality of charge transport in different classes of glass-forming ionic liquids.

  3. Transport in charged colloids driven by thermoelectricity.

    PubMed

    Würger, Alois

    2008-09-01

    We study the thermal diffusion coefficient D{T} of a charged colloid in a temperature gradient, and find that it is to a large extent determined by the thermoelectric response of the electrolyte solution. The thermally induced salinity gradient leads in general to a strong increase with temperature. The difference of the heat of transport of coions and counterions gives rise to a thermoelectric field that drives the colloid to the cold or to the warm, depending on the sign of its charge. Our results provide an explanation for recent experimental findings on thermophoresis in colloidal suspensions. PMID:18851262

  4. Transport in Charged Colloids Driven by Thermoelectricity

    E-print Network

    Alois Würger

    2014-01-29

    We study the thermal diffusion coefficient DT of a charged colloid in a temperature gradient, and find that it is to a large extent determined by the thermoelectric response of the electrolyte solution. The thermally induced salinity gradient leads in general to a strong increase with temperature. The difference of the heat of transport of coions and counterions gives rise to a thermoelectric field that drives the colloid to the cold or to the warm, depending on the sign of its charge. Our results provide an explanation for recent experimental findings on thermophoresis in colloidal suspensions.

  5. Characterization of charge carrier lateral conduction in irradiated dielectric materials

    Microsoft Academic Search

    R. Hanna; T. Paulmier; M. Belhaj; P. Molinie; B. Dirassen; D. Payan; N. Balcon

    2011-01-01

    A characterization method for surface charging analysis on insulators submitted to electron irradiation has been developed. This method, based on the use of two Kelvin probes (KPs), provides details on the transit time motion for injection of both holes and electrons. It can also be used to assess the isotropy of lateral electrical conduction on the sample. The feasibility of

  6. Charge transport and injection in amorphous organic electronic materials

    Microsoft Academic Search

    Shing Chi Tse

    2007-01-01

    This thesis presents how we use various measuring techniques to study the charge transport and injection in organic electronic materials. Understanding charge transport and injection properties in organic solids is of vital importance for improving performance characteristics of organic electronic devices, including organic-light-emitting diodes (OLEDs), photovoltaic cells (OPVs), and field effect transistors (OFETs). The charge transport properties of amorphous organic

  7. Variational multiscale models for charge transport.

    PubMed

    Wei, Guo-Wei; Zheng, Qiong; Chen, Zhan; Xia, Kelin

    2012-01-01

    This work presents a few variational multiscale models for charge transport in complex physical, chemical and biological systems and engineering devices, such as fuel cells, solar cells, battery cells, nanofluidics, transistors and ion channels. An essential ingredient of the present models, introduced in an earlier paper (Bulletin of Mathematical Biology, 72, 1562-1622, 2010), is the use of differential geometry theory of surfaces as a natural means to geometrically separate the macroscopic domain from the microscopic domain, meanwhile, dynamically couple discrete and continuum descriptions. Our main strategy is to construct the total energy functional of a charge transport system to encompass the polar and nonpolar free energies of solvation, and chemical potential related energy. By using the Euler-Lagrange variation, coupled Laplace-Beltrami and Poisson-Nernst-Planck (LB-PNP) equations are derived. The solution of the LB-PNP equations leads to the minimization of the total free energy, and explicit profiles of electrostatic potential and densities of charge species. To further reduce the computational complexity, the Boltzmann distribution obtained from the Poisson-Boltzmann (PB) equation is utilized to represent the densities of certain charge species so as to avoid the computationally expensive solution of some Nernst-Planck (NP) equations. Consequently, the coupled Laplace-Beltrami and Poisson-Boltzmann-Nernst-Planck (LB-PBNP) equations are proposed for charge transport in heterogeneous systems. A major emphasis of the present formulation is the consistency between equilibrium LB-PB theory and non-equilibrium LB-PNP theory at equilibrium. Another major emphasis is the capability of the reduced LB-PBNP model to fully recover the prediction of the LB-PNP model at non-equilibrium settings. To account for the fluid impact on the charge transport, we derive coupled Laplace-Beltrami, Poisson-Nernst-Planck and Navier-Stokes equations from the variational principle for chemo-electro-fluid systems. A number of computational algorithms is developed to implement the proposed new variational multiscale models in an efficient manner. A set of ten protein molecules and a realistic ion channel, Gramicidin A, are employed to confirm the consistency and verify the capability. Extensive numerical experiment is designed to validate the proposed variational multiscale models. A good quantitative agreement between our model prediction and the experimental measurement of current-voltage curves is observed for the Gramicidin A channel transport. This paper also provides a brief review of the field. PMID:23172978

  8. Elastic tunneling charge transport mechanisms in silicon quantum dots / Si O 2 thin films and superlattices

    NASA Astrophysics Data System (ADS)

    Illera, S.; Prades, J. D.; Cirera, A.

    2015-05-01

    The role of different charge transport mechanisms in Si / Si O 2 structures has been studied. A theoretical model based on the Transfer Hamiltonian Formalism has been developed to explain experimental current trends in terms of three different elastic tunneling processes: (1) trap assisted tunneling; (2) transport through an intermediate quantum dot; and (3) direct tunneling between leads. In general, at low fields carrier transport is dominated by the quantum dots whereas, for moderate and high fields, transport through deep traps inherent to the SiO2 is the most relevant process. Besides, current trends in Si / Si O 2 superlattice structure have been properly reproduced.

  9. 41 CFR 301-72.100 - What must my travel accounting system do in relation to common carrier transportation?

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... false What must my travel accounting system do in relation to common...COMMON CARRIER TRANSPORTATION Accounting for Common Carrier Transportation...301-72.100 What must my travel accounting system do in relation to...

  10. 41 CFR 301-72.100 - What must my travel accounting system do in relation to common carrier transportation?

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... false What must my travel accounting system do in relation to common...COMMON CARRIER TRANSPORTATION Accounting for Common Carrier Transportation...301-72.100 What must my travel accounting system do in relation to...

  11. 41 CFR 301-72.100 - What must my travel accounting system do in relation to common carrier transportation?

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... false What must my travel accounting system do in relation to common...COMMON CARRIER TRANSPORTATION Accounting for Common Carrier Transportation...301-72.100 What must my travel accounting system do in relation to...

  12. 41 CFR 301-72.100 - What must my travel accounting system do in relation to common carrier transportation?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...2012-07-01 true What must my travel accounting system do in relation to common...COMMON CARRIER TRANSPORTATION Accounting for Common Carrier Transportation...301-72.100 What must my travel accounting system do in relation to...

  13. 41 CFR 301-72.100 - What must my travel accounting system do in relation to common carrier transportation?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... false What must my travel accounting system do in relation to common...COMMON CARRIER TRANSPORTATION Accounting for Common Carrier Transportation...301-72.100 What must my travel accounting system do in relation to...

  14. Mapping the spatial distribution of charge carriers in quantum-confined heterostructures

    PubMed Central

    Smith, Andrew M.; Lane, Lucas A.; Nie, Shuming

    2014-01-01

    Quantum-confined nanostructures are considered ‘artificial atoms’ because the wavefunctions of their charge carriers resemble those of atomic orbitals. For multiple-domain heterostructures, however, carrier wavefunctions are more complex and still not well understood. We have prepared a unique series of cation-exchanged HgxCd1?xTe quantum dots (QDs) and seven epitaxial core–shell QDs and measured their first and second exciton peak oscillator strengths as a function of size and chemical composition. A major finding is that carrier locations can be quantitatively mapped and visualized during shell growth or cation exchange simply using absorption transition strengths. These results reveal that a broad range of quantum heterostructures with different internal structures and band alignments exhibit distinct carrier localization patterns that can be used to further improve the performance of optoelectronic devices and enhance the brightness of QD probes for bioimaging. PMID:25080298

  15. Mapping the spatial distribution of charge carriers in quantum-confined heterostructures.

    PubMed

    Smith, Andrew M; Lane, Lucas A; Nie, Shuming

    2014-01-01

    Quantum-confined nanostructures are considered 'artificial atoms' because the wavefunctions of their charge carriers resemble those of atomic orbitals. For multiple-domain heterostructures, however, carrier wavefunctions are more complex and still not well understood. We have prepared a unique series of cation-exchanged Hg(x)Cd(1-x)Te quantum dots (QDs) and seven epitaxial core-shell QDs and measured their first and second exciton peak oscillator strengths as a function of size and chemical composition. A major finding is that carrier locations can be quantitatively mapped and visualized during shell growth or cation exchange simply using absorption transition strengths. These results reveal that a broad range of quantum heterostructures with different internal structures and band alignments exhibit distinct carrier localization patterns that can be used to further improve the performance of optoelectronic devices and enhance the brightness of QD probes for bioimaging. PMID:25080298

  16. Mapping the spatial distribution of charge carriers in quantum-confined heterostructures

    NASA Astrophysics Data System (ADS)

    Smith, Andrew M.; Lane, Lucas A.; Nie, Shuming

    2014-07-01

    Quantum-confined nanostructures are considered ‘artificial atoms’ because the wavefunctions of their charge carriers resemble those of atomic orbitals. For multiple-domain heterostructures, however, carrier wavefunctions are more complex and still not well understood. We have prepared a unique series of cation-exchanged HgxCd1-xTe quantum dots (QDs) and seven epitaxial core-shell QDs and measured their first and second exciton peak oscillator strengths as a function of size and chemical composition. A major finding is that carrier locations can be quantitatively mapped and visualized during shell growth or cation exchange simply using absorption transition strengths. These results reveal that a broad range of quantum heterostructures with different internal structures and band alignments exhibit distinct carrier localization patterns that can be used to further improve the performance of optoelectronic devices and enhance the brightness of QD probes for bioimaging.

  17. Subsurface Imaging and Sensing of Charge Carrier Movements in the Earth's Crust

    Microsoft Academic Search

    R. Dahlgren; F. T. Freund; M. Lazarus; J. S. Wang; D. Rekenthaler; R. D. Peters; G. Duma

    2009-01-01

    The DUSEL facility will enable unique opportunities for field experiments that would otherwise not be possible at surface facilities (Lesko, K.T., TAUP, 2007) and support a host of undergraduate and graduate educational projects. In this presentation, some of the proposed geophysics experiments will be described as part of the subsurface Imaging and Sensing (SIS) project to study charge carrier movement

  18. Nonequilibrium population of charge carriers in structures with InGaN deep quantum dots

    SciTech Connect

    Sizov, D. S., E-mail: Dsizov@mail.ioffe.ru; Zavarin, E. E.; Ledentsov, N. N.; Lundin, V. V.; Musikhin, Yu. G.; Sizov, V. S.; Suris, R. A.; Tsatsul'nikov, A. F. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation)

    2007-05-15

    Electronic and optical properties of ensembles of quantum dots with various energies of activation from the ground-state level to the continuous-spectrum region were studied theoretically and experimentally with the InGaN quantum dots as an example. It is shown that, depending on the activation energy, both the quasi-equilibrium statistic of charge carriers at the levels of quantum dots and nonequilibrium statistic at room temperature are possible. In the latter case, the position of the maximum in the emission spectrum is governed by the value of the demarcation transition: the quantum dots with the transition energy higher than this value feature the quasi-equilibrium population of charge carriers, while the quantum dots with the transition energy lower than the demarcation-transition energy feature the nonequilibrium population. A model based on kinetic equations was used in the theoretical analysis. The key parameters determining the statistic are the parameters of thermal ejection of charge carriers; these parameters depend exponentially on the activation energy. It is shown experimentally that the use of stimulated phase decomposition makes it possible to appreciably increase the activation energy. In this case, the thermal-activation time is found to be much longer than the recombination time for an electron-hole pair, which suppresses the redistribution of charge carriers between the quantum dots and gives rise to the nonequilibrium population. The effect of nonequilibrium population on the luminescent properties of the structures with quantum dots is studied in detail.

  19. A photoconductivity cell for investigating charge-carrier injection at electrolyte-solid interfaces

    Microsoft Academic Search

    J. Cairns; T. F. Evans; R. A. Hann; G. Read; D. R. Rosseinsky

    1973-01-01

    The cell described is used for measuring dark and light current through thin organic crystals and similar specimens and for studying the charge carrier injection into these materials from the electrolytes which provide the electrical contacts with the specimens. The cell can be used with degassed solutions.

  20. Spin-polarized charge carrier injection by tunneling from ferromagnetic contacts into organic semiconductors

    Microsoft Academic Search

    M. Yunus; P. P. Ruden; D. L. Smith

    2010-01-01

    Tunnel-injection of spin-polarized charge carriers from ferromagnetic contacts into organic semiconductors is modeled. Tunneling matrix elements and transition rates for the two spin types are calculated using a transfer Hamiltonian. The tunneling process occurs between extended states of the contact and model ``molecular'' orbitals. We explore the effects of the tunnel barrier height and of the ferromagnetic contact's Fermi wave

  1. Spin-polarized charge carrier injection by tunneling from ferromagnetic metals into organic semiconductors

    Microsoft Academic Search

    Mohammad Yunus; P. Paul Ruden; Darryl L. Smith

    2010-01-01

    Efficient spin-polarized charge carrier injection from a ferromagnetic metal (FM) into a semiconductor is a challenging task. Because of the large differences between the conductivities of metals and semiconductors a spin-dependent injection mechanism, such as tunneling, is a critical requirement. We discuss a new model for such a mechanism for the specific case of organic semiconductors (OS), such as conjugated

  2. Monte Carlo Simulation of Charge Carrier Injection in Twin Flash Memory Devices during Program and Erase

    Microsoft Academic Search

    R. Hagenbeckl; S. Decker; P. Haibachl; C. Jungemann; T. Mikolajick; G. Tempel; M. Isler; B. Meinerzhagen

    2006-01-01

    An iterative and time-dependent simulation method based on a full band Monte Carlo algorithm is presented to describe the injection behavior of hot electrons and holes during program and erase of Twin flashtrade memory cells. Secondaries during programming and the feedback of already injected and trapped charge carriers in the ONO nitride on subsequent injection processes are taken into account.

  3. Effect of a High-kappa Environment on Charge Carrier Mobility in Graphene

    Microsoft Academic Search

    L. A. Ponomarenko; R. Yang; T. M. Mohiuddin; M. I. Katsnelson; K. S. Novoselov; S. V. Morozov; A. A. Zhukov; F. Schedin; E. W. Hill; A. K. Geim

    2009-01-01

    It is widely assumed that the dominant source of scattering in graphene is charged impurities in a substrate. We have tested this conjecture by studying graphene placed on various substrates and in high-kappa media. Unexpectedly, we have found no significant changes in carrier mobility either for different substrates or by using glycerol, ethanol, and water as a top dielectric layer.

  4. New charge-carrier blocking materials for high efficiency OLEDs

    Microsoft Academic Search

    Vadim I. Adamovich; Steven R. Cordero; Peter I. Djurovich; Arnold Tamayo; Mark E. Thompson; Brian W. D’Andrade; Stephen R. Forrest

    2003-01-01

    Three strategies for preparing high efficiency OLEDs are demonstrated, which involve the use of hole and electron blocking layers. The first of these strategies involves the use of a cyclometallated iridium compound (bis(2-(4,6-difluorophenyl)pyridyl-N,C2?)iridium(III) picolinate, FIrpic) as a hole-blocking material for green and blue emissive OLEDs. Devices which utilized FIrpic as a combined hole blocking and electron transporting layer gave external

  5. The nature of charge carriers in high-temperature superconductors

    NASA Astrophysics Data System (ADS)

    Azzouz, Mohamed

    2004-03-01

    Experimental data from Hall effect measurements on cuprate superconductors remain unexplained despite tremendous efforts by both theorists and experimentalists. The Hall coefficient displays a very unusual temperature dependence which cannot be interpreted in the framework of the Fermi-liquid theory. Recently, I proposed that this unusual temperature dependence may be explained by assuming that the copper-oxygen layers form open systems in contact with a charge reservoir. The latter consists of the atoms doped between these layers. In this talk, I will explain this idea, and present some of its very interesting consequences. The results are found using the Rotating Antiferromagnetism Theory.

  6. Dust Charging and Transport on Surfaces

    NASA Astrophysics Data System (ADS)

    Wang, X.; Robertson, S.; Horányi, M.

    2011-11-01

    In this paper, we review laboratory studies of dust transport on surfaces in plasmas, performed for a number of different mechanisms: 1) Dust particles were levitated in plasma sheaths by electrostatic forces balancing the gravitational force. 2) Dust was observed to spread over and lift off a surface that repels electrons in a plasma. 3) Dust was transported on surfaces having different secondary electron yields in plasma with an electron beam as a consequence of differential charging. 4) We also report a mechanism of dust transport by electric fields occurring at electron beam impact/shadow boundaries. These processes are candidates to explain the formation of dust ponds that were recently observed in craters on the asteroid Eros by the NEAR Shoemaker spacecraft.

  7. Dust Charging and Transport on Surfaces

    SciTech Connect

    Wang, X. [Colorado Center for Lunar Dust And Atmospheric Studies, University of Colorado, Boulder, CO 80309 (United States); Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80309 (United States); Robertson, S. [Colorado Center for Lunar Dust And Atmospheric Studies, University of Colorado, Boulder, CO 80309 (United States); Department of Physics, University of Colorado, Boulder, CO 80309 (United States); Horanyi, M. [Colorado Center for Lunar Dust And Atmospheric Studies, University of Colorado, Boulder, CO 80309 (United States); Department of Physics, University of Colorado, Boulder, CO 80309 (United States); Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80309 (United States)

    2011-11-29

    In this paper, we review laboratory studies of dust transport on surfaces in plasmas, performed for a number of different mechanisms: 1) Dust particles were levitated in plasma sheaths by electrostatic forces balancing the gravitational force. 2) Dust was observed to spread over and lift off a surface that repels electrons in a plasma. 3) Dust was transported on surfaces having different secondary electron yields in plasma with an electron beam as a consequence of differential charging. 4) We also report a mechanism of dust transport by electric fields occurring at electron beam impact/shadow boundaries. These processes are candidates to explain the formation of dust ponds that were recently observed in craters on the asteroid Eros by the NEAR Shoemaker spacecraft.

  8. Studies of the mobility of charge carriers in low-dimensional systems in a transverse DC electric field

    SciTech Connect

    Sinyavskii, E. P., E-mail: sinyavskii@gmail.com [Academy of Sciences of Moldova, Institute of Applied Physics (Moldova, Republic of); Karapetyan, S. A., E-mail: karapetyan.sa@gmail.com [Shevchenko Pridnestrovskii State University (Moldova, Republic of)

    2011-08-15

    The mobility of charge carriers {mu} in a parabolic quantum well in an electric field E directed along the size-confinement axis is calculated. With consideration for scattering of charge carriers at a rough surface, the mobility {mu} is shown to decrease with increasing E. A physical interpretation of this effect is proposed.

  9. Charge carriers in alkaline direct oxidation fuel cells Liang An, T. S. Zhao,* Yinshi Li and Qixing Wu

    E-print Network

    Zhao, Tianshou

    Charge carriers in alkaline direct oxidation fuel cells Liang An, T. S. Zhao,* Yinshi Li and Qixing to conventional wisdom, this study demonstrates that the main charge carrier of alkaline direct oxidation fuel,2 However, in alkaline direct oxidation fuel cells (DOFCs) running on various fuels (including methanol

  10. Charge transport in organic crystals: role of disorder and topological connectivity.

    PubMed

    Vehoff, Thorsten; Baumeier, Björn; Troisi, Alessandro; Andrienko, Denis

    2010-08-25

    We analyze the relationship among the molecular structure, morphology, percolation network, and charge carrier mobility in four organic crystals: rubrene, indolo[2,3-b]carbazole with CH(3) side chains, and benzo[1,2-b:4,5-b']bis[b]benzothiophene derivatives with and without C(4)H(9) side chains. Morphologies are generated using an all-atom force field, while charge dynamics is simulated within the framework of high-temperature nonadiabatic Marcus theory or using semiclassical dynamics. We conclude that, on the length scales reachable by molecular dynamics simulations, the charge transport in bulk molecular crystals is mostly limited by the dynamic disorder, while in self-assembled monolayers the static disorder, which is due to the slow motion of the side chains, enhances charge localization and influences the transport dynamics. We find that the presence of disorder can either reduce or increase charge carrier mobility, depending on the dimensionality of the charge percolation network. The advantages of charge transporting materials with two- or three-dimensional networks are clearly shown. PMID:20666495

  11. Energy Models for One-Carrier Transport in Semiconductor Devices

    NASA Technical Reports Server (NTRS)

    Jerome, Joseph W.; Shu, Chi-Wang

    1991-01-01

    Moment models of carrier transport, derived from the Boltzmann equation, made possible the simulation of certain key effects through such realistic assumptions as energy dependent mobility functions. This type of global dependence permits the observation of velocity overshoot in the vicinity of device junctions, not discerned via classical drift-diffusion models, which are primarily local in nature. It was found that a critical role is played in the hydrodynamic model by the heat conduction term. When ignored, the overshoot is inappropriately damped. When the standard choice of the Wiedemann-Franz law is made for the conductivity, spurious overshoot is observed. Agreement with Monte-Carlo simulation in this regime required empirical modification of this law, or nonstandard choices. Simulations of the hydrodynamic model in one and two dimensions, as well as simulations of a newly developed energy model, the RT model, are presented. The RT model, intermediate between the hydrodynamic and drift-diffusion model, was developed to eliminate the parabolic energy band and Maxwellian distribution assumptions, and to reduce the spurious overshoot with physically consistent assumptions. The algorithms employed for both models are the essentially non-oscillatory shock capturing algorithms. Some mathematical results are presented and contrasted with the highly developed state of the drift-diffusion model.

  12. Exciton transport, charge extraction, and loss mechanisms in organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Scully, Shawn Ryan

    Organic photovoltaics have attracted significant interest over the last decade due to their promise as clean low-cost alternatives to large-scale electric power generation such as coal-fired power, natural gas, and nuclear power. Many believe power conversion efficiency targets of 10-15% must be reached before commercialization is possible. Consequently, understanding the loss mechanisms which currently limit efficiencies to 4-5% is crucial to identify paths to reach higher efficiencies. In this work, we investigate the dominant loss mechanisms in some of the leading organic photovoltaic architectures. In the first class of architectures, which include planar heterojunctions and bulk heterojunctions with large domains, efficiencies are primarily limited by the distance photogenerated excitations (excitons) can be transported (termed the exciton diffusion length) to a heterojunction where the excitons may dissociate. We will discuss how to properly measure the exciton diffusion length focusing on the effects of optical interference and of energy transfer when using fullerenes as quenching layers and show how this explains the variety of diffusion lengths reported for the same material. After understanding that disorder and defects limit exciton diffusion lengths, we suggest some approaches to overcome this. We then extensively investigate the use of long-range resonant energy transfer to increase exciton harvesting. Using simulations and experiments as support, we discuss how energy transfer can be engineered into architectures to increase the distance excitons can be harvested. In an experimental model system, DOW Red/PTPTB, we will show how the distance excitons are harvested can be increased by almost an order of magnitude up to 27 nm from a heterojunction and give design rules and extensions of this concept for future architectures. After understanding exciton harvesting limitations we will look at other losses that are present in planar heterojunctions. One of the primary losses that puts stringent requirements on the charge carrier mobilities in these cells is the recombination losses due to space charge build up at the heterojunction. Because electrons are confined to the acceptor and holes to the donor, net charge density always exists even when mobilities are matched, in contrast to bulk heterojunctions wherein matched mobilities lead to zero net charge. This net charge creates an electric field which opposes the built-in field and limits the current that can be carried away from this heterojunction. Using simulations we show that for relevant current densities charge carrier mobilities must be higher than 10-4 cm2/V.s to avoid significant losses due to space charge formation. In the last part of this work, we will focus on the second class of architectures in which exciton harvesting is efficient. We will present a systematic analysis of one of the leading polymer:fullerene bulk heterojunction cells to show that losses in this architecture are due to charge recombination. Using optical measurements and simulations, exciton harvesting measurements, and device characteristics we will show that the dominant loss is likely due to field-dependent geminate recombination of the electron and hole pair created immediately following exciton dissociation. No losses in this system are seen due to bimolecular recombination or space charge which provides information on charge-carrier mobility targets necessary for the future design of high efficiency organic photovoltaics.

  13. Charge and Spin Transport in Dilute Magnetic Semiconductors

    SciTech Connect

    Ullrich, Carsten A.

    2009-07-23

    This proposal to the DOE outlines a three-year plan of research in theoretical and computational condensed-matter physics, with the aim of developing a microscopic theory for charge and spin dynamics in disordered materials with magnetic impurities. Important representatives of this class of materials are the dilute magnetic semiconductors (DMS), which have attracted great attention as a promising basis for spintronics devices. There is an intense experimental effort underway to study the transport properties of ferromagnetic DMS such as (Ga,Mn)As, and a number of interesting features have emerged: negative magnetoresistance, anomalous Hall effect, non-Drude dynamical conductivity, and resistivity maxima at the Curie temperature. Available theories have been able to account for some of these features, but at present we are still far away from a systematic microscopic understanding of transport in DMS. We propose to address this challenge by developing a theory of charge and spin dynamics based on a combination of the memory-function formalism and time-dependent density functional theory. This approach will be capable of dealing with two important issues: (a) the strong degree of correlated disorder in DMS, close to the localization transition (which invalidates the usual relaxation-time approximation to the Boltzmann equation), (b) the essentially unknown role of dynamical many-body effects such as spin Coulomb drag. We will calculate static and dynamical conductivities in DMS as functions of magnetic order and carrier density, which will advance our understanding of recent transport and infrared absorption measurements. Furthermore, we will study collective plasmon excitations in DMS (3D, 2D and quantum wells), whose linewidths could constitute a new experimental probe of the correlation of disorder, many-body effects and charge and spin dynamics in these materials.

  14. Non-Markovian stochastic Schrödinger equation at finite temperatures for charge carrier dynamics in organic crystals

    NASA Astrophysics Data System (ADS)

    Zhong, Xinxin; Zhao, Yi

    2013-01-01

    A new non-Markovian stochastic Schrödinger equation at finite temperatures is presented to correctly describe charge carrier dynamics in organic molecular crystals. The electron-phonon interactions in both site energies and electronic couplings are incorporated by the time-dependent complex-valued random fluctuations which are generated from corresponding spectral density functions. The approach is thus easily extended to investigate coherent-to-hopping charge transfer in systems with thousands of molecular sites. The capability of present approach is demonstrated by numerical simulations of carrier dynamics in the spin-boson model and a realistic Fenna-Matthews-Olson complex. The results manifest that the non-Markovian effect and complex-valued random forces are essential to guarantee the detailed balance. In an application to a long-chain donor-acceptor system, it is also interesting to find a property of coherent-to-hopping charge transfer from temperature dependence of diffusion coefficients.

  15. A novel method of identifying the carrier transport path in metal oxide resistive random access memory

    NASA Astrophysics Data System (ADS)

    Lu, Nianduan; Li, Ling; Sun, Pengxiao; Wang, Ming; Liu, Qi; Lv, Hangbing; Long, Shibing; Liu, Ming

    2015-02-01

    Characterization of defect energy levels is of crucial importance to understand the carrier transport and conduction mechanism of a conducting filament. Currently, it is difficult to probe the defect energy level of a conducting filament in random access memory (RRAM) by experiment. Based on the activation energy of carrier transport from the first-principles calculations, we present a physical model correlating macroscopic I–V characteristics with material microstructure to analyze the defect energy level of a conducting filament in metal oxide RRAM. The carrier transport path in the conducting filament can be specially extracted using the defect energy level.

  16. Exploring carrier transport phenomena in a CVD-assembled graphene FET on hexagonal boron nitride

    NASA Astrophysics Data System (ADS)

    Kim, Edwin; Jain, Nikhil; Jacobs-Gedrim, Robin; Xu, Yang; Yu, Bin

    2012-03-01

    The supporting substrate plays a crucial role in preserving the superb electrical characteristics of an atomically thin 2D carbon system. We explore carrier transport behavior in a chemical-vapor-deposition- (CVD-) assembled graphene monolayer on hexagonal boron nitride (h-BN) substrate. Graphene-channel field-effect transistors (GFETs) were fabricated on ultra-thin h-BN multilayers to screen out carrier scattering from the underlying SiO2 substrate. To explore the transport phenomena, we use three different approaches to extract carrier mobility, namely, effective carrier mobility (?eff), intrinsic carrier mobility (?), and field-effect mobility (?FE). A comparative study has been conducted based on the electrical characterization results, uncovering the impacts of supporting substrate material and device geometry scaling on carrier mobility in GFETs with CVD-assembled graphene as the active channel.

  17. Exploring carrier transport phenomena in a CVD-assembled graphene FET on hexagonal boron nitride.

    PubMed

    Kim, Edwin; Jai, Nikhil; Jacobs-Gedri, Robin; Xu, Yang; Yu, Bin

    2012-03-30

    The supporting substrate plays a crucial role in preserving the superb electrical characteristicsof an atomically thin 2D carbon system. We explore carrier transport behavior in achemical-vapor-deposition- (CVD-) assembled graphene monolayer on hexagonal boron nitride (h-BN) substrate. Graphene-channel field-effect transistors (GFETs) were fabricated on ultra-thin h-BN multilayers to screen out carrier scattering from the underlying SiO2 substrate. To explore the transport phenomena, we use three different approaches to extract carrier mobility, namely, effective carrier mobility (?FE), intrinsic carrier mobility (?), and field-effect mobility (?FE). A comparative study has been conducted based on the electrical characterization results, uncovering the impacts of supporting substrate material and device geometry scaling on carrier mobility in GFETs with CVD-assembled graphene as the active channel. PMID:22414953

  18. Visualization of charge-carrier propagation in water.

    PubMed

    Klimov, Andrey; Pollack, Gerald H

    2007-11-01

    The electrical properties of water in the region between parallel electrodes were investigated using pH indicator dyes. Different pH values corresponded to different colors, which could be registered by a video camera. Imposition of electrical current was able to produce zones of constant pH around, and well beyond each electrode: extremely low pH around the positive electrode and extremely high pH around the negative electrode. The border between alkaline and acid zones was jagged and separated by only a narrow layer of water with neutral pH. When the water was replaced by various salt solutions, similar zones were observed. Again, passage of current produced large zones of extreme pH values near and beyond each electrode. Alkaline zones appeared to propagate from the negative to the positive electrode in narrow channels through the neutral solution. When the power supply was disconnected from the electrodes and replaced by a resistive load, a potential difference was registered, and current flowed through the resistor for some period of time. Hence, the acid and alkaline zones appear to carry opposite charges throughout their volume. PMID:17939693

  19. On the nature of charge carrier scattering in Ag{sub 2}Se at low temperatures

    SciTech Connect

    Jafarov, M. B., E-mail: cmentiq@box.az [Azerbaijan State Agrarian University (Azerbaijan)

    2010-10-15

    The electric and thermoelectric properties of silver selenide in the temperature range of 4.2-300 K have been studied. The data obtained are interpreted within the theory of one-type carriers and Kane dispersion relation, with allowance for the character of electron-electron interaction. It is established that, for the concentrations n {<=} 7.8 x 10{sup 18} cm{sup -3}, charge carriers are scattered by impurity ions at T {<=} 30 K and by acoustic and optical phonons and point defects at T {>=} 30 K. Electron-electron interactions are found to be elastic at T < 30 K.

  20. Charge transport in ultra thin silicon nitrides

    SciTech Connect

    Kobayashi, Kiyoteru; Teramoto, Akinobu; Hirayama, Makoto [Mitsubishi Electric Corp., Hyogo (Japan). ULSI Lab.

    1995-03-01

    The conduction current in silicon nitride increases even at constant electric field as the nitride thickness is reduced to less than 5 nm in oxide equivalent thickness (t{sub eq}). In order to analyze the charge transport in the ultra thin nitrides less than 5 nm t{sub eq}, the authors measured the thickness and temperature dependence of conduction current through nitrides of 3.4 to 10.2 nm t{sub eq}, in the temperature range from 77 to 398 K. Current increase was observed in both the tunnel emission component, which is thickness dependent, and in the temperature-dependent component. The temperature-dependent current component was dominant at high temperatures and low fields in the ultra thin nitride. The method of separating the electron and hole currents was used for both n and p-channel metal-nitride-silicon transistors, to study the charge transport in nitrides from 3.8 to 8.6 nm t{sub eq}, at 296 and 398 K. The increase in the number of electrons injected into the nitride was larger than the increase in the number of holes injected into the nitride when the nitride thickness was reduced. The increase in electron current flowing out of the nitride was also large compared with the increase in hole current flowing out of the nitride. The authors claim that the contribution of electrons to the total charge transport is increased with the reduction in nitride thickness. Finally, they discussed the dependence of the breakdown field on nitride thickness in oxide/nitride/oxide structures. They claim that top and bottom oxides should be as thin as possible to obtain the high breakdown field.

  1. Dielectric Force Microscopy: Imaging Charge Carriers in Nanomaterials without Electrical Contacts.

    PubMed

    Zhang, Jie; Lu, Wei; Li, Yize Stephanie; Cai, Jinhua; Chen, Liwei

    2015-07-21

    Nanomaterials are increasingly used in electronic, optoelectronic, bioelectronic, sensing, and energy nanodevices. Characterization of electrical properties at nanometer scales thus becomes not only a pursuit in basic science but also of widespread practical need. The conventional field-effect transistor (FET) approach involves making electrical contacts to individual nanomaterials. This approach faces serious challenges in routine characterization due to the small size and the intrinsic heterogeneity of nanomaterials, as well as the difficulties in forming Ohmic contact with nanomaterials. Since the charge carrier polarization in semiconducting and metallic materials dominates their dielectric response to external fields, detecting dielectric polarization is an alternative approach in probing the carrier properties and electrical conductivity in nanomaterials. This Account reviews the challenges in the electrical conductivity characterization of nanomaterials and demonstrates that dielectric force microscopy (DFM) is a powerful tool to address the challenges. DFM measures the dielectric polarization via its force interaction with charges on the DFM tip and thus eliminates the need to make electrical contacts with nanomaterials. Furthermore, DFM imaging provides nanometer-scaled spatial resolution. Single-walled carbon nanotubes (SWNTs) and ZnO nanowires are used as model systems. The transverse dielectric permittivity of SWNTs is quantitatively measured to be ?10, and the differences in longitudinal dielectric polarization are exploited to distinguish metallic SWNTs from semiconducting SWNTs. By application of a gate voltage at the DFM tip, the local carrier concentration underneath the tip can be accumulated or depleted, depending on charge carrier type and the density of states near the Fermi level. This effect is exploited to identify the conductivity type and carrier type in nanomaterials. By making comparison between DFM and FET measurements on the exact same SWNTs, it is found that the DFM gate modulation ratio, which is the ratio of DFM signal strengths at different gate voltage, is linearly proportional to the logarithm of FET device on/off ratio. A Drude-level model is established to explain the semilogarithmic correlation between DFM gate modulation ration and FET device on/off ratio and simulate the dependence of DFM force on charge carrier concentration and mobility. Future developments towards DFM imaging of charge carrier concentration or mobility in nanomaterials and nanodevices can thus be expected. PMID:26061707

  2. Nanoscale Orientation Effects on Carrier Transport in a Low-Band-Gap Polymer

    NASA Astrophysics Data System (ADS)

    Dong, Ban; Huang, Bingyuan; Tan, Aaron; Green, Peter

    2015-03-01

    We show that the out-of-plane hole mobility of the low-band-gap polymer poly[4,8-bis-(2-ethylhexyloxy)-benzo[1,2-b:4,5-b']dithiophene-2,6-diyl-alt-4-(2-ethylhexyloxy-1-one)thieno-[3,4-b]thiophene-2,6-diyl] (PBDTTT-C) is film thickness dependence; and this behavior is associated with the morphology. Due to a geometric confinement and to polymer/substrate interactions, the average orientation of the chains in the thinnest films was predominantly parallel to the substrate. In this thickness range, the out-of-plane hole mobilities ? were necessarily low and ?, a measure of the strength of the field dependence of the mobility, was largest. Within the framework of the Gaussian Disorder model, the relative value of ? suggests that the largest effect of positional disorder on the carrier transport was most significant in the thinnest films. The hole mobility ? increased and depended less on the electric field (? decreases in magnitude) with increasing thickness, due evidently to the increased degree of orientation of the domains with respect to the direction of the field (normal to the interfaces). These findings demonstrated the profound impact of the substrate on the morphology and of the morphology on the charge carrier mobility.

  3. Self-consistent analytical solution of a problem of charge-carrier injection at a conductor\\/insulator interface

    Microsoft Academic Search

    F. Neumann; Y. A. Genenko; C. Melzer; S. V. Yampolskii; H. von Seggern

    2007-01-01

    We present a closed description of the charge-carrier injection process from a conductor into an insulator. Common injection models are based on single electron descriptions, being problematic especially once the amount of charge-carriers injected is large. Accordingly, we developed a model, which incorporates space-charge effects in the description of the injection process. The challenge of this task is the problem

  4. Electrode configuration and signal subtraction technique for single polarity charge carrier sensing in ionization detectors

    DOEpatents

    Luke, P.

    1996-06-25

    An ionization detector electrode and signal subtraction apparatus and method provide at least one first conductive trace formed onto the first surface of an ionization detector. The first surface opposes a second surface of the ionization detector. At least one second conductive trace is also formed on the first surface of the ionization detector in a substantially interlaced and symmetrical pattern with the at least one first conductive trace. Both of the traces are held at a voltage potential of a first polarity type. By forming the traces in a substantially interlaced and symmetric pattern, signals generated by a charge carrier are substantially of equal strength with respect to both of the traces. The only significant difference in measured signal strength occurs when the charge carrier moves to within close proximity of the traces and is received at the collecting trace. The measured signals are then subtracted and compared to quantitatively measure the magnitude of the charge and to determine the position at which the charge carrier originated within the ionization detector. 9 figs.

  5. Study of charge transport in a MOS line

    Microsoft Academic Search

    K. Hoffmann

    1975-01-01

    The principles of operation of a MOS line are considered, taking into account the determination of the surface potential, the derivation of the charge transport equation and its numerical solution, approaches for the reduction of transmission time, and charge losses. An equivalent circuit of a MOS line is presented and the effect of the various parameters on the charge transport

  6. The composite picture of the charge carriers in La2-xSrxCuO4 (0.063 <= x <= 0.11) superconductors

    Microsoft Academic Search

    Y. H. Kim; P. H. Hor; X. L. Dong; F. Zhou; Z. X. Zhao; Y. S. Song; W. X. Ti

    2003-01-01

    Through far-infrared studies of La2-xSrxCuO4 single crystals for x = 0.063, 0.07, 0.09, and 0.11, we found that only {\\\\sim }0.2{%} of the total holes participated in the nearly dissipationless normal state charge transport and superconductivity. We have also observed characteristic collective modes at \\\\omega \\\\sim 18 and 22 cm-1 due to the bound carriers in an electronic lattice (EL)

  7. Effects of charge carrier concentration in hybrid conjugated polymer/oxide photovoltaic devices

    NASA Astrophysics Data System (ADS)

    White, Matthew Schuette

    2009-12-01

    Organic photovoltaics (OPV) represent an attractive route towards inexpensive, lightweight, and abundant renewable energy. The principal criticisms of OPV are low power conversion efficiency and unstable materials resulting in short device lifetimes. Hybrid OPV (h-OPV) devices with ZnO functioning either as the electron acceptor in the heterojunction, or as an electron transport layer in a polymer/fullerene based heterojunction, present useful device structures for investigating the functional mechanisms within OPV devices and a possible pathway towards air-stable high efficiency devices. Such use allows the vast knowledge surrounding oxide nanostructure morphology, band position, and carrier concentration control to be used in designing bulk-heterojunction OPV devices. The work presented in this thesis explores the effects of carrier concentration modulation in the polymer and/or oxide layers of these devices. Exposure to air is known to induce chemical defects in polymer semiconductors, which act as dopants in OPV devices. This increase in doping density can be used to improve OPV devices, however the low work-function metallic electrodes are often highly air sensitive. Using a silver back electrode and a ZnO interlayer at the transparent front contact in a polymer-based bulk heterojunction device allows for fabrication and testing in air. Relatively efficient devices are fabricated in this manner, but the devices show a characteristic aging time that indicates that air is a requirement to function as a quality diode. Air exposure may be effecting any of the layers in the device, but evidence is presented that shows the increased doping density in the polymer is largely responsible for the change in device quality over this time period. When oxides are used as the electron acceptor material in the device heterojunction, the carrier concentration in both the oxide and the polymer determine the strength of the electric field at the junction. Oxygen related doping of the polymer is a requisite for functional devices, but intentional doping of the oxide provides an additional degree of control over interfacial electric fields. By using planar hybrid heterojunctions, the utility of this effect is shown by increasing the driving force for charge separation. Interfacial barrier layers are required on highly doped ZnO to prevent recombination and preserve high fill factors. The measurable carrier concentration in the depletion region of polymer and polymer-fullerene blend films is shown to be significantly larger under illumination than in the dark. This effect is not related to breaking of the conjugated bonds in the polymer, as is the device aging phenomenon, but stems from low mobility of photo-generated electrons. The depletion width and maximum electric field in devices are influenced by the presence of an increased effective doping density under illumination.

  8. Activationless charge transport across 4.5 to 22 nm in molecular electronic junctions

    PubMed Central

    Yan, Haijun; Bergren, Adam Johan; McCreery, Richard; Della Rocca, Maria Luisa; Martin, Pascal; Lafarge, Philippe; Lacroix, Jean Christophe

    2013-01-01

    In this work, we bridge the gap between short-range tunneling in molecular junctions and activated hopping in bulk organic films, and greatly extend the distance range of charge transport in molecular electronic devices. Three distinct transport mechanisms were observed for 4.5–22-nm-thick oligo(thiophene) layers between carbon contacts, with tunneling operative when d?< 8 nm, activated hopping when d > 16 nm for high temperatures and low bias, and a third mechanism consistent with field-induced ionization of highest occupied molecular orbitals or interface states to generate charge carriers when d = 8–22 nm. Transport in the 8–22-nm range is weakly temperature dependent, with a field-dependent activation barrier that becomes negligible at moderate bias. We thus report here a unique, activationless transport mechanism, operative over 8–22-nm distances without involving hopping, which severely limits carrier mobility and device lifetime in organic semiconductors. Charge transport in molecular electronic junctions can thus be effective for transport distances significantly greater than the 1–5 nm associated with quantum-mechanical tunneling. PMID:23509271

  9. Charge carrier motion in disordered conjugated polymers: a multiscale ab-initio study

    SciTech Connect

    Vukmirovic, Nenad; Wang, Lin-Wang

    2009-11-10

    We developed an ab-initio multiscale method for simulation of carrier transport in large disordered systems, based on direct calculation of electronic states and electron-phonon coupling constants. It enabled us to obtain the never seen before rich microscopic details of carrier motion in conjugated polymers, which led us to question several assumptions of phenomenological models, widely used in such systems. The macroscopic mobility of disordered poly(3- hexylthiophene) (P3HT) polymer, extracted from our simulation, is in agreement with experimental results from the literature.

  10. Hot Carrier Transport and Photocurrent Response in Graphene

    E-print Network

    Song, Justin Chien Wen

    Strong electron–electron interactions in graphene are expected to result in multiple-excitation generation by the absorption of a single photon. We show that the impact of carrier multiplication on photocurrent response ...

  11. Effective mass of a charged carrier in a nonpolar liquid: Snowball effect in superfluid helium

    SciTech Connect

    Chikina, I. [DRECAM/SCM/LIONS CEA-Saclay, 91191 Gif-sur-Yvette Cedex (France); Shikin, V. [ISSP, RAS, Chernogolovka, Moscow District, 142432 (Russian Federation); Varlamov, A. A. [INFM-CNR, COHERENTIA, via del Politecnico 1, I-00133 Rome (Italy)

    2007-05-01

    The problem of a correct definition of the charged carrier effective mass in superfluid helium is revised. It is shown that the effective mass of such a quasiparticle can be introduced without Atkins's idea about the solidification of liquid He{sup 4} in the close vicinity of an ion (the so-called ''snowball'' model). Moreover, in addition to the generalization of Atkins's model, the charged carrier effective mass formation is considered within the framework of the two-fluid scenario. The physical reasons of the normal-fluid contribution divergency and the way of the corresponding regularization procedure are discussed. Agreement between the theory and the available experimental data is found in a wide range of temperatures.

  12. Encounter-limited charge-carrier recombination in phase-separated organic semiconductor blends.

    PubMed

    Heiber, Michael C; Baumbach, Christoph; Dyakonov, Vladimir; Deibel, Carsten

    2015-04-01

    The theoretical effects of phase separation on encounter-limited charge carrier recombination in organic semiconductor blends are investigated using kinetic Monte Carlo simulations of pump-probe experiments. Using model bulk heterojunction morphologies, the dependence of the recombination rate on domain size and charge carrier mobility are quantified. Unifying competing models and simulation results, we show that the mobility dependence of the recombination rate can be described using the power mean of the electron and hole mobilities with a domain-size-dependent exponent. Additionally, for domain sizes typical of organic photovoltaic devices, we find that phase separation reduces the recombination rate by less than one order of magnitude compared to the Langevin model and that the mobility dependence can be approximated by the geometric mean. PMID:25884132

  13. The role of non-equilibrium charge carriers in thermoelectric cooling

    NASA Astrophysics Data System (ADS)

    Gurevich, Yu. G.; Velázquez-Pérez, J. E.

    2013-07-01

    This paper is devoted to the analysis of thermoelectric cooling phenomena in semiconductors containing potential barriers (p-n-junction). The formulation of an adequate self-consistent theoretical model describing the effect is presented. The role of the recombination rate in lineal approximation of the electric current leads to a new formulation of the set of equations describing the Peltier effect that is discussed in detail. The importance of re-distribution of non-equilibrium charge carriers, which has been ignored in most of the publications on this subject, is also shown. Moreover, it is proved that the conventional theory of thermoelectric cooling, which does not take into account the influence of non-equilibrium charge carriers, is not correct in general. In the present work, it is demonstrated that the Peltier effect strongly depends on the recombination rate. In particular, it is shown that the sign of the Peltier effect changes with the value of the recombination rate.

  14. Printing technique dependent charge carrier velocity distribution in organic thin film transistors

    NASA Astrophysics Data System (ADS)

    Ganz, Simone; Pankalla, Sebastian; Sauer, Hans Martin; Glesner, Manfred; Doersam, Edgar

    2013-09-01

    In this study we investigated the influence of the deposition technique on the surface topology and the resulting device performance in organic thin film transistors (OTFT). We varied the parameters of flexographic and gravure printing for the organic semiconductor (OSC) and did multilayer gravure printing for the dielectric, respectively. Therefore, we manufactured transistors in bottom contact top gate architecture and compared them to spin coated samples. As investigation tool for OTFTs, the charge carrier velocity distribution is correlated with the optical characteristics of the printed layers. We found a dependency of the printing technique on the surface topology of the semiconductor and, due to the resulting increase of the channel length, a broadening of the charge carrier velocity distribution. For the dielectric we found a dependency on the layer thickness which seems to be independent from the deposition technique.

  15. Molecular ion battery: a rechargeable system without using any elemental ions as a charge carrier.

    PubMed

    Yao, Masaru; Sano, Hikaru; Ando, Hisanori; Kiyobayashi, Tetsu

    2015-01-01

    Is it possible to exceed the lithium redox potential in electrochemical systems? It seems impossible to exceed the lithium potential because the redox potential of the elemental lithium is the lowest among all the elements, which contributes to the high voltage characteristics of the widely used lithium ion battery. However, it should be possible when we use a molecule-based ion which is not reduced even at the lithium potential in principle. Here we propose a new model system using a molecular electrolyte salt with polymer-based active materials in order to verify whether a molecular ion species serves as a charge carrier. Although the potential of the negative-electrode is not yet lower than that of lithium at present, this study reveals that a molecular ion can work as a charge carrier in a battery and the system is certainly a molecular ion-based "rocking chair" type battery. PMID:26043147

  16. Molecular ion battery: a rechargeable system without using any elemental ions as a charge carrier

    PubMed Central

    Yao, Masaru; Sano, Hikaru; Ando, Hisanori; Kiyobayashi, Tetsu

    2015-01-01

    Is it possible to exceed the lithium redox potential in electrochemical systems? It seems impossible to exceed the lithium potential because the redox potential of the elemental lithium is the lowest among all the elements, which contributes to the high voltage characteristics of the widely used lithium ion battery. However, it should be possible when we use a molecule-based ion which is not reduced even at the lithium potential in principle. Here we propose a new model system using a molecular electrolyte salt with polymer-based active materials in order to verify whether a molecular ion species serves as a charge carrier. Although the potential of the negative-electrode is not yet lower than that of lithium at present, this study reveals that a molecular ion can work as a charge carrier in a battery and the system is certainly a molecular ion-based “rocking chair” type battery. PMID:26043147

  17. Charge transport and structural dynamics in carboxylic-acid-based deep eutectic mixtures.

    PubMed

    Griffin, Philip J; Cosby, Tyler; Holt, Adam P; Benson, Roberto S; Sangoro, Joshua R

    2014-08-01

    Charge transport and structural dynamics in the 1:2 mol ratio mixture of lidocaine and decanoic acid (LID-DA), a model deep eutectic mixture (DEM), have been characterized over a wide temperature range using broad-band dielectric spectroscopy and depolarized dynamic light scattering. Additionally, Fourier transform infrared spectroscopy measurements were performed to assess the degree of proton transfer between the neutral parent molecules. From our detailed analysis of the dielectric spectra, we have determined that this carboxylic-acid-based DEM is approximately 25% ionic at room temperature. Furthermore, we have found that the characteristic diffusion rate of mobile charge carriers is practically identical to the rate of structural relaxation at all measured temperatures, indicating that fast proton transport does not occur in LID-DA. Our results demonstrate that while LID-DA exhibits the thermal characteristics of a DEM, its charge transport properties resemble those of a protic ionic liquid. PMID:25025600

  18. Nanoscale quantification of charge injection and transportation process in Si-nanocrystal based sandwiched structure.

    PubMed

    Xu, Jie; Xu, Jun; Zhang, Pengzhan; Li, Wei; Chen, Kunji

    2013-10-21

    Si nanocrystals are formed by using KrF pulsed laser crystallization of an amorphous SiC/ultrathin amorphous Si/amorphous SiC sandwiched structure. Electrons and holes are injected into Si nanocrystals via a biased conductive AFM tip and the carrier decay and transportation behaviours at the nanoscale are studied by joint characterization techniques of Kelvin probe force microscopy (KPFM) and conductive atomic force microscopy (CAFM). Quantification of the surface charge density is realized by solving the Poisson equation based on KPFM measurements. Besides, the asymmetric barrier height for electrons and holes is considered to play a dominant role in controlling the charge retention and transportation characteristics. The methodology developed in this work is promising for studying the charge injection and transportation process in other materials and structures at the nanoscale. PMID:23989206

  19. 41 CFR 302-10.402 - What costs must we pay a commercial carrier for transporting a mobile home?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...commercial carrier for transporting a mobile home? 302-10.402 Section... Federal Travel Regulation System RELOCATION ALLOWANCES TRANSPORTATION...10-ALLOWANCES FOR TRANSPORTATION OF MOBILE HOMES AND BOATS USED AS A PRIMARY...commercial carrier for transporting a mobile home? The costs you...

  20. 41 CFR 302-10.402 - What costs must we pay a commercial carrier for transporting a mobile home?

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...commercial carrier for transporting a mobile home? 302-10.402 Section... Federal Travel Regulation System RELOCATION ALLOWANCES TRANSPORTATION...10-ALLOWANCES FOR TRANSPORTATION OF MOBILE HOMES AND BOATS USED AS A PRIMARY...commercial carrier for transporting a mobile home? The costs you...

  1. Hot carrier diffusion in graphene

    E-print Network

    Ruzicka, Brian Andrew; Wang, Shuai; Werake, Lalani Kumari; Weintrub, Ben; Loh, Kian Ping; Zhao, Hui

    2010-11-01

    We report an optical study of charge transport in graphene. Diffusion of hot carriers in epitaxial graphene and reduced graphene oxide samples are studied using an ultrafast pump-probe technique with a high spatial resolution. Spatiotemporal...

  2. Nonequilibrium population of charge carriers in structures with InGaN deep quantum dots

    Microsoft Academic Search

    D. S. Sizov; E. E. Zavarin; N. N. Ledentsov; V. V. Lundin; Yu. G. Musikhin; V. S. Sizov; R. A. Suris; A. F. Tsatsul’nikov

    2007-01-01

    Electronic and optical properties of ensembles of quantum dots with various energies of activation from the ground-state level\\u000a to the continuous-spectrum region were studied theoretically and experimentally with the InGaN quantum dots as an example.\\u000a It is shown that, depending on the activation energy, both the quasi-equilibrium statistic of charge carriers at the levels\\u000a of quantum dots and nonequilibrium statistic

  3. Controlling charge carrier injection in solution processed pentacene transistors by molecular engineering of the electrodes

    Microsoft Academic Search

    Sangameshwar Rao Saudari; Cherie Kagan

    2009-01-01

    We present the device performance of pentacene transistors fabricated from a solution deposited precursor. The bottom-contact pentacene transistors are fabricated by spin-coating N-sulfinylacetamidopentacene precursor followed by thermal conversion of the precursor into pentacene. Hole mobilities >0.1 cm^2\\/Vs and Ion\\/Ioff>10^5 are repeatedly achieved by this process. The metal-semiconductor interface in organic transistors plays a very important role in charge carrier injection

  4. Analytical solution for charge-carrier injection into an insulating layer in the drift diffusion approximation

    Microsoft Academic Search

    V. I. Shashkin; N. V. Vostokov

    2008-01-01

    Using a drift-diffusion approximation, we obtain an analytical solution to the problem of charge-carrier injection into an insulating i layer of finite thickness with account of self-consistent boundary conditions. The main assumption is that the self-doping of the i layer is neglected. The solution makes it possible to calculate the potential, electric field, and current-voltage characteristics of a variety of

  5. Simulation of the dynamic charge carrier injection and motion in technical XLPE insulation systems

    Microsoft Academic Search

    S. Gottlich; D. Meurer

    1992-01-01

    A method for the simulation of dynamic carrier injection and motion in cross-linked polyethylene (XLPE) insulation systems is presented. In a first study the influence of a cylindrical 50-?m conducting impurity on the surface of the conducting layer is investigated. For the simulation of the dynamic space charge formation and motion in the high-voltage cable under investigation the influence of

  6. Migration of excited charge carriers in arrays of phosphorus-doped silicon nanocrystals

    SciTech Connect

    Belyakov, V. A., E-mail: dragon_bel@mail.ru; Konakov, A. A.; Burdov, V. A. [Nizhni Novgorod State University (Russian Federation)

    2010-11-15

    The rate of tunnel migration of excited charge carriers (electrons and holes) in the array of silicon nanocrystals doped with phosphorus is calculated. It is shown that, starting from certain phosphorus concentrations dependent on the relation between the dimensions of the emitting and accepting nanocrystals, the rate of tunneling of electrons sharply decreases (by several orders of magnitude) and becomes lower than the rate of interband radiative recombination

  7. Energy barrier, charge carrier balance, and performance improvement in organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Benor, Amare; Takizawa, Shin-ya; Pérez-Bolivar, C.; Anzenbacher, Pavel

    2010-06-01

    The charge injection properties of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate anodes are crucial for performance of organic photovoltaics and organic light-emitting diodes (OLEDs). A simple method for tuning hole injection efficiency using UV-ozone is shown to change anode work-function and optimized carriers balance in the devices and improved efficiency in OLEDs. The optimum time of treatment and work-function differs with device architecture.

  8. Charge collection microscopy on p-WSe2 - Recombination sites and minority carrier diffusion length

    NASA Astrophysics Data System (ADS)

    Lewerenz, H. J.; Ferris, S. D.; Doherty, C. J.; Leamy, H. J.

    1982-02-01

    Charge collection microscopy of the layered semiconductor WSe2 is reported. Steps on the surfaces of layered material, bulk dislocations, and growth irregularities are identified as recombination sites. The minority carrier diffusion length perpendicular to the layer structure is determined to be 1.6 + or - 0.2 microns on a smooth surface. The results demonstrate a correlation between step-like surface structures and loss of current collection efficiency in solar energy-converting devices made from layered semiconductors.

  9. Temperature dependence and anisotropy of charge-carrier mobilities in crystalline durene

    NASA Astrophysics Data System (ADS)

    Ortmann, Frank; Hannewald, Karsten; Bechstedt, Friedhelm

    2007-03-01

    We report on the theoretical analysis of charge-carrier mobilities in durene crystals. The crystal is studied with DFT methods to examine structural, vibrational, and electronic properties. On that basis we employ a Holstein-Peierls model (see Hannewald et al. PRB 69, 075211 (2004); PRB 69, 075212 (2004)) to simulate the temperature dependence of the mobilities. The relation between the anisotropy of electron/hole mobilities and the band structure as well as lattice vibrations is discussed.

  10. Relation of open circuit voltage to charge carrier density in organic bulk heterojunction solar cells

    Microsoft Academic Search

    Daniel Rauh; Alexander Wagenpfahl; Carsten Deibel; Vladimir Dyakonov

    2011-01-01

    The open circuit voltage V(oc) and the corresponding charge carrier\\u000a density were measured in dependence of temperature and illumination\\u000a intensity by current-voltage and charge extraction measurements for\\u000a poly(3-hexylthiophene-2,5-diyl) (P3HT):{[}6,]-phenyl-C(61) butyric acid\\u000a methyl ester (PCBM) and P3HT:bisPCBM solar cells. At lower temperatures\\u000a a saturation of V(oc) was observed which can be explained by energetic\\u000a barriers at the contacts (metal-insulator-metal model). Such

  11. Statics and dynamics of electroactuation with single-charge-carrier ionomers.

    PubMed

    Lee, Alpha A; Colby, Ralph H; Kornyshev, Alexei A

    2013-02-27

    A simple theory of electromechanical transduction for single-charge-carrier double-layer electroactuators is developed, in which the ion distribution and curvature are mutually coupled. The obtained expressions for the dependence of the curvature and charge accumulation on the applied voltage, as well as the electroactuation dynamics, are compared with literature data. The mechanical or sensor performance of such electroactuators appears to be determined by just three cumulative parameters, with all of their constituents measurable, permitting a scaling approach to their design. PMID:23364047

  12. Detection of Negative Charge Carriers in Superfluid Helium Droplets: The Metastable Anions He*– and He2*–

    PubMed Central

    2014-01-01

    Helium droplets provide the possibility to study phenomena at the very low temperatures at which quantum mechanical effects are more pronounced and fewer quantum states have significant occupation probabilities. Understanding the migration of either positive or negative charges in liquid helium is essential to comprehend charge-induced processes in molecular systems embedded in helium droplets. Here, we report the resonant formation of excited metastable atomic and molecular helium anions in superfluid helium droplets upon electron impact. Although the molecular anion is heliophobic and migrates toward the surface of the helium droplet, the excited metastable atomic helium anion is bound within the helium droplet and exhibits high mobility. The atomic anion is shown to be responsible for the formation of molecular dopant anions upon charge transfer and thus, we clarify the nature of the previously unidentified fast exotic negative charge carrier found in bulk liquid helium. PMID:25068008

  13. Carrier transport mechanisms of p-type amorphous-n-type crystalline silicon heterojunctions

    NASA Astrophysics Data System (ADS)

    Mimura, Hidenori; Hatanaka, Yoshinori

    1992-03-01

    Measured current-voltage characteristics of undoped and p-type hydrogenated amorphous silicon (a-Si:H)/n-type crystalline silicon (c-Si) heterojunctions are used to discuss the carrier transport mechanisms. The forward current was characterized by two parts: The forward current increased with applied voltage exponentially (region 1), and nonexponentially (region 2). In region 1, it was found that the current was dominated by the tunneling process in which electrons tunneled from the c-Si into gap states in the a-Si:H and recombinated holes captured by the gap states in the a-Si:H. In region 2, the current was found to be a space-charge-limited current due to both electrons injected from the c-Si and holes injected from an ohmic contact. The carrier transport mechanism of reverse currents depended on the magnitude of boron doping in the a-Si:H. The reverse current was considered to be mainly generated in the depletion layer of the a-Si:H for the heterojunction with undoped a-Si:H, generated in the depletion layer of both the a-Si:H and the c-Si for that with boron-doped a-Si:H of B2H6/SiH4=1×10-5, and generated in the depletion layer of the c-Si for that with boron-doped a-Si:H of B2H6/SiH4=1×10-4.

  14. Collection of photogenerated charge carriers in small-pitched infrared photovoltaic focal plane arrays

    NASA Astrophysics Data System (ADS)

    Chekanova, Galina V.; Drugova, Albina A.; Kholodnov, Viacheslav; Nikitin, Mikhail S.

    2010-10-01

    Technology of infrared (IR) photovoltaic (PV) focal plane arrays (FPA) covering spectral range from 1.6 to 14 ?m gradually moves from simple quasi-matrix (linear) arrays like as 4×288 pixels to large format high definition arrays 1280×1024 pixels and more. Major infrared detector materials for PV technology are InSb and its alloys and ternary alloys Hg1-xCdxTe. Progress in IR PV technology was provided in last decade by serious improvement in material growing techniques. Increasing of PV array format is related always to decreasing of pixel size and spacing between neighbor pixels to minimal size reasonable from point of view of infrared physics. So pitch is small (15-25 ?m) in large format arrays. Ambipolar diffusion length of photogenerated charge carriers can exceed pitch many times in high quality absorption layers of PV arrays. It means that each pixel can collect excess charge carriers generated far from n+-p junction border. Optimization of resolution, filling factor and cross-talking level of small-pitched PV FPA requires comprehensive estimation of photodiode's (PD) pixel performance depending on pixel and array design, material properties and operating conditions. Objective of the present work was to develop general approach to estimate collection of photogenerated charge carriers in small-pitched arrays.

  15. Impact of charge transport on current–voltage characteristics and power-conversion efficiency of organic solar cells

    PubMed Central

    Würfel, Uli; Neher, Dieter; Spies, Annika; Albrecht, Steve

    2015-01-01

    This work elucidates the impact of charge transport on the photovoltaic properties of organic solar cells. Here we show that the analysis of current–voltage curves of organic solar cells under illumination with the Shockley equation results in values for ideality factor, photocurrent and parallel resistance, which lack physical meaning. Drift-diffusion simulations for a wide range of charge-carrier mobilities and illumination intensities reveal significant carrier accumulation caused by poor transport properties, which is not included in the Shockley equation. As a consequence, the separation of the quasi Fermi levels in the organic photoactive layer (internal voltage) differs substantially from the external voltage for almost all conditions. We present a new analytical model, which considers carrier transport explicitly. The model shows excellent agreement with full drift-diffusion simulations over a wide range of mobilities and illumination intensities, making it suitable for realistic efficiency predictions for organic solar cells. PMID:25907581

  16. Carrier control via charge transfer at the topological-insulator/organic-molecule interface

    NASA Astrophysics Data System (ADS)

    Tanigaki, Katsumi; Tanabe, Yoichi; Kuynh, Khuong; Urata, Takahiro; Nouchi, Ryo; Heguri, Satoshi; Shimotani, Hidekazu; AIMR, Tohoku University Collaboration; Department of Pysics, Graduate School of Science, Tohoku University Collaboration; Osaka Prefecture University Collaboration

    2013-03-01

    A topological insulator is a material that behaves as an insulator as a bulk state, while permitting metallicity on its Dirac cone surface state. One of the most serious issues of recent researches in this field, however, has been the fact that the Fermi levels in many TIs actually fall in either the conduction or valence band due to the naturally occurring defects and must be controlled by further doping. We report here that the major electron carriers on the SS of a Bi2-xSbxTe3-ySey(BSTS) single crystal can be converted to the hole carriers via interface control using 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane(F4-TCNQ), with strong electron affinity. The evidence can be elucidated using a detailed three-carrier model. The results apparently demonstrate that the charge transfer at the TI/organic-molecule interface is very efficient in order to control the carrier density of TIs, particularly on the SS. Our present results will be very important for studying the fundamental aspects of TIs as well as their future device applications. A topological insulator is a material that behaves as an insulator as a bulk state, while permitting metallicity on its Dirac cone surface state. One of the most serious issues of recent researches in this field, however, has been the fact that the Fermi levels in many TIs actually fall in either the conduction or valence band due to the naturally occurring defects and must be controlled by further doping. We report here that the major electron carriers on the SS of a Bi2-xSbxTe3-ySey(BSTS) single crystal can be converted to the hole carriers via interface control using 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane(F4-TCNQ), with strong electron affinity. The evidence can be elucidated using a detailed three-carrier model. The results apparently demonstrate that the charge transfer at the TI/organic-molecule interface is very efficient in order to control the carrier density of TIs, particularly on the SS. Our present results will be very important for studying the fundamental aspects of TIs as well as their future device applications. Osaka Prefecture University

  17. Spatial and temporal imaging of long-range charge transport in perovskite thin films by ultrafast microscopy.

    PubMed

    Guo, Zhi; Manser, Joseph S; Wan, Yan; Kamat, Prashant V; Huang, Libai

    2015-01-01

    Charge carrier diffusion coefficient and length are important physical parameters for semiconducting materials. Long-range carrier diffusion in perovskite thin films has led to remarkable solar cell efficiencies; however, spatial and temporal mechanisms of charge transport remain unclear. Here we present a direct measurement of carrier transport in space and in time by mapping carrier density with simultaneous ultrafast time resolution and ?50-nm spatial precision in perovskite thin films using transient absorption microscopy. These results directly visualize long-range carrier transport of ?220?nm in 2?ns for solution-processed polycrystalline CH3NH3PbI3 thin films. Variations of the carrier diffusion coefficient at the ?m length scale have been observed with values ranging between 0.05 and 0.08?cm(2)?s(-1). The spatially and temporally resolved measurements reported here underscore the importance of the local morphology and establish an important first step towards discerning the underlying transport properties of perovskite materials. PMID:26101051

  18. Charge carrier injection and transport in organic thin films

    Microsoft Academic Search

    Toshinori Matsushima; Guang-He Jin; Yoshihiro Kanai; Tomoyuki Yokota; Seiki Kitada; Toshiyuki Kishi; Hideyuki Murata

    2008-01-01

    Current density-voltage (J-V) characteristics of hole-only devices using indium tin oxide (ITO) anode and N,N'- diphenyl-N,N'-bis(1-naphthyl)-1,1'-biphenyl-4,4'-diamine (alpha-NPD) layer were measured with various thicknesses of a molybdenum oxide (MoO3) buffer layer inserted between ITO and alpha-NPD. The device with a 0.75-nm-thick MoO3 layer forms Ohmic hole injection at the ITO\\/MoO3\\/alpha-NPD interfaces and J-V characteristics of this device are controlled by a

  19. Charge carrier transport and injection across organic heterojunctions

    Microsoft Academic Search

    Sai Wing Tsang

    2009-01-01

    The discovery of highly efficient organic light-emitting diodes (OLEDs) in the 1980s has stimulated extensive research on organic semiconductors and devices. Underlying this breakthrough is the realization of the organic heterojunction (OH). Besides OLEDs, the implementation of the OH also significantly improves the power conversion efficiency in organic photovoltaic cells (OPVs). The continued technological advancements in organic electronic devices depend

  20. Charge-carrier transport in amorphous organic semiconductors

    E-print Network

    Limketkai, Benjie, 1982-

    2008-01-01

    Since the first reports of efficient luminescence and absorption in organic semiconductors, organic light-emitting devices (OLEDs) and photovoltaics (OPVs) have attracted increasing interest. Organic semiconductors have ...

  1. Molecular semiconductor blends: Microstructure, charge carrier transport, and application in

    E-print Network

    Schreiber, Frank

    -complementary organic field- effect transistors and organic photovoltaic cells. Many inves- tigations in the latter, and electrical properties in two model systems for organic photovoltaic cells. We have investigated blends in photovoltaic cells Andreas Opitz*,1 , Julia Wagner 1 , Wolfgang Bru¨ tting 1 , Alexander Hinderhofer 2

  2. Charge-carrier concentration and temperature in quantum wells of laser heterostructures under spontaneous-and stimulated-emission conditions

    Microsoft Academic Search

    L. E. Vorob’ev; V. L. Zerova; K. S. Borshchev; Z. N. Sokolova; I. S. Tarasov; G. Belenky

    2008-01-01

    The charge-carrier concentration and the temperature of hot electrons and holes in quantum-well laser nanostructures in the\\u000a regimes of spontaneous and stimulated emission are determined as functions of the current density j, with InGaAs\\/GaAs structures as an example. Under spontaneous-emission conditions, the carrier concentration in the active\\u000a region of a laser structure grows as the current increases, while carrier heating

  3. Charge transport scaling in turbulent electroconvection

    NASA Astrophysics Data System (ADS)

    Tsai, Peichun; Daya, Zahir A.; Morris, Stephen W.

    2005-10-01

    We describe a local-power-law scaling theory for the mean dimensionless electric current Nu in turbulent electroconvection. The experimental system consists of a weakly conducting, submicron-thick liquid-crystal film supported in the annulus between concentric circular electrodes. It is driven into electroconvection by an applied voltage between its inner and outer edges. At sufficiently large voltage differences, the flow is unsteady and electric charge is turbulently transported between the electrodes. Our theoretical development, which closely parallels the Grossmann-Lohse model for turbulent thermal convection, predicts the local-power law N?F(?)R?P? . R and P are dimensionless numbers that are similar to the Rayleigh and Prandtl numbers of thermal convection, respectively. The dimensionless function F(?) , which is specified by the model, describes the dependence of Nu on the aspect ratio ? . We find that measurements of Nu are consistent with the theoretical model.

  4. Charge Transport in Magnetite Nanoparticle Arrays

    NASA Astrophysics Data System (ADS)

    Jang, Seongjin; Zeng, Hao

    2007-03-01

    Charge transport properties of magnetite (Fe3O4) nanoparticle arrays were studied as a function of annealing conditions. These arrays were prepared by self-assembling chemically synthesized nanoparticles with micro-gaps between lateral electrodes. Annealing removed surfactant molecules and varied the interparticle spacing systematically. Arrays annealed under 200 ^oC are insulating. Arrays annealed between 200 ^oC to 500 ^oC show thermally assisted tunneling behavior, with the tunneling barrier decreasing with increasing annealing temperatures. Above 500 ^oC, a transition from tunneling to hopping mechanism is observed. Magnetoresistance decreases with increasing annealing temperature. For the hopping samples, Verway transition is observed from both the resistivity and magnetoresistance measurements. Work supported by NSF DMR 0547036

  5. Spin Relaxation in Materials Lacking Coherent Charge Transport

    NASA Astrophysics Data System (ADS)

    Harmon, Nicholas

    2015-03-01

    As semiconductor spintronics research extends to materials beyond intrinsic or lightly doped semiconductors (e. g. organic materials, amorphous semiconductors, and impurity bands), the need is readily apparent for new theories of spin relaxation that encompass highly disordered materials, where charge transport is incoherent. We describe a broadly applicable theory of spin relaxation in materials with incoherent charge transport. The theory is based on continuous-time-random-walk theory and can incorporate many different relaxation mechanisms. We focus primarily on spin relaxation caused by spin-orbit and hyperfine effects in conjunction with carrier hopping. Analytic and numerical results from the theory are compared in various regimes with Monte Carlo simulations. Three different systems were examined: a polymer (MEH-PPV), amorphous silicon, and heavily doped n-GaAs. In the organic and amorphous systems, we predict spin relaxation and spin diffusion dependences on temperature and disorder for three different mechanisms (hyperfine, hopping-induced spin-orbit, and intra-site spin relaxation). The resulting unique experimental signatures predicted by the theory for each mechanism in these disordered systems provide a prescription for determining the dominant spin relaxation mechanism. We find our theory to be in agreement with available measurements in these materials. We also predict that large disorder modifies certain mechanisms to be algebraic instead of exponential in time. Our results should assist in evaluating the suitability of various disordered materials for spintronic devices. All work done in collaboration with Michael E. Flatté. Timothy Peterson and Paul Crowell collaborated as well on the n-GaAs study. This work was supported by an ARO MURI and by C-SPIN, one of six centers of STARnet, a Semiconductor Research Corporation program, sponsored by MARCO and DARPA.

  6. Aspects of charge recombination and charge transport in organic solar cells and light-emitting devices

    E-print Network

    Difley, Seth

    2010-01-01

    In this thesis, aspects of charge reconbination and charge transport in organic solar cells and light-emitting devices are presented. These devices show promise relative to traditional inorganic semiconductors. We show ...

  7. Carrier class metro ethernet services over T-MPLS packet transport network

    NASA Astrophysics Data System (ADS)

    Li, Zhicheng; Jia, Wu; Zhang, Yongjun; Gu, Wanyi

    2007-11-01

    Discusses the network architecture designed for providing carrier class metro Ethernet services over T-MPLS packet transport network. Analyzes its characteristics and advantages from the aspects of data transport, OAM, end-to-end QoS, protection mechanism and interworking.

  8. 77 FR 38747 - Reports by Air Carriers on Incidents Involving Animals During Air Transport

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-29

    ...definition of ``animal'' to include all cats and dogs transported by the carrier, regardless of whether the cat or dog is transported as a pet by its owner...involving the loss, injury, or death of cats and dogs that occur while they are...

  9. Subsurface Imaging and Sensing of Charge Carrier Movements in the Earth’s Crust

    NASA Astrophysics Data System (ADS)

    Dahlgren, R.; Freund, F. T.; Lazarus, M.; Wang, J. S.; Rekenthaler, D.; Peters, R. D.; Duma, G.

    2009-12-01

    The DUSEL facility will enable unique opportunities for field experiments that would otherwise not be possible at surface facilities (Lesko, K.T., TAUP, 2007) and support a host of undergraduate and graduate educational projects. In this presentation, some of the proposed geophysics experiments will be described as part of the subsurface Imaging and Sensing (SIS) project to study charge carrier movement in crustal rock as a function of various perturbations. The electric conductivity of the Earth’s crust is dominated by positive hole charge carriers, e.g. mobile electron vacancy defects (EVD) in the oxygen anion sublattice of minerals that make up the bulk of crustal rocks. We are interested in (i) coupling of fundamental processes linked to the activation of additional EVDs in rocks deep in the crust subjected to tectonic stresses and the outflow of these charge carriers into the surrounding rocks, (ii) their manifestation across the electromagnetic spectrum and other measuands, (iii) induced forces that arise when these charge carriers are subjected to the episodic or daily magnetic field variations coming from geomagnetic storms or from the ionospheric current vortex, and (iv) in the movement of positive holes in the shallow crust when a thunderstorm system drifts overhead, dragging along a charge cloud in the ground. We propose to conduct active rock stressing experiments in situ using expanding grout technique (performing electrical, electromagnetic, and VolksMeter tilt measurements) and to monitor the electric and magnetic field variations penetrating into the Earth’s crust. Additionally optical phenomena will be investigated (anomalous infrared signatures, visible light arising from atomic oxygen and corona discharge, and infrared imaging). If budget permits, measurement of changes of acoustic velocity, evolution of chemical species (H2, O*, Rn, etc) and radar reflectivity as a function of stresses will also be attempted. We propose to study the charge distribution on the inside walls of cavities or along drifts and how the local electric field is modified when a geomagnetic storm passes overhead or lightning strikes nearby. Detection of signals with this passive experiment at different depths will greatly improve understanding of propagation mechanisms and test predictive capabilities. We have demonstrated with 20 earthquake events that we can provide 1 - 3 day predictions of the earthquakes, using ground-based receivers, a combination of GPS and UHF/VHF satellite signals, and radio-tomography of the ionosphere as the analytical tool. Based on that methodology, we hope to correlate crustal plate boundary, precursory signatures with the sub-surface currents and fields evident at DUSEL.

  10. Coupled simulation of carrier transport and electrodynamics: the EMC/FDTD/MD technique

    NASA Astrophysics Data System (ADS)

    Willis, K. J.; Sule, N.; Hagness, S. C.; Knezevic, I.

    2015-03-01

    In order to understand the response of conductive materials to high-frequency electrical or optical excitations, the interplay between carrier transport and electrodynamics must be captured. We present our recent work on developing EMC/FDTD/MD, a self-consistent coupled simulation of semiclassical carrier transport, described by ensemble Monte Carlo (EMC), with full-wave electrodynamics, described by the finite-difference time-domain (FDTD) technique and molecular dynamics (MD) for sub-grid-cell interactions. Examples of room-temperature terahertz-frequency transport simulation of doped silicon and back-gated graphene are shown.

  11. Relationship between composition and charge carrier concentration in Eu8Ga16-xGe30+x clathrates

    Microsoft Academic Search

    V. Pacheco; A. Bentien; W. Carrillo-Cabrera; S. Paschen; F. Steglich; Yu. Grin

    2005-01-01

    The charge carrier concentratioin is an important parameter in the search for intermetallic clathrates adequate for thermoelectric applications. This work reveals the influence of the exact composition of Eu8Ga16-xGe30+x on the charge carrier concentration. The samples with initial composition Eu8Ga16Ge30 were processed according to two different heat treatments. Slow cooling of the melt and subsequent annealing produced the beta phase

  12. Charge transport properties of single crystal CVD-diamond particle detectors

    Microsoft Academic Search

    M. Pomorski; E. Berdermann; W. de Boer; A. Furgeri; C. Sander; J. Morse

    2007-01-01

    The charge transport properties of virgin and heavily irradiated intrinsic Single-Crystal CVD-Diamond Detectors (SC-CVD-DD) are discussed by means of the Transient-Current Technique (TCT), which proved to be a sensitive tool to detect the first changes of the detector's performance. Charge-carrier mobilities ?e=1300–3100 cm2\\/V s, ?h=2400 cm2\\/V s and effective deep-trapping lifetimes ?eff-h=300–900 ns, ?eff-e=160–360 ns were measured in the non-irradiated state, decreasing slightly after irradiation

  13. Hot-carrier transport in diamond controlled by femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Kozák, Martin; Trojánek, František; Malý, Petr

    2015-05-01

    A laser-induced transient grating technique with femtosecond temporal resolution was used for the study of hot-carrier diffusion and anisotropy of an ambipolar diffusion coefficient in monocrystalline diamond. A hot-carrier transport regime observed at temperatures below 200 K and excited carrier densities lower than 1016 cm?3 persist in the sample 20–30 ps after photoexcitation. Measured drift velocity of hot carriers was approximately 4–8 times higher compared to thermalized carriers. At low sample temperatures and excited carrier densities, the ambipolar diffusion coefficient was found to be anisotropic between <100> and <110> crystallographic directions. We demonstrated experimentally that the carrier energy distribution can be controlled on a sub-picosecond timescale by an additional laser pulse with photon energy below the width of a diamond band gap absorbed by the excited carrier system. Our experimental data were reproduced well by Monte Carlo simulations that confirm the presence of a hot-carrier diffusion regime in diamond.

  14. Influence of charge carrier mobility and morphology on solar cell parameters in devices of mono- and bis-fullerene adducts.

    PubMed

    Muth, Mathis-Andreas; Mitchell, William; Tierney, Steven; Lada, Thomas A; Xue, Xiang; Richter, Henning; Carrasco-Orozco, Miguel; Thelakkat, Mukundan

    2013-12-01

    Herein, we analyze charge carrier mobility and morphology of the active blend layer in thin film organic solar cells and correlate them with device parameters. A low band gap donor-acceptor copolymer in combination with phenyl-C61-butyric acid methyl ester (PCBM) or two bis-adduct fullerenes, bis-PCBM and bis-o-quino-dimethane C60 (bis-oQDMC), is investigated. We study the charge transport of polymer:fullerene blends in hole- and electron-only devices using the space-charge limited current method. Lower electron mobilities are observed in both bis-adduct fullerene blends. Hole mobility, however, is decreased only in the blend containing bis-oQDMC. Both bis-adduct fullerene blends show very high open circuit voltage in solar cell devices, but poor photocurrent compared to the standard PCBM blend for an active layer thickness of 200 nm. Therefore, a higher short circuit current is feasible for the polymer:bis-PCBM blend by reducing the active layer thickness in order to compensate for the low electron mobility, which results in a PCE of 4.3%. For the polymer:bis-oQDMC blend, no such improvement is achieved due to an unfavorable morphology in this particular blend system. The results are supported by external quantum efficiency measurements, atomic force microscopy, transmission electron microscopy and UV/vis spectroscopy. Based on these results, the investigations presented herein give a more scientific basis for the optimization of solar cells. PMID:24196215

  15. Separation of Carrier-Transport and Light-Emission Functions in a Light-Emitting Organic Transistor with Bilayer Configuration

    NASA Astrophysics Data System (ADS)

    Shang, Hui; Shimotani, Hidekazu; Thangavel, Kanagasekaran; Tanigaki, Katsumi; Nano Solid State Physics Team

    2015-03-01

    Organic single crystal based ambipolar light-emitting field effect transistors is treated as the candidate to realize laser. However, the active layer should contain both superb luminescent property and high charge-carrier mobility, which are always competing with each other in one material. Our basic concept for solving this problem is divide these two factors into two layers, and the combination of these two layers acts as the active layer of LEFET Bottom layer with high carrier mobility can be assigned as carrier transporter, and top layer with high PL efficiency was assigned as light emitter. After injection, the carriers will have a recombination in the bottom layer and formed exciton will transfer into the top layer with light emission. In this work, we have fabricated bilayer structure device, in which tetracene was used as bottom crystaland 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM) doped tetracene was laminated on tetracene as light emitter. We have successfully observed light emission from top crystal, from which our aforementioned hypothesis was preliminary proved. Details will be reported in the presentation.

  16. Brownian dynamics determine universality of charge transport in ionic liquids

    SciTech Connect

    Sangoro, Joshua R [ORNL; Iacob, Ciprian [University of Leipzig; Mierzwa, Michal [University of Silesia, Uniwersytecka, Katowice, Poland; Paluch, Marian [University of Silesia, Uniwersytecka, Katowice, Poland; Kremer, Friedrich [University of Leipzig

    2012-01-01

    Broadband dielectric spectroscopy is employed to investigate charge transport in a variety of glass-forming ionic liquids over wide frequency, temperature and pressure ranges. Using a combination of Einstein, Einstein-Smoluchowski, and Langevin relations, the observed universal scaling of charge transport in ionic liquids is traced back to the dominant role of Brownian dynamics.

  17. Selection of Metal Oxide Charge Transport Layers for Colloidal Quantum

    E-print Network

    Selection of Metal Oxide Charge Transport Layers for Colloidal Quantum Dot LEDs V. Wood,* M. J study extends this line of investiga- tion by considering a series of semiconduct- ing metal oxides in layered QD-LED structures. Recently we demonstrated that metal oxides can be used as charge transport lay

  18. Charge transport modeling in organic light emitting diodes

    Microsoft Academic Search

    M. N. Bussac; E. Tuti; L. Zuppiroli

    We present a microscopic theory of charge transport and electrode injection in otganic light emitting diodes which accounts for most of the molecular aspects of these mate- rials. The rational optimization of classical semiconductor optoelectronics devices required a good knowledge of the basic transport and light emission processes. The same work should be done in organic devices where charge trans-

  19. Determination of uniformity for the lifetime distribution of minority charge carriers in monocrystalline silicon

    SciTech Connect

    Kudin, A.V.

    1986-08-01

    To check the minority charge carrier (MCC) lifetimes over the end of an ingot (or over plates) of monocrystalline silicon an automatic arrangement has been developed that measures by modulating the conductivity of a point contact. Provision is made in the measuring apparatus, along with rapid action and digital registration of the individual measurements on a video terminal, for the possibility of analyzing measured results by means of a built-in (or interfaced) microprocessor. In order to evaluate the localization of a measurement with a given method the authors solved the problem concerning the distribution of injected carriers and the potential in a semiconductor of a semidefinite size for the moment of time corresponding to the end of an injecting pulse having a long duration.

  20. Field-direction control of the type of charge carriers in nonsymmorphic IrO2

    NASA Astrophysics Data System (ADS)

    Uchida, M.; Sano, W.; Takahashi, K. S.; Koretsune, T.; Kozuka, Y.; Arita, R.; Tokura, Y.; Kawasaki, M.

    2015-06-01

    In the quest for switching of the charge carrier type in conductive materials, we focus on nonsymmorphic crystals, which are expected to have highly anisotropic folded Fermi surfaces due to symmetry requirements. Following a simple tight-binding model simulation, we prepare nonsymmorphic IrO2 single-crystalline films with various growth orientations by molecular beam epitaxy, and systematically quantify their Hall effect for the corresponding field directions. The results clearly demonstrate that the dominant carrier type can be intrinsically controlled by the magnetic field direction, as also evidenced by first-principles calculations revealing nontrivial momentum dependence of the group velocity and mass tensor on the folded Fermi surfaces and its anisotropic nature for the field direction.

  1. Sustained release micellar carrier systems for iontophoretic transport of dexamethasone across human sclera

    PubMed Central

    Chopra, Poonam; Hao, Jinsong; Li, S. Kevin

    2012-01-01

    A challenge in ocular drug delivery is to maintain the therapeutic concentration of a drug at the site of action in the eye. The objective of the present study was to investigate the feasibility of micellar carrier systems for sustained drug delivery in transscleral iontophoresis in vitro. Simple and mixed micelles prepared using sodium taurocholate (TA) alone or with egg lecithin (LE) were the carrier systems studied. Dexamethasone (DEX), a poorly water soluble corticosteroid, was the model drug. The micellar carrier systems were first characterized for their solubilization and encapsulation of the drug. Passive and 2-mA iontophoretic (both cathodal and anodal) transport experiments were conducted using these micellar carrier systems in side-by-side diffusion cells with excised human sclera in vitro. Drug release studies were performed after the transport experiments. Saturated DEX solution without the micellar carriers was used as a control. It was found that the solubilization capacity of the micellar carrier systems increased as the total lipid concentration of the systems increased. Drug release from the sclera was significantly prolonged with the micellar carrier systems as compared to the control after passive and iontophoretic delivery. Less than ~ 20% of DEX was released from the sclera in approximately 2 hours after cathodal iontophoretic delivery of the micellar carrier systems, whereas more than ~ 50% of DEX was released from the control in the same time period under the same condition. Micellar carrier systems can be a suitable transscleral drug delivery system for poorly water soluble drugs by enhancing their aqueous solubilities and providing sustained drug delivery. These micellar carrier systems can be efficiently delivered into and across the sclera by iontophoresis for drug delivery. PMID:22306336

  2. Carrier-mediated transport of actinides and rare earth elements through liquid and plasticized membranes

    Microsoft Academic Search

    R. Kopunec; Th. Ngo Manh

    1994-01-01

    The first works in this field were realized approximately 25 years ago, when BLOCK et al. reported1,2 their studies about carrier-mediated transport (also called pertraction or membrane extraction) of uranium through plasticized membranes with neutral esters derived from phosphoric acid. At this time, the methodical principles of selective pertraction of ionic compounds through so-called bulk liquid membranes containing carriers were

  3. Mitochondrial ADP/ATP carrier: preventing conformational changes by point mutations inactivates nucleotide transport activity.

    PubMed

    Babot, Marion; Blancard, Corinne; Zeman, Igor; Lauquin, Guy J-M; Trézéguet, Véronique

    2012-09-18

    The mitochondrial ADP/ATP carrier (Ancp) is a paradigm of the mitochondrial carrier family (MCF); its members allow metabolic fluxes between mitochondria and the cytosol. The members of the MCF share numerous structural and functional characteristics. Ancp is very specifically inhibited by two classes of compounds, which stabilize the carrier in two different conformations involved in nucleotide transport. Resolution of the atomic structure of the bovine Ancp, in complex with one of its specific inhibitors, is that of the carrier open toward the intermembrane space. To gain insights into the interconversion from one conformation to the other, we introduced point mutations in the yeast carrier at positions Cys73 in the first matrix loop and Tyr97 and Gly298 in transmembrane helices 2 and 6. We demonstrate in this paper that they impair stabilization of the carrier in one conformation or the other, resulting in an almost complete inactivation of nucleotide transport in both cases. The results are discussed on the basis of the atomic structure of the conformation open to the cytosol. These mutant proteins could afford convenient tools for undertaking structural studies of both conformations of the yeast carrier. PMID:22928843

  4. Experimental measurements of charge carrier mobility: lifetime products for large sample of pixilated CZT detectors

    NASA Astrophysics Data System (ADS)

    Vadawale, S. V.; Shanmugam, M.; Purohit, Shishir; Acharya, Y. B.; Sudhakar, Manju

    2012-07-01

    Cadmium-Zinc-Telluride (CZT) is thought to be a primary work horse for hard X-ray astronomy in future. Due to the relatively large band-gap, it offers near room temperature operation while maintaining much better energy resolution then scintillator detectors operating in similar energy range. Further, CZT detectors are available in the form of pixilated detectors with area up to few cm2 and hence it is possible to realize very large detector area by having an array of such pixilated CZT detectors. However, it is well known that the energy spectrum of mono-energetic X-ray measured by CZT detectors does not have a Gaussian shape but has significant low-energy tail. This is mainly due to relatively poor mobility and small life time of the charge carriers, particularly of holes, in the CZT crystals. Thus, in order to understand spectral response for a large array of CZT detectors consisting of multiple elements / pixels, it is essential to characterize the mobility-lifetime products of charge carriers for each individual elements / pixels. Here we present experimental measurements of charge carrier mobility-lifetime products for large sample of multi-pixel CZT detectors. The mobility-lifetime products are measured by simultaneously fitting a ‘CZT line’ model to pixel wise spectra of 122 keV X-rays from 57Co at three different bias voltages. These were carried out as a part of selection of CZT detector modules for the “High Energy X-ray spectrometer (HEX)” onboard Indian moon mission - Chandrayaan-1.

  5. Ultrafast Carrier Relaxation in InN Nanowires Grown by Reactive Vapor Transport

    PubMed Central

    2009-01-01

    We have studied femtosecond carrier dynamics in InN nanowires grown by reactive vapor transport. Transient differential absorption measurements have been employed to investigate the relaxation dynamics of photogenerated carriers near and above the optical absorption edge of InN NWs where an interplay of state filling, photoinduced absorption, and band-gap renormalization have been observed. The interface between states filled by free carriers intrinsic to the InN NWs and empty states has been determined to be at 1.35 eV using CW optical transmission measurements. Transient absorption measurements determined the absorption edge at higher energy due to the additional injected photogenerated carriers following femtosecond pulse excitation. The non-degenerate white light pump-probe measurements revealed that relaxation of the photogenerated carriers occurs on a single picosecond timescale which appears to be carrier density dependent. This fast relaxation is attributed to the capture of the photogenerated carriers by defect/surface related states. Furthermore, intensity dependent measurements revealed fast energy transfer from the hot photogenerated carriers to the lattice with the onset of increased temperature occurring at approximately 2 ps after pulse excitation.

  6. Carrier Transport Properties of p-Type Silicon-Metal Silicide Nanocrystal Composite Films

    NASA Astrophysics Data System (ADS)

    Ohishi, Yuji; Miyazaki, Yoshinobu; Muta, Hiroaki; Kurosaki, Ken; Yamanaka, Shinsuke; Uchida, Noriyuki; Tada, Tetsuya

    2015-06-01

    In this study, we synthesized p-type nanocomposite films consisting of Si-nickel silicide and Si-molybdenum silicide nanocrystals and measured the temperature dependence of their electrical properties. To evaluate grain boundary potential barrier height, we developed a theoretical model taking into account the effect of ionized impurities, acoustic phonons, and grain boundaries. The potential barrier height was sufficiently low not to substantially affect carrier transport in the Si-nickel silicide composite film. Carrier transport in the Si-molybdenum silicide composite film was found to be affected by a scattering mechanism not included in this model. Thus, the transition metal significantly affects carrier transport and the thermoelectric properties of Si-metal silicide nanocomposite films.

  7. Negative differential resistance and carrier transport of electrically bistable devices based on poly(N-vinylcarbazole)-silver sulfide composites

    PubMed Central

    2014-01-01

    An electrically bistable device has been fabricated based on poly(N-vinylcarbazole) (PVK)-silver sulfide (Ag2S) composite films using a simple spin-coating method. Current–voltage (I-V) characteristics of the as-fabricated devices exhibit a typical electrical bistability and negative differential resistance (NDR) effect. The NDR effect can be tuned by varying the positive charging voltage and the charging time. The maximum current ratio between the high-conducting state (ON state) and low-conducting state (OFF state) can reach up to 104. The carrier transport mechanisms in the OFF and ON states are described by using different models on the basis of the experimental result. PMID:24641989

  8. Localized excited charge carriers generate ultrafast inhomogeneous strain in the multiferroic BiFeO3.

    PubMed

    Schick, Daniel; Herzog, Marc; Wen, Haidan; Chen, Pice; Adamo, Carolina; Gaal, Peter; Schlom, Darrell G; Evans, Paul G; Li, Yuelin; Bargheer, Matias

    2014-03-01

    We apply ultrafast x-ray diffraction with femtosecond temporal resolution to monitor the lattice dynamics in a thin film of multiferroic BiFeO3 after above-band-gap photoexcitation. The sound-velocity limited evolution of the observed lattice strains indicates a quasi-instantaneous photoinduced stress which decays on a nanosecond time scale. This stress exhibits an inhomogeneous spatial profile evidenced by the broadening of the Bragg peak. These new data require substantial modification of existing models of photogenerated stresses in BiFeO3: the relevant excited charge carriers must remain localized to be consistent with the data. PMID:24655276

  9. Long-lived charge carrier dynamics in polymer/quantum dot blends and organometal halide perovskites

    NASA Astrophysics Data System (ADS)

    Nagaoka, Hirokazu

    Solution-processable semiconductors offer a potential route to deploy solar panels on a wide scale, based on the possibility of reduced manufacturing costs by using earth-abundant materials and inexpensive production technologies, such as inkjet or roll-to-roll printing. Understanding the fundamental physics underlying device operation is important to realize this goal. This dissertation describes studies of two kinds of solar cells: hybrid polymer/PbS quantum dot solar cells and organometal halide perovskite solar cells. Chapter two discusses details of the experimental techniques. Chapter three and four explore the mechanisms of charge transfer and energy transfer spectroscopically, and find that both processes contribute to the device photocurrent. Chapter four investigates the important question of how the energy level alignment of quantum dot acceptors affects the operation of hybrid polymer/quantum dot solar cells, by making use of the size-tunable energy levels of PbS quantum dots. We observe that long-lived charge transfer yield is diminished at larger dot sizes as the energy level offset at the polymer/quantum dot interface is changed through decreasing quantum confinement using a combination of spectroscopy and device studies. Chapter five discusses the effects of TiO2 surface chemistry on the performance of organometal halide perovskite solar cells. Specifically, chapter five studies the effect of replacing the conventional TiO2 electrode with Zr-doped TiO2 (Zr-TiO2). We aim to explore the correlation between charge carrier dynamics and device studies by incorporating zirconium into TiO2. We find that, compared to Zr-free controls, solar cells employing Zr-TiO2 give rise to an increase in overall power conversion efficiency, and a decrease in hysteresis. We also observe longer carrier lifetimes and higher charge carrier densities in devices on Zr-TiO2 electrodes at microsecond times in transient photovoltage experiments, as well as at longer persistent photovoltages extending from ~millisecond to tens of sec. Finally, we characterize the combined effects of pyridine treatment and Zr-TiO2 on device performance and carrier lifetimes.

  10. Investigation of charge-carrier injection characteristics in NPB\\/Alq 3 heterojunction devices

    Microsoft Academic Search

    Jiangshan Chen; Dongge Ma

    2006-01-01

    The effect of copper phthalocyanine (CuPc) and LiF interfacial layers on the charge-carrier injection in N,N?-di(naphthalene-1-yl)-N,N?-diphenyl-benzidine (NPB)\\/tris(8-hydroxyquinoline) aluminium (Alq3) organic heterojunction devices have been studied through the analysis of current–voltage characteristics. The investigation clearly demonstrated that the hole injection into NPB from anode is Fowler–Nordheim (FN) tunneling and the electron injection into Alq3 from cathode is Richardson–Schottky (RS) thermionic emission.

  11. Influence of exciton lifetime on charge carrier dynamics in an organic heterostructure

    SciTech Connect

    Agrawal, Kanika L. [Univ. of Michigan, Ann Arbor, MI (United States). Center for Solar and Thermal Energy Conversion; Sykes, Matthew E. [Univ. of Michigan, Ann Arbor, MI (United States). Center for Solar and Thermal Energy Conversion; An, Kwang Hyup [GE Global Research, Niskayuna, New York (United States); Frieberg, Bradley [Univ. of Michigan, Ann Arbor, MI (United States); Green, P. F. [Univ. of Michigan, Ann Arbor, MI (United States). Center for Solar and Thermal Energy Conversion; Shtein, Max [Univ. of Michigan, Ann Arbor, MI (United States). Center for Solar and Thermal Energy Conversion

    2013-01-01

    Interactions between charge carriers and excitons, as well as between excitons and optical cavity modes in organic optoelectronic devices are fundamental to their operational limits and chief in preventing the realization of certain phenomena, such as electrically pumped organic lasing. We uncovered a previously unreported phenomenon, wherein optical cavity-modulated exciton decay rate leads to a concomitant modulation in the electrical current of an archetypal NPD/Alq? organic light emitting device operated in forward bias. The magnitude of this variation is sensitive to the local dielectric environment of the device and is found to be as large as 15%.

  12. Photosensitive Properties and a Mechanism for Photogeneration of Charge Carriers in Polymeric Layers Containing Organometallic Complexes

    SciTech Connect

    Aleksandrova, E.L. [Ioffe Physicotechnical Institute, Russian Academy of Sciences, Politekhnicheskaya ul. 26, St. Petersburg, 194021 (Russian Federation); Goikhman, M.Ya.; Podeshvo, I.V.; Kudryavtsev, V.V. [Institute of Macromolecular Compounds, Russian Academy of Sciences, Bol'shoi proezd 31, St. Petersburg, 199004 (Russian Federation)

    2005-07-15

    New polyamide acids (prepolymers of polybenzoxazinimides) containing 2,2-biquinolyl units in their main chain are synthesized. It is shown that these polymers form stable complexes with acids derived from the transition and rare-earth metals. The results of photophysical studies support the assumption that the process of generation of free charge carriers via a state of a pair bound by a Coulomb interaction includes two stages and that metal-polymer complexes are involved in this process. The quantum yield of photogeneration amounts to 0.007-0.05.

  13. Influence of defects on excess charge carrier kinetics studied by transient PC and transient PA

    SciTech Connect

    Feist, H.; Kunst, M.; Swiatkowski, C.

    1997-07-01

    By comparison of transient photoconductivity (TPC) and transient photoinduced absorption (PA) the influence of the density of states in the bandgap on excess charge carrier kinetics is studied for a-Si:H films deposited at different temperatures and for state of the art a-Si:H films in two different states of light soaking. In both series the rising deep defect density leads to an enhancement of electron trapping rather than recombination via deep defects. The samples deposited at temperatures lower than 250 C additionally show a lower effective electron mobility, i.e., a broader conduction band tail.

  14. Physical properties of solvated charge carriers on one-dimensional semiconductors

    NASA Astrophysics Data System (ADS)

    Ussery, Geoffrey Leigh

    When an excess charge carrier is added to a one-dimensional (1D) wide-band semiconductor nanostructure immersed in a polar solvent, the carrier can undergo self-localization into a large-radius adiabatic polaron. Using a simplified theoretical model for small-diameter structures, we study physical properties of the resulting 1D polarons: low-frequency dynamics, local optical absorption, and electron transfer to/from polarons. We show that the combined microscopic dynamics of the electronic charge density and the solvent leads to macroscopic Langevin dynamics of a polaron and to the appearance of local dielectric relaxation modes. Polaron mobility is evaluated as a function of system parameters. Numerical estimates indicate that the solvated carriers can have mobilities orders of magnitude lower than the intrinsic values. We find that about 90% of the local optical absorption strength is contained in the transition to the second lowest-energy localized electronic level formed in the polarization potential well, with the equilibrium transition energy larger than the binding energy of the polaron. Thermal fluctuations, however, can cause a very substantial---an order of magnitude larger than the thermal energy---broadening of the transition. The resulting broad absorption feature may serve as a signature for the optical detection of solvated charge carriers. To examine the activation energy of electron transfer from/to a 1D semiconductor, we generalize the Marcus theory description to the case of variable distributed charge densities. We specifically analyze thermally-activated electron transfer between a small species and a 1D semiconductor and between two parallel 1D structures. While quantitatively the activation energy would ordinarily be largely determined by small species, the qualitative difference for 1D polarons is clearly delineated. A useful observation is made that traditional Marcus expressions for transfer between two small species may be a good approximation for the discussed electron transfer process. For practical values of polaron binding energies, we find that thermal fluctuations can readily facilitate the electron transfer between neighboring 1D nanostructures.

  15. Effect of a high-kappa environment on charge carrier mobility in graphene.

    PubMed

    Ponomarenko, L A; Yang, R; Mohiuddin, T M; Katsnelson, M I; Novoselov, K S; Morozov, S V; Zhukov, A A; Schedin, F; Hill, E W; Geim, A K

    2009-05-22

    It is widely assumed that the dominant source of scattering in graphene is charged impurities in a substrate. We have tested this conjecture by studying graphene placed on various substrates and in high-kappa media. Unexpectedly, we have found no significant changes in carrier mobility either for different substrates or by using glycerol, ethanol, and water as a top dielectric layer. This suggests that Coulomb impurities are not the scattering mechanism that limits the mean free path attainable for graphene on a substrate. PMID:19519058

  16. Theoretical predictions on the electronic structure and charge carrier mobility in 2D Phosphorus sheets

    PubMed Central

    Xiao, Jin; Long, Mengqiu; Zhang, Xiaojiao; Ouyang, Jun; Xu, Hui; Gao, Yongli

    2015-01-01

    We have investigated the electronic structure and carrier mobility of four types of phosphorous monolayer sheet (?-P, ?-P,?-P and ?-P) using density functional theory combined with Boltzmann transport method and relaxation time approximation. It is shown that ?-P, ?-P and ?-P are indirect gap semiconductors, while ?-P is a direct one. All four sheets have ultrahigh carrier mobility and show anisotropy in-plane. The highest mobility value is ~3?×?105?cm2V?1s?1, which is comparable to that of graphene. Because of the huge difference between the hole and electron mobilities, ?-P, ?-P and ?-P sheets can be considered as n-type semiconductors, and ?-P sheet can be considered as a p-type semiconductor. Our results suggest that phosphorous monolayer sheets can be considered as a new type of two dimensional materials for applications in optoelectronics and nanoelectronic devices. PMID:26035176

  17. Theoretical predictions on the electronic structure and charge carrier mobility in 2D Phosphorus sheets.

    PubMed

    Xiao, Jin; Long, Mengqiu; Zhang, Xiaojiao; Ouyang, Jun; Xu, Hui; Gao, Yongli

    2015-01-01

    We have investigated the electronic structure and carrier mobility of four types of phosphorous monolayer sheet (?-P, ?-P,?-P and ?-P) using density functional theory combined with Boltzmann transport method and relaxation time approximation. It is shown that ?-P, ?-P and ?-P are indirect gap semiconductors, while ?-P is a direct one. All four sheets have ultrahigh carrier mobility and show anisotropy in-plane. The highest mobility value is ~3?×?10(5)?cm(2)V(-1)s(-1), which is comparable to that of graphene. Because of the huge difference between the hole and electron mobilities, ?-P, ?-P and ?-P sheets can be considered as n-type semiconductors, and ?-P sheet can be considered as a p-type semiconductor. Our results suggest that phosphorous monolayer sheets can be considered as a new type of two dimensional materials for applications in optoelectronics and nanoelectronic devices. PMID:26035176

  18. Verification of the dispersive charge transport in a hydrazone:polycarbonate molecularly doped polymer

    NASA Astrophysics Data System (ADS)

    Tyutnev, Andrey P.; Saenko, Vladimir S.; Pozhidaev, Evgenii D.; Kolesnikov, Vladislav A.

    2009-03-01

    We report results of specially planned experiments intended to verify the dispersive character of the charge carrier transport in polycarbonate molecularly doped with hydrazone at 30 wt% loading, using for this purpose samples specifically featuring a well-defined plateau on a linear-linear plot. For this purpose we propose a new variant of the time-of-flight technique which allows easy changing of the generation zone width from about 0.5 µm (surface excitation) through intermediate values to full sample thickness (bulk excitation). To achieve this, we use electron pulses of 3-50 keV energy rather than traditional light pulses provided by lasers. Experimental results corroborated by numerical calculations uniquely prove that carrier transport in this molecularly doped polymer is dispersive, with the dispersion parameter equal to 0.75. Nevertheless, the mobility field dependence follows the famous Poole-Frenkel law.

  19. An electrochemically synthesized sulfonated polyaniline layer for positive charge carrier injection improvement in conjugated polymer devices

    Microsoft Academic Search

    L. S. Roman; R. M. Q. Mello; F. Cunha; I. A. Hümmelgen

    2004-01-01

    We report the use of sulfonated polyaniline, SPAN, as a positive charge transporting layer in organic electronic devices, demonstrating that it can be used to significantly improve injection into conjugated polymers. The introduction of an intermediate SPAN layer improves device rectification, even when low-work-function anode materials such as tin oxide are used.

  20. Charge transport in ion-gated mono-, bi-, and trilayer MoS2 field effect transistors

    PubMed Central

    Chu, Leiqiang; Schmidt, Hennrik; Pu, Jiang; Wang, Shunfeng; Özyilmaz, Barbaros; Takenobu, Taishi; Eda, Goki

    2014-01-01

    Charge transport in MoS2 in the low carrier density regime is dominated by trap states and band edge disorder. The intrinsic transport properties of MoS2 emerge in the high density regime where conduction occurs via extended states. Here, we investigate the transport properties of mechanically exfoliated mono-, bi-, and trilayer MoS2 sheets over a wide range of carrier densities realized by a combination of ion gel top gate and SiO2 back gate, which allows us to achieve high charge carrier (>1013?cm?2) densities. We discuss the gating properties of the devices as a function of layer thickness and demonstrate resistivities as low as 1?k? for monolayer and 420 ? for bilayer devices at 10?K. We show that from the capacitive coupling of the two gates, quantum capacitance can be roughly estimated to be on the order of 1??F/cm2 for all devices studied. The temperature dependence of the carrier mobility in the high density regime indicates that short-range scatterers limit charge transport at low temperatures. PMID:25465059

  1. Charge transport in ion-gated mono-, bi-, and trilayer MoS2 field effect transistors.

    PubMed

    Chu, Leiqiang; Schmidt, Hennrik; Pu, Jiang; Wang, Shunfeng; Ozyilmaz, Barbaros; Takenobu, Taishi; Eda, Goki

    2014-01-01

    Charge transport in MoS2 in the low carrier density regime is dominated by trap states and band edge disorder. The intrinsic transport properties of MoS2 emerge in the high density regime where conduction occurs via extended states. Here, we investigate the transport properties of mechanically exfoliated mono-, bi-, and trilayer MoS2 sheets over a wide range of carrier densities realized by a combination of ion gel top gate and SiO2 back gate, which allows us to achieve high charge carrier (>10(13) cm(-2)) densities. We discuss the gating properties of the devices as a function of layer thickness and demonstrate resistivities as low as 1 k? for monolayer and 420 ? for bilayer devices at 10 K. We show that from the capacitive coupling of the two gates, quantum capacitance can be roughly estimated to be on the order of 1 ?F/cm(2) for all devices studied. The temperature dependence of the carrier mobility in the high density regime indicates that short-range scatterers limit charge transport at low temperatures. PMID:25465059

  2. Inorganic/organic hybrid solar cells: optimal carrier transport in vertically aligned silicon nanowire arrays.

    PubMed

    Sato, Keisuke; Dutta, Mrinal; Fukata, Naoki

    2014-06-01

    Inorganic/organic hybrid radial heterojunction solar cells that combine vertically-aligned n-type silicon nanowires (SiNWs) with poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) have great potential for replacing commercial Si solar cells. The chief advantage of such solar cells is that they exhibit higher absorbance for a given thickness than commercial Si solar cells, due to incident light-trapping within the NW arrays, thus enabling lower-cost solar cell production. We report herein on the effects of NW length, annealing and surface electrode on the device performance of SiNW/PEDOT:PSS hybrid radial heterojunction solar cells. The power conversion efficiency (PCE) of the obtained SiNW/PEDOT:PSS hybrid solar cells can be optimized by tuning the thickness of the surface electrode, and the etching conditions during NW formation and post-annealing. The PCE of 9.3% is obtained by forming efficient transport pathways for photogenerated charge carriers to electrodes. Our approach is a significant contribution to design of high-performance and low-cost inorganic/organic hybrid heterojunction solar cells. PMID:24789210

  3. Effect of reduction of trap charge carrier density in organic field effect transistors by surface treatment of dielectric layer

    NASA Astrophysics Data System (ADS)

    Dagar, Janardan; Yadav, Vandana; Tyagi, Priyanka; Kumar Singh, Rajiv; Suman, C. K.; Srivastava, Ritu

    2013-12-01

    In this work, we have studied the effect of surface treatment of SiO2 dielectric layer on the reduction of the trap charge carrier density at dielectric/semiconducting interface by fabricating a metal-insulator-semiconductor (MIS) device using ?, ?-dihexylcarbonylquaterthiophene as semiconducting layer. SiO2 dielectric layer has been treated with 1,1,1,3,3,3-hexamethyldisilazane (HMDS) to modify the chemical group acting as charge traps. Capacitance-voltage measurements have been performed on MIS devices fabricated on SiO2 and HMDS treated SiO2. These data have been used for the calculation of trap charge carrier density and Debye length at the dielectric-semiconductor interface. The calculated trap charge carrier density has been found to reduce from (2.925 ± 0.049) × 1016 cm-3 to (2.025 ± 0.061) × 1016 cm-3 for the MIS device with HMDS treated SiO2 dielectric in comparison to that of untreated SiO2. Next, the effect of reduction in trap charge carrier density has been studied on the performance of organic field effect transistors. The improvement in the device parameters like mobility, on/off ratio, and gate leakage current has been obtained with the effect of the surface treatment. The charge carrier mobility has been improved by a factor of 2 through this treatment. Further, the influence of the treatment was observed by atomic force microscope and Fourier transform infrared spectroscopy techniques.

  4. Accessing the transport properties of graphene and its multilayers at high carrier density

    PubMed Central

    Ye, Jianting; Craciun, Monica F.; Koshino, Mikito; Russo, Saverio; Inoue, Seiji; Yuan, Hongtao; Shimotani, Hidekazu; Morpurgo, Alberto F.; Iwasa, Yoshihiro

    2011-01-01

    We present a comparative study of high carrier density transport in mono-, bi-, and trilayer graphene using electric double-layer transistors to continuously tune the carrier density up to values exceeding 1014 cm-2. Whereas in monolayer the conductivity saturates, in bi- and trilayer filling of the higher-energy bands is observed to cause a nonmonotonic behavior of the conductivity and a large increase in the quantum capacitance. These systematic trends not only show how the intrinsic high-density transport properties of graphene can be accessed by field effect, but also demonstrate the robustness of ion-gated graphene, which is crucial for possible future applications. PMID:21828007

  5. VOLUME 86, NUMBER 2 P H Y S I C A L R E V I E W L E T T E R S 8 JANUARY 2001 Charge Transport and Carrier Dynamics in Liquids Probed by THz Time-Domain Spectroscopy

    E-print Network

    Heinz, Tony F.

    VOLUME 86, NUMBER 2 P H Y S I C A L R E V I E W L E T T E R S 8 JANUARY 2001 Charge Transport electromagnetic pulse as a probe. The complex dielectric response of the photogenerated electrons is determined over a broad range of frequencies, from which we infer the electron scattering time and density through

  6. User charges in international air transportation

    E-print Network

    Seagrave, Norman P.

    1979-01-01

    The charges dealt with here are those paid by international airline operators for the use of airports and airways. At airports, there are charges for landings and takeoffs and various fees or rentals for other facilities ...

  7. A fundamental study of the charge transport and morphology of regioregular poly(3-hexylthiophene)

    NASA Astrophysics Data System (ADS)

    Kline, R. Joseph

    Conjugated polymers include some of the most promising candidates for the active layer of low-cost thin-film transistors (TFTs) and bulk heterojunction photovoltaic (PV) cells. The charge carrier mobility of these conjugated polymers is the key materials property limiting the performance of both of these devices. This thesis outlines a fundamental investigation of the charge transport and morphology of the first high mobility conjugated polymer, regioregular poly(3-hexylthiophene) (P3HT). The charge carrier mobility in TFTs was found to increase by four orders-of-magnitude as the molecular weight (MW) of P3HT is increased from 3000 g/mole to 36,000 g/mole. P3HT films with different MWs provided an ideal system for correlating morphological changes in conjugated polymers to resulting changes in charge transport. Atomic force microscopy, x-ray diffraction and grazing incidence x-ray scattering (GIXS) were used to measure changes in the crystallinity and crystal orientation associated with varying the spin-casting solvent, annealing conditions, substrate surface treatment, and drop-casting at a constant MW. The GIXS results showed that at a constant MW in both low- and high-MW films, the mobility correlated to the strength of in-plane pi-stacking. When comparing different MWs, however, this correlation broke down. Rocking curves on samples with a chemically modified surface showed highly oriented crystals that were nucleated from the substrate and correlate with variations in charge transport. Switching to low-MW P3HT improves the overall crystallinity, the intensity of in-plane pi-stacking, and the concentration of highly oriented crystals, but the mobility is more than a factor of 100 lower than high-MW P3HT. These counterintuitive results clearly show that the charge carrier mobility of conjugated polymers is coupled to several different aspects of the morphology. In the case of the low-MW films, the strong driving force for ordering creates grain boundaries that isolate the ordered regions from their neighbors. Whereas in high-MW films, the long chains connect the small ordered regions and provide a clear pathway for charges to move through the film. These results were used to develop a model for relating charge transport and structure that can be used as a guide for the development of new, improved chemical structures.

  8. Transportation of carriers in silicon implanted SiO 2 films during ionizing radiation

    NASA Astrophysics Data System (ADS)

    Chen, Ming; Zhang, Zhengxuan; Wei, Xing; Bi, Dawei; Zou, Shichang; Wang, Xi

    2012-02-01

    Silicon ion implantation has been proved to be an effective method for total-dose hardening of SiO 2 in MOS devices such as buried oxides in SOI devices, while the mechanisms are still in discussion. In this work, behavior of 10 keV X-ray induced carriers in silicon implanted thermal SiO 2 was investigated by comparing with Ar implanted SiO 2. Photoluminescence (PL) spectroscopy and TRIM calculation were used to characterize the defects of the ion implanted SiO 2 films. Metal-Oxide-Semiconductor (MOS) structures were fabricated for electrical characterization of the oxides. Positive or negative gate bias was applied during the irradiation to control the separation and transportation of radiation induced electrons and holes. Flatband voltage shifts and are extracted from high frequency capacitance-voltage (C-V) measurement results which are taken prior to and after certain total dose irradiation. The experiment result shows that both Ar and Si implantation and followed anneal could eliminate the net positive charge in SiO 2 irradiated by X-ray. But different with Ar implanted oxide, in Si implanted oxide, the reduction of positive charge is highly dependent on the implanted Si ion fluence, and is well consistent with silicon nanoclusters evolvement tendency. From these results we conclude that along with increased electron trapping at the nanostructures which is suggested by previous studies, enhanced hole trapping and recombination caused by implantation induced vacancy defects are critical mechanism of reduced total ionizing dose effects on Si implanted oxides.

  9. A new charge pumping method for determining the spatial distribution of hot-carrier-induced fixed charge in p-MOSFETs

    Microsoft Academic Search

    Masakatsu Tsuchiaki; Hisashi Hara; Toyota Morimoto; Hiroshi Iwai

    1993-01-01

    A charge pumping method is proposed for the direct measurement of the hot-carrier-induced fixed charge near the drain junction of p-MOSFETs. By holding the rising and falling slopes of the gate pulse constant and then varying the highest and lowest levels, the local threshold and local flatband voltages are readily obtained. The spatial distribution of fixed charges is directly calculated

  10. Proton intercalated two-dimensional WO3 nano-flakes with enhanced charge-carrier mobility at room temperature

    NASA Astrophysics Data System (ADS)

    Zhuiykov, Serge; Kats, Eugene; Carey, Benjamin; Balendhran, Sivacarendran

    2014-11-01

    Quasi two-dimensional (Q2D) semiconducting metal oxides with enhanced charge carrier mobility hold tremendous promise for nano-electronics, photonics, catalysis, nano-sensors and electrochromic applications. In addition to graphene and metal dichalcogenides MX2 (M = Mo, W; X = S, Se, Te), 2D sub-stoichiometric WO3-x is gaining importance as a promising semiconductor material for field-effect-transistor (FET) based devices. A combination of high permittivity, suppression of the Coulomb effects, and their stratified structure enhances the carrier mobility in such a material. Additionally, the sub-stoichiometry of this semiconductor oxide allows the reduction of the bandgap and increase of the free charge carriers at the same time. Here, we report for the first time H+ intercalated WO3 FETs, made of Q2D nano-flakes, with enhanced charge-carrier mobility exceeding 319 cm2 V-1 s-1 comparable with the charge-carrier mobility of Q2D dichalcogenides MoS2 and WSe2. Analyses indicate that the enhanced electrical properties of the sub-stoichiometric WO3-x depend on the oxygen vacancies in the intercalated nano-flakes. These findings confirmed that Q2D sub-stoichiometric WO3-x is a promising material for various functional FET devices.Quasi two-dimensional (Q2D) semiconducting metal oxides with enhanced charge carrier mobility hold tremendous promise for nano-electronics, photonics, catalysis, nano-sensors and electrochromic applications. In addition to graphene and metal dichalcogenides MX2 (M = Mo, W; X = S, Se, Te), 2D sub-stoichiometric WO3-x is gaining importance as a promising semiconductor material for field-effect-transistor (FET) based devices. A combination of high permittivity, suppression of the Coulomb effects, and their stratified structure enhances the carrier mobility in such a material. Additionally, the sub-stoichiometry of this semiconductor oxide allows the reduction of the bandgap and increase of the free charge carriers at the same time. Here, we report for the first time H+ intercalated WO3 FETs, made of Q2D nano-flakes, with enhanced charge-carrier mobility exceeding 319 cm2 V-1 s-1 comparable with the charge-carrier mobility of Q2D dichalcogenides MoS2 and WSe2. Analyses indicate that the enhanced electrical properties of the sub-stoichiometric WO3-x depend on the oxygen vacancies in the intercalated nano-flakes. These findings confirmed that Q2D sub-stoichiometric WO3-x is a promising material for various functional FET devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr05008h

  11. Electrical Conductivity of Rocks and Dominant Charge Carriers. Part 1; Thermally Activated Positive Holes

    NASA Technical Reports Server (NTRS)

    Freund, Friedemann T.; Freund, Minoru M.

    2012-01-01

    The prevailing view in the geophysics community is that the electrical conductivity structure of the Earth's continental crust over the 5-35 km depth range can best be understood by assuming the presence of intergranular fluids and/or of intragranular carbon films. Based on single crystal studies of melt-grown MgO, magma-derived sanidine and anorthosite feldspars and upper mantle olivine, we present evidence for the presence of electronic charge carriers, which derive from peroxy defects that are introduced during cooling, under non-equilibrium conditions, through a redox conversion of pairs of solute hydroxyl arising from dissolution of H2O.The peroxy defects become thermally activated in a 2-step process, leading to the release of defect electrons in the oxygen anion sublattice. Known as positive holes and symbolized by h(dot), these electronic charge carriers are highly mobile. Chemically equivalent to O(-) in a matrix of O(2-) they are highly oxidizing. Being metastable they can exist in the matrix of minerals, which crystallized in highly reduced environments. The h(dot) are highly mobile. They appear to control the electrical conductivity of crustal rocks in much of the 5-35 km depth range.

  12. An autonomous photosynthetic device in which all charge carriers derive from surface plasmons

    NASA Astrophysics Data System (ADS)

    Mubeen, Syed; Lee, Joun; Singh, Nirala; Krämer, Stephan; Stucky, Galen D.; Moskovits, Martin

    2013-04-01

    Solar conversion to electricity or to fuels based on electron-hole pair production in semiconductors is a highly evolved scientific and commercial enterprise. Recently, it has been posited that charge carriers either directly transferred from the plasmonic structure to a neighbouring semiconductor (such as TiO2) or to a photocatalyst, or induced by energy transfer in a neighbouring medium, could augment photoconversion processes, potentially leading to an entire new paradigm in harvesting photons for practical use. The strong dependence of the wavelength at which the local surface plasmon can be excited on the nanostructure makes it possible, in principle, to design plasmonic devices that can harvest photons over the entire solar spectrum and beyond. So far, however, most such systems show rather small photocatalytic activity in the visible as compared with the ultraviolet. Here, we report an efficient, autonomous solar water-splitting device based on a gold nanorod array in which essentially all charge carriers involved in the oxidation and reduction steps arise from the hot electrons resulting from the excitation of surface plasmons in the nanostructured gold. Each nanorod functions without external wiring, producing 5 × 1013 H2 molecules per cm2 per s under 1 sun illumination (AM 1.5 and 100 mW cm-2), with unprecedented long-term operational stability.

  13. 41 CFR 302-7.103 - How are the charges calculated when a carrier charges a minimum weight, but the actual weight of...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...actual weight of HHG, PBP&E and temporary storage is less than the minimum weight charged...RELOCATION ALLOWANCES TRANSPORTATION AND STORAGE OF PROPERTY 7-TRANSPORTATION AND TEMPORARY STORAGE OF HOUSEHOLD GOODS AND PROFESSIONAL...

  14. 41 CFR 302-7.103 - How are the charges calculated when a carrier charges a minimum weight, but the actual weight of...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...actual weight of HHG, PBP&E and temporary storage is less than the minimum weight charged...RELOCATION ALLOWANCES TRANSPORTATION AND STORAGE OF PROPERTY 7-TRANSPORTATION AND TEMPORARY STORAGE OF HOUSEHOLD GOODS AND PROFESSIONAL...

  15. 41 CFR 302-7.103 - How are the charges calculated when a carrier charges a minimum weight, but the actual weight of...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...actual weight of HHG, PBP&E and temporary storage is less than the minimum weight charged...RELOCATION ALLOWANCES TRANSPORTATION AND STORAGE OF PROPERTY 7-TRANSPORTATION AND TEMPORARY STORAGE OF HOUSEHOLD GOODS, PROFESSIONAL...

  16. Transport of Molybdenum Across a Bulk Liquid Membrane Using 8?Hydroxy Quinoline as a Carrier

    Microsoft Academic Search

    Jayshree Ramkumar; B. Maiti

    2005-01-01

    8?Hydroxy quinoline was used successfully as a carrier for the transport of molybdenum across a bulk liquid membrane of chloroform. The pH of the feed solution was adjusted to 5.5. A mixture of 0.1?M nitric acid and 0.2?M hydrogen peroxide served as receiving phase for the maximum transport of the metal ion. Under the optimized experimental conditions, 80% of molybdenum

  17. Analytical Carrier Transport Model for Arbitrarily Shallow p-n Junctions

    E-print Network

    Technische Universiteit Delft

    Analytical Carrier Transport Model for Arbitrarily Shallow p-n Junctions Milos Popadi, Gianpaolo Lorito and Lis K. Nanver Abstract - This paper presents for the first time an analytical model extent be simulated by physics-based simulators [2]- [4]. Compact and efficient analytical models can

  18. Theory of high field carrier transport and impact ionization in ZnO

    Microsoft Academic Search

    Francesco Bertazzi; Michele Penna; Michele Goano; Enrico Bellotti

    2010-01-01

    We present a full band Monte Carlo study of high field carrier transport and impact ionization properties of wurtzite ZnO. The proposed model is based on an accurate electronic structure calculated with a nonlocal empirical pseudopotential method and a phonon dispersion determined with density functional theory. The model includes the full details of the lowest eight conduction bands and the

  19. Integrative Literature Review: Organizational Commitment and Workplace Outcomes: A Conceptual Model for Truckload Transportation Carriers

    Microsoft Academic Search

    Carroll M. Graham; Fredrick Muyia Nafukho

    2010-01-01

    A selective literature review resulted in the conceptualization of a model illustrating the expected relationships of antecedents, processes, practices, and consequences of truckload carriers in the transportation industry. Thus, collection of data and analysis is recommended if the model and applicable theory are to be developed to the fullest extent possible. Accordingly, the authors provide a working model that illustrates

  20. Studying of hot-carrier effect in floating body SOI MOSFETs by the transient charge pumping technique

    Microsoft Academic Search

    Mikhail Nagoga; Serguei Okhonin; Pierre Fazan

    2004-01-01

    The newly introduced transient charge pumping (TCP) technique is used to characterize hot-carrier effects in floating body SOI MOSFETs for the first time. Its unique advantage is the possibility to characterize SOI transistors without a body contact. The method was tested on state-of-the-art 0.13-?m partially depleted devices. TCP measurements performed in the course of a hot-carrier stress allow monitoring the

  1. Heating of charge carriers and rectification of current in asymmetrical p-n junction in a microwave field

    SciTech Connect

    Dadamirzayev, M. G., E-mail: Gulyamov1949@rambler.ru [Namangan Engineering Pedagogical Institute (Uzbekistan)

    2011-03-15

    The emf U{sub oc} of hot charge carriers generated in an asymmetrical p-n junction in a microwave electromagnetic field is determined by hot holes despite the fact that the temperature of electrons is much higher than that of holes. It is established that the open-circuit voltage depends on the temperature of the carriers, which determine the total current through p-n junction.

  2. CHARACTERIZING COUPLED CHARGE TRANSPORT WITH MULTISCALE MOLECULAR DYNAMICS

    SciTech Connect

    Swanson, Jessica

    2011-08-31

    This is the final progress report for Award DE-SC0004920, entitled 'Characterizing coupled charge transport with multi scale molecular dynamics'. The technical abstract will be provided in the uploaded report.

  3. Apical membrane proteins are transported in distinct vesicular carriers

    Microsoft Academic Search

    Ralf Jacob; Hassan Y. Naim

    2001-01-01

    The function of polarized epithelial cells and neurons is achieved through intracellular sorting mechanisms that recognize classes of proteins in the trans-Golgi network (TGN) and deliver them into separate vesicles for transport to the correct surface domain. Some proteins are delivered to the apical membrane after their association with membrane detergent-insoluble glycophosphatidylinositol\\/cholesterol (DIG) membrane microdomains [1], while some do not

  4. Long-circulation of hemoglobin-loaded polymeric nanoparticles as oxygen carriers with modulated surface charges.

    PubMed

    Xu, Feng; Yuan, Yuan; Shan, Xiaoqian; Liu, Changsheng; Tao, Xinyi; Sheng, Yan; Zhou, Huanjun

    2009-07-30

    The aim of this study was to investigate the effects of the surface charges on the in vitro macrophage cellular uptake and in vivo blood clearance and biodistribution of the hemoglobin-loaded polymeric nanoparticles (HbPNPs). The surface charges of the HbPNPs fabricated from mPEG-PLA-mPEG were modulated with cationized cetyltrimethylammonium bromide (CTAB) and anionized sodium dodecyl sulphate (SDS), respectively. In vitro macrophage cellular uptake and in vivo biodistribution of the coumarin 6-labeled HbPNPs with different electric charges were investigated, and the half-lives in the circulation were pharmacokinetically analyzed. The particle sizes of the HbPNPs were all below 200 nm with a narrow size distribution and high encapsulation efficiency (>84%). And the zeta-potentials of the untreated, cationized and anionized HbPNPs in phosphate buffered sodium chloride solution (PBS) were -12.3, +3.28 and -25.4 mV, respectively. The HbPNPs did not occur significant aggregation or sedimentation, even after 5 days. Compared with the untreated HbPNPs, 1-fold decrease/increase of the uptake percentage associated with the cationized/anionized HbPNPs was observed. In vivo experiment demonstrated that the calculated half-life of the cationized HbPNPs was 10.991 h, 8-fold longer than that of the untreated HbPNPs (1.198 h). But the anionized HbPNPs displayed opposite effect. Furthermore, the cationized HbPNPs mainly accumulated in the liver, lung and spleen after 48 h injection. MTT results showed that the HbPNPs with different surface charges all exhibited slight toxicity. These results demonstrated that the CTAB-modulated HbPNPs with low positive charge and suitable size have a promising potential as a long-circulating oxygen carrier system with desirable biocompatibility and biofunctionality. PMID:19454305

  5. Spin polarization of free charge carriers underlies the principles of operation of the spintronics devices. HgTe is a good candidate for spintronics as its spin

    E-print Network

    Spin polarization of free charge carriers underlies the principles of operation of the spintronics, USA 3Institute of Semiconductor Physics, Novosibirsk 630090, Russia Facilities: DC Field Facility; SCM

  6. An acoustic charge transport imager for high definition television applications

    NASA Technical Reports Server (NTRS)

    Hunt, William D.; Brennan, Kevin F.; Summers, Chris J.

    1992-01-01

    In this report we present the progress during the second six month period of the project. This includes both experimental and theoretical work on the acoustic charge transport (ACT) portion of the chip, the theoretical program modelling of both the avalanche photodiode (APD) and the charge transfer and overflow transistor and the materials growth and fabrication part of the program.

  7. Proton intercalated two-dimensional WO3 nano-flakes with enhanced charge-carrier mobility at room temperature.

    PubMed

    Zhuiykov, Serge; Kats, Eugene; Carey, Benjamin; Balendhran, Sivacarendran

    2014-12-21

    Quasi two-dimensional (Q2D) semiconducting metal oxides with enhanced charge carrier mobility hold tremendous promise for nano-electronics, photonics, catalysis, nano-sensors and electrochromic applications. In addition to graphene and metal dichalcogenides MX2 (M = Mo, W; X = S, Se, Te), 2D sub-stoichiometric WO(3-x) is gaining importance as a promising semiconductor material for field-effect-transistor (FET) based devices. A combination of high permittivity, suppression of the Coulomb effects, and their stratified structure enhances the carrier mobility in such a material. Additionally, the sub-stoichiometry of this semiconductor oxide allows the reduction of the bandgap and increase of the free charge carriers at the same time. Here, we report for the first time H(+) intercalated WO(3) FETs, made of Q2D nano-flakes, with enhanced charge-carrier mobility exceeding 319 cm(2) V(-1) s(-1) comparable with the charge-carrier mobility of Q2D dichalcogenides MoS(2) and WSe(2). Analyses indicate that the enhanced electrical properties of the sub-stoichiometric WO(3-x) depend on the oxygen vacancies in the intercalated nano-flakes. These findings confirmed that Q2D sub-stoichiometric WO(3-x) is a promising material for various functional FET devices. PMID:25367432

  8. Carriers transport properties in GaInP solar cells grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Dai, P.; Lu, S. L.; Arimochi, M.; Uchida, S.; Watanabe, T.; Luo, X. D.; Yang, H.

    2014-12-01

    The transport properties of carriers in GaInP solar cells grown by molecular beam epitaxy are investigated by temperature-dependent current-voltage (I-V) measurements. In contrast to GaInP/AlGaInP heterostructure, a long PL decay time is observed in GaInP/AlInP, which is ascribed to a lower interface recombination due to an improved carriers' confinement in the case of the high-energy barrier. However, the series resistance induced by the high potential barrier at GaInP/AlInP interface due to a big valence band offset prevents the improvement of solar cell's performance. An S-shape like I-V characteristic observed at low temperatures indicates that the transport of major carriers is limited by the barrier. A calculation based on the combination of a normal photovoltaic device with a barrier-affected thermal carriers transport explicitly explains this abnormal I-V characteristic. Our study demonstrates the critical role of the barrier-induced series resistance in the determination of solar cell's performance.

  9. Railway transport of low temperature heat from large power stations by means of alternative heat carriers and water

    Microsoft Academic Search

    G. Luchtman; T. Bracke

    1981-01-01

    The feasibility of railway transport of liquid and solid heat carriers in tank cars so as to replace pipeline transport of small to medium large heat loads was investigated. The typical characteristics of railway transport were analyzed and all essential technical and economical variables were integrated in a transport model. Over 1000 complex chemical compounds were evaluated for their suitability

  10. On the mechanisms of photogeneration of charge carriers in PEPC-C60 composites

    NASA Astrophysics Data System (ADS)

    Zabolotny, M. A.; Barabash, Yu. M.; Dmitrenko, O. P.; Kulish, N. P.; Davidenko, N. A.; Studzinskii, S. L.; Olasyuk, A. P.; Demchenko, A. V.

    2013-08-01

    Photogeneration of electric charge carriers at high strengths of the external electric field and the temperature of transition to the viscous-flow state ( T visc) of thin PEPC-C60 composite films obtained by casting from a toluene solution have been studied. The rheology of the composite films has been investigated by the nondestructive optical method. The consistent correlated change in the values of T visc and the effective temperature in the expression for the photogeneration quantum yield ( T 0) in the Meltz representation with variations in the C60 concentration has been established. The difference between T visc and T 0 in thin composite films does not exceed 2-3% of T visc ( T 0).

  11. Effect of charge carrier trapping on germanium coaxial detector line shapes

    NASA Astrophysics Data System (ADS)

    Raudorf, Thomas W.; Pehl, Richard H.

    1987-04-01

    A theoretical method to predict and quantify the effects of charge carrier trapping on germanium coaxial detector line shapes has been developed. This model was used to calculate line shapes which closely matched the measured line shapes of both conventional and reverse electrode high-purity germanium coaxial detectors that had suffered fast neutron damage. In accordance with experimentally established behavior, the theory predicts that reverse electrode detectors are vastly more resistent to the effects of neutron damage than conventional electrode detectors. The theory also predicts that the energy resolution and line shape of neutron-damaged conventional electrode detectors are far more dependent on detector diameter than are detectors of the reverse electrode configuration. The generally observed variation of the energy resolution and line shape as a function of bias voltage is shown to arise from an ¢E -1 dependence of the trap cross section on electric field.

  12. Quantifying charge carrier concentration in ZnO thin films by Scanning Kelvin Probe Microscopy

    NASA Astrophysics Data System (ADS)

    Maragliano, C.; Lilliu, S.; Dahlem, M. S.; Chiesa, M.; Souier, T.; Stefancich, M.

    2014-02-01

    In the last years there has been a renewed interest for zinc oxide semiconductor, mainly triggered by its prospects in optoelectronic applications. In particular, zinc oxide thin films are being widely used for photovoltaic applications, in which the determination of the electrical conductivity is of great importance. Being an intrinsically doped material, the quantification of its doping concentration has always been challenging. Here we show how to probe the charge carrier density of zinc oxide thin films by Scanning Kelvin Probe Microscopy, a technique that allows measuring the contact potential difference between the tip and the sample surface with high spatial resolution. A simple electronic energy model is used for correlating the contact potential difference with the doping concentration in the material. Limitations of this technique are discussed in details and some experimental solutions are proposed. Two-dimensional doping concentration images acquired on radio frequency-sputtered intrinsic zinc oxide thin films with different thickness and deposited under different conditions are reported. We show that results inferred with this technique are in accordance with carrier concentration expected for zinc oxide thin films deposited under different conditions and obtained from resistivity and mobility measurements.

  13. Charge transport by holographic Fermi surfaces

    E-print Network

    Faulkner, Thomas

    We compute the contribution to the conductivity from holographic Fermi surfaces obtained from probe fermions in an AdS charged black hole. This requires calculating a certain part of the one-loop correction to a vector ...

  14. Tuning transport properties of nanofluidic devices with local charge inversion

    PubMed Central

    He, Yan; Gillespie, Dirk; Boda, Dezs?; Vlassiouk, Ivan; Eisenberg, Robert S.; Siwy, Zuzanna S.

    2009-01-01

    Nanotubes can selectively conduct ions across membranes to make ionic devices with transport characteristics similar to biological ion channels and semiconductor electron devices. Depending on the surface charge profile of the nanopore, ohmic resistors, rectifiers, and diodes can be made. Here we show that a uniformly charged conical nanopore can have all these transport properties by changing the ion species and their concentrations on each side of the membrane. Moreover, the cation vs. anion selectivity of the pores can be changed. We find that polyvalent cations like Ca2+ and the trivalent cobalt sepulchrate produce localized charge inversion to change the effective pore surface charge profile from negative to positive. These effects are reversible so that the transport and selectivity characteristics of ionic devices can be tuned, much as the gate voltage tunes the properties of a semiconductor. PMID:19317490

  15. Carrier-mediated system for transport of biotin in rat intestine in vitro

    SciTech Connect

    Said, H.M.; Redha, R.

    1987-01-01

    Transport of biotin was examined in rat intestine using the everted sac technique. Transport of 0.1 ..mu..M biotin was linear with time for at least 30 min of incubation and occurred at a rate 3.7 pmol g initial tissue wet wt/sup -1/ min/sup -1/. Transport of biotin was higher in the jejunum than the ileum and was minimum in the colon (85 +/- 6, 36 +/- 6, and 2.8 +/- 0.6 pmol x g initial tissue wet wt/sup -1/ x 25 min/sup -1/, respectively). In the jejunum, transport of biotin was saturable at low concentrations but linear at higher concentrations. The transport of low concentrations of biotin was 1) inhibited by structural analogues (desthiobiotin, biotin methyl ester, diaminobiotin, and biocytin), 2) Na/sup +/ dependent, 3) energy dependent, 4) temperature dependent, and 5) proceeded against a concentration gradient in the serosal compartment. No metabolic alteration occurs to the biotin molecule during transport. This study demonstrates that biotin transport in rat intestine occurs by a carrier-mediated process at low concentrations and by simple diffusion at high concentrations. Furthermore, the carrier-mediated process is Na/sup +/, energy, and temperature dependent.

  16. Verification of three dimensional charge transport simulations using ion microbeams

    SciTech Connect

    Horn, K.M.; Dodd, P.E. [Sandia National Labs., Albuquerque, NM (United States); Breese, M.B.H. [Oxford Univ. (United Kingdom). Dept. of Physics; Doyle, B.L. [Sandia National Labs., Albuquerque, NM (United States)

    1996-12-31

    Optically targeted, ion microbeams provide a useful means of exposing individual structures within an integrated circuit to ionizing radiation. With this tool, calibrated, low damage, charge collection spectra can be measured from specific circuit structures without preceding ion damage to the structure or surrounding circuitry. This paper presents comparisons of calibrated, low damage, ion microbeam- based charge collection measurements and three-dimensional, charge transport simulations of charge collection for isolated n- and p- channel field effect transistors under conducting and non-conducting bias conditions.

  17. Effect of reduction of trap charge carrier density in organic field effect transistors by surface treatment of dielectric layer

    SciTech Connect

    Dagar, Janardan; Yadav, Vandana; Kumar Singh, Rajiv; Suman, C. K.; Srivastava, Ritu, E-mail: ritu@mail.nplindia.org [Physics of Energy Harvesting Division, CSIR-National Physical Laboratory, CSIR-Network of Institute for Solar Energy (NISE), Dr. K.S.Krishnan Road, New Delhi 110012 (India); Tyagi, Priyanka [Physics of Energy Harvesting Division, CSIR-National Physical Laboratory, CSIR-Network of Institute for Solar Energy (NISE), Dr. K.S.Krishnan Road, New Delhi 110012 (India); Center for Applied Research in Electronics, Indian Institute of Technology Delhi, New Delhi 110016 (India)

    2013-12-14

    In this work, we have studied the effect of surface treatment of SiO{sub 2} dielectric layer on the reduction of the trap charge carrier density at dielectric/semiconducting interface by fabricating a metal–insulator–semiconductor (MIS) device using ?, ?-dihexylcarbonylquaterthiophene as semiconducting layer. SiO{sub 2} dielectric layer has been treated with 1,1,1,3,3,3-hexamethyldisilazane (HMDS) to modify the chemical group acting as charge traps. Capacitance-voltage measurements have been performed on MIS devices fabricated on SiO{sub 2} and HMDS treated SiO{sub 2}. These data have been used for the calculation of trap charge carrier density and Debye length at the dielectric-semiconductor interface. The calculated trap charge carrier density has been found to reduce from (2.925?±?0.049) × 10{sup 16}?cm{sup ?3} to (2.025?±?0.061) × 10{sup 16}?cm{sup ?3} for the MIS device with HMDS treated SiO{sub 2} dielectric in comparison to that of untreated SiO{sub 2}. Next, the effect of reduction in trap charge carrier density has been studied on the performance of organic field effect transistors. The improvement in the device parameters like mobility, on/off ratio, and gate leakage current has been obtained with the effect of the surface treatment. The charge carrier mobility has been improved by a factor of 2 through this treatment. Further, the influence of the treatment was observed by atomic force microscope and Fourier transform infrared spectroscopy techniques.

  18. 41 CFR 302-10.300 - May I receive an advance of funds when a commercial carrier transports the mobile home?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...advance of funds when a commercial carrier transports the mobile home? 302-10.300...advance of funds when a commercial carrier transports the mobile home? Yes, you may...arranging and paying a commercial carrier to transport your mobile home. However, the...

  19. Terahertz conductivity and ultrafast dynamics of photoinduced charge carriers in intrinsic 3C and 6H silicon carbide

    NASA Astrophysics Data System (ADS)

    Rubano, Andrea; Wolf, Martin; Kampfrath, Tobias

    2014-07-01

    The terahertz (THz) conductivity of photoinduced charge carriers in two common polytypes of silicon carbide, 3C-SiC and 6H-SiC, is studied on picosecond time scales using an optical-pump THz-probe technique. We find that the conductivity, measured from 0.7 to 3 THz, is well described by the Drude model, and obtain a velocity relaxation time of 75 fs, independent of sample and charge-carrier density. In contrast, the carrier relaxation rates in the two polytypes differ by orders of magnitude: in 6H- and 3C-SiC, recombination proceeds on a time scale of few picoseconds and beyond nanoseconds, respectively.

  20. Imaging of nanoscale charge transport in bulk heterojunction solar cells

    NASA Astrophysics Data System (ADS)

    Hamadani, Behrang H.; Gergel-Hackett, Nadine; Haney, Paul M.; Zhitenev, Nikolai B.

    2011-06-01

    We have studied the local charge transport properties of organic bulk heterojunction solar cells based on the blends of poly(3-hexylthiophene) and phenyl-C61-butyric acid methyl ester with a photoconductive atomic force microscope (PCAFM). We explore the role of morphology on transport of photogenerated electrons or holes by careful consideration of the sample geometry and the choice of the atomic force microscope (AFM) tip. We then consider the role of the film/tip contact on the local current-voltage characteristics of these structures and present a model based on a drift and diffusion description of transport. We find that our simple 1D model can only reproduce qualitative features of the data using unphysical parameters, indicating that more sophisticated modeling is required to capture all the nonideal characteristics of the AFM transport measurements. Our results show that interpretation of PCAFM contrast and its relation to material morphology or charge transport is not very straightforward.

  1. High-field charge transport on the surface of Bi2Se3

    NASA Astrophysics Data System (ADS)

    Weng, M. Q.; Wu, M. W.

    2015-03-01

    We present a theoretical study on the high-field charge transport on the surface of Bi2Se3 and reproduce all the main features of the recent experimental results, i.e., the incomplete current saturation and the finite residual conductance in the high applied field regime. Due to the hot-electron effect, the conductance decreases and the current shows a tendency of saturation with the increase of the applied electric field. Moreover, the electric field can excite carriers within the surface bands through interband precession and leads to a higher conductance. As a joint effect of the hot-electron transport and the carrier excitation, the conductance approaches a finite residual value in the high-field regime and the current saturation becomes incomplete. We thus demonstrate that, contrary to the conjecture in the literature, the observed transport phenomena can be understood qualitatively in the framework of surface transport alone. Furthermore, if a constant bulk conductance which is insensitive to the field is introduced, one can obtain a good quantitative agreement between the theoretical results and the experimental data.

  2. Surface charge transport and decay in dielectric barrier discharges

    NASA Astrophysics Data System (ADS)

    Wild, R.; Benduhn, J.; Stollenwerk, L.

    2014-10-01

    In this work, we investigate the decay of electric charge that remains after the extinction of a barrier discharge on top of a dielectric surface. The amount of surface charge is determined spatially and temporally resolved via the Pockels effect of a BSO crystal. It is shown that the decay of charge is performed by two different processes. One channel of decay can be identified as the photoconductivity of the BSO crystal. The other decay channel is found to depend on the polarity of charge and the working gas parameters. For an inhomogeneous surface charge distribution, charge transport on the crystal surface has been observed. It takes place on a time scale of several seconds.

  3. Carrier transport in reverse-biased graphene/semiconductor Schottky junctions

    NASA Astrophysics Data System (ADS)

    Tomer, D.; Rajput, S.; Hudy, L. J.; Li, C. H.; Li, L.

    2015-04-01

    Reverse-biased graphene (Gr)/semiconductor Schottky diodes exhibit much enhanced sensitivity for gas sensing. However, carrier transport across these junctions is not fully understood yet. Here, Gr/SiC, Gr/GaAs, and Gr/Si Schottky junctions under reverse bias are investigated by temperature-dependent current-voltage measurements. A reduction in barrier height with increasing bias is observed for all junctions, suggesting electric-field enhanced thermionic emission. Further analysis of the field dependence of the reverse current reveals that while carrier transport in Gr/SiC Schottky junctions follows the Poole-Frenkel mechanism, it deviates from both the Poole-Frankel and Schottky mechanisms in Gr/Si and Gr/GaAs junctions, particularly for low temperatures and fields.

  4. Gene Amplification and Increased Expression of the Reduced Folate Carrier in Transport Elevated K562 Cells

    Microsoft Academic Search

    So C Wong; Long Zhang; Susan A Proefke; Bharati Hukku; Larry H Matherly

    1998-01-01

    The molecular bases for the 6-fold elevated methotrexate transport capacity of K562.4CF cells (Matherly et al., Cancer Res. 51: 3420–3426, 1991) were studied with reduced folate carrier (RFC) cDNA, genomic, and antibody probes. Southern analysis showed that RFC gene copies were increased (?4- to 5-fold) in K562.4CF over wild-type K562 cells. Fluorescence in situ hybridization using a genomic RFC probe

  5. Interface roughness estimate from carrier transport in InAs\\/GaSb superlattices

    Microsoft Academic Search

    F. Szmulowicz; S. Elhamri; H. J. Haugan; G. J. Brown; W. C. Mitchel

    2008-01-01

    The performance of infrared focal plane arrays and quantum cascade lasers manufactured from InAs\\/GaSb type- II superlattices (SLs) depends on the mobility of carriers along the growth axis. In turn, the longitudinal mobility depends on the quality of SL interfaces. In-plane transport is a sensitive measure of interface quality and the degree of interface roughness scattering (IRS). In this paper,

  6. Charge transport by dislocations in II-VI compounds

    NASA Astrophysics Data System (ADS)

    Hutson, A. R.

    1983-02-01

    A theory of the charge flow associated with plastic deformation in II-VI compounds is presented. It is based upon the realization that the piezoelectric polarizations about the dislocation in a slip band add constructively. Static solutions of the non-linear screening of this polarization indicate a mechanism by which majority charge is transferred from one electrode to the other as the slip band moves across the sample. In particular for CdS they show why ? dislocations transport about twice as much charge as ? dislocations. An analysis of the magnitude of charge transported vs. piezoelectric constant suggests that in the strong piezoelectrics, ZnO, CdS, and CdSe, piezoelectric fields become high enough at dislocation pileups on obstacles for holes to be produced by avalanche breakdown so that the screening becomes bipolar.

  7. Dynamical- and static-disorder effects on charge transport property of organic semiconductors

    NASA Astrophysics Data System (ADS)

    Ishii, Hiroyuki; Kobayashi, Nobuhiko; Hirose, Kenji

    2014-03-01

    In comparison with inorganic materials, electron transfer energy of typical organic semiconductors is small in the range of 10 - 100meV, which is comparable to the magnitude of dynamical disorder of transfer energy originating from the thermal fluctuations of molecular motions. Furthermore, the static disorder inevitably exists in realistic organic devices and disturbs the transport of charge carrier. To clarify the influence of the dynamical and static disorders on the mobility, we employ a realistic static-disorder potential, which is deduced from the data obtained by electron-spin-resonance spectroscopy. We evaluate the carrier mobilities of pentacene and rubrene semiconductors under the realistic situation, using our time-dependent wave-packet diffusion method. In this methodology, we carry out the quantum-mechanical time-evolution calculations of wave packets and the classical molecular dynamics simulations simultaneously. We clarify the relation between the charge transport property and these disorders. We will talk about these results in my presentation. This work was supported by JST, PRESTO, and a Grant-in-Aid for Scientific Research from the JSPS.

  8. Fuzzy fixed charge solid transportation problem and algorithm

    Microsoft Academic Search

    Lixing Yang; Linzhong Liu

    2007-01-01

    This paper mainly investigates the fixed charge solid transportation problem under fuzzy environment, in which the direct costs, the fixed charges, the supplies, the demands and the conveyance capacities are supposed to be fuzzy variables. As a result, several new models, i.e., expected value model, chance-constrained programming model and dependent-chance programming model, are constructed on the basis of credibility theory.

  9. Model for transport and reaction of defects and carriers within displacement cascades in gallium arsenide

    NASA Astrophysics Data System (ADS)

    Wampler, William R.; Myers, Samuel M.

    2015-01-01

    A model is presented for recombination of charge carriers at evolving displacement damage in gallium arsenide, which includes clustering of the defects in atomic displacement cascades produced by neutron or ion irradiation. The carrier recombination model is based on an atomistic description of capture and emission of carriers by the defects with time evolution resulting from the migration and reaction of the defects. The physics and equations on which the model is based are presented, along with the details of the numerical methods used for their solution. The model uses a continuum description of diffusion, field-drift and reaction of carriers, and defects within a representative spherically symmetric cluster of defects. The initial radial defect profiles within the cluster were determined through pair-correlation-function analysis of the spatial distribution of defects obtained from the binary-collision code MARLOWE, using recoil energies for fission neutrons. Properties of the defects are discussed and values for their parameters are given, many of which were obtained from density functional theory. The model provides a basis for predicting the transient response of III-V heterojunction bipolar transistors to displacement damage from energetic particle irradiation.

  10. Charge transport and ac response under light illumination in gate-modulated DNA molecular junctions

    NASA Astrophysics Data System (ADS)

    Zhang, Yan; Zhu, Wen-Huan; Ding, Guo-Hui; Dong, Bing; Wang, Xue-Feng

    2015-05-01

    Using a two-strand tight-binding model and within nonequilibrium Green's function approach, we study charge transport through DNA sequences {{(GC)}{{NGC}}} and {{(GC)}1}{{(TA)}{{NTA}}}{{(GC)}3} sandwiched between two Pt electrodes. We show that at low temperature DNA sequence {{(GC)}{{NGC}}} exhibits coherent charge carrier transport at very small bias, since the highest occupied molecular orbital in the GC base pair can be aligned with the Fermi energy of the metallic electrodes by a gate voltage. A weak distance dependent conductance is found in DNA sequence {{(GC)}1}{{(TA)}{{NTA}}}{{(GC)}3} with large NTA. Different from the mechanism of thermally induced hopping of charges proposed by the previous experiments, we find that this phenomenon is dominated by quantum tunnelling through discrete quantum well states in the TA base pairs. In addition, ac response of this DNA junction under light illumination is also investigated. The suppression of ac conductances of the left and right lead of DNA sequences at some particular frequencies is attributed to the excitation of electrons in the DNA to the lead Fermi surface by ac potential, or the excitation of electrons in deep DNA energy levels to partially occupied energy levels in the transport window. Therefore, measuring ac response of DNA junctions can reveal a wealth of information about the intrinsic dynamics of DNA molecules.

  11. Charge transport and recombination in P3HT:PbS solar cells

    NASA Astrophysics Data System (ADS)

    Firdaus, Yuliar; Vandenplas, Erwin; Khetubol, Adis; Cheyns, David; Gehlhaar, Robert; Van der Auweraer, Mark

    2015-03-01

    The charge carrier transport in thin film hybrid solar cells is analyzed and correlated with device performance and the mechanisms responsible for recombination loss. The hybrid bulk heterojunction consisted of a blend of poly(3-hexylthiophene) (P3HT) and small size (2.4 nm) PbS quantum dots (QDs). The charge transport in the P3HT:PbS blends was determined by measuring the space-charge limited current in hole-only and electron-only devices. When the loading of PbS QDs exceeds the percolation threshold, a significant increase of the electron mobility is observed in the blend with PbS QDs. The hole mobility, on the other hand, only slightly decreased upon increasing the loading of PbS QDs. We also showed that the photocurrent is limited by the low shunt resistance rather than by space-charge effects. The significant reduction of the fill factor at high light intensity suggests that under these conditions the non-geminate recombination dominates. However, at open-circuit conditions, the trap-assisted recombination dominates over non-geminate recombination.

  12. Heme oxygenase-1 enhances renal mitochondrial transport carriers and cytochrome C oxidase activity in experimental diabetes.

    PubMed

    Di Noia, Maria Antonietta; Van Driesche, Sarah; Palmieri, Ferdinando; Yang, Li-Ming; Quan, Shuo; Goodman, Alvin I; Abraham, Nader G

    2006-06-01

    Up-regulation of heme oxygenase (HO-1) by either cobalt protoporphyrin (CoPP) or human gene transfer improves vascular and renal function by several mechanisms, including increases in antioxidant levels and decreases in reactive oxygen species (ROS) in vascular and renal tissue. The purpose of the present study was to determine the effect of HO-1 overexpression on mitochondrial transporters, cytochrome c oxidase, and anti-apoptotic proteins in diabetic rats (streptozotocin, (STZ)-induced type 1 diabetes). Renal mitochondrial carnitine, deoxynucleotide, and ADP/ATP carriers were significantly reduced in diabetic compared with nondiabetic rats (p < 0.05). The citrate carrier was not significantly decreased in diabetic tissue. CoPP administration produced a robust increase in carnitine, citrate, deoxynucleotide, dicarboxylate, and ADP/ATP carriers and no significant change in oxoglutarate and aspartate/glutamate carriers. The increase in mitochondrial carriers (MCs) was associated with a significant increase in cytochrome c oxidase activity. The administration of tin mesoporphyrin (SnMP), an inhibitor of HO-1 activity, prevented the restoration of MCs in diabetic rats. Human HO-1 cDNA transfer into diabetic rats increased both HO-1 protein and activity, and restored mitochondrial ADP/ATP and deoxynucleotide carriers. The increase in HO-1 by CoPP administration was associated with a significant increase in the phosphorylation of AKT and levels of BcL-XL proteins. These observations in experimental diabetes suggest that the cytoprotective mechanism of HO-1 against oxidative stress involves an increase in the levels of MCs and anti-apoptotic proteins as well as in cytochrome c oxidase activity. PMID:16595661

  13. Charge transport in 4H-SiC detector structures under conditions of a high electric field

    SciTech Connect

    Ivanov, A. M., E-mail: alexandr.ivanov@mail.ioffe.ru; Mynbaeva, M. G.; Sadokhin, A. V.; Strokan, N. B.; Lebedev, A. A. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation)

    2009-08-15

    Transport of nonequilibrium charge packets in a structure with a Schottky barrier fabricated on a CVD-grown n-4H-SiC film has been studied at the maximum strength of an electric field at 1.1 MV/cm. The charge was introduced by separate {alpha}-particles and recorded by nuclear spectrometric techniques. A superlinear rise in the recorded charge as a function of the reverse bias applied to the structure was observed. Simultaneously, and also superlinearly increased the scatter in the spectrum of the charge amplitude. The observed effect is attributed to the initial stage of impact ionization. The manifestation of the process at unconventionally low fields ({approx}1 MV/cm) is accounted for by specific features of the process of charge generation. Carriers generated by slowing-down {alpha}-particles are 'hot' from the very beginning.

  14. Imaging of nanoscale charge transport in bulk heterojunction solar cells

    Microsoft Academic Search

    Behrang H. Hamadani; Nadine Gergel-Hackett; Paul M. Haney; Nikolai B. Zhitenev

    2011-01-01

    We have studied the local charge transport properties of organic bulk heterojunction solar cells based on the blends of poly(3-hexylthiophene) and phenyl-C61-butyric acid methyl ester with a photoconductive atomic force microscope (PCAFM). We explore the role of morphology on transport of photogenerated electrons or holes by careful consideration of the sample geometry and the choice of the atomic force microscope

  15. Simulation of bipolar charge transport in nanocomposite polymer films

    NASA Astrophysics Data System (ADS)

    Lean, Meng H.; Chu, Wei-Ping L.

    2015-03-01

    This paper describes 3D particle-in-cell simulation of bipolar charge injection and transport through nanocomposite film comprised of ferroelectric ceramic nanofillers in an amorphous polymer matrix. The classical electrical double layer (EDL) model for a monopolar core is extended (eEDL) to represent the nanofiller by replacing it with a dipolar core. Charge injection at the electrodes assumes metal-polymer Schottky emission at low to moderate fields and Fowler-Nordheim tunneling at high fields. Injected particles migrate via field-dependent Poole-Frenkel mobility and recombine with Monte Carlo selection. The simulation algorithm uses a boundary integral equation method for solution of the Poisson equation coupled with a second-order predictor-corrector scheme for robust time integration of the equations of motion. The stability criterion of the explicit algorithm conforms to the Courant-Friedrichs-Levy limit assuring robust and rapid convergence. The model is capable of simulating a wide dynamic range spanning leakage current to pre-breakdown. Simulation results for BaTiO3 nanofiller in amorphous polymer matrix indicate that charge transport behavior depend on nanoparticle polarization with anti-parallel orientation showing the highest leakage conduction and therefore lowest level of charge trapping in the interaction zone. Charge recombination is also highest, at the cost of reduced leakage conduction charge. The eEDL model predicts the meandering pathways of charge particle trajectories.

  16. Charge transport in gapless electron-hole systems with arbitrary band dispersion

    NASA Astrophysics Data System (ADS)

    Das Sarma, S.; Hwang, E. H.

    2015-05-01

    Using the semiclassical Boltzmann transport theory, we analytically consider dc charge transport in gapless electron-hole (both chiral and nonchiral) systems in the presence of resistive scattering due to static disorder arising from random quenched impurities in the background. We obtain the dependence of the Boltzmann conductivity on carrier density and temperature for arbitrary band dispersion in arbitrary dimensionality assuming long-range (˜1 /r ) Coulomb disorder and zero-range white-noise disorder [˜? (r ) ]. We establish that the temperature and the density dependence of the Boltzmann conductivity manifests scaling behaviors determining, respectively, the intrinsic semimetallic or the extrinsic metallic property of the gapless system. Our results apply equally well to both chiral and nonchiral gapless systems, and provide a qualitative understanding of the dependence of the Boltzmann conductivity on the band dispersion in arbitrary dimensionality.

  17. Quantum Chemical Analysis of Electronic Structure and n-and p-Type Charge Transport in Perfluoroarene-Modified Oligothiophene Semiconductors

    E-print Network

    Medvedeva, Julia E.

    molecular properties and intermolecular interactions. It is well-known that the carrier mobility of organicQuantum Chemical Analysis of Electronic Structure and n- and p-Type Charge Transport,§,| Antonio Facchetti, Arthur J. Freeman,*,§ Tobin J. Marks,*, and Mark A. Ratner*, Department of Chemistry

  18. Charge carriers' trapping states in pentacene films studied by modulated photocurrent

    NASA Astrophysics Data System (ADS)

    Gorgolis, S.; Giannopoulou, A.; Kounavis, P.

    2013-03-01

    The modulated photocurrent (MPC) technique is employed to study the charge carriers' trapping states of pentacene films. The characteristics of the experimental MPC spectra were found to be compatible with trapping-detrapping process of holes in gap states in which their occupancy can be modified by the bias illumination. A demarcation energy level separating empty from partially occupied traps was deduced from the MPC spectra, which can be used to monitor bias-light induced changes in the quasi Fermi level. An exponential trap distribution from structural disorder and a deep metastable gaussian trap distribution from adsorbed environmental impurities were extracted by means of the MPC spectroscopy. An attempt to escape frequency of the order of 1010s-1 was deduced for the gap sates. The derived trap distributions agree with those found before by means of other techniques. The present results indicate that the MPC technique can be used as a valuable tool for pentacene films characterization since it can be also applied to field effect samples.

  19. Modulation of phase behaviors and charge carrier mobilities by linkage length in discotic liquid crystal dimers.

    PubMed

    Wang, Yi-Fei; Zhang, Chun-Xiu; Wu, Hao; Zhang, Ao; Wang, Jian-Chuang; Zhang, Shuai-Feng; Pu, Jia-Ling

    2015-01-28

    A clear structure-property relationship was revealed in a series of triphenylene-based dimers, which contained two triphenylene nuclei each bearing five ?-OC4H9 substituents and are linked through a flexible O(CH2)nO polymethylene chain (n=6-12). Dimers with the linkage close to twice the length of the free side chains (n=8, 9) exhibited a single Colhp phase, while others with the linkage shorter (n=6, 7) or longer (n=10, 11, 12) showed multiphase behaviors with a transition from the Colhp phase to Colh phase; hole mobilities of Colhp phases reached 1.4×10(-2) cm2 V(-1) s(-1) in the dimer for which the linkage is exactly twice the length of the free side chains (n=8), and decreased regularly both with linkage length becoming shorter or longer. This modulation of phase behaviors and charge carrier mobilities was demonstrated to be generated by various steric perturbations introduced by linkages with different lengths, which result in different degrees of lateral fluctuations of discotic moieties in the columns. PMID:25467212

  20. Effect of high-{kappa} gate dielectrics on charge transport in graphene-based field effect transistors

    SciTech Connect

    Konar, Aniruddha; Fang Tian; Jena, Debdeep [Department of Physics and Department of Electrical Engineering, University of Notre Dame, Notre Dame, Indiana 46556 (United States)

    2010-09-15

    The effect of various dielectrics on charge mobility in single-layer graphene is investigated. By calculating the remote optical phonon scattering arising from the polar substrates, and combining it with their effect on Coulombic impurity scattering, a comprehensive picture of the effect of dielectrics on charge transport in graphene emerges. It is found that though high-{kappa} dielectrics can strongly reduce Coulombic scattering by dielectric screening, scattering from surface phonon modes arising from them wash out this advantage. Calculation shows that within the available choice of dielectrics, there is not much room for improving carrier mobility in actual devices at room temperatures.

  1. Two-dimensional mineral [Pb2BiS3][AuTe2]: high-mobility charge carriers in single-atom-thick layers.

    PubMed

    Fang, Lei; Im, Jino; Stoumpos, Constantinos C; Shi, Fengyuan; Dravid, Vinayak; Leroux, Maxime; Freeman, Arthur J; Kwok, Wai-Kwong; Chung, Duck Young; Kanatzidis, Mercouri

    2015-02-18

    Two-dimensional (2D) electronic systems are of wide interest due to their richness in chemical and physical phenomena and potential for technological applications. Here we report that [Pb2BiS3][AuTe2], known as the naturally occurring mineral buckhornite, hosts 2D carriers in single-atom-thick layers. The structure is composed of stacking layers of weakly coupled [Pb2BiS3] and [AuTe2] sheets. The insulating [Pb2BiS3] sheet inhibits interlayer charge hopping and confines the carriers in the basal plane of the single-atom-thick [AuTe2] layer. Magneto-transport measurements on synthesized samples and theoretical calculations show that [Pb2BiS3][AuTe2] is a multiband semimetal with a compensated density of electrons and holes, which exhibits a high hole carrier mobility of ?1360 cm(2)/(V s). This material possesses an extremely large anisotropy, ? = ?(c)/?(ab) ? 10(4), comparable to those of the benchmark 2D materials graphite and Bi2Sr2CaCu2O(6+?). The electronic structure features linear band dispersion at the Fermi level and ultrahigh Fermi velocities of 10(6) m/s, which are virtually identical to those of graphene. The weak interlayer coupling gives rise to the highly cleavable property of the single crystal specimens. Our results provide a novel candidate for a monolayer platform to investigate emerging electronic properties. PMID:25612093

  2. Two-dimensional Mineral [Pb2BiS3 ][AuTe2 ]: High mobility Charge Carriers in Single-atom-thick Layers

    NASA Astrophysics Data System (ADS)

    Fang, Lei; Im, J.; Stoumpos, C.; Shi, F.; Dravid, V.; Leroux, M.; Freeman, A.; Kwok, W.-K.,; Chung, D.-Y.; Kanatzidis, M.

    2015-03-01

    We report that [Pb2BiS3][AuTe2], known as a naturally occurring mineral buckhornite, hosts 2D carriers in single-atom-thick layers. The structure is composed of stacking layers of weakly coupled [Pb2BiS3] and [AuTe2] sheets. The insulating [Pb2BiS3] sheet inhibits interlayer charge hopping and confines the carriers in the basal plane of the single-atom-thick [AuTe2] layer. Magneto-transport measurements and theoretical calculations show a property of multiband semimetal with compensated density of electrons and holes, which exhibit high hole carrier mobility of 1360 cm2/Vs. This material possesses an extremely large anisotropy 104, comparable to benchmark materials graphite. The electronic structure features linear band dispersion at the Fermi level and ultrahigh Fermi velocities of 106 m/s which are virtually identical to that of graphene. The weak interlayer coupling gives rise to the highly cleavable property of single crystal specimens, indicating a prospect for monolayer system. This research was supported by the DoE, BES, under Contract No. DE-AC02-06CH11357, and NUANCE Center at the Northwestern Univeristy.

  3. 41 CFR 302-10.300 - May I receive an advance of funds when a commercial carrier transports the mobile home?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...commercial carrier transports the mobile home? 302-10.300 Section... Federal Travel Regulation System RELOCATION ALLOWANCES TRANSPORTATION...10-ALLOWANCES FOR TRANSPORTATION OF MOBILE HOMES AND BOATS USED AS A PRIMARY...commercial carrier transports the mobile home? Yes, you may...

  4. 41 CFR 302-10.300 - May I receive an advance of funds when a commercial carrier transports the mobile home?

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...commercial carrier transports the mobile home? 302-10.300 Section... Federal Travel Regulation System RELOCATION ALLOWANCES TRANSPORTATION...10-ALLOWANCES FOR TRANSPORTATION OF MOBILE HOMES AND BOATS USED AS A PRIMARY...commercial carrier transports the mobile home? Yes, you may...

  5. Transport Facilitation Committee Contributory Bus Service Charges from 1st

    E-print Network

    Shyamasundar, R.K.

    Transport Facilitation Committee Contributory Bus Service Charges from 1st May 2010 For TIFR and temporary staff on fix salary Sr.No. Category Contribution per month 1 Gross salary less than 10,000/- Rs/Manager Rs.330/- 2 Clerical Staff /Peon/Attendant Rs. 180/- The daily wages/casual labours may form

  6. Transport in charged colloids driven by thermoelectricity Alois Wrger

    E-print Network

    Paris-Sud XI, Université de

    Transport in charged colloids driven by thermoelectricity Alois Würger CPMOH, Université Bordeaux 1 by the thermoelectric response of the electrolyte solution. The thermally induced salinity gradient leads in general rise to a thermoelectric ...eld that drives the colloid to the cold or to the warm, depending

  7. Molecular Gas Adsorption Induced Carrier Transport Studies of Epitaxial Graphene using IR Reflection Spectroscopy

    E-print Network

    Daas, B K; Daniels, K M; Sudarshan, T S; Koley, Goutam; Chandrashekhar, M V S

    2012-01-01

    We investigate molecular adsorption doping by electron withdrawing NO2 and electron donating NH3 on epitaxial graphene grown on C-face SiC substrates. Amperometric measurements show conductance changes upon introduction of molecular adsorbents on epitaxial graphene. Conductance changes are a trade-off between carrier concentration and scattering, and manifest at direct current and optical frequencies. We therefore investigate changes in the infrared (IR) reflection spectra to correlate these two frequency domains, as reflectance changes are due to a change of epitaxial graphene (EG) surface conductance. We match theory with experimental IR data and extract changes in carrier concentration and scattering due to gas adsorption. Finally, we separate the intraband and interband scattering contributions to the electronic transport under gas adsorption. The results indicate that, under gas adsorption, the influence of interband scattering cannot be neglected, even at DC.

  8. Carrier transport in green AlInGaN based structures on c-plane substrates

    NASA Astrophysics Data System (ADS)

    Hager, T.; Binder, M.; Brüderl, G.; Eichler, C.; Avramescu, A.; Wurm, T.; Gomez-Iglesias, A.; Stojetz, B.; Tautz, S.; Galler, B.; Gerhard, S.; Zeisel, R.; Strauss, U.

    2013-06-01

    In this paper, the carrier transport in (Al)InGaN based test structures with In-rich quantum wells on c-plane substrates is investigated under high current operation. To get access to the injection efficiency, the devices are processed as ridge waveguide lasers and examined above threshold. The slope efficiency reveals a slight decrease as a function of current even under pulsed operation that can be related to a reduction of the injection efficiency based on carrier leakage. As the test structure contains an InGaN detection layer on the n-side, it is possible to verify hole overflow across the active region. Moreover, by analysing the current dependence of the radiative recombination in the detection layer, the reduction of slope efficiency can be correlated to increasing hole leakage.

  9. Carrier of Wingless (Cow), a Secreted Heparan Sulfate Proteoglycan, Promotes Extracellular Transport of Wingless

    PubMed Central

    Chang, Yung-Heng; Sun, Yi Henry

    2014-01-01

    Morphogens are signaling molecules that regulate growth and patterning during development by forming a gradient and activating different target genes at different concentrations. The extracellular distribution of morphogens is tightly regulated, with the Drosophila morphogen Wingless (Wg) relying on Dally-like (Dlp) and transcytosis for its distribution. However, in the absence of Dlp or endocytic activity, Wg can still move across cells along the apical (Ap) surface. We identified a novel secreted heparan sulfate proteoglycan (HSPG) that binds to Wg and promotes its extracellular distribution by increasing Wg mobility, which was thus named Carrier of Wg (Cow). Cow promotes the Ap transport of Wg, independent of Dlp and endocytosis, and this function addresses a previous gap in the understanding of Wg movement. This is the first example of a diffusible HSPG acting as a carrier to promote the extracellular movement of a morphogen. PMID:25360738

  10. Charge transport and magnetization profile at the interface between the correlated metal CaRuO3 and the antiferromagnetic insulator CaMnO3

    Microsoft Academic Search

    J. W. Freeland; J. Chakhalian; A. V. Boris; J.-M. Tonnerre; J. J. Kavich; P. Yordanov; S. Grenier; P. Zschack; E. Karapetrova; P. Popovich; H. N. Lee; B. Keimer

    2010-01-01

    A combination of spectroscopic probes was used to develop a detailed experimental description of the transport and magnetic properties of superlattices composed of the paramagnetic metal CaRuO3 and the antiferromagnetic insulator CaMnO3 . The charge-carrier density and Ru valence state in the superlattices are not significantly different from those of bulk CaRuO3 . The small charge transfer across the interface

  11. Charge Transport in Azobenzene-Based Single-Molecule Junctions

    NASA Astrophysics Data System (ADS)

    Garcia-Lekue, Aran; Kim, Youngsang; Sysoiev, Dmytro; Frederiksen, Thomas; Groth, Ulrich; Scheer, Elke

    2013-03-01

    The azobenzene class of molecules has become an archetype of molecular photoswitch research, due to their simple structure and the significant difference of the electronic system between their cis and trans isomers. However, a detailed understanding of the charge transport for the two isomers, when embedded in a junction with electrodes is still lacking. In order to clarify this issue, we investigate charge transport properties through single Azobenzene-ThioMethyl (AzoTM) molecules in a mechanically controlled break junction (MCBJ) system at 4.2 K. Single-molecule conductance, I-V characteristics, and IETS spectra of molecular junctions are measured and compared with first-principles transport calculations. Our studies elucidate the origin of a slightly higher conductance of junctions with cis isomer and demonstrate that IETS spectra of cis and trans forms show distinct vibrational fingerprints that can be used for identifying the isomer.

  12. Computational investigation of charge injection and transport properties of a series of thiophene-pyrrole based oligo-azomethines.

    PubMed

    Sahu, Harikrishna; Panda, Aditya N

    2014-05-14

    The present study explores the structural, charge carrier injection and transport properties of a series of thiophene-pyrrole based oligo-azomethines using density functional theory (DFT) methods. Our findings show that the presence of a bulky substituent adversely affects these properties. However, the electronic effect of substituents may be utilized to tune these properties by substitutions at suitable positions. Values of frontier orbitals, ionization energies, and electron affinities are calculated for each compound to predict the ease of charge injection from metal electrodes to these azomethines and the stabilities of their ionic forms. In addition to having large injection barriers, lack of stability of the anions may hinder the electron injection. However, most of the compounds have excellent hole injection capability. Computation of reorganization energies and electronic couplings followed by charge transfer rates and mobilities show large carrier mobilities for some of the studied compounds. Considering both the injection capability and carrier mobilities, it is found that a thiophene-pyrrole azomethine without any substituent and substituted azomethines with a methyl, methoxy or amine group at the 3 position of the pyrrole ring may act as efficient materials for the hole transport layer. PMID:24671604

  13. Charge transport in porous nanocrystalline titanium dioxide

    NASA Astrophysics Data System (ADS)

    Eppler, Anuradha M.; Ballard, Ian M.; Nelson, Jenny

    2002-04-01

    The dark conductivity and photoconductivity of porous, anatase titanium dioxide films have been studied in different ambient conditions. The films are nanocrystalline with a particle size of 5- 15 nm and porosity of around 50%. Films are resistive (10 4- 10 6 ? m ) in the dark in ambient air, and exhibit space charge limited current-voltage behaviour, modified by the presence of traps. Vacuum reduces the dark conductivity by a factor of 10 2-10 3. This effect is tentatively attributed to the removal of water, which is known to adsorb dissociatively on TiO 2 surfaces and may dope the material by proton insertion and Ti 3+ formation. The photoconductivity in vacuum is 10 6 larger than that in air at maximum photocurrent and increases with decreasing pressure. In this case the effect is attributed to the loss of surface adsorbed oxygen, a known electron scavenger, in vacuum. Removal of oxygen extends the electron lifetime and results in a much larger saturation photocurrent. In vacuum, a point of inflexion is observed in the transient rise and the shapes of the curves are intensity dependent. Both these observations are consistent with the presence of traps. No correlation was observed between the photoconductivity decays and temperature, which suggests that the decay occurs by band-to-band recombination and not thermionic emission. On the basis of these observations, a model based on competition between photogeneration, trapping and scavenging has been developed. By varying the trapping and recombination rates we can simulate the effects of air and vacuum. The intensity dependent results can be simulated by changing the generation rate alone which allows us to estimate a trap density of less than 10 20 cm-3. We propose that photoconductivity may be used as a direct probe of the electron lifetime and can serve to evaluate different chemical environments for dye sensitised solar cells, and to study photocatalytic function.

  14. An Efficient Scheduling Scheme on Charging Stations for Smart Transportation

    NASA Astrophysics Data System (ADS)

    Kim, Hye-Jin; Lee, Junghoon; Park, Gyung-Leen; Kang, Min-Jae; Kang, Mikyung

    This paper proposes a reservation-based scheduling scheme for the charging station to decide the service order of multiple requests, aiming at improving the satisfiability of electric vehicles. The proposed scheme makes it possible for a customer to reduce the charge cost and waiting time, while a station can extend the number of clients it can serve. A linear rank function is defined based on estimated arrival time, waiting time bound, and the amount of needed power, reducing the scheduling complexity. Receiving the requests from the clients, the power station decides the charge order by the rank function and then replies to the requesters with the waiting time and cost it can guarantee. Each requester can decide whether to charge at that station or try another station. This scheduler can evolve to integrate a new pricing policy and services, enriching the electric vehicle transport system.

  15. Towards a unified description of the charge transport mechanisms in conductive atomic force microscopy studies of semiconducting polymers.

    PubMed

    Moerman, D; Sebaihi, N; Kaviyil, S E; Leclère, P; Lazzaroni, R; Douhéret, O

    2014-09-21

    In this work, conductive atomic force microscopy (C-AFM) is used to study the local electrical properties in thin films of self-organized fibrillate poly(3-hexylthiophene) (P3HT), as a reference polymer semiconductor. Depending on the geometrical confinement in the transport channel, the C-AFM current is shown to be governed either by the charge transport in the film or by the carrier injection at the tip-sample contact, leading to either bulk or local electrical characterization of the semiconducting polymer, respectively. Local I-V profiles allow discrimination of the different dominating electrical mechanisms, i.e., resistive in the transport regime and space charge limited current (SCLC) in the local regime. A modified Mott-Gurney law is analytically derived for the contact regime, taking into account the point-probe geometry of the contact and the radial injection of carriers. Within the SCLC regime, the probed depth is shown to remain below 12 nm with a lateral electrical resolution below 5 nm. This confirms that high resolution is reached in those C-AFM measurements, which therefore allows for the analysis of single organic semiconducting nanostructures. The carrier density and mobility in the volume probed under the tip under steady-state conditions are also determined in the SCLC regime. PMID:25079791

  16. Enhanced Charge Carriers Injection by Using High-doped Silicon in Organic-inorganic Light-emitting Diodes

    Microsoft Academic Search

    Shengyi Yang; Xiulong Zhang; Zhidong Lou; Feng Teng; Zheng Xu; Yanbing Hou

    2006-01-01

    Summary form only given. In this paper, the emission of organic material inserted between two amorphous silicon dioxides (a-SiO2 ) by using high-doped p-type silicon as anode or n-type silicon as cathode has been studied under AC and DC applied voltages. Enhanced charge carrier injection and luminance were observed, which shows high-doped silicon as electrodes can increase the quantity of

  17. Dependence of the conductivity on the concentration and the hopping frequency of charge carriers in fluoride glasses

    Microsoft Academic Search

    M. Sural; A. Ghosh

    2000-01-01

    The conductivity spectra of fluoride glasses in the system ZrF4-BaF2-YF2-LiF with varying LiF content has been reported at different temperatures in the frequency range 10 Hz-2 MHz. The experimental data have been analyzed in the framework of the Almond-West formalism. The concentration and hopping frequency of the charge carriers, the dc conductivity, and the activation energy have been determined from

  18. Charge transport measurements of vertically aligned carbon nanofibers

    NASA Astrophysics Data System (ADS)

    Zhang, Lan

    2005-07-01

    Vertically aligned carbon nanofibers (VACNFs) have found a variety of electronic applications. To further realize these applications, a good understanding of the charge transport properties is essential. In this work, charge transport properties have been systematically measured for three types of VACNF forests with Ni as catalyst, namely VACNFs grown by direct current PECVD, and inductively coupled PECVD at both normal pressure and low pressure. The structure and composition of these nanofibers have also been investigated in detail prior to the charge transport measurements. Four-probe I-V measurements on individual nanofibers have been enabled by the fabrication of multiple metal ohmic contacts on individual fibers that exhibited resistance of only a few kO. An O2 plasma reactive ion etch method has been used to achieve ohmic contacts between the nanofibers and Ti/Au, Ag/Au, Cd/Au, and Cr/Au electrodes. Direct current VACNFs exhibit linear I-V behavior at room temperature, with a resistivity of approximately 4.2 x 10-3 O·cm. Our measurements are consistent with a dominant transport mechanism of electrons traveling through intergraphitic planes in the dc VACNFs. The resistivity of these fibers is almost independent of temperature, and the contact resistance decreases as temperature increases. Further studies reveal that the 10--15 nm thick graphitic outer layer dominates the charge transport properties of do VACNFs. This is demonstrated by comparison of charge transport properties of as-grown VACNFs and VACNFs with the outer layer partially removed by oxygen plasma reactive ion etch. The linear I-V behavior of the fibers does not vary as this outer layer becomes thinner, but displays a drastic shift to a rectifying behavior when this layer is completely stripped away from some regions of the nanofiber. This shift may be related with the compositional differences in the outer layer and the inner core of the nanofibers. Two-probe charge transport measurements on inductively coupled PECVD grown VACNFs indicate linear I-V behavior, and the resistivity of both types of inductively coupled PECVD grown VACNFs is on the order of 10-3 to 10-4 O·cm.

  19. Charge Transport Characteristics Of Cobalt Phthalocyanine Thin Films Grown By Molecular Beam Epitaxy

    SciTech Connect

    Gupta, S. K.; Singh, Ajay; Samanta, Soumen; Kumar, Arvind; Debnath, A. K.; Aswal, D. K. [Technical Physics Division, Bhabha Atomic Research Center, Mumbai 400 085 (India)

    2010-12-01

    In the recent times organic semiconductors (OSC) have received attention because of their application in low-cost, flexible, and large area electronics devices. The application of OSC thin films has been limited due to their low charge carrier mobility ({approx}0.1 cm{sup 2}/V-s). We have investigated the effect of substrate on structure and charge transport characteristics of cobalt phthalocyanine (CoPc) films. Thin films have been grown on both single crystal (sapphire and LaAlO{sub 3}) and amorphous (quartz) substrates using molecular beam epitaxy system. The films grown on LaAlO{sub 3} substrates exhibited a higher value of mobility ({approx}4 cm{sup 2}/V-s) while those grown on Al{sub 2}O{sub 3} and quartz showed mobility value of {approx}1 cm{sup 2}/V-s. High mobility for LaAlO{sub 3} substrates has been attributed to the enhanced ordering of the molecules due to natural twin boundaries of substrates. In order to further confirm role of grain boundaries in aligning the CoPc molecules, we measured the charge transport on films deposited at bi-crystal SrTiO{sub 3} substrates. The results showed that current along bi-crystal grain boundary is three orders of magnitude higher than for films on SrTiO{sub 3} substrate without grain boundary, which confirms our hypothesis of ordering of molecules along grain boundaries.

  20. Correlated conformation and charge transport in multiwall carbon nanotube-conducting polymer nanocomposites.

    PubMed

    Choudhury, Paramita Kar; Ramaprabhu, S; Ramesh, K P; Menon, Reghu

    2011-07-01

    The strikingly different charge transport behaviours in nanocomposites of multiwall carbon nanotubes (MWNTs) and conducting polymer polyethylenedioxythiophene-polystyrene-sulfonic-acid (PEDOT-PSS) at low temperatures are explained by probing their conformational properties using small-angle x-ray scattering (SAXS). The SAXS studies indicate the assembly of elongated PEDOT-PSS globules on the walls of nanotubes, coating them partially, thereby limiting the interaction between the nanotubes in the polymer matrix. This results in a charge transport governed mainly by small polarons in the conducting polymer despite the presence of metallic MWNTs. At T > 4 K, hopping of the charge carriers following one-dimensional variable range hopping is evident which also gives rise to a positive magnetoresistance (MR) with an enhanced localization length (?5 nm) due to the presence of MWNTs. However, at T < 4 K, the observation of an unconventional positive temperature coefficient of resistivity is attributed to small polaron tunnelling. The exceptionally large negative MR observed in this temperature regime is conjectured to be due to the presence of quasi-1D MWNTs that can aid in lowering the tunnelling barrier across the nanotube-polymer boundary resulting in large delocalization. PMID:21673397

  1. The solute carrier family 10 (SLC10): beyond bile acid transport

    PubMed Central

    da Silva, Tatiana Claro; Polli, James E.; Swaan, Peter W.

    2012-01-01

    The solute carrier (SLC) family 10 (SLC10) comprises influx transporters of bile acids, steroidal hormones, various drugs, and several other substrates. Because the seminal transporters of this family, namely, sodium/taurocholate cotransporting polypeptide (NTCP; SLC10A1) and the apical sodium-dependent bile acid transporter (ASBT; SLC10A2), were primarily bile acid transporters, the term “sodium bile salt cotransporting family” was used for the SLC10 family. However, this notion became obsolete with the finding of other SLC10 members that do not transport bile acids. For example, the sodium-dependent organic anion transporter (SOAT; SLC10A6) transports primarily sulfated steroids. Moreover, NTCP was shown to also transport steroids and xenobiotics, including HMG-CoA inhibitors (statins). The SLC10 family contains four additional members, namely, P3 (SLC10A3; SLC10A3), P4 (SLC10A4; SLC10A4), P5 (SLC10A5; SLC10A5) and SLC10A7 (SLC10A7), several of which were unknown or considered hypothetical until approximately a decade ago. While their substrate specificity remains undetermined, great progress has been made towards their characterization in recent years. SLC10A4 may participate in vesicular storage or exocytosis of neurotransmitters or mastocyte mediators, whereas SLC10A5 and SLC10A7 may be involved in solute transport and SLC10A3 may have a role as a housekeeping protein. Finally, the newly found role of bile acids in glucose and energy homeostasis, via the TGR5 receptor, sheds new light on the clinical relevance of ASBT and NTCP. The present mini-review provides a brief summary of recent progress on members of the SLC10 family. PMID:23506869

  2. Particle Dynamics and Energy Transfer in High - Quantum Well Lasers: Effects of Spectral Hole Burning, Carrier Heating, and Carrier Transport

    Microsoft Academic Search

    Chin-Yi. Tsai

    1995-01-01

    Theoretical models are presented to study the physical processes of particle dynamics and energy transfer between electrons, holes, photons, LO phonons, and acoustic phonons in high-speed semiconductor quantum well lasers. We simultaneously study the effects of spectral hole burning, carrier heating, and carrier diffusion-capture-escape on the modulation response of the quantum well laser. Our theoretical results indicate that the degradation

  3. Pore network model of electrokinetic transport through charged porous media.

    PubMed

    Obliger, Amaël; Jardat, Marie; Coelho, Daniel; Bekri, Samir; Rotenberg, Benjamin

    2014-04-01

    We introduce a method for the numerical determination of the steady-state response of complex charged porous media to pressure, salt concentration, and electric potential gradients. The macroscopic fluxes of solvent, salt, and charge are computed within the framework of the Pore Network Model (PNM), which describes the pore structure of the samples as networks of pores connected to each other by channels. The PNM approach is used to capture the couplings between solvent and ionic flows which arise from the charge of the solid surfaces. For the microscopic transport coefficients on the channel scale, we take a simple analytical form obtained previously by solving the Poisson-Nernst-Planck and Stokes equations in a cylindrical channel. These transport coefficients are upscaled for a given network by imposing conservation laws for each pores, in the presence of macroscopic gradients across the sample. The complex pore structure of the material is captured by the distribution of channel diameters. We investigate the combined effects of this complex geometry, the surface charge, and the salt concentration on the macroscopic transport coefficients. The upscaled numerical model preserves the Onsager relations between the latter, as expected. The calculated macroscopic coefficients behave qualitatively as their microscopic counterparts, except for the permeability and the electro-osmotic coupling coefficient when the electrokinetic effects are strong. Quantitatively, the electrokinetic couplings increase the difference between the macroscopic coefficients and the corresponding ones for a single channel of average diameter. PMID:24827338

  4. FAST TRACK COMMUNICATION: Electronic transport properties of charge-ordered Bi0.4Ca0.6MnO3 film

    NASA Astrophysics Data System (ADS)

    Chen, Y. Z.; Sun, J. R.; Wang, D. J.; Liang, S.; Wang, J. Z.; Han, Y. N.; Han, B. S.; Shen, B. G.

    2007-11-01

    The electronic transport properties of charge-ordered Bi0.4Ca0.6MnO3 films grown on a (110) SrTiO3 substrate are experimentally studied. Special attention has been paid to the Hall effect around the charge-ordering (CO) transition. The charge carriers are found to be electron-like, and the carrier density n exhibits a significant change upon the CO transition: it is nearly constant above the transition temperature Tco, ~0.36 electrons/Mn, and reduces with decrease of the temperature below Tco following the formula n \\propto \\exp (-E_{\\mathrm {H}}/k_{\\mathrm {B}}T) , with an activation energy EH of ~0.13 eV. In contrast, no obvious signatures of thermal activation for Hall mobility were observed. Meanwhile, it is revealed that magnetic field affects the resistivity by enhancing the carrier mobility of the film in the course of the CO transition.

  5. Utilizing carbon nanotube electrodes to improve charge injection and transport in bis(trifluoromethyl)-dimethyl-rubrene ambipolar single crystal transistors.

    PubMed

    Xie, Wei; Prabhumirashi, Pradyumna L; Nakayama, Yasuo; McGarry, Kathryn A; Geier, Michael L; Uragami, Yuki; Mase, Kazuhiko; Douglas, Christopher J; Ishii, Hisao; Hersam, Mark C; Frisbie, C Daniel

    2013-11-26

    We have examined the significant enhancement of ambipolar charge injection and transport properties of bottom-contact single crystal field-effect transistors (SC-FETs) based on a new rubrene derivative, bis(trifluoromethyl)-dimethyl-rubrene (fm-rubrene), by employing carbon nanotube (CNT) electrodes. The fundamental challenge associated with fm-rubrene crystals is their deep-lying HOMO and LUMO energy levels, resulting in inefficient hole injection and suboptimal electron injection from conventional Au electrodes due to large Schottky barriers. Applying thin layers of CNT network at the charge injection interface of fm-rubrene crystals substantially reduces the contact resistance for both holes and electrons; consequently, benchmark ambipolar mobilities have been achieved, reaching 4.8 cm(2) V(-1) s(-1) for hole transport and 4.2 cm(2) V(-1) s(-1) for electron transport. We find that such improved injection efficiency in fm-rubrene is beneficial for ultimately unveiling its intrinsic charge transport properties so as to exceed those of its parent molecule, rubrene, in the current device architecture. Our studies suggest that CNT electrodes may provide a universal approach to ameliorate the charge injection obstacles in organic electronic devices regardless of charge carrier type, likely due to the electric field enhancement along the nanotube located at the crystal/electrode interface. PMID:24175573

  6. The Human Gene SLC25A29, of Solute Carrier Family 25, Encodes a Mitochondrial Transporter of Basic Amino Acids*

    PubMed Central

    Porcelli, Vito; Fiermonte, Giuseppe; Longo, Antonella; Palmieri, Ferdinando

    2014-01-01

    The human genome encodes 53 members of the solute carrier family 25 (SLC25), also called the mitochondrial carrier family, many of which have been shown to transport carboxylates, amino acids, nucleotides, and cofactors across the inner mitochondrial membrane, thereby connecting cytosolic and matrix functions. In this work, a member of this family, SLC25A29, previously reported to be a mitochondrial carnitine/acylcarnitine- or ornithine-like carrier, has been thoroughly characterized biochemically. The SLC25A29 gene was overexpressed in Escherichia coli, and the gene product was purified and reconstituted in phospholipid vesicles. Its transport properties and kinetic parameters demonstrate that SLC25A29 transports arginine, lysine, homoarginine, methylarginine and, to a much lesser extent, ornithine and histidine. Carnitine and acylcarnitines were not transported by SLC25A29. This carrier catalyzed substantial uniport besides a counter-exchange transport, exhibited a high transport affinity for arginine and lysine, and was saturable and inhibited by mercurial compounds and other inhibitors of mitochondrial carriers to various degrees. The main physiological role of SLC25A29 is to import basic amino acids into mitochondria for mitochondrial protein synthesis and amino acid degradation. PMID:24652292

  7. Intermediate tunnelling-hopping regime in DNA charge transport.

    PubMed

    Xiang, Limin; Palma, Julio L; Bruot, Christopher; Mujica, Vladimiro; Ratner, Mark A; Tao, Nongjian

    2015-03-01

    Charge transport in molecular systems, including DNA, is involved in many basic chemical and biological processes, and its understanding is critical if they are to be used in electronic devices. This important phenomenon is often described as either coherent tunnelling over a short distance or incoherent hopping over a long distance. Here, we show evidence of an intermediate regime where coherent and incoherent processes coexist in double-stranded DNA. We measure charge transport in single DNA molecules bridged to two electrodes as a function of DNA sequence and length. In general, the resistance of DNA increases linearly with length, as expected for incoherent hopping. However, for DNA sequences with stacked guanine-cytosine (GC) base pairs, a periodic oscillation is superimposed on the linear length dependence, indicating partial coherent transport. This result is supported by the finding of strong delocalization of the highest occupied molecular orbitals of GC by theoretical simulation and by modelling based on the Büttiker theory of partial coherent charge transport. PMID:25698331

  8. 950809 Charged particle transport updated multi-group diffusion

    SciTech Connect

    Corman, E.G.; Perkins, S.T.; Dairiki, N.T.

    1995-09-01

    In 1974, a charged particle transport scheme was introduced which utilized a multi-group diffusion method for the spatial transport and slowing down of energetic ions in a hot plasma. In this treatment a diffusion coefficient was used which was flux-limited to provide, hopefully, some degree of accuracy when the slowing down of an energetic charged particle is dominated by Coulomb collisions with thermal ions and electrons in a plasma medium. An advantage of this method was a very fast, memory-contained program for calculating the behavior of energetic charged particles which resulted in smoothly varying particle number densities and energy depositions. The main limitation of the original multi-group charged particle diffusion scheme is its constraint to a basic ten group structure; the same ten group structure for each of the five energetic ions tracked. This is regarded as a severe limitation, inasmuch as more groups would be desired to simulate more accurately the corresponding Monte Carlo results of energies deposited over spatial zones from a charged particle source. More generally, it seems preferable to have a different group structure for each particle type since they are created at inherently different energies. In this paper, the basic theory and multi-group description will be given. This is followed by the specific techniques that were used to solve the resultant equations. Finally, the modifications that were made to the cross section data as well as the methods used for energy and momentum deposition are described.

  9. Modeling charge carrier collection in multiple exciton generating PbSe quantum dots

    Microsoft Academic Search

    Thomas Kirchartz; Uwe Rau

    2009-01-01

    The detailed balance model for quantum dot solar cells with quantum efficiencies above unity is extended to the case of non-ideal extraction of carriers from dots and finite mobilities of free carriers. For more realistic estimations of maximum efficiencies, we include experimental values for Auger lifetimes and absorption coefficients. Thus, for a given material, the model is capable of determining

  10. Secondary electron emission and self-consistent charge transport in semi-insulating samples

    SciTech Connect

    Fitting, H.-J. [Institute of Physics, University of Rostock, Universitaetsplatz 3, D-18051 Rostock (Germany); Touzin, M. [Unite Materiaux et Transformations, UMR CNRS 8207, Universite de Lille 1, F-59655 Villeneuve d'Ascq (France)

    2011-08-15

    Electron beam induced self-consistent charge transport and secondary electron emission (SEE) in insulators are described by means of an electron-hole flight-drift model (FDM) now extended by a certain intrinsic conductivity (c) and are implemented by an iterative computer simulation. Ballistic secondary electrons (SE) and holes, their attenuation to drifting charge carriers, and their recombination, trapping, and field- and temperature-dependent detrapping are included. As a main result the time dependent ''true'' secondary electron emission rate {delta}(t) released from the target material and based on ballistic electrons and the spatial distributions of currents j(x,t), charges {rho}(x,t), field F(x,t), and potential V(x,t) are obtained where V{sub 0} = V(0,t) presents the surface potential. The intrinsic electronic conductivity limits the charging process and leads to a conduction sample current to the support. In that case the steady-state total SE yield will be fixed below the unit: i.e., {sigma} {eta} + {delta} < 1.

  11. Charge Transport and Structural Dynamics in Deep Eutectic Mixtures

    NASA Astrophysics Data System (ADS)

    Cosby, Tyler; Holt, Adam; Terheggen, Logan; Griffin, Philip; Benson, Roberto; Sangoro, Joshua

    2015-03-01

    Charge transport and structural dynamics in a series of imidazole and carboxylic acid-based deep eutectic mixtures are investigated by broadband dielectric spectroscopy, dynamic light scattering, 1H nuclear magnetic resonance spectroscopy, calorimetry, and Fourier transform infrared spectroscopy. It is found that the extended hydrogen-bonded networks characteristic of imidazoles are broken down upon addition of carboxylic acids, resulting in an increase in dc conductivity of the mixtures. These results are discussed within the framework of recent theories of hydrogen bonding and proton transport.

  12. A model for anisotropic Coulomb screening : application to Auger relaxation by 2D and 3D charge carriers in a quantum

    E-print Network

    Paris-Sud XI, Université de

    wells.1-4 Current injection efficiency and modulation dynamics depend crucially on carrier capture for these processes is however associated in another work13 to carriers remaining in the barrier after injection (3DA model for anisotropic Coulomb screening : application to Auger relaxation by 2D and 3D charge

  13. Scale-Free Networks and Commercial Air Carrier Transportation in the United States

    NASA Technical Reports Server (NTRS)

    Conway, Sheila R.

    2004-01-01

    Network science, or the art of describing system structure, may be useful for the analysis and control of large, complex systems. For example, networks exhibiting scale-free structure have been found to be particularly well suited to deal with environmental uncertainty and large demand growth. The National Airspace System may be, at least in part, a scalable network. In fact, the hub-and-spoke structure of the commercial segment of the NAS is an often-cited example of an existing scale-free network After reviewing the nature and attributes of scale-free networks, this assertion is put to the test: is commercial air carrier transportation in the United States well explained by this model? If so, are the positive attributes of these networks, e.g. those of efficiency, flexibility and robustness, fully realized, or could we effect substantial improvement? This paper first outlines attributes of various network types, then looks more closely at the common carrier air transportation network from perspectives of the traveler, the airlines, and Air Traffic Control (ATC). Network models are applied within each paradigm, including discussion of implied strengths and weaknesses of each model. Finally, known limitations of scalable networks are discussed. With an eye towards NAS operations, utilizing the strengths and avoiding the weaknesses of scale-free networks are addressed.

  14. Vertical minority carrier electron transport in p-type InAs/GaSb type-II superlattices

    NASA Astrophysics Data System (ADS)

    Umana-Membreno, G. A.; Klein, B.; Kala, H.; Antoszewski, J.; Gautam, N.; Kutty, M. N.; Plis, E.; Krishna, S.; Faraone, L.

    2012-12-01

    Vertical minority carrier electron transport parameters in p-type InAs/GaSb type-II superlattices for long wavelength infrared (LWIR) detection have been extracted from magnetic field dependent geometrical magneto-resistance. The measurements, performed at low electric fields and at magnetic field intensities up to 12 T, exhibited multiple-carrier conduction characteristics that required mobility spectrum analysis for the extraction of individual carrier mobilities and concentrations. Within the common operating temperature range for LWIR photodiodes (80 to 150 K), the conductivity was found to be dominated by three distinct carriers, attributed to majority holes (? =280±27 cm2/Vs), minority electrons (? =2,460±75 cm2/Vs), and parasitic sidewall inversion layer electrons (? =930±55 cm2/Vs). A miniband energy gap of 140 ± 15 meV for the 14/7-monolayer InAs/GaSb superlattice was estimated from the thermal activation of the minority carrier electron density.

  15. 19 CFR 351.515 - Internal transport and freight charges for export shipments.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...2013-04-01 2013-04-01 false Internal transport and freight charges for export shipments...Countervailable Subsidies § 351.515 Internal transport and freight charges for export shipments...In general. In the case of internal transport and freight charges on export...

  16. 19 CFR 351.515 - Internal transport and freight charges for export shipments.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...2011-04-01 2011-04-01 false Internal transport and freight charges for export shipments...Countervailable Subsidies § 351.515 Internal transport and freight charges for export shipments...In general. In the case of internal transport and freight charges on export...

  17. 19 CFR 351.515 - Internal transport and freight charges for export shipments.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...2010-04-01 2010-04-01 false Internal transport and freight charges for export shipments...Countervailable Subsidies § 351.515 Internal transport and freight charges for export shipments...In general. In the case of internal transport and freight charges on export...

  18. 19 CFR 351.515 - Internal transport and freight charges for export shipments.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...2012-04-01 2012-04-01 false Internal transport and freight charges for export shipments...Countervailable Subsidies § 351.515 Internal transport and freight charges for export shipments...In general. In the case of internal transport and freight charges on export...

  19. 19 CFR 351.515 - Internal transport and freight charges for export shipments.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...2014-04-01 2014-04-01 false Internal transport and freight charges for export shipments...Countervailable Subsidies § 351.515 Internal transport and freight charges for export shipments...In general. In the case of internal transport and freight charges on export...

  20. Direct Observation of Anisotropic Carrier Transport in Organic Semiconductor by Time-Resolved Microscopic Optical Second-Harmonic Imaging

    NASA Astrophysics Data System (ADS)

    Manaka, Takaaki; Matsubara, Kohei; Abe, Kentaro; Iwamoto, Mitsumasa

    2013-10-01

    In-plane anisotropic carrier transport in single-crystalline grains of the dip-coated 6,13-bis(triisopropylsilylethynyl) (TIPS) pentacene film is studied by using the time-resolved microscopic optical second-harmonic generation (TRM-SHG). The TRM-SHG imaging directly visualizes the directional dependence of the carrier velocity, indicating the anisotropic carrier mobility of the TIPS pentacene single crystal. Results showed that the mobility anisotropy is smaller than that obtained from the current-voltage (I-V) characteristics. Overestimation of the mobility anisotropy using the I-V characteristics, compared with that obtained from the TRM-SHG measurement, is ascribed to the effect of the grain boundary on the carrier transport.

  1. 41 CFR 302-10.200 - What costs are allowable when a commercial carrier transports my mobile home overland or over water?

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...are allowable when a commercial carrier transports my mobile home overland or over water...are allowable when a commercial carrier transports my mobile home overland or over water...government authority for permits to transport mobile homes in or through its...

  2. Comparison of two dynamic transportation models: The case of Stockholm congestion charging

    E-print Network

    Paris-Sud XI, Université de

    1 Comparison of two dynamic transportation models: The case of Stockholm congestion charging Leonid) Abstract This paper reviews the transportation models used for predicting impacts of congestion charging for the Stockholm baseline situation without charges and applied for modeling effects of congestion charging

  3. Improved understanding of the electronic and energetic landscapes of perovskite solar cells: high local charge carrier mobility, reduced recombination, and extremely shallow traps.

    PubMed

    Oga, Hikaru; Saeki, Akinori; Ogomi, Yuhei; Hayase, Shuzi; Seki, Shu

    2014-10-01

    The intriguing photoactive features of organic-inorganic hybrid perovskites have enabled the preparation of a new class of highly efficient solar cells. However, the fundamental properties, upon which the performance of these devices is based, are currently under-explored, making their elucidation a vital issue. Herein, we have investigated the local mobility, recombination, and energetic landscape of charge carriers in a prototype CH3NH3PbI3 perovskite (PVK) using a laser-flash time-resolved microwave conductivity (TRMC) technique. PVK was prepared on mesoporous TiO2 and Al2O3 by one or two-step sequential deposition. PVK on mesoporous TiO2 exhibited a charge carrier mobility of 20 cm(2) V(-1) s(-1), which was predominantly attributed to holes. PVK on mesoporous Al2O3, on the other hand, exhibited a 50% lower mobility, which was resolved into balanced contributions from both holes and electrons. A general correlation between crystal size and mobility was revealed irrespective of the fabrication process and underlying layer. Modulating the microwave frequency from 9 toward 23 GHz allowed us to determine the intrinsic mobilities of each PVK sample (60-75 cm(2) V(-1) s(-1)), which were mostly independent of the mesoporous scaffold. Kinetic and frequency analysis of the transient complex conductivity strongly support the superiority of the perovskite, based on a significant suppression of charge recombination, an extremely shallow trap depth (10 meV), and a low concentration of these trapped states (less than 10%). The transport mechanism was further investigated by examining the temperature dependence of the TRMC maxima. Our study provides a basis for understanding perovskite solar cell operation, while highlighting the importance of the mesoporous layer and the perovskite fabrication process. PMID:25188538

  4. Efficient organic electroluminescent devices using single-layer doped polymer thin films with bipolar carrier transport abilities

    Microsoft Academic Search

    Chung-Chih Wu; James C. Sturm; Richard A. Register; Jing Tian; Elena P. Dana; M. E. Tnompson

    1997-01-01

    Detailed studies of electroluminescent devices made from single-layer doped polymer blend thin films having bipolar carrier transport abilities are presented. The active organic layer consists of the hole-transport polymer poly(N-vinylcarbazole) (PVK) containing dispersed electron-transport molecules, as well as different fluorescent small molecules or polymers as emitting centers to vary the emission color. Both the photoluminescence and electroluminescence (EL) properties are

  5. Carrier transport and capture in GaN single crystals and radiation detectors and effect of the neutron irradiation

    Microsoft Academic Search

    V. Kažukauskas; V. Kalendra; J.-V. Vaitkus

    2006-01-01

    Carrier transport and trapping were investigated in GaN single crystals and semi-insulating epitaxial MOCVD layers by thermally stimulated current (TSC) and thermally stimulated depolarization (TSD) spectroscopy. Effect of irradiation by 100keV reactor neutrons with fluencies of up to 1016n\\/cm2 was identified. We demonstrate that in the unirradiated samples TSC spectra might be caused not by carrier generation from traps, but

  6. Change in carrier type in high-k gate carbon nanotube field-effect transistors by interface fixed charges

    NASA Astrophysics Data System (ADS)

    Moriyama, N.; Ohno, Y.; Kitamura, T.; Kishimoto, S.; Mizutani, T.

    2010-04-01

    We study the phenomenon of change in carrier type in carbon nanotube field-effect transistors (CNFETs) caused by the atomic layer deposition (ALD) of a HfO2 gate insulator. When a HfO2 layer is deposited on a CNFET, the type of carrier changes from p-type to n-type. The so-obtained n-type device has good performance and stability in air. The conductivity of such a device with a channel length of 0.7 µm is 11% of the quantum conductance 4e2/h. The contact resistance for electron current is estimated to be 14 k?. The n-type conduction of this CNFET is maintained for more than 100 days. The change in carrier type is attributed to positive fixed charges introduced at the interface between the HfO2 and SiO2 layers. We also propose a novel technique to control the type of conduction by utilizing interface fixed charges; this technique is compatible with Si CMOS process technology.

  7. Structures, electronic states, photoluminescence, and carrier transport properties of 1,1-disubstituted 2,3,4,5-tetraphenylsiloles.

    PubMed

    Yu, Gui; Yin, Shiwei; Liu, Yunqi; Chen, Jiangshan; Xu, Xinjun; Sun, Xiaobo; Ma, Dongge; Zhan, Xiaowei; Peng, Qian; Shuai, Zhigang; Tang, Benzhong; Zhu, Daoben; Fang, Weihai; Luo, Yi

    2005-05-01

    The excellent electroluminescent (EL) properties of 1,1-disubstituted 2,3,4,5-tetraphenylsiloles, 1-methyl-1,2,3,4,5-pentaphenylsilole (MPPS), and 1,1,2,3,4,5-hexaphenylsilole (HPS) have been found. Despite some studies devoted to these materials, very little is known about the real origin of their unique EL properties. Therefore, we investigated the structures, photoluminescence (PL), and charge carrier transport properties of 1,1-disubstituted 2,3,4,5-tetraphenylsiloles as well as the effect of substituents on these characteristics. The single crystals of the three siloles involving 1,1-dimethyl-2,3,4,5-tetraphenylsilole (DMTPS), MPPS, and HPS were grown and their crystal structures were determined by X-ray diffraction. Three siloles have nonplanar molecular structures. The substituents at 1,1-positions enhance the steric hindrance and have predominant influence on the twisted degree of phenyl groups at ring carbons. This nonplanar structure reduces the intermolecular interaction and the likelihood of excimer formation, and increases PL efficiency in the solid state. The silole films show high fluorescence quantum yields (75-85%), whereas their dilute solutions exhibit a faint emission. The electronic structures of the three siloles were investigated using quantum chemical calculations. The highest occupied molecular orbitals (HOMOs) and the lowest unoccupied molecular orbitals (LUMOs) are mainly localized on the silole ring and two phenyl groups at 2,5-positions in all cases, while the LUMOs have a significant orbital density at two exocyclic Si-C bonds. The extremely theoretical studies of luminescent properties were carried out. We calculated the nonradiative decay rate of the first excited state as well as the radiative one. It is found that the faint emission of DMTPS in solutions mainly results from the huge nonradiative decay rate. In solid states, molecular packing can remarkably restrict the intramolecular rotation of the peripheral side phenyl ring, which has a large contribution to the nonradiative transition process. This explains why the 1,1-disubstituted 2,3,4,5-tetraphenylsiloles in the thin films exhibit high fluorescence quantum yields. The charge carrier mobilities of the MPPS and HPS films were measured using a transient EL technique. We obtained a mobility of 2.1 x 10(-)(6) cm(2)/V.s in the MPPS film at an electric field of 1.2 x 10(6) V/cm. This mobility is comparable to that of Alq(3), which is one of the most extensively used electron transport materials in organic light-emitting diodes (LEDs), at the same electric field. The electron mobility of the HPS film is about approximately 1.5 times higher than that of the MPPS film. To the best of our knowledge, this kind of material is one of the most excellent emissive materials that possess both high charge carrier mobility and high PL efficiency in the solid states simultaneously. The excellent EL performances of MPPS and HPS are presumably ascribed to these characteristics. PMID:15853340

  8. Investigation of free charge carrier dynamics in single-crystalline CVD diamond by two-photon absorption

    NASA Astrophysics Data System (ADS)

    Ivakin, E. V.; Kisialiou, I. G.; Ralchenko, V. G.; Bolshakov, A. P.; Ashkinazi, E. E.; Sharonov, G. V.

    2014-11-01

    By using the methods of transient gratings (TGs) and induced absorption, we have studied the kinetics of plasma of free charge carriers (FCCs) created by the action of a picosecond laser pulse in two high-purity diamond single crystals synthesised from the gas phase. The gratings with different spatial periods have been excited at the wavelengths of 266 or 213 nm (above and below the fundamental absorption edge in diamond) and probed with continuous-wave radiation in the visible region. At the moderate FCC concentrations (~7 × 1017 cm-3), the coefficient of ambipolar diffusion and the carrier recombination time of two crystals are 20.3 and 18.9 cm2 s-1 and 30 and 190 ns, respectively. The increase in the carrier concentration up to 5 × 1019 cm-3 reduces the TG lifetime. We have determined the conditions under which the relaxation of the grating of carriers leads to the formation of a thermal grating, with the amplitude sufficient for its experimental observation.

  9. Modulation waves of charge carriers in n- and p-type semiconductor layers

    SciTech Connect

    Mnatsakanov, T. T. [All-Russia Electrotechnical Institute (Russian Federation); Levinshtein, M. E., E-mail: Melev@nimis.ioffe.ru [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation); Tandoev, A. G.; Yurkov, S. N. [All-Russia Electrotechnical Institute (Russian Federation)

    2011-02-15

    The effect of the carrier mobility dependence on the electric field strength, {mu}(F), on the propagation of waves of injected carriers in n- and p-type layers in the quasi-neutral drift mode has been studied. It is shown that consideration of the dependence {mu}(F) differently affects the motion of minority carriers in n- and p-type layers. The motion of an electron wave in the p-type base of a p{sup +}-p-n{sup +} structure is slowed down, and that of a hole wave in the n-base of a p{sup +}-n-n{sup +} structure is speeded up. The results obtained supplement the previously suggested classical description of the propagation of a wave of minority carriers, which disregarded the effect of {mu}(F) dependences. The results of an analytical calculation are confirmed using a numerical experiment.

  10. Two different carriers transport both ammonium and methylammonium in Chlamydomonas reinhardtii.

    PubMed

    Franco, A R; Cárdenas, J; Fernández, E

    1988-10-01

    A new methylammonium-resistant mutant strain from Chlamydomonas reinhardtii, henceforth termed 2172 (ma-2), has been isolated. This mutant is affected in a single mendelian gene different from and linked to the ma-1 locus which is defective in the methylammonium-resistant mutant 2170. Both mutations in ma-1 (2170) and ma-2 (2172) are linked to the nit-1 gene coding for the nitrate reductase apoenzyme. Mutant 2172 is affected in methylammonium but not in ammonium uptake capacity and shows derepressed nitrate and nitrite reductase activities in media containing nitrate plus methylammonium but not in nitrate plus ammonium media. The following two enzymatic components for the transport of both ammonium and methylammonium in wild-type cells have been identified: component 1, with high Vmax and K values, which is constitutive, and component 2, with low Vmax and K values, which is ammonium-repressible. Mutant 2170 lacks component 1 whereas mutant 2172 lacks component 2 for both methylammonium and ammonium transport. From genetic and kinetic evidences we conclude that in C. reinhardtii two different carriers are responsible for the transport of both ammonium and methylammonium and that methylammonium (ammonium) transport is a reversible process probably inhibited by the intracellular ammonium which, in turn, regulates nitrate and nitrite reductase levels. PMID:3170537

  11. Interaction of the bioactive flavonol, icariin, with the essential human solute carrier transporters.

    PubMed

    Li, Zhen; Cheung, Florence Shin Gee; Zheng, Jian; Chan, Ting; Zhu, Ling; Zhou, Fanfan

    2014-02-01

    Solute carrier transporters (SLCs), in particular the organic anion transporting polypeptides (OATPs) and organic anion/cation transporters (OATs/OCTs), are responsible for the cellular entry of many clinically important drugs in body. They largely influence drug safety and efficacy. Icariin is a flavonol widely present in many herbal preparations, which is used to improve sexual function and prevent osteogenesis. However, precautions are necessary in therapies containing icariin due to its involvement in drug-drug/herb interactions, possibly mediated through competing drug uptake via membrane-transporter proteins. This study is the first to comprehensively evaluate the interactions between icariin and a range of essential SLCs. Our data demonstrated that icariin can significantly inhibit OATP1B3- and OATP2B1-mediated cellular uptake of specific substrates (IC?? of 3.0 ± 1.3 and 6.4 ± 1.9 ?M, respectively). Our study revealed that icariin can potentially compete with coadministrated drugs for particular SLCs, which may impact the therapeutic outcome of regimens. PMID:24265111

  12. Solute carrier transporters as targets for drug delivery and pharmacological intervention for chemotherapy.

    PubMed

    Nakanishi, Takeo; Tamai, Ikumi

    2011-09-01

    Many solute carrier transporters that interact with anticancer agents and contribute to their pharmacokinetics have been shown to be differentially upregulated in cancer cells as a result of adaptive response to altered nutritional requirements. This review focuses on pathophysiological function of membrane transporters responsible for the influx of physiological substances including oligopeptides, amino acids, and organic cations and anions, and summarizes the recent knowledge regarding mechanisms in their gene expressions. Broad substrate specificity of enhanced oligopeptide H(+) /peptide cotransporter 1 activity in cancer cells is useful for tumor tissue-specific delivery of chemotherapeutic agents and positron emission tomography diagnostic probes. Amino acid transporters such as LAT1 and ASCT2 are upregulated in human cancer cells and are thought to stimulate tumor growth by regulating mammalian target of rapamycin through nutrient pathway. Especially, LAT1 could be a molecular target to deprive cancer cells of amino acids in combination with aminopeptidase inhibitors. As organic anion transporting polypeptides carry estrone-3-sulfate that is intracellularly hydrolyzed to estrone, their overexpression may provide a pharmacological merit to treat hormone-responsive breast tumors. Therefore, it is important to understand the pathophysiological significance and gene expression in cancer to develop new rationales for drug delivery and pharmacological interventions for chemotherapy. PMID:21630275

  13. Demonstration of the difference Casimir force for samples with different charge carrier densities

    E-print Network

    F. Chen; G. L. Klimchitskaya; V. M. Mostepanenko; U. Mohideen

    2006-09-26

    A measurement of the Casimir force between a gold coated sphere and two Si plates of different carrier densities is performed using a high vacuum based atomic force microscope. The results are compared with the Lifshitz theory and good agreement is found. Our experiment demonstrates that by changing the carrier density of the semiconductor plate by several orders of magnitude it is possible to modify the Casimir interaction. This result may find applications in nanotechnology.

  14. Functional characterization of the carrier-mediated transport system for glycerol in everted sacs of the rat small intestine.

    PubMed

    Kato, Toyonori; Hayashi, Yayoi; Inoue, Katsuhisa; Yuasa, Hiroaki

    2004-11-01

    The mechanism of intestinal glycerol transport was investigated by using the in vitro everted sac method involving the rat small intestine. The uptake of glycerol into everted sacs was saturable with a Michaelis constant (K(m)) of 0.77 mM and a maximum transport rate (J(max)) of 11.5 nmol/min/100 mg wet tissue weight (wtw), suggesting the involvement of carrier-mediated transport, and was accompanied by unsaturable transport (passive transport) with a membrane permeability clearance (CL(m,d)) of 4.9 microl/min/100 mg wtw. The carrier-mediated uptake of glycerol was inhibited by the removal of Na(+) and also by the addition of 2,4-dinitrophenol (DNP) and sodium azide (NaN(3)), which are metabolic inhibitors. These results suggest that the carrier-mediated glycerol transport is Na(+)-dependent and secondary active. Since glycerol uptake was also inhibited by p-chloromercuribenzene sulfonate (pCMBS), a thiol-modifying reagent, cysteine residues, which have a thiol group, seem to play an important role in the function of the carrier. We further found that glycerol uptake was selectively inhibited by glycerol-3-phosphate, chloramphenicol and voglibose, which are alcohol-related compounds analogous to glycerol. Several other compounds that did not inhibit glycerol uptake included D-glucose and 5-fluorouracil, which are known to be transported by specific carriers, and none of the selective inhibitors of glycerol uptake inhibited the uptake of D-glucose and 5-fluorouracil. Therefore, the carriers for these two compounds do not seem to be involved in glycerol uptake. It is likely that the carrier-mediated transport system involved in glycerol uptake is specific to glycerol and, possibly, some analogous compounds with hydroxyl groups. It would be interesting to examine the possibility that the carrier-mediated glycerol transport system might be involved in drug absorption and also that it might be used for oral drug delivery. PMID:15516731

  15. Dissociation of Charge Transfer States and Carrier Separation in Bilayer Organic Solar Cells: A Time-Resolved Electroabsorption Spectroscopy Study.

    PubMed

    Devižis, Andrius; De Jonghe-Risse, Jelissa; Hany, Roland; Nüesch, Frank; Jenatsch, Sandra; Gulbinas, Vidmantas; Moser, Jacques-E

    2015-07-01

    Ultrafast optical probing of the electric field by means of Stark effect in planar heterojunction cyanine dye/fullerene organic solar cells enables one to directly monitor the dynamics of free electron formation during the dissociation of interfacial charge transfer (CT) states. Motions of electrons and holes is scrutinized separately by selectively probing the Stark shift dynamics at selected wavelengths. It is shown that only charge pairs with an effective electron-hole separation distance of less than 4 nm are created during the dissociation of Frenkel excitons. Dissociation of the coulombically bound charge pairs is identified as the major rate-limiting step for charge carriers' generation. Interfacial CT states split into free charges on the time-scale of tens to hundreds of picoseconds, mainly by electron escape from the Coulomb potential over a barrier that is lowered by the electric field. The motion of holes in the small molecule donor material during the charge separation time is found to be insignificant. PMID:26037526

  16. Mass Transport Investigated with the Electrochemical and Electrogravimetric Impedance Techniques. 3. Complex Charge Transport in PPy/PSS Films

    E-print Network

    Kwak, Juhyoun

    Mass Transport Investigated with the Electrochemical and Electrogravimetric Impedance Techniques. 3. Complex Charge Transport in PPy/PSS Films Haesik Yang and Juhyoun Kwak* Department of Chemistry, Korea AdVember 24, 1997 For the first time, the complex charge transport mechanism for polypyrrole

  17. Charge transport in dye-sensitized solar cell

    NASA Astrophysics Data System (ADS)

    Yanagida, Masatoshi

    2015-03-01

    The effect of charge transport on the photovoltaic properties of dye-sensitized solar cells (DSCs) was investigated by the experimental results and the ion transport. The short current photocurrent density (Jsc) is determined by the electron transport in porous TiO2 when the diffusion limited current (Jdif) due to the {{I}3}- transport is larger than the photo-generated electron flux (Jg) estimated from the light harvesting efficiency of dye-sensitized porous TiO2 and the solar spectrum. However, the Jsc value is determined by the ion transport in the electrolyte solution at Jdif < Jg. The J value becomes constant against light intensity, and is expressed as the saturated current (Jscs). The {{J}s} value depends on the thickness (d) of the TiO2 layer, the initial concentration (COX0), and the diffusion coefficient (DOXb) of {{I}3}-. These suitable parameters were determined by using the ion transport. Invited talk at the 7th International Workshop on Advanced Materials Science and Nanotechnology IWAMSN2014, 2-6 November, 2014, Ha Long, Vietnam.

  18. All-optical technique to correlate defect structure and carrier transport in transferred graphene films.

    PubMed

    Rochford, Caitlin; Kumar, Nardeep; Liu, Jianwei; Zhao, Hui; Wu, Judy

    2013-08-14

    Chemical vapor deposition of graphene on copper foil is an attractive method of producing large-area graphene films, but the electronic performance is limited by defects such as creases from the film transfer process, wrinkles due to the thermal expansion coefficient mismatch, and grain boundaries from the growth process. Here we present an all-optical technique to correlate defect structure with electronic properties using spatially resolved Raman spectroscopy and transient absorption microscopy. This technique is especially attractive since it does not require any lithographic steps to probe the electronic properties of the graphene film. As a first demonstration, we focus on the effects of both wrinkles and creases while averaging over many small grains. It was found that wrinkles and creases may decrease the charge carrier diffusion coefficient by over 50% due to increased defect scattering. This technique may easily be extended to large grain graphene films in order to study the effect of different types of grain boundaries. PMID:23855775

  19. Role of proton hopping in surface charge transport on tin dioxide as revealed by the thermal dependence of conductance.

    PubMed

    Wexler, Robert B; Sohlberg, Karl

    2014-12-26

    The presence of water on an oxide surface can dramatically alter its electrical properties with important consequences for electrical measurements by scanning probe microscopy, and for the use of semiconducting oxides in sensing applications. Here, the thermal dependence of the conductance of tin dioxide is interpreted by combining semiconductor equilibrium carrier statistics with a proton hopping mechanism. First, the functional form of this charge transport model is fit to experimental conductance data for tin dioxide. Next, the important energy parameters in the model are computed with density functional theory. Comparing the values of the energy parameters obtained by fitting, to the values for the same parameters obtained from electronic structure calculations, yields new insight into the surface charge transport in tin dioxide. In particular, it is found that mobile protons, freed from the dissociative adsorption of water on the [110] surface, are an essential component of the observed thermal dependence of conductance in tin dioxide. PMID:25275726

  20. The role of water in surface charge transport on tin dioxide as revealed by the thermal dependence of conductance

    NASA Astrophysics Data System (ADS)

    Wexler, Robert; Sohlberg, Karl

    2013-03-01

    The presence of water on an oxide surface can dramatically alter its electrical properties with important consequences for electrical measurements by scanning probe microscopy, and for the use of semiconducting oxides in sensing applications. Here, the thermal dependence of the surface conductance of tin dioxide is interpreted by combining equilibrium carrier statistics with the Grotthuss mechanism for proton hopping. The functional form of this charge transport model is fit to experimental conductance data for tin dioxide. Next, the important energy parameters in the model are computed with electronic structure methods. Comparing the values of the energy parameters obtained by fitting to those obtained from electronic structure calculations yields new insight into the surface charge transport in tin dioxide. In particular, it is found that mobile protons, freed by the dissociative adsorption of water on the [110] surface, are an essential component of the observed thermal dependence of surface conductance in tin dioxide.

  1. Ring-shaped spatial pattern of exciton luminescence formed due to the hot carrier transport in a locally photoexcited electron-hole bilayer

    SciTech Connect

    Paraskevov, A. V., E-mail: avp.workbox@yandex.ru [National Research Center 'Kurchatov Institute,' (Russian Federation)

    2012-06-15

    A consistent explanation of the formation of a ring-shaped pattern of exciton luminescence in GaAs/AlGaAs double quantum wells is suggested. The pattern consists of two concentric rings around the laser excitation spot. It is shown that the luminescence rings appear due to the in-layer transport of hot charge carriers at high photoexcitation intensity. Interestingly, one of two causes of this transport might involve self-organized criticality (SOC) that would be the first case of the SOC observation in semiconductor physics. We test this cause in a many-body numerical model by performing extensive molecular dynamics simulations. The results show good agreement with experiments. Moreover, the simulations have enabled us to identify the particular kinetic processes underlying the formation of each of these two luminescence rings.

  2. Effect of Mg doping on the structural and free-charge carrier properties of InN films

    SciTech Connect

    Xie, M.-Y.; Ben Sedrine, N.; Hung, L.; Monemar, B.; Darakchieva, V., E-mail: vanya@ifm.liu.se [Department of Physics, Chemistry, and Biology, IFM, Linköping University, SE-581 83 Linköping (Sweden); Schöche, S.; Hofmann, T.; Schubert, M. [Center for Nanohybrid Functional Materials, Department of Electrical Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588-0511 (United States); Wang, X. [State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, Peking University, Beijing (China); Yoshikawa, A. [Center for SMART Green Innovation Research, Chiba University, Chiba (Japan); Department of Information and Communication Engineering, Kogakuin University, Tokyo (Japan); Wang, K.; Araki, T. [Department of Photonics, Ritsumeikan University, 1-1-1 Noji Higashi, Kusatsu, Shiga 525-8577 (Japan); Nanishi, Y. [Department of Photonics, Ritsumeikan University, 1-1-1 Noji Higashi, Kusatsu, Shiga 525-8577 (Japan); WCU Hybrid Materials Program, Department of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of)

    2014-04-28

    We present a comprehensive study of free-charge carrier and structural properties of two sets of InN films grown by molecular beam epitaxy and systematically doped with Mg from 1.0?×?10{sup 18}?cm{sup ?3} to 3.9?×?10{sup 21}?cm{sup ?3}. The free electron and hole concentration, mobility, and plasmon broadening parameters are determined by infrared spectroscopic ellipsometry. The lattice parameters, microstructure, and surface morphology are determined by high-resolution X-ray diffraction and atomic force microscopy. Consistent results on the free-charge carrier type are found in the two sets of InN films and it is inferred that p-type conductivity could be achieved for 1.0?×?10{sup 18}?cm{sup ?3}???[Mg]???9.0?×?10{sup 19}?cm{sup ?3}. The systematic change of free-charge carrier properties with Mg concentration is discussed in relation to the evolution of extended defect density and growth mode. A comparison between the structural characteristics and free electron concentrations in the films provides insights in the role of extended and point defects for the n-type conductivity in InN. It further allows to suggest pathways for achieving compensated InN material with relatively high electron mobility and low defect densities. The critical values of Mg concentration for which polarity inversion and formation of zinc-blende InN occurred are determined. Finally, the effect of Mg doping on the lattice parameters is established and different contributions to the strain in the films are discussed.

  3. Charge Localization and Transport in Lithiated Olivine Phosphate Materials

    SciTech Connect

    Yu, Jianguo; Rosso, Kevin M.; Liu, Jun

    2011-11-10

    We report density functional theory (DFT) calculations for olivine-type LiTMPO4 and TMPO4 (TM=Mn, Fe, Co, Ni) structures, using GGA+U and the B3LYP hybrid density functional that includes nonlocal Fock exchange. TM is typically characterized in terms of the formal oxide states of 2+ or 3+, corresponding to TM with localized charge in LiTMPO4 and TMPO4 structures, respectively, in which electron transport would take place by thermally activated hopping of electrons strongly localized on the transition metal (small polarons). In this work, we assess the validity of the concept of formal TM oxidation states in these materials, and conclude that the valence depends in large part on the strength of d-p hybridization. Stable small polaron formation, i.e., mixed 2+ and 3+ valence states, appears to require that the ratio of differences in the metal and oxygen ionic charges (dQTM/dQO) of the two end member phases is larger than 2, corresponding to the mixed-valence TM system. If the ratio of dQTM/dQO is smaller than 2, excess electrons prefer delocalization and the system behaves more single-valence like with charge transport more akin to metallic conduction. The critical ratio emerging from our analysis may turn out to be relevant to other transition metal systems as well, as a criterion to discriminate single-valence or mixed-valence characteristics and hence the predominant conduction mechanism.

  4. Carrier transport mechanism in indium tin oxide (ITO)/silicon heterojunctions: effect of chlorine

    NASA Astrophysics Data System (ADS)

    Vasu, V.; Subrahmanyam, A.

    2005-02-01

    Transparent-conducting-oxide (TCO)-based photovoltaic junctions have shown complexity in the transport phenomena at the interface. The present study is an attempt to understand the effect of chlorine at the interface between indium tin oxide (ITO) and Si. The ITO/Si junctions have been prepared by depositing transparent and conducting tin-doped indium oxide (ITO) thin films on as-cleaned and chlorine-treated single-crystal p-type and n-type silicon substrates using the reactive electron-beam evaporation technique. ITO/n-Si junctions have shown photovoltaic properties. The photoconversion efficiency of these junctions is observed to increase from 2.3% to 5.5% under chlorine treatment. The transport mechanism across these junctions has been studied by current voltage (I V , both dark and illuminated) and capacitance voltage (C V ) characterisation techniques. The carrier transport mechanism is found to be dominated by recombination at the depletion region for the junctions prepared with chlorine treatment, whereas for the other junctions, the thermionic process seems to be prominent. The unrealistic barrier heights observed in these junctions by the C V technique confirms the complex nature of the interface.

  5. Inkjet printing of carrier transport layers for inverted organic solar cells

    NASA Astrophysics Data System (ADS)

    Danielson, Eric; Subbaraman, Harish; Dodabalapur, Ananth

    2013-09-01

    Inverted organic solar cells, which utilize a transparent cathode and a high work function metal anode, have been the subject of extensive research. Their advantages over conventional organic solar cells include increased resistance to environmental degradation and compatibility with large area fabrication techniques. Carrier transport layers are essential for achieving high power conversion efficiencies in inverted organic solar cells and therefore need to be compatible with these large area fabrication techniques. Inkjet printing is one such technique that can be integrated into the low cost mass production of these cells via roll to roll fabrication. N-type metal oxides such as ZnO or zinc tin oxide (ZTO) have been previously used as electron transport layers for inverted cells, but only as spin coated films. We have developed inkjet printable ZTO solutions for use as electron transport layers in inverted organic solar cells, and achieve power conversion efficiencies of over 3% in inverted P3HT:PC71BM solar cells. We also discuss the effect of printing parameters on the electrical performance of these layers in inverted organic solar cells.

  6. Excellent spin transport in spin valves based on the conjugated polymer with high carrier mobility

    PubMed Central

    Li, Feng; Li, Tian; Chen, Feng; Zhang, Fapei

    2015-01-01

    Organic semiconductors (OSCs) are characteristic of long spin-relaxation lifetime due to weak spin-orbit interaction and hyperfine interaction. However, short spin diffusion length and weak magnetoresistance (MR) effect at room temperature (RT) was commonly found on spin valves (SVs) using an organic spacer, which should be correlated with low carrier mobility of the OSCs. Here, N-type semiconducting polymer P(NDI2OD-T2) with high carrier mobility is employed as the spacer in the SV devices. Exceedingly high MR ratio of 90.0% at 4.2?K and of 6.8% at RT are achieved, respectively, via improving the interface structure between the polymer interlayer and top cobalt electrode as well as optimal annealing of manganite bottom electrode. Furthermore, we observe spin dependent transport through the polymeric interlayer and a large spin diffusion length with a weak temperature dependence. The results indicate that this polymer material can be used as a good medium for spintronic devices. PMID:25797862

  7. In-situ strain monitoring in liquid containers of LNG transporting carriers

    NASA Astrophysics Data System (ADS)

    Oh, Min-Cheol; Seo, Jun-Kyu; Kim, Kyung-Jo; Lee, Sang-Min; Kim, Myung-Hyun

    2008-08-01

    Liquefied natural gas (LNG) transport carriers are exposed to a risk by the repeated bump in the LNG container during the vessel traveling over the wave in ocean. The liquid inside the container, especially when it was not fully contained, make a strong bump onto the insulation panel of the tank wall. The insulation panel consists of several layers of thick polyurethane foam (PUF) to maintain the LNG below the cryogenic temperature, -162°C. Due to the repeated shock on the PUF, a crack could be developed on the tank wall causing a tremendous disaster for LNG carriers. To prevent the accidental crack on the tank, a continuous monitoring of the strain imposed on the PUF is recommended. In this work, a fiber-optic Bragg grating was imbedded inside the PUF for monitoring the strain parallel to the impact direction. The optical fiber sensor with a small diameter of 125 ?m was suitable to be inserted in the PUF through a small hole drilled after the PUF was cured. In-situ monitoring of the strain producing the change of Bragg reflection wavelength, a high speed wavelength interrogation method was employed by using an arrayed waveguide grating. By dropping a heavy mass on the PUF, we measured the strain imposed on the insulation panel.

  8. Photogeneration and carrier transport in amorphous silicon/crystalline silicon devices

    SciTech Connect

    Jagannathan, B.; Anderson, W.A.

    1997-07-01

    Hydrogenated amorphous silicon (a-Si:H)/crystalline silicon (c-Si) type heterodiodes in solar cell structures have been studied by rf glow discharge, dc magnetron sputtering, and a remote plasma deposition of a-Si:H onto p type c-Si. Carrier transport and photogeneration in such structures have been investigated by current-voltage-temperature, thermally stimulated capacitance (TSCAP), and spectral response experiments. Dark carrier conduction is found to be a combination of tunneling and interface recombination, but is dominated by either one depending on the deposition/sputtering conditions. The conditions investigated include energy of the plasma species, type of plasma cleaning, and substrate preparation techniques. For each of the conditions, the trap type, energy and concentration have been identified by TSCAP. Solar cells fabricated by the optimized fabrication scheme routinely yield 10.5% efficient devices having a short circuit current density (J{sub sc}) of 30 mA/cm{sup 2}, a open circuit voltage of 0.55 volts and a fill factor (FF) of 0.64, without an AR coating, over 0.3 cm{sup 2} area.

  9. Theory of high field carrier transport and impact ionization in ZnO

    NASA Astrophysics Data System (ADS)

    Bertazzi, Francesco; Penna, Michele; Goano, Michele; Bellotti, Enrico

    2010-03-01

    We present a full band Monte Carlo study of high field carrier transport and impact ionization properties of wurtzite ZnO. The proposed model is based on an accurate electronic structure calculated with a nonlocal empirical pseudopotential method and a phonon dispersion determined with density functional theory. The model includes the full details of the lowest eight conduction bands and the top six valence bands derived from the empirical pseudopotential method and a numerically calculated impact ionization transition rate based on a wave-vector dependent dielectric function. The carrier-phonon interaction is treated using the rigid pseudoion formalism, thus removing adjustable parameters such as deformation potential coefficients. Electric-field-induced interband transitions are included in the model by the direct solution of the time-dependent multiband Schrödinger equation. The hole ionization coefficient is found to be very low compared to the electron ionization coefficient. The low ratio of hole and electron ionization coefficients k = ?/? holds the promise for high speed and low noise avalanche photodetection in the ultraviolet spectral range.

  10. Influence of charge carrier injection at emitter electrode\\/emitter interface on the performance of metal-base organic transistors

    Microsoft Academic Search

    Kai Zhao; Jia-Chun Deng; Xiao-Man Cheng; Xiao-Ming Wu; Li-Ying Yang; Yu-Lin Hua; Jun Wei; Shou-Gen Yin

    2010-01-01

    Pentacene-based metal-base organic transistors (MBOTs) are fabricated. The influence of the charge carrier injection efficiency\\u000a at the emitter electrode\\/emitter interface on the device performance is investigated. It is found that the current modulation\\u000a and the on\\/off ratio increase with the injection efficiency. By inserting poly(3,4-ethylenedioxythiophene) (PEDOT): PSS\\/m-MTDATA\\u000a layers at the emitter electrode\\/emitter interface, the current modulation and the on\\/off ratio

  11. Charge-carrier injection assisted by space-charge field in AC-driven organic light-emitting transistors

    Microsoft Academic Search

    Xuhai Liu; Jakob Kjelstrup-Hansen; Henri Boudinov; Horst-Günter Rubahn

    2011-01-01

    Organic light-emitting transistors can be operated by an alternating gate voltage to provide high light output intensity. We propose a model for the light generation process in such light-emitting transistors based on systematic measurements of how the light output intensity depends on the biasing parameters. Following injection of holes, which form a positively charged space-charge region, subsequent electron tunneling from

  12. Photoinduced charge carriers at surfaces and interfaces of poly 2-methoxy-5-,,2 -ethyl-hexyloxy...-1,4-phenylenevinylene with Au and GaAs

    E-print Network

    Shalish, Ilan

    Photoinduced charge carriers at surfaces and interfaces of poly 2-methoxy-5-,,2 -ethyl June 2001 The electronic structure and photoinduced surface/interface charge transfer processes have produced at low spinning rate, perhaps due to surface roughness. Efficient photoinduced electron injection

  13. Local Charge Neutrality Condition, Fermi Level, and Carrier Compensation of CdTe Polycrystalline Thin Film in CdS/CdTe Solar Cells

    E-print Network

    1 Local Charge Neutrality Condition, Fermi Level, and Carrier Compensation of CdTe Polycrystalline Thin Film in CdS/CdTe Solar Cells Ken K. Chin1 and Su-Huai Wei 2 1 Department of Physics and Apollo CdTe vacancies VCd (o/-) and VCd (-/2-) in CdTe thin film), the general formulation of charge neutrality

  14. Structural factors impacting carrier transport and electroluminescence from Si nanocluster-sensitized Er ions.

    PubMed

    Cueff, Sébastien; Labbé, Christophe; Jambois, Olivier; Berencén, Yonder; Kenyon, Anthony J; Garrido, Blas; Rizk, Richard

    2012-09-24

    We present an analysis of factors influencing carrier transport and electroluminescence (EL) at 1.5 µm from erbium-doped silicon-rich silica (SiOx) layers. The effects of both the active layer thickness and the Si-excess content on the electrical excitation of erbium are studied. We demonstrate that when the thickness is decreased from a few hundred to tens of nanometers the conductivity is greatly enhanced. Carrier transport is well described in all cases by a Poole-Frenkel mechanism, while the thickness-dependent current density suggests an evolution of both density and distribution of trapping states induced by Si nanoinclusions. We ascribe this observation to stress-induced effects prevailing in thin films, which inhibit the agglomeration of Si atoms, resulting in a high density of sub-nm Si inclusions that induce traps much shallower than those generated by Si nanoclusters (Si-ncs) formed in thicker films. There is no direct correlation between high conductivity and optimized EL intensity at 1.5 µm. Our results suggest that the main excitation mechanism governing the EL signal is impact excitation, which gradually becomes more efficient as film thickness increases, thanks to the increased segregation of Si-ncs, which in turn allows more efficient injection of hot electrons into the oxide matrix. Optimization of the EL signal is thus found to be a compromise between conductivity and both number and degree of segregation of Si-ncs, all of which are governed by a combination of excess Si content and sample thickness. This material study has strong implications for many electrically-driven devices using Si-ncs or Si-excess mediated EL. PMID:23037398

  15. 41 CFR 302-10.200 - What costs are allowable when a commercial carrier transports my mobile home overland or over water?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Your agency will allow the following costs for use of a commercial carrier transporting...law. (b) When transporting over water cost must include, but not limited to the cost of: (1) Fuel and oil used for propulsion of the...

  16. Charge transport studies of proton and ion conducting materials

    NASA Astrophysics Data System (ADS)

    Versek, Craig Wm

    The development of a high-throughput impedance spectroscopy instrumentation platform for conductivity characterization of ion transport materials is outlined. Collaborative studies using this system are summarized. Charge conduction mechanisms and conductivity data for small molecule proton conducting liquids, pyrazole, imidazole, 1,2,3-triazole, 1,2,4-triazole, and select mixtures of these compounds are documented. Furthermore, proton diffusivity measurements using a Pulse Field Gradient Nuclear Magnetic Resonance (PFG NMR) technique for imidazole and 1,2,3-triazole binary mixtures are compared. Studies of azole functionalized discotic and linear mesogens with conductivity, structural, and thermal characterizations are detailed.

  17. Charge transport in melt-dispersed carbon nanotubes.

    PubMed

    Hobbie, E K; Obrzut, J; Kharchenko, S B; Grulke, E A

    2006-07-28

    We investigate the effect of interfacial stabilizer on charge transport in polymer-dispersed carbon nanotubes. Despite mechanical contact, samples with dispersant show poor conductivity, which we attribute to a robust interfacial layer between contacted nanotubes. In comparison, results obtained when nanotubes are mechanically mixed into polymer melts without dispersant show much better conductivity. The difference is striking; at comparable loading, neat melt composites have resistivities five orders of magnitude smaller than those containing interfacial stabilizer. Our results highlight a fundamental issue for the engineering of conducting carbon nanotube composites; dispersion stability will typically be achieved at the expense of conductivity. PMID:16942179

  18. Morphology and charge transport in ammonium based polymerized ionic liquids

    NASA Astrophysics Data System (ADS)

    Heres, Maximilian; Minutolo, Joseph; Shamblin, Jacob; Long, Maik; Berdzinski, Stefan; Stremel, Veronika; Sangoro, Joshua

    2015-03-01

    Ionic conduction, structural dynamics and morphology in a series of ammonium based polymerized ionic liquids are investigated using broadband dielectric spectroscopy, temperature-modulated differential scanning calorimetry, and neutron as well as x-ray scattering techniques. The dielectric spectra are dominated on the low frequency regime by electrode polarization while hopping conduction is the underlying mechanism at higher frequencies. At their respective calorimetric glass transition temperatures, a strong correlation between the morphology and ionic conductivity is found. These results are discussed within the recent approaches proposed to explain the decoupling of charge transport from structural dynamics. UT/ORNL Science Alliance.

  19. Acoustic charge transport technology investigation for advanced development transponder

    NASA Technical Reports Server (NTRS)

    Kayalar, S.

    1993-01-01

    Acoustic charge transport (ACT) technology has provided a basis for a new family of analog signal processors, including a programmable transversal filter (PTF). Through monolithic integration of ACT delay lines with GaAs metal semiconductor field effect transistor (MESFET) digital memory and controllers, these devices significantly extend the performance of PTF's. This article introduces the basic operation of these devices and summarizes their present and future specifications. The production and testing of these devices indicate that this new technology is a promising one for future space applications.

  20. Unusual charge transport and reduced bimolecular recombination in PDTSiTzTz:PC71BM bulk heterojunction blend

    NASA Astrophysics Data System (ADS)

    Slobodyan, O. V.; Danielson, E. L.; Moench, S. J.; Dinser, J. A.; Gutierrez, M.; Vanden Bout, D. A.; Holliday, B. J.; Dodabalapur, A.

    2015-06-01

    Solar cells with bulk heterojunction active layers containing donor-acceptor copolymer PDTSiTzTz exhibit persistent high fill factors with thicknesses up to 400 nm. Transport and recombination in a blend of PDTSiTzTz and fullerene derivative PC71BM is studied using lateral organic photovoltaic structures. This material system is characterized by carrier-concentration-dependent charge carrier mobilities, a strongly reduced bimolecular recombination factor, and a negative Poole–Frenkel coefficient. The analysis provides an explanation for the relatively thickness-independent fill factor behaviour seen in solar cells using the copolymer PDTSiTzTz. Cumulative insights from this copolymer can be employed for future organic photovoltaic material development, study of existing high performance bulk heterojunciton blends, and improved solar cell design.

  1. The Altered Renal and Hepatic Expression of Solute Carrier Transporters (SLCs) in Type 1 Diabetic Mice

    PubMed Central

    Xu, Chenghao; Zhu, Ling; Chan, Ting; Lu, Xiaoxi; Shen, Weiyong; Gillies, Mark C.; Zhou, Fanfan

    2015-01-01

    Diabetes mellitus is a chronic metabolic disorder that significantly affects human health and well-being. The Solute carrier transporters (SLCs), particularly the Organic anion/cation transporters (Oats/Octs/Octns), Organic anion transporting polypeptides (Oatps) and Oligopeptide transporters (Pepts) are essential membrane proteins responsible for cellular uptake of many endogenous and exogenous substances such as clinically important drugs. They are widely expressed in mammalian key organs especially the kidney and liver, in which they facilitate the influx of various drug molecules, thereby determining their distribution and elimination in body. The altered expression of SLCs in diabetes mellitus could have a profound and clinically significant influence on drug therapies. In this study, we extensively investigated the renal and hepatic expression of twenty essential SLCs in the type 1 diabetic Ins2Akita murine model that develops both hyperglycemia and diabetes-related complications using real-time PCR and immunoblotting analysis. We found that the renal expression of mOatp1a1, mOatp1a6, mOat1, mOat3, mOat5, mOct2 and mPept2 was decreased; while that of mPept1 was increased at the mRNA level in the diabetic mice compared with non-diabetic controls. We found up-regulated mRNA expression of mOatp1a4, mOatp1c1, mOctn2, mOct3 and mPept1 as well as down-regulation of mOatp1a1 in the livers of diabetic mice. We confirmed the altered protein expression of several SLCs in diabetic mice, especially the decreased renal and hepatic expression of mOatp1a1. We also found down-regulated protein expression of mOat3 and mOctn1 in the kidneys as well as increased protein expression of mOatp1a4 and mOct3 in the livers of diabetic mice. Our findings contribute to better understanding the modulation of SLC transporters in type 1 diabetes mellitus, which is likely to affect the pharmacokinetic performance of drugs that are transported by these transporters and therefore, forms the basis of future therapeutic optimization of regimens in patients with type 1 diabetes mellitus. PMID:25789863

  2. The altered renal and hepatic expression of solute carrier transporters (SLCs) in type 1 diabetic mice.

    PubMed

    Xu, Chenghao; Zhu, Ling; Chan, Ting; Lu, Xiaoxi; Shen, Weiyong; Gillies, Mark C; Zhou, Fanfan

    2015-01-01

    Diabetes mellitus is a chronic metabolic disorder that significantly affects human health and well-being. The Solute carrier transporters (SLCs), particularly the Organic anion/cation transporters (Oats/Octs/Octns), Organic anion transporting polypeptides (Oatps) and Oligopeptide transporters (Pepts) are essential membrane proteins responsible for cellular uptake of many endogenous and exogenous substances such as clinically important drugs. They are widely expressed in mammalian key organs especially the kidney and liver, in which they facilitate the influx of various drug molecules, thereby determining their distribution and elimination in body. The altered expression of SLCs in diabetes mellitus could have a profound and clinically significant influence on drug therapies. In this study, we extensively investigated the renal and hepatic expression of twenty essential SLCs in the type 1 diabetic Ins2Akita murine model that develops both hyperglycemia and diabetes-related complications using real-time PCR and immunoblotting analysis. We found that the renal expression of mOatp1a1, mOatp1a6, mOat1, mOat3, mOat5, mOct2 and mPept2 was decreased; while that of mPept1 was increased at the mRNA level in the diabetic mice compared with non-diabetic controls. We found up-regulated mRNA expression of mOatp1a4, mOatp1c1, mOctn2, mOct3 and mPept1 as well as down-regulation of mOatp1a1 in the livers of diabetic mice. We confirmed the altered protein expression of several SLCs in diabetic mice, especially the decreased renal and hepatic expression of mOatp1a1. We also found down-regulated protein expression of mOat3 and mOctn1 in the kidneys as well as increased protein expression of mOatp1a4 and mOct3 in the livers of diabetic mice. Our findings contribute to better understanding the modulation of SLC transporters in type 1 diabetes mellitus, which is likely to affect the pharmacokinetic performance of drugs that are transported by these transporters and therefore, forms the basis of future therapeutic optimization of regimens in patients with type 1 diabetes mellitus. PMID:25789863

  3. Charge Transport in Azobenzene-Based Single-Molecule Junctions

    NASA Astrophysics Data System (ADS)

    Kim, Youngsang; Garcia-Lekue, Aran; Sysoiev, Dmytro; Frederiksen, Thomas; Groth, Ulrich; Scheer, Elke

    2012-11-01

    Azobenzene-derivative molecules change their conformation as a result of a cis-trans transition when exposed to ultraviolet or visible light irradiation and this is expected to induce a significant variation in the conductance of molecular devices. Despite extensive investigations carried out on this type of molecule, a detailed understanding of the charge transport for the two isomers is still lacking. We report a combined experimental and theoretical analysis of electron transport through azobenzene-derivative single-molecule break junctions with Au electrodes. Current-voltage and inelastic electron tunneling spectroscopy (IETS) measurements performed at 4.2 K are interpreted based on first-principles calculations of electron transmission and IETS spectra. This qualitative study unravels the origin of a slightly higher conductance of junctions with the cis isomer and demonstrates that IETS spectra of cis and trans forms show distinct vibrational fingerprints that can be used for identifying the isomer.

  4. Direct minority carrier transport characterization of InAs/InAsSb superlattice nBn photodetectors

    NASA Astrophysics Data System (ADS)

    Zuo, Daniel; Liu, Runyu; Wasserman, Daniel; Mabon, James; He, Zhao-Yu; Liu, Shi; Zhang, Yong-Hang; Kadlec, Emil A.; Olson, Benjamin V.; Shaner, Eric A.

    2015-02-01

    We present an extensive characterization of the minority carrier transport properties in an nBn mid-wave infrared detector incorporating a Ga-free InAs/InAsSb type-II superlattice as the absorbing region. Using a modified electron beam induced current technique in conjunction with time-resolved photoluminescence, we were able to determine several important transport parameters of the absorber region in the device, which uses a barrier layer to reduce dark current. For a device at liquid He temperatures, we report a minority carrier diffusion length of 750 nm and a minority carrier lifetime of 200 ns, with a vertical diffusivity of 3 × 10-2 cm2/s. We also report on the device's optical response characteristics at 78 K.

  5. Towards a unified description of the charge transport mechanisms in conductive atomic force microscopy studies of semiconducting polymers

    NASA Astrophysics Data System (ADS)

    Moerman, D.; Sebaihi, N.; Kaviyil, S. E.; Leclère, P.; Lazzaroni, R.; Douhéret, O.

    2014-08-01

    In this work, conductive atomic force microscopy (C-AFM) is used to study the local electrical properties in thin films of self-organized fibrillate poly(3-hexylthiophene) (P3HT), as a reference polymer semiconductor. Depending on the geometrical confinement in the transport channel, the C-AFM current is shown to be governed either by the charge transport in the film or by the carrier injection at the tip-sample contact, leading to either bulk or local electrical characterization of the semiconducting polymer, respectively. Local I-V profiles allow discrimination of the different dominating electrical mechanisms, i.e., resistive in the transport regime and space charge limited current (SCLC) in the local regime. A modified Mott-Gurney law is analytically derived for the contact regime, taking into account the point-probe geometry of the contact and the radial injection of carriers. Within the SCLC regime, the probed depth is shown to remain below 12 nm with a lateral electrical resolution below 5 nm. This confirms that high resolution is reached in those C-AFM measurements, which therefore allows for the analysis of single organic semiconducting nanostructures. The carrier density and mobility in the volume probed under the tip under steady-state conditions are also determined in the SCLC regime.In this work, conductive atomic force microscopy (C-AFM) is used to study the local electrical properties in thin films of self-organized fibrillate poly(3-hexylthiophene) (P3HT), as a reference polymer semiconductor. Depending on the geometrical confinement in the transport channel, the C-AFM current is shown to be governed either by the charge transport in the film or by the carrier injection at the tip-sample contact, leading to either bulk or local electrical characterization of the semiconducting polymer, respectively. Local I-V profiles allow discrimination of the different dominating electrical mechanisms, i.e., resistive in the transport regime and space charge limited current (SCLC) in the local regime. A modified Mott-Gurney law is analytically derived for the contact regime, taking into account the point-probe geometry of the contact and the radial injection of carriers. Within the SCLC regime, the probed depth is shown to remain below 12 nm with a lateral electrical resolution below 5 nm. This confirms that high resolution is reached in those C-AFM measurements, which therefore allows for the analysis of single organic semiconducting nanostructures. The carrier density and mobility in the volume probed under the tip under steady-state conditions are also determined in the SCLC regime. Electronic supplementary information (ESI) available: SI-1: tapping mode AFM image of fibrillar P3HT. SI-2: current-distance profile of a high aspect ratio channel exhibiting both the contact and transport resistance dominating regimes. SI-3: full analytical derivation of the Mott-Gurney law, describing the SCLC regime in a point probe geometrical configuration for C-AFM measurements. See DOI: 10.1039/c4nr02577f

  6. Selective and Efficient Liquid Membrane Transport of Thallium (III) Ion by Potassium?dicyclohexyl?18?crown?6 as Specific Carrier

    Microsoft Academic Search

    Javad Zolgharnein; Hassan Shams; Gholamhassan Azimi

    2007-01-01

    Potassium?dicyclohexyl?18?crown?6 was used as a selective and efficient carrier for the uphill transport of thallium (III) ion as [TlCl4] complex ion through a chloroform bulk liquid membrane. By using oxalate anion as a metal ion acceptor in the receiving phase, the amount of thallium (III) transported across the liquid membrane after 120 min was 96±2%. The selectivity and efficiencies of thallium

  7. Secondary Electron Emission and Self-consistent Charge Transport and Storage in Bulk Insulators

    E-print Network

    Boyer, Edmond

    and applications of these materials, see e.g. the conference series on Electric Charges in Non-Conductive MaterialsSecondary Electron Emission and Self-consistent Charge Transport and Storage in Bulk Insulators: (33) 5 59 92 30 63, Fax: (33) 5 59 80 83 50 1 #12;ABSTRACT The selfconsistent charge transport in bulk

  8. A liquefied energy chain for transport and utilization of natural gas for power production with CO 2 capture and storage – Part 3: The combined carrier and onshore storage

    Microsoft Academic Search

    Audun Aspelund; Steinar P. Tveit; Truls Gundersen

    2009-01-01

    A novel energy and cost effective transport chain for stranded natural gas utilized for power production with CO2 capture and storage is developed. It includes an offshore section, a combined gas carrier and an integrated receiving terminal. The combined carrier will transport liquid carbon dioxide (LCO2) and liquid nitrogen (LIN) outbound, where natural gas (NG) is cooled and liquefied to

  9. Dielectric and carrier transport properties of vanadium dioxide thin films across the phase transition utilizing gated capacitor devices

    E-print Network

    Yang, Zheng

    Dielectric and carrier transport properties of vanadium dioxide thin films across the phase; published 1 November 2010 Vanadium dioxide VO2 is a strongly correlated oxide that undergoes a sharp metal.22.Ch I. INTRODUCTION Vanadium dioxide VO2 is a material of great interest in condensed-matter physics

  10. Charge transport and electrochemical response of poly(3,4-ethylenedioxypyrrole) films improved by noble-metal nanoparticles.

    PubMed

    Deepa, Melepurath; Kharkwal, Aneeta; Joshi, Amish G; Srivastava, Avanish Kumar

    2011-06-01

    Charge-transport phenomena and redox switching of poly(3,4-ethylenedioxypyrrole) (PEDOP) films embedded with Au and Ag nanoparticles have been investigated. In the bulk, charge transport can be described by an ohmic regime at low voltages and a space-charge-limited current regime at high voltages in PEDOP-Au, which is in contrast to trap-filled domains deduced for neat PEDOP and PEDOP-Ag nanocomposites, all indicating transitions driven by an external bias. This also allowed a direct estimation of a fairly high charge-carrier mobility at room temperature in PEDOP-Au, in addition to a higher donor density, which are advantageous for device applications. X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy affirmed the prevalence of Au/Ag nanoparticles as nonleachable entities in PEDOP, thus allowing the movement of electrons through the conducting nanoaparticles during electrochemical switching, an effect that is absent in the neat PEDOP film. Valence-band spectra and optical studies revealed that nanoparticles narrowed the band gap and increased the absorption coefficient of PEDOP, which enhanced the electrochromic switching ability of PEDOP. A coloration efficiency enhancement by an order of magnitude, higher electrochemical charge intercalation capacity, and higher diffusion rates reflect the role of noble-metal nanoparticles in improving the conduction and electrochemical activity of PEDOP. PMID:21585212

  11. The relation between charge movement and transport-associated currents in the rat GABA cotransporter rGAT1.

    PubMed

    Fesce, Riccardo; Giovannardi, Stefano; Binda, Francesca; Bossi, Elena; Peres, Antonio

    2002-12-15

    Most cotransporters characteristically display two main kinds of electrical activity: in the absence of organic substrate, transient presteady-state currents (I(pre)) are generated by charge relocation during voltage steps; in the presence of substrate, sustained, transport-associated currents (I(tr)) are recorded. Quantitative comparison of these two currents, in Xenopus oocytes expressing the neural GABA cotransporter rGAT1, revealed several unforeseen consistencies between I(pre) and I(tr), in terms of magnitude and kinetic parameters. The decay rate constant (r) of I(pre) and the quantity of charge displaced to an inner position in the transporter (Q(in)(0)) depended on voltage and ionic conditions. Saturating GABA concentrations, applied under the same conditions, suppressed I(pre) (i.e. Q(in)( infinity ) = 0) and produced a transport-associated current with amplitude I(tr) = Q(in)(0)r. At non-saturating levels of GABA, changes of I(tr) were compensated by corresponding variations in Q(in), such that I(pre) and I(tr) complemented each other, according to the relation: I(tr) = (Q(in)(0) - Q(in)) r. Complementarity of magnitude, superimposable kinetic properties and equal dependence on voltage and [Na(+)](o) point to the uniqueness of the charge carrier for both processes, suggesting that transport and charge migration arise from the same molecular mechanism. The observed experimental relations were correctly predicted by a simple three-state kinetic model, in which GABA binding takes place after charge binding and inward migration have occurred. The model also predicts the observed voltage dependence of the apparent affinity of the transporter for GABA, and suggests a voltage-independent GABA binding rate with a value around 0.64 microM(-1) s(-1). PMID:12482883

  12. Doping dependence of coupling between charge carriers and bosonic modes in the normal state of high- Tc superconductors

    NASA Astrophysics Data System (ADS)

    Saadaoui, H.; Azzouz, M.

    2005-11-01

    Recently, the doping dependence of the optical-conductivity scattering rate has been used by Hwang, Timusk, and Gu to gain some insight in the way the coupling between the charge carriers and the bosonic modes in high- Tc superconductors depends on doping. These authors used the extended Drude analysis, which does not take into account the normal-state pseudogap explicitly. In this work, we calculated the optical conductivity within the rotating antiferromagnetism theory, which models explicitly the pseudogap. Then we analyzed the resistivity as a function of temperature T and doping p . We extracted the scattering rate 1/? by fitting the La2-xSrxCuO4 resistivity data. We found that for p smaller than a critical value pc , 1/? shows a marginal-Fermi-liquid dependence for T greater than a p -dependent temperature T?* . But for Tcharge carriers and the normal-state bosonic modes. Both this coupling and T?* vanish at pc while superconductivity continues to be significant well above it. pc is interpreted as a quantum critical point, and T?* as the pseudogap temperature T* because it is found to agree with the experimental data on T* . We propose that a possible candidate for the bosonic modes may be the spin-wave excitations in the rotating frame of the rotating antiferromagnetic order.

  13. The Effect of Diiodooctane on the Charge Carrier Generation in Organic Solar Cells Based on the Copolymer PBDTTT-C

    NASA Astrophysics Data System (ADS)

    Zusan, Andreas; Gieseking, Björn; Zerson, Mario; Dyakonov, Vladimir; Magerle, Robert; Deibel, Carsten

    2015-02-01

    Microstructural changes and the understanding of their effect on photocurrent generation are key aspects for improving the efficiency of organic photovoltaic devices. We analyze the impact of a systematically increased amount of the solvent additive diiodooctane (DIO) on the morphology of PBDTTT-C:PC71BM blends and related changes in free carrier formation and recombination by combining surface imaging, photophysical and charge extraction techniques. We identify agglomerates visible in AFM images of the 0% DIO blend as PC71BM domains embedded in an intermixed matrix phase. With the addition of DIO, a decrease in the size of fullerene domains along with a demixing of the matrix phase appears for 0.6% and 1% DIO. Surprisingly, transient absorption spectroscopy reveals an efficient photogeneration already for the smallest amount of DIO, although the largest efficiency is found for 3% DIO. It is ascribed to a fine-tuning of the blend morphology in terms of the formation of interpenetrating donor and acceptor phases minimizing geminate and nongeminate recombination as indicated by charge extraction experiments. An increase in the DIO content to 10% adversely affects the photovoltaic performance, most probably due to an inefficient free carrier formation and trapping in a less interconnected donor-acceptor network.

  14. Carrier-collision-induced formation of charged excitons and ultrafast dynamics fluorescence spectra.

    PubMed

    Chen, Ren-Ai; Wang, Cong; Li, Sheng; George, Thomas F

    2012-12-13

    After a hole injection layer is inserted into a polymer light-emitting material, the injection of positive charge not only easily causes distortion in the conjugated polymer chain but also produces positive polarons. The ultrafast dynamics shows that, when the positive polaron approaches and collides with the triplet exciton, that exciton will become charged, whereby the non-emissive triplet exciton becomes radiative and emits light. Furthermore, the lifetime of the charged triplet exciton is longer than the singlet exciton. This paper explicitly depicts the dynamic fluorescence spectra of the radiative transition of the charged triplet exciton occurring during the decay of the charged exciton, and also exhibits the difference between traditional adiabatic dynamics and non-adiabatic dynamics. PMID:23186537

  15. Gene amplification and increased expression of the reduced folate carrier in transport elevated K562 cells.

    PubMed

    Wong, S C; Zhang, L; Proefke, S A; Hukku, B; Matherly, L H

    1998-04-01

    The molecular bases for the 6-fold elevated methotrexate transport capacity of K562.4CF cells (Matherly et al., Cancer Res. 51: 3420-3426, 1991) were studied with reduced folate carrier (RFC) cDNA, genomic, and antibody probes. Southern analysis showed that RFC gene copies were increased (approximately 4- to 5-fold) in K562.4CF over wild-type K562 cells. Fluorescence in situ hybridization using a genomic RFC probe confirmed the localization of the RFC gene to the q-arm of chromosome 21. In K562.4CF cells, the frequent loss of a normal copy of chromosome 21 (61% of metaphases) was accompanied by RFC gene amplification and translocations of amplified RFC gene fragments to several (2 to 6) different chromosomal loci not seen in wild-type cells. Particularly intense RFC signals were mapped to homogeneously staining regions in chromosomes 2 and 15. Increased RFC gene copies were accompanied by a similar increase in the major 3.1 kb RFC transcript by northern blotting and an approximately 7-fold elevated level of the broadly migrating (80-95 kDa) RFC protein on a western blot probed with an RFC C-terminal peptide antibody. These results demonstrate that selection of cells with a growth-limiting concentration of reduced folates (0.4 nM of leucovorin) is sufficient to promote chromosomal aberrations, including gene amplification and translocations that result in increased RFC expression and folate transport. PMID:9605439

  16. The role of public transport for feasibility and acceptability of congestion charging – The case of Stockholm

    Microsoft Academic Search

    Karl Kottenhoff; Karin Brundell Freij

    2009-01-01

    In the Stockholm Trial, congestion charges and the expansion of public transport services were closely linked together in marketing efforts, as well as in political decisions. In this paper, we analyse the role that public transport may have played in increasing acceptability and feasibility of the scheme. We study four aspects of the relationship between charging and public transport provision:

  17. Effects of cytosine methylation on DNA charge transport

    NASA Astrophysics Data System (ADS)

    Hihath, Joshua; Guo, Shaoyin; Zhang, Peiming; Tao, Nongjian

    2012-04-01

    The methylation of cytosine bases in DNA commonly takes place in the human genome and its abnormality can be used as a biomarker in the diagnosis of genetic diseases. In this paper we explore the effects of cytosine methylation on the conductance of DNA. Although the methyl group is a small chemical modification, and has a van der Waals radius of only 2 Å, its presence significantly changes the duplex stability, and as such may also affect the conductance properties of DNA. To determine if charge transport through the DNA stack is sensitive to this important biological modification we perform multiple conductance measurements on a methylated DNA molecule with an alternating G:C sequence and its non-methylated counterpart. From these studies we find a measurable difference in the conductance between the two types of molecules, and demonstrate that this difference is statistically significant. The conductance values of these molecules are also compared with a similar sequence that has been previously studied to help elucidate the charge transport mechanisms involved in direct DNA conductance measurements.

  18. Controlling polymer translocation and ion transport via charge correlations

    E-print Network

    Sahin Buyukdagli; Tapio Ala-Nissila

    2014-10-10

    We develop a correlation-corrected transport theory in order to predict ionic and polymer transport properties of membrane nanopores in physical conditions where mean-field electrostatics breaks down. The experimentally observed low KCl conductivity of open alpha-Hemolysin pores is quantitatively explained by the presence of surface polarization effects. Upon the penetration of a DNA molecule into the pore, these polarization forces combined with the electroneutrality of DNA sets a lower boundary for the ionic current, explaining the weak salt dependence of blocked pore conductivities at dilute ion concentrations. The addition of multivalent counterions into the solution results in the reversal of the polymer charge and the direction of the electroosmotic flow. With trivalent spermidine or quadrivalent spermine molecules, the charge inversion is strong enough to stop the translocation of the polymer and to reverse its motion. This mechanism can be used efficiently in translocation experiments in order to improve the accuracy of DNA sequencing by minimizing the translocation velocity of the polymer.

  19. Charge carrier concentration optimization of thermoelectric p-type half-Heusler compounds

    NASA Astrophysics Data System (ADS)

    Rausch, Elisabeth; Balke, Benjamin; Deschauer, Torben; Ouardi, Siham; Felser, Claudia

    2015-04-01

    The carrier concentration in the p-type half-Heusler compound Ti0.3Zr0.35Hf0.35CoSb1-xSnx was optimized, which is a fundamental approach to enhance the performance of thermoelectric materials. The optimum carrier concentration is reached with a substitution level x = 0.15 of Sn, which yields the maximum power factor, 2.69 × 10-3 W m-1 K-2, and the maximum ZT = 0.8. This is an enhancement of about 40% in the power factor and the figure of merit compared to samples with x = 0.2. To achieve low thermal conductivities in half-Heusler compounds, intrinsic phase separation is an important key point. The present work addresses the influence of different preparation procedures on the quality and reproducibility of the samples, leading to the development of a reliable fabrication method.

  20. Specific features of charge carrier scattering mechanisms in Co-Cr alloys at high temperatures

    NASA Astrophysics Data System (ADS)

    Ivliyev, A. D.; Glagoleva, Yu. V.

    2011-06-01

    The temperature and concentration dependences of the electrical resistivity ? and thermal diffusivity a of Co-Cr alloys have been studied at temperatures of 400-1600 K. It has been shown that, as the temperature increases, the specific features of the electrical properties of the alloys are mainly determined by phonon scattering of carriers, and the character of the polytherms and concentration dependences is determined by the multiband scattering mechanism.

  1. Suppression of Charge Carrier Tunneling through Organic Self-Assembled Monolayers

    Microsoft Academic Search

    C. Boulas; J. V. Davidovits; F. Rondelez; D. Vuillaume

    1996-01-01

    Self-assembled monolayers of long chain alkanes deposited on silicon wafers using an optimally designed procedure exhibit very large energy barriers ( ~4.5 eV) to carrier tunneling. The dc conductivity is found to be ~4.6×10-15 S\\/cm, close to that of bulk polyethylene, and independent of monolayer thickness. This demonstrates that the tunneling contribution to the overall conductivity can be made negligible

  2. Charge Transport in one Dimension:Dissipative and Non-Dissipative Space-Charge Limited Currents

    E-print Network

    S. R. Holcombe; E. R. Smith

    2012-04-06

    We consider charge transport in nanopores where the dielectric constant inside the nanopore is much greater than in the surrounding material, so that the flux of the electric fields due to the charges is almost entirely confined to the nanopore. That means that we may model the electric fields due to charge densities in the nanopore in terms of average properties across the nanopore as solutions of one dimensional Poisson equations. We develop basic equations for an M component system using equations of continuity to relate concentrations to currents, and flux equations relating currents to concentration gradients and conductivities. We then derive simplified scaled versions of the equations. We develop exact solutions for the one component case in a variety of boundary conditions using a Hopf-Cole transformation, Fourier series, and periodic solutions of the Burgers equation. These are compared with a simpler model in which the scaled diffusivity is zero so that all charge motion is driven by the electric field. In this non-dissipative case, recourse to an admissibility condition is utilised to obtain the physically relevant weak solution of a Riemann problem concerning the electric field. It is shown that the admissibility condition is Poynting's theorem.

  3. A numerical study on the charge transport in TPD/Alq3-based organic light emitting diodes.

    PubMed

    Kim, K S; Hwang, Y W; Lee, H G; Won, T Y

    2014-08-01

    We report our simulation study on the charge transport characteristic of the multi-layer structure for organic light emitting diodes (OLEDs). We performed a numerical simulation on a multilayer structure comprising a hole transport layer (HTL), an emission layer (EML), and an electron transport layer (ETL) between both electrodes. The material of the HTL is TPD (N,N'-Bis (3-methylphenyl)-N,N'-bis(phenyl) benzidine), and the ETL includes Alq3 (Tris (8-hyroxyquinolinato) aluminium). Here, we investigated the parameters such as recombination rates which influence the efficiency of the charge transport between layers in bilayer OLEDs. We also analyzed a transient response during the turn on/off period and the carrier transport in accordance with the variation of the injection barrier and applied voltage. In addition, our numerical simulation revealed that the insertion of the EML affects the photonic characteristics in bilayer structure and also the efficiency due to the difference in the internal barrier height. PMID:25936012

  4. Novel electrode design for single-carrier charge collection in semiconductor nuclear radiation detectors

    Microsoft Academic Search

    Jack F Butler

    1997-01-01

    A new electrode configuration comprising a cathode, a small anode and a “control electrode” resulted in energy resolutions as low as 0.72% and photopeak efficiencies near unity at 511 keV with CdZnTe room temperature nuclear detectors. The control electrode transiently accepts a large fraction of charge that would otherwise be induced on the anode by mobile charges in transit and,

  5. Charge transport and charge clustering in polymer electrolytes: Results from simulations

    SciTech Connect

    Payne, V.A.; Forsyth, M.; Shriver, D.F.; DeLeeuw, S.W.; Ratner, M.A. [Northeastern Univ., Evanston, IL (United States)

    1993-12-31

    This paper reports results of molecular dynamics simulations on models for polymer electrolytes. These initial models use reasonable potentials, with proper thermal dynamics and appropriate treatment of boundary conditions. The solvents themselves range in complexity from simple Lennar-Jones spheres with embedded dipoles to constraint geometry models for small etheric solvents. The paper reports structural, transport and thermal dependences of these model electrolytes. The authors observe some important changes in the extent of clustering with temperature and with dielectric constant, as well as with concentration. Mechanistic interpretation, in terms of effective ion flows and charge transport characteristics, are reported. In particular, the authors find an analysis of pairing using the thermal dependence of the potential of mean force shows clearly that entropic effects, as well as reduced dielectric screening, result in cluster stabilization. In the extreme limit of oversaturation, such stabilization can actually lead to changes in the mechanism, in agreement with recent suggestions by Angell based on ionene materials.

  6. Carrier transport in quantum dot quantum well microstructures of the self-assembled CdTe/CdS/ligand core-shell system

    NASA Astrophysics Data System (ADS)

    Li, K. Y.; Shan, Q. S.; Zhu, R. P.; Yin, H.; Lin, Y. Y.; Wang, L. Q.

    2015-04-01

    The study on the quantum dot quantum well (QDQW) microstructure modified by choosing different ligands containing a sulfhydryl group is of significance because it enables one to regulate photoexcited free charge carriers' (FCCs') transport behaviours in high-quality CdTe/ligand QDs via a self-assembled way. The photoelectron characteristics of ligand-capped CdTe nanoparticles were probed by a combination of surface photovoltaic (SPV) and photoacoustic technologies, supplemented by a computer simulation method of the CASTEP module. The experiment reveals that the D-value ?EWi obtained by the associated two parameters of the SPV spectroscopy was closely related to the quantum confinement energy in the self-assembled CdTe/CdS/ligand core-shell system. In the paper the D-value was termed the depth of QWs, which were buried in the space charge regions located in the graded-band-gap and on either side of the shell-CdS. Obvious resonance quantum tunnelling may occur in the energy band structure with deep QWs on using certain ligands, resulting in an extended diffusion length of the FCCs on illumination of the photon energy h? >= Eg, core-CdTe, and in a strong SPV response at a specific wavelength region. In addition, the carrier-longitudinal optical phonon interaction is the reciprocal of the carriers' lifetime. The d-frontier orbital in the graded-band-gap plays an important role in both the microstructure and the resonance quantum tunnelling of the QDQW system according to the CASTEP calculations.The study on the quantum dot quantum well (QDQW) microstructure modified by choosing different ligands containing a sulfhydryl group is of significance because it enables one to regulate photoexcited free charge carriers' (FCCs') transport behaviours in high-quality CdTe/ligand QDs via a self-assembled way. The photoelectron characteristics of ligand-capped CdTe nanoparticles were probed by a combination of surface photovoltaic (SPV) and photoacoustic technologies, supplemented by a computer simulation method of the CASTEP module. The experiment reveals that the D-value ?EWi obtained by the associated two parameters of the SPV spectroscopy was closely related to the quantum confinement energy in the self-assembled CdTe/CdS/ligand core-shell system. In the paper the D-value was termed the depth of QWs, which were buried in the space charge regions located in the graded-band-gap and on either side of the shell-CdS. Obvious resonance quantum tunnelling may occur in the energy band structure with deep QWs on using certain ligands, resulting in an extended diffusion length of the FCCs on illumination of the photon energy h? >= Eg, core-CdTe, and in a strong SPV response at a specific wavelength region. In addition, the carrier-longitudinal optical phonon interaction is the reciprocal of the carriers' lifetime. The d-frontier orbital in the graded-band-gap plays an important role in both the microstructure and the resonance quantum tunnelling of the QDQW system according to the CASTEP calculations. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr00494b

  7. Deep-trapping kinematics of charge carriers in amorphous semiconductors: A theoretical and experimental study

    NASA Astrophysics Data System (ADS)

    Kasap, S. O.; Aiyah, Viswanath; Polischuk, B.; Bhattacharyya, A.; Liang, Z.

    1991-03-01

    There has been much recent interest in the determination of drift-mobility (?) -lifetime (?) products in amorphous semiconductors by various measurement techniques. Although most measurements have utilized time-of-flight types of transient-photoconductivity experiments, xerographic measurements have also been used, since they provide a clear measurement of the residual potential VR, i.e., the electrostatic potential on the surface of a high-resistivity solid, due to trapped charges in the bulk. This paper identifies and critically examines the theoretical problems involved in the determination of ?? from such xerographic measurements. The deep-trapping model of Kanazawa and Batra, which relates the residual potential to the ?? product, is reformulated by specifically including the effect of the rate of trapping as being proportional to the instantaneous unoccupied density of traps. The latter description had been neglected in previous models of deep-trapping kinematics. A partial differential equation is derived that describes the space and time evolution of the electric field within the material. By numerically solving the differential equation and integrating the electric field, the residual potential VR has been related to the ?? product. It is found that VR depends not only on the ?? product but also on the capture coefficient to the microscopic mobility ratio, Ct/?0. Universal curves relating VR to the ?? product and parametric in Ct/?0 have been obtained that clearly show the importance of including the effect of trap filling in the theory. Furthermore, it is shown that the ?? product cannot be uniquely determined via xerographic measurements unless (?Ct/e?0)<<1, where ? is the permittivity of the material. Xerographic first-cycle residual-potential experiments in conjunction with interrupted-field time-of-flight (IFTOF) transient-photoconductivity measurements have been carried out on vacuum-deposited pure a-Se and chlorine-doped a-Se:0.3 at. % As alloy films to experimentally correlate the residual potential with the ?? values. It is shown that the Kanazawa-Batra universal curve is completely inadequate in describing the present experimental VR versus ?? data, by as much as a factor of 5, whereas the theory developed herein can account for the experiments, provided that the capture coefficient Ct is 1.22×10-7 cm3 s-1. The limitations of the present model and its implications are also addressed. The simple range-limited transport concept of Warter leading to the expression VR=L2/2?? for the residual potential under weak-trapping conditions has been found to predict the residual voltage surprisingly well and to within a factor of 2. By carrying out cycled-up xerographic residual-potential experiments on the same films for which the deep-trapping times have been determined, the capture radius of deep hole traps in a-Se and chlorinated a-Se:0.3 at. % As films have been determined. Application of ballistic and diffusional trapping models of Street to the IFTOF lifetime and cycled-up residual-potential data imply capture radii of 2-3 Å for both pure a-Se and Cl-doped 0.3 at. % As alloys. The first-cycle residual-potential model developed herein in combination with IFTOF results, however, leads to capture radii of ~20 and 85 Å for ballistic and diffusional capture, respectively. The results are discussed in terms of valence-alternation-pair (VAP) and intimate-VAP (IVAP) centers in amorphous semiconductors. The energy spectrum of the density of localized midgap states for both a-Se and Cl-doped a-Se:0.3 at. % As films have been obtained via the xerographic-spectroscopy technique of Abkowitz and Markovics.

  8. Charge Transport in Organic Semiconductors Veaceslav Coropceanu, Jero^me Cornil,, Demetrio A. da Silva Filho, Yoann Olivier, Robert Silbey,# and

    E-print Network

    Wu, Zhigang

    . The charge carriers are either injected into the organic semiconductors from metal or conducting oxide 934 2.3.6. Pressure 934 2.3.7. Charge-Carrier Density 934 2.3.8. Size/molecular Weight 935 3 on the efficiency with which charge carriers (electrons and/or holes) move within the -conjugated materials

  9. Transient luminescence induced by electrical refilling of charge carrier traps of dislocation network at hydrophilically bonded Si wafers interface

    NASA Astrophysics Data System (ADS)

    Bondarenko, Anton; Vyvenko, Oleg

    2014-02-01

    Dislocation network (DN) at hydrophilically bonded Si wafers interface is placed in space charge region (SCR) of a Schottky diode at a depth of about 150 nm from Schottky electrode for simultaneous investigation of its electrical and luminescent properties. Our recently proposed pulsed traps refilling enhanced luminescence (Pulsed-TREL) technique based on the effect of transient luminescence induced by refilling of charge carrier traps with electrical pulses is further developed and used as a tool to establish DN energy levels responsible for D1 band of dislocation-related luminescence in Si (DRL). In present work we do theoretical analysis and simulation of traps refilling kinetics dependence on refilling pulse magnitude (Vp) in two levels model: shallow and deep. The influence of initial charge state of deep level on shallow level occupation-Vp dependence is discussed. Characteristic features predicted by simulations are used for Pulsed-TREL experimental results interpretation. We conclude that only shallow (˜0.1 eV from conduction and valence band) energetic levels in the band gap participate in D1 DRL.

  10. Acceptor-compensated charge transport and surface chemical reactions in Au-implanted SnO? nanowires.

    PubMed

    Katoch, Akash; Sun, Gun-Joo; Choi, Sun-Woo; Hishita, Shunichi; Kulish, Vadym V; Wu, Ping; Kim, Sang Sub

    2014-01-01

    A new deep acceptor state is identified by density functional theory calculations, and physically activated by an Au ion implantation technique to overcome the high energy barriers. And an acceptor-compensated charge transport mechanism that controls the chemical sensing performance of Au-implanted SnO2 nanowires is established. Subsequently, an equation of electrical resistance is set up as a function of the thermal vibrations, structural defects (Au implantation), surface chemistry (1?ppm NO2), and solute concentration. We show that the electrical resistivity is affected predominantly not by the thermal vibrations, structural defects, or solid solution, but the surface chemistry, which is the source of the improved chemical sensing. The response and recovery time of chemical sensing is respectively interpreted from the transport behaviors of major and minor semiconductor carriers. This acceptor-compensated charge transport mechanism provides novel insights not only for sensor development but also for research in charge and chemical dynamics of nano-semiconductors. PMID:24713609

  11. Charge-carrier mobilities in Cd(0.8)Zn(0.2)Te single crystals used as nuclear radiation detectors

    Microsoft Academic Search

    Z. Burshtein; H. N. Jayatirtha; A. Burger; J. F. Butler; B. Apotovsky; F. P. Doty

    1993-01-01

    Charge-carrier mobilities were measured for the first time in Cd(0.8)Zn(0.2)Te single crystals using time-of-flight measurements of charge carriers produced by short (10 ns) light pulses from a frequency-doubled Nd:YAG laser (532 nm). The electron mobility displayed a T exp -1.1 dependence on the absolute temperature T in the range 200-320 K, with a room-temperature mobility of 1350 sq cm\\/V s.

  12. Thermoelectric Detection of Chiral Heat Transport in Graphene in the Quantum Hall Regime Seung-Geol Nam,1

    E-print Network

    Lee, Hu-Jong

    Hall regime. Hot charge carriers are injected to the edge channels, and the thermoelectric voltage primarily result from the massless low-energy Dirac- fermionic nature of the charge carriers [1­4]. Recently in the carrier scattering rates than charge transport itself. As such, it provides a useful tool to probe key

  13. Symmetric and asymmetric charge transport in interacting asymmetric quantum impurities

    NASA Astrophysics Data System (ADS)

    Roy, Dibyendu

    2010-02-01

    We study steady-state charge transfer across an interacting resonance-level model connected asymmetrically to two leads. For a linear energy dispersion relation of the leads, we calculate current-voltage characteristics of the model exactly employing the scattering Bethe ansatz of Mehta-Andrei and find symmetric transport showing the absence of diode effect. Next we study a lattice version of this model with a nonlinear dispersion for the leads using the Lippmann-Schwinger scattering theory. We find that the inclusion of nonlinearity in the leads’ dispersion causes rectification for asymmetric junctions but does not rectify for asymmetric interactions and perfect junctions. The model in the latter case can be mapped into a model of a single noninteracting electron in higher dimensions.

  14. Perovskite solar cells employing organic charge-transport layers

    NASA Astrophysics Data System (ADS)

    Malinkiewicz, Olga; Yella, Aswani; Lee, Yong Hui; Espallargas, Guillermo Mínguez; Graetzel, Michael; Nazeeruddin, Mohammad K.; Bolink, Henk J.

    2014-02-01

    Thin-film photovoltaics play an important role in the quest for clean renewable energy. Recently, methylammonium lead halide perovskites were identified as promising absorbers for solar cells. In the three years since, the performance of perovskite-based solar cells has improved rapidly to reach efficiencies as high as 15%. To date, all high-efficiency perovskite solar cells reported make use of a (mesoscopic) metal oxide, such as Al2O3, TiO2 or ZrO2, which requires a high-temperature sintering process. Here, we show that methylammonium lead iodide perovskite layers, when sandwiched between two thin organic charge-transporting layers, also lead to solar cells with high power-conversion efficiencies (12%). To ensure a high purity, the perovskite layers were prepared by sublimation in a high-vacuum chamber. This simple planar device structure and the room-temperature deposition processes are suitable for many conducting substrates, including plastic and textiles.

  15. Short chain molecular junctions: Charge transport versus dipole moment

    NASA Astrophysics Data System (ADS)

    Ikram, I. Mohamed; Rabinal, M. K.

    2015-03-01

    The investigation of the influence of dipole moment of short chain organic molecules having three carbon atoms varying in end group on silicon surface was carried on. Here, we use three different molecules of propargyl series varying in dipole moment and its orientation to constitute molecular junctions. The charge transport mechanism in metal-molecules-semiconductor (MMS) junction obtained from current-voltage (I-V) characteristics shows the rectification behavior for two junctions whereas the other junction shows a weak rectification. The electronic properties of the molecules were calculated using Gaussian software package. The observed rectification behavior of these junctions is examined and found to be accounted to the orientation of dipole moment and electron cloud density distribution inside the molecules.

  16. Monte Carlo simulation of charge transport in amorphous chalcogenides

    NASA Astrophysics Data System (ADS)

    Piccinini, E.; Buscemi, F.; Rudan, M.; Brunetti, R.; Jacoboni, C.

    2009-11-01

    The I(V) characteristics of amorphous GST devices show a peculiar S-shape behavior, that is a swift rise of the current along with a voltage snap-back. This type of characteristics led to a growing research interest in view of the future application of such materials to the manufacturing of phase-change memory devices. In this work we adopt a generalization of the variable-range hopping theory to simulate charge transport in a layer of amorphous Ge2Sb2Te5 sandwiched between two planar metallic electrodes. The numerical implementation of a current-driven Monte Carlo code allows one both to provide a complete microscopic particle picture of electrical conduction in the device and to better analyze the mechanisms governing the snap-back effect.

  17. Study of tunneling transport of carriers in structures with an InGaN/GaN active region

    SciTech Connect

    Sizov, V. S., E-mail: vsizov@mail.ioffe.ru; Neploh, V. V.; Tsatsulnikov, A. F.; Sakharov, A. V.; Lundin, W. V.; Zavarin, E. E.; Nikolaev, A. E. [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation); Mintairov, A. M.; Merz, J. L. [University of Notre Dame, EE Department (United States)

    2010-12-15

    Properties of light-emitting structures with an InGaN/GaN active region emitting in a range of 500-550 nm are studied. Photoluminescence of the structures is studied at various values of external bias and temperature as well as with time resolution. With the reverse bias, a decrease in the carrier lifetime associated with tunneling exit of the carriers from the active region is found. The mechanism of tunneling leakage is simulated allowing for the Boltzmann distribution of carriers by energy; it is shown that the calculated and experimental dependences agree well. It is shown that the tunneling transport exerts a considerable effect on the characteristics of structures with an InGaN/GaN active region.

  18. Field-effect modulation of structure and carrier transport of LaNiO3 thin films

    NASA Astrophysics Data System (ADS)

    Malashevich, Andrei; Marshall, Matthew S. J.; Disa, Ankit S.; Walker, Frederick J.; Ahn, Charles H.; Ismail-Beigi, Sohrab

    2014-03-01

    Materials exhibiting large changes in resistivity in response to applied electric fields are of importance due to their technological applicability, e.g., in field-effect transistors. Of particular interest are thin film oxide/ferroelectric interfaces: the ferroelectric permits dynamic modulation of electronic transport in the oxide film which is crucial for non-volatile memory applications. In the standard field effect, resistance modulations result from changes in carrier density created by the applied electric field. At ferroelectric interfaces, however, other mechanisms can come into play. Our experiments show that at the (001) interface of rare-earth nickelates and ferroelectric Pb0.8Zr0.2TiO3 (PZT), the change of carrier mobility plays a critical role in the electronic transport. Here, we present a first-principles study of the interface between a thin film of conducting LaNiO3 and ferroelectric PbTiO3 (PTO). We analyze the dependence of the atomic structure of the interface on the PTO polarization and the effect of the structural changes on the electronic bands and associated carrier transport. We also describe the methodological challenges in transport calculations of metal/ferroelectric interfaces and some ways to address them.

  19. EPR, charge transport, and spin dynamics in doped polyanilines

    NASA Astrophysics Data System (ADS)

    Kon'kin, A. L.; Shtyrlin, V. G.; Garipov, R. R.; Aganov, A. V.; Zakharov, A. V.; Krinichnyi, V. I.; Adams, P. N.; Monkman, A. P.

    2002-08-01

    Charge transport and magnetic properties of films of polyaniline (PAN) doped with 10-camphorsulfonic acid and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPSA) have been studied by conductivity, magnetic-susceptibility superconducting quantum interference device measurements, and 3-cm and 8-mm electron paramagnetic resonance (EPR) spectroscopy at doping levels (x) from 0.3 to 0.9 over a temperature range from 15 to 300 K. The temperature dependences of conductivities were explained in terms of the advanced multiphase heterogeneous granular metallic (HGM) model with percolation including disordered metallic (DM) and nonmetallic (NM) phases. The anomalous conductivity change in the PAN-AMPSAx system at T>240 K was accounted quantitatively for a solid-phase equilibrium with the occurrence of the disordered anion phase from the metallic islands. A means for analysis of the EPR line shape in conducting media has been developed and, with this, conductivity and microwave dielectric constants were estimated and two EPR signals, R1 and R2, were detected in both systems. It was shown that R1 signal belongs to pinned radicals of isolated polymer chains, whereas R2 is the weight-averaged signal, resulting from three types of paramagnetic centers, localized and mobile spins in the NM and DM phases, which interact via exchange. From the temperature and frequency dependences of the R2 linewidth the spin-diffusion parameters for the NM phase in both systems were determined. It was found that the HGM model allows good explanation of both charge transport and spin diffusion in the doped polyaniline films.

  20. Simulation and modelling of charge transport in dye-sensitized solar cells based on carbon nano-tube electrodes

    NASA Astrophysics Data System (ADS)

    Gacemi, Yahia; Cheknane, Ali; Hilal, Hikmat S.

    2013-03-01

    For a better understanding of the mechanisms of dye-sensitized solar cells (DSSCs), based on carbon nano-tube (CNT) electrodes, a phenomenological model is proposed. For modelling purposes, the meso-scopic porous CNT electrode is considered as a homogeneous nano-crystalline structure with thickness L. The CNT electrode is covered with light-absorbing dye molecules, and interpenetrated by the tri-iodide (I-/I3-) redox couple. A simulation platform, designed to study coupled charge transport in such cells, is presented here. The work aims at formulating a mathematical model that describes charge transfer and charge transport within the porous CNT window electrode. The model is based on a pseudo-homogeneous active layer using drift-diffusion transport equations for free electron and ion transport. Based on solving the continuity equation for electrons, the model uses the numerical finite difference method. The numerical solution of the continuity equation produces current-voltage curves that fit the diode equation with an ideality factor of unity. The calculated current-voltage (J-V) characteristics of the illuminated idealized DSSCs (100 mW cm-2, AM1.5), and the different series resistances of the transparent conductor oxide (TCO) layer were introduced into the idealized simulated photo J-V characteristics. The results obtained are presented and discussed in this paper. Thus, for a series resistance of 4 ? of the TCO layer, the conversion efficiency (?) was 7.49% for the CNT-based cell, compared with 6.11% for the TiO2-based cell. Two recombination kinetic models are used, the electron transport kinetics within the nano-structured CNT film, or the electron transfer rate across the CNT-electrolyte interface. The simulations indicate that both electron and ion transport properties should be considered when modelling CNT-based DSSCs and other similar systems. Unlike conventional polycrystalline solar cells which exhibit carrier recombination, which limits their efficiency, the CNT matrix (in CNT-based cells) serves as the conductor for majority carriers and prevents recombination. This is because of special conductivity and visible-near-infrared transparency of the CNT. Charge transfer mechanisms within the porous CNT matrix and at the semiconductor-dye-electrolyte interfaces are described in this paper.