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1

Charge Carrier Transport in Liquid Crystalline Semiconductors  

NASA Astrophysics Data System (ADS)

In this chapter, we describe the electrical properties in liquid crystals after a brief description of historical studies on them, including ionic and electronic conduction in liquid crystals, the anisotropy and dimensionality in charge carrier transport, charge carrier transport itself, mesophase structure, temperature and electric field dependence, the effect of impurities and structural defects, a model for electronic carrier transport depending upon the chemical and mesophase structure of the liquid crystalline semiconductor responsible for the charge transport.

Hanna, Jun-Ichi

2

Charge carrier transport and injection across organic heterojunctions  

NASA Astrophysics Data System (ADS)

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 on the accumulation of knowledge of the intrinsic properties of organic materials and related interfaces. Among them, charge-carrier transport and carrier injection are two key factors that govern the performance of a device. This thesis mainly focuses on the charge carrier injection and transport at organic heterojunctions. The carrier transport properties of different organic materials used in this study are characterized by time-of-flight (TOF) and admittance spectroscopy (AS). An injection model is formulated by considering the carrier distribution at both sides of the interface. Using a steady-state simulation approach, the effect of accumulated charges on energy level alignment at OH is revealed. Instead of a constant injection barrier, it is found that the barrier varies with applied voltage. Moreover, an escape probability function in the injection model is modified by taking into account the total hopping rate and available hopping sites at the interface. The model predicts that the injection current at low temperature can be dramatically modified by an extremely small density of deep trap states. More importantly, the temperature dependence of the injection current is found to decrease with increasing barrier height. This suggests that extracting the barrier height from the J vs 1/T plot, as commonly employed in the literature, is problematic. These theoretical predictions are confirmed by a series of experiments on heterojunction devices with various barrier heights. In addition, the presence of deep trap states is also consistent with carrier mobility measurements at low temperature. From the point of view of application, an interface chemical doping method is proposed to engineer the carrier injection at an organic heterojunction. It is found that the injection current can be effectively increased or suppressed by introducing a thin (2 nm) doped organic layer at the interface. This technique is further extended to study the impact of an injection barrier at the OH, in OLEDs, on device performance. It is shown that a 0.3 eV injection barrier at the OH, that is normally negligible at metal/organic interface, can reduce the device efficiency by 25%. This is explained by the carrier distribution in the density-of-states at the OH. Furthermore, the carrier transport properties in a bulk heterojunction system are investigated. The bulk heterojunction consists of an interpenetrating network of a polymeric electron donor and a molecular electron acceptor. This material system has been studied in the last few years as an attractive power conversion efficiency (5% under AM 1.5) of OPV cells has been demonstrated. It is found that the electron mobility is greatly dependent on the thermal treatment of the film. Interfacial dipole effect at the heterojunction between the donor and the acceptor is proposed to be the determining factor that alters the carrier mobility in different nanoscale structures.

Tsang, Sai Wing

3

Charge carrier transport properties in layer structured hexagonal boron nitride  

NASA Astrophysics Data System (ADS)

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.

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

2014-10-01

4

Charge transport studies in organic semiconductors using carrier extraction by linearly increasing voltage (CELIV) technique  

NASA Astrophysics Data System (ADS)

Organic optoelectronic devices, such as solar cells, light emitting diodes and transistors, share a common feature: their performance critically depends on the efficiency with which charge carriers (electrons and/or holes) move in the material. Understanding and improving the charge transport is the main goal when improving the device performance or designing novel organic compounds through chemical engineering. Due to low carrier mobility in disordered films, as well as due to its time, electric field and carrier density dependence, standard measurement technique like Hall effect and Time-of-Flight are either inapplicable or limited in applicability. Charge Carrier Extraction by Linearly Increasing Voltage (CELIV) technique has become a world standard used by many scientific groups to measure charge transport and recombination in inorganic and organic semiconductors. The method can be used to study the charge carrier mobility dependence on time, carrier concentration, electric field, temperature, film thickness and morphology directly in the operational devices. However, the latest research have shown that CELIV current transients and extraction maximum used for mobility evaluation is strongly dependent on experimental conditions such as carrier density, light absorption profile and electric field. Procedure, allowing estimating the correction factor in mobility relation will be presented. In contrast to inorganic crystalline semiconductors, the long-range disorder in the films of organic devices makes the charge transport properties strongly dependent on the degree of disorder and nanomorphology of the films. Carrier density, electric field and temperature dependent mobility in disordered organic semiconductors is shown to obey Arrhenius-type, Poole-Frenkel-type, Meyer-Neldel rule, and Gill's law. Stochastic transport theories are used to describe charge carrier hopping within localized Density-Of-States as opposed to delocalized band-transport in the crystals.

Pivrikas, Almantas

2011-03-01

5

Quantitative description of charge-carrier transport in a white organic light-emitting diode  

NASA Astrophysics Data System (ADS)

We present a simulation model for the analysis of charge-carrier transport in organic thin-film devices, and apply it to a three-color white hybrid organic light-emitting diode (OLED) with fluorescent blue and phosphorescent red and green emission. We simulate a series of single-carrier devices, which reconstruct the OLED layer sequence step by step. Thereby, we determine the energy profiles for hole and electron transport, show how to discern bulk from interface limitation, and identify trap states.

Schober, M.; Anderson, M.; Thomschke, M.; Widmer, J.; Furno, M.; Scholz, R.; Lüssem, B.; Leo, K.

2011-10-01

6

Ambipolar charge carrier transport in mixed organic layers of phthalocyanine and fullerene  

E-print Network

Mixed layers of copper-phthalocyanine (p-conductive) and fullerene (n-conductive) are used for the fabrication of organic field-effect transistors (OFETs) and inverters. Regarding the electrical characteristics of these donor-acceptor blends they show ambipolar charge carrier transport, whereas devices made from only one of the materials show unipolar behavior. Such mixed films are model systems for ambipolar transport with adjustable field-effect mobilities for electrons and holes. By variation of the mixing ratio it is possible to balance the transport of both charge-carrier types. In this paper we discuss the variation of mobility and threshold voltage with the mixing ratio and demonstrate ambipolar inverters as a leadoff application. The gained results were analyzed by simulations using an analytical model for ambipolar transistors and subsequently compared to complementary inverters.

A. Opitz; M. Bronner; W. Bruetting

2006-12-21

7

Effect of gamma irradiation on transport of charge carriers in Cu nanowires  

NASA Astrophysics Data System (ADS)

In this paper, we report the effect of gamma ray photons on the electrical conductivity of 100 nm Cu nanowires prepared by the technique of electrodeposition using track-etched membranes. Different fluences of photons have been used to observe the effect and in each case of post-irradiation, electrical conductivity is found to increase in a linear manner with increase in applied potential difference; however the rate of increase of conductivity is different in different cases of radiation fluence. Grain boundary scattering is of significance for the post-irradiation parabolic nature of the I-V characteristics (IVC), which are of a linear pattern following Ohm's law before irradiation. Increase or decrease in the number of charge carriers during their transport through the nanowires is the result of two competitive processes—specular and diffusive scattering of charge carriers (electrons) from grain boundaries, which are itself a region of high resistance rather than inter-grain regions. The results have been discussed in light of the Mayadas and Shatzkes (MS) model with a slight modification for irradiated nanowires.

Gehlawat, Devender; Chauhan, R. P.; Sonkawade, R. G.; Chakarvarti, S. K.

2012-01-01

8

Relationship between defect density and charge carrier transport in amorphous and microcrystalline silicon  

SciTech Connect

The influence of dangling-bond defects and the position of the Fermi level on the charge carrier transport properties in undoped and phosphorous doped thin-film silicon with structure compositions all the way from highly crystalline to amorphous is investigated. The dangling-bond density is varied reproducibly over several orders of magnitude by electron bombardment and subsequent annealing. The defects are investigated by electron-spin-resonance and photoconductivity spectroscopies. Comparing intrinsic amorphous and microcrystalline silicon, it is found that the relationship between defect density and photoconductivity is different in both undoped materials, while a similar strong influence of the position of the Fermi level on photoconductivity via the charge carrier lifetime is found in the doped materials. The latter allows a quantitative determination of the value of the transport gap energy in microcrystalline silicon. The photoconductivity in intrinsic microcrystalline silicon is, on one hand, considerably less affected by the bombardment but, on the other hand, does not generally recover with annealing of the defects and is independent from the spin density which itself can be annealed back to the as-deposited level. For amorphous silicon and material prepared close to the crystalline growth regime, the results for nonequilibrium transport fit perfectly to a recombination model based on direct capture into neutral dangling bonds over a wide range of defect densities. For the heterogeneous microcrystalline silicon, this model fails completely. The application of photoconductivity spectroscopy in the constant photocurrent mode (CPM) is explored for the entire structure composition range over a wide variation in defect densities. For amorphous silicon previously reported linear correlation between the spin density and the subgap absorption is confirmed for defect densities below 10{sup 18} cm{sup -3}. Beyond this defect level, a sublinear relation is found i.e., not all spin-detected defects are also visible in the CPM spectra. Finally, the evaluation of CPM spectra in defect-rich microcrystalline silicon shows complete absence of any correlation between spin-detected defects and subband gap absorption determined from CPM: a result which casts considerable doubt on the usefulness of this technique for the determination of defect densities in microcrystalline silicon. The result can be related to the inhomogeneous structure of microcrystalline silicon with its consequences on transport and recombination processes.

Astakhov, Oleksandr; Carius, Reinhard; Finger, Friedhelm; Petrusenko, Yuri; Borysenko, Valery; Barankov, Dmytro [Forschungszentrum Juelich, Institute of Energy Research-Photovoltaic, 52425 Juelich, Germany and National Science Center-Kharkov Institute of Physics and Technology, Cyclotron Science and Research Establishment, 61108 Kharkov (Ukraine); Forschungszentrum Juelich, Institute of Energy Research-Photovoltaic, 52425 Juelich (Germany); National Science Center-Kharkov Institute of Physics and Technology, Cyclotron Science and Research Establishment, 61108 Kharkov (Ukraine)

2009-03-01

9

Electric field dependence of charge carrier hopping transport within the random energy landscape in an organic field effect transistor  

NASA Astrophysics Data System (ADS)

We extended our analytical effective medium theory [Phys. Rev. BPRBMDO0163-182910.1103/PhysRevB.81.045202 81, 045202 (2010)] to describe the temperature-dependent hopping charge carrier mobility at arbitrary electric fields in the large carrier density regime. Special emphasis was made to analyze the influence of the lateral electric field on the Meyer-Neldel (MN) phenomenon observed when studying the charge mobilities in thin-film organic field-effect transistors (OFET). Our calculations are based on the average hopping transition time approach, generalized for large carrier concentration limit finite fields, and taking into account also spatial energy correlations. The calculated electric field dependences of the hopping mobility at large carrier concentrations are in good agreement with previous computer simulations data. The shift of the MN temperature in an OFET upon applied electric field is shown to be a consequence of the spatial energy correlation in the organic semiconductor film. Our calculations show that the phenomenological Gill equation is clearly inappropriate for describing conventional charge carrier transport at low carrier concentrations. On the other hand a Gill-type behavior has been observed in a temperature range relevant for measurements of the charge carrier mobility in OFET structures. Since the present model is not limited to zero-field mobility, it allows a more accurate evaluation of important material parameters from experimental data measured at a given electric field. In particular, we showed that both the MN and Gill temperature can be used for estimating the width of the density of states distribution.

Fishchuk, I. I.; Kadashchuk, A.; Ullah, Mujeeb; Sitter, H.; Pivrikas, A.; Genoe, J.; Bässler, H.

2012-07-01

10

Charge carrier transport and collection enhancement of copper indium diselenide photoactive nanoparticle-ink by laser crystallization  

NASA Astrophysics Data System (ADS)

There has been increasing needs for cost-effective and high performance thin film deposition techniques for photovoltaics. Among all deposition techniques, roll-to-roll printing of nanomaterials has been a promising method. However, the printed thin film contains many internal imperfections, which reduce the charge-collection performance. Here, direct pulse laser crystallization (DPLC) of photoactive nanoparticles-inks is studied to meet this challenge. In this study, copper indium selenite (CIS) nanoparticle-inks is applied as an example. Enhanced crystallinity, densified structure in the thin film is resulted after DLPC under optimal conditions. It is found that the decreased film internal imperfections after DPLC results in reducing scattering and multi-trapping effects. Both of them contribute to better charge-collection performance of CIS absorber material by increasing extended state mobility and carrier lifetime, when carrier transport and kinetics are coupled. Charge carrier transport was characterized after DPLC, showing mobility increased by 2 orders of magnitude. Photocurrent under AM1.5 illumination was measured and shown 10 times enhancement of integrated power density after DPLC, which may lead to higher efficiency in photo-electric energy conversion.

Nian, Qiong; Zhang, Martin Y.; Wang, Yuefeng; Das, Suprem R.; Bhat, Venkataprasad S.; Huang, Fuqiang; Cheng, Gary J.

2014-09-01

11

Carrier Mobilities in Organic Electron Transport Materials Determined from Space Charge Limited Current  

Microsoft Academic Search

We report the mobility in organic electron transport materials determined from current-voltage characteristics in the regime of space charge limited current. The electron mobilities obtained are highly dependent on applied electric field, similar to the cases using a conventional time-of-flight method. The electron mobilities of phenanthroline derivatives are high and comparable to hole mobilities of conventional hole transport materials. Two

Takeshi Yasuda; Yoshihisa Yamaguchi; De-Chun Zou; Tetsuo Tsutsui

2002-01-01

12

Charge carrier generation and transport in different stoichiometry APFO3:PC61BM solar cells.  

PubMed

In this paper we studied carrier drift dynamics in APFO3:PC61BM solar cells of varied stoichiometry (2:1, 1:1, and 1:4 APFO3:PC61BM) over a wide time range, from subpicoseconds to microseconds with a combination of ultrafast optical electric field probing and conventional transient integrated photocurrent techniques. Carrier drift and extraction dynamics are strongly stoichiometry dependent: the speed of electron or hole drift increases with higher concentration of PC61BM or polymer, respectively. The electron extraction from a sample with 80% PC61BM takes place during hundreds of picoseconds, but slows down to sub-microseconds in a sample with 33% PC61BM. The hole extraction is less stoichiometry dependent: it varies form sub-nanoseconds to tens of nanoseconds when the PC61BM concentration changes from 33% to 80%. The electron extraction rate correlates with the conversion efficiency of solar cells, leading to the conclusion that fast electron motion is essential for efficient charge carrier separation preventing their geminate recombination. PMID:25025885

Pranculis, Vytenis; Infahsaeng, Yingyot; Tang, Zheng; Devižis, Andrius; Vithanage, Dimali A; Ponseca, Carlito S; Inganäs, Olle; Yartsev, Arkady P; Gulbinas, Vidmantas; Sundström, Villy

2014-08-13

13

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

NASA Astrophysics Data System (ADS)

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.

Osses-Márquez, Juan; Calderón-Muñoz, Williams R.

2014-10-01

14

Charge-carrier transport and recombination in heteroepitaxial CdTe  

NASA Astrophysics Data System (ADS)

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.

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

15

Analysis of carrier transport and carrier trapping in organic diodes with polyimide-6,13-Bis(triisopropylsilylethynyl)pentacene double-layer by charge modulation spectroscopy and optical second harmonic generation measurement  

NASA Astrophysics Data System (ADS)

We studied the carrier transport and carrier trapping in indium tin oxide/polyimide (PI)/6,13-Bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene)/Au diodes by using charge modulation spectroscopy (CMS) and time-resolved electric field induced optical second harmonic generation (TR-EFISHG) measurements. TR-EFISHG directly probes the spatial carrier behaviors in the diodes, and CMS is useful in explaining the carrier motion with respect to energy. The results clearly indicate that the injected carriers move across TIPS-pentacene thorough the molecular energy states of TIPS-pentacene and accumulate at the PI/TIPS-pentacene interface. However, some carriers are trapped in the PI layers. These findings take into account the capacitance-voltage and current-voltage characteristics of the diodes.

Lim, Eunju; Taguchi, Dai; Iwamoto, Mitsumasa

2014-08-01

16

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

SciTech Connect

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.

Han, S.S.

1993-09-01

17

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

NASA Astrophysics Data System (ADS)

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.

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

2013-01-01

18

Charge Carriers in Few-Layer Graphene Films  

Microsoft Academic Search

The nature of the charge carriers in 2D few-layer graphites (FLGs) has been recently questioned by transport measurements [K. S. Novoselov , Science 306, 666 (2004)SCIEAS0036-807510.1126\\/science.1102896] and a strong ambipolar electric field effect has been revealed. Our density functional calculations demonstrate that the electronic band dispersion near the Fermi level, and consequently the nature of the charge carriers, is highly

Sylvain Latil; Luc Henrard

2006-01-01

19

Clustered impurities and carrier transport in supported graphene  

NASA Astrophysics Data System (ADS)

We investigate the effects of charged impurity distributions and carrier-carrier interactions on electronic transport in graphene on SiO2 by employing a self-consistent coupled simulation of carrier transport and electrodynamics. We show that impurity clusters of characteristic width 40-50 nm generate electron-hole puddles of experimentally observed sizes. The residual conductivity and the linear-region slope of the conductivity versus carrier density dependence are determined by the impurity distribution, and the measured slope can be used to estimate the impurity density in experiment. Furthermore, we show that the high-density sublinearity in the conductivity stems from carrier-carrier interactions.

Sule, N.; Hagness, S. C.; Knezevic, I.

2014-04-01

20

Charge carrier dynamics and interactions in electric force microscopy.  

PubMed

In electric force microscopy, a charged atomic force microscope tip in vacuum senses a fluctuating electrical force generated by the sample. Such measurements can in principle probe electrical noise generated by moving charge carriers in an organic semiconductor. We present a theory of cantilever frequency fluctuations in electric force microscopy, driven by coupled charge carrier dynamics and dielectric fluctuations. The connection between observable frequency fluctuations in electric force microscopy and the Casimir-Lifshitz force is described. This classical electrodynamic calculation is based on Maxwell's equations coupled to diffusive carrier transport. The effects of carrier transport and inter-carrier interactions on the spectrum of cantilever frequency noise are elucidated. We find that a simplified model of freely diffusing carriers can overestimate cantilever frequency noise by several orders of magnitude because of the neglect of interactions. Electric force microscopy measurements on an organic field effect transistor are reported and qualitatively interpreted in terms of the suppression of electrical noise from charge carriers by Coulomb interactions. PMID:23020344

Lekkala, Swapna; Hoepker, Nikolas; Marohn, John A; Loring, Roger F

2012-09-28

21

Electrical Transport in a Disordered Medium: NMR Measurement of Diffusivity and Electrical Mobility of Ionic Charge Carriers  

NASA Astrophysics Data System (ADS)

Electrical transport in porous media plays an important role in many fields of pure and applied science. The basic microscopic processes of the charge transport have attracted considerable theoretical interest for a long time. However, on a microscopic level there was up to now no experimental access to this problem. In the present paper we demonstrate, by using a suited porous system, that two combined NMR methods can offer such a first experimental access. We apply common PFG NMR methods and the special electrophoretic NMR (ENMR) technique for the measurement of self-diffusion coefficient D +and electric mobility u +of a cation ((C 4H 9) +4) in a disordered gel-like medium (Sephadex LH-20) filled with electrolyte solution. We find a, qualitatively expected, observation time-dependence of D +, but for the first time such a time-dependence is also observed for u +, which means the detection of the phenomenon of "anomalous field assisted diffusion" or "anomalous mobility." For the measurement of the short-time behavior of the mobility a new pulse sequence is presented. The time-dependent mobilities were measured at three different external electrical fields E.From the long-time behavior of D +, u +, and DH 2Othree independent values for the tortuosity Tof the porous system could be derived. We find equality of the tortuosities T(D +) and T(u +), which represents a first experimental proof of the validity of the Einstein relation (D +˜ u +) in a disordered medium. Finally, we discuss advantages of the possible use of "anomalous field assisted diffusion" over the commonly used "anomalous diffusion" in morphology studies by dynamic imaging in porous media.

Heil, Stefan R.; Holz, Manfred

1998-11-01

22

Probing surface states in PbS nanocrystal films using pentacene field effect transistors: controlling carrier concentration and charge transport in pentacene.  

PubMed

We used a bilayer field effect transistor (FET) consisting of a thin PbS nanocrystals (NCs) film interfaced with vacuum-deposited pentacene to probe trap states in NCs. We interpret the observed threshold voltage shift in context of charge carrier trapping by PbS NCs and relate the magnitude of the threshold voltage shift to the number of trapped carriers. We explored a series of NC surface ligands to modify the interface between PbS NCs and pentacene and demonstrate the impact of interface chemistry on charge carrier density and the FET mobility in a pentacene FET. PMID:25017003

Park, Byoungnam; Whitham, Kevin; Bian, Kaifu; Lim, Yee-Fun; Hanrath, Tobias

2014-12-21

23

Mobile charge carriers in photosynthesis  

Microsoft Academic Search

CURRENT mechanistic models of energy transduction in photosynthesis, envision that the energy of the photons collected by the bulk antenna chlorophyll, is funnelled to special sites called reaction centres, where the primary charge separation events occur1. If the primary oxidant and reductant are separated physically by only a few, or few tens of angstroms, changes in the dielectric properties should

Roberto A. Bogomolni; Melvin P. Klein

1975-01-01

24

Charge carrier relaxation model in disordered organic semiconductors  

SciTech Connect

The relaxation phenomena of charge carrier in disordered organic semiconductors have been demonstrated and investigated theoretically. An analytical model describing the charge carrier relaxation is proposed based on the pure hopping transport theory. The relation between the material disorder, electric field and temperature and the relaxation phenomena has been discussed in detail, respectively. The calculated results reveal that the increase of electric field and temperature can promote the relaxation effect in disordered organic semiconductors, while the increase of material disorder will weaken the relaxation. The proposed model can explain well the stretched-exponential law by adopting the appropriate parameters. The calculation shows a good agreement with the experimental data for organic semiconductors.

Lu, Nianduan; Li, Ling, E-mail: lingli@ime.ac.cn; Sun, Pengxiao; Liu, Ming, E-mail: liuming@ime.ac.cn [Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China)] [Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China)

2013-11-15

25

Charge transport in disordered materials  

NASA Astrophysics Data System (ADS)

This thesis is focused on on using Monte Carlo simulation to extract device relevant properties, such as the current voltage behavior of transistors and the efficiency of photovoltaics, from the hopping transport of molecules. Specifically, simulation is used to study organic field-effect transistors (OFETs) and organic photo-voltaics (OPVs). For OFETs, the current was found to decrease with increasing concentration of traps and barriers in the system. As the barrier/trap concentration approaches 100%, the current recovers as carrier begin to travel through the manifold of connected trap states. Coulomb interactions between like charges are found to play a role in removing carriers from trap states. The equilibrium current in OFETs was found to be independent of charge injection method, however, the finite size of devices leads to an oscillatory current. Fourier transforms of the electrical current show peaks that vary non-linearly with device length, while being independent of device width. This has implications for the mobility of carriers in finite sized devices. Lastly, the presence of defects and high barriers (> 0.4 eV) was found to produce negative differential resistance in the saturation region of OFET curves, unlike traps. While defects and barriers prohibit carriers from reaching the drain at high voltages, the repulsive interaction between like charged carriers pushes charges around the defects. For OPVs, the effects of device morphology and charge delocalization were studied. Fill factors increased with domain size in monolayer isotropic morphologies, but decreased for band morphologies. In single-phase systems without Coulomb interactions, astonishingly high fill factors (. 70%) were found. In multilayer OPVs,a complex interplay of domain size, connectivity, tortuosity, interface trapping, and delocalization determined efficiency.

Gagorik, Adam Gerald

26

Evaluation of Intrinsic Charge Carrier Transport at Insulator-Semiconductor Interfaces Probed by a Non-Contact Microwave-Based Technique  

PubMed Central

We have successfully designed the geometry of the microwave cavity and the thin metal electrode, achieving resonance of the microwave cavity with the metal-insulator-semiconductor (MIS) device structure. This very simple MIS device operates in the cavity, where charge carriers are injected quantitatively by an applied bias at the insulator-semiconductor interface. The local motion of the charge carriers was clearly probed through the applied external microwave field, also giving the quantitative responses to the injected charge carrier density and charge/discharge characteristics. By means of the present measurement system named field-induced time-resolved microwave conductivity (FI-TRMC), the pentacene thin film in the MIS device allowed the evaluation of the hole and electron mobility at the insulator-semiconductor interface of 6.3 and 0.34?cm2 V?1 s?1, respectively. This is the first report on the direct, intrinsic, non-contact measurement of charge carrier mobility at interfaces that has been fully experimentally verified. PMID:24212382

Honsho, Yoshihito; Miyakai, Tomoyo; Sakurai, Tsuneaki; Saeki, Akinori; Seki, Shu

2013-01-01

27

Theoretical modeling of influence of the structural disorder on the charge carrier mobility in triphenylene stacks  

NASA Astrophysics Data System (ADS)

The tight-binding Hamiltonian is used to describe the charge carrier transport in a stack of triphenylene molecules. The influence of different levels of structural disorder on the on-stack charge carrier mobility is discussed. Structural disorder simulation considers three geometrical parameters: the distance between molecular planes, the twist angle around molecule symmetry axis, and the lateral slide in the direction perpendicular to the stack axis. The calculated values of the charge carrier mobility are compared with experimental data.

Miko?ajczyk, Miko?aj M.; Toman, Petr; Bartkowiak, Wojciech

2010-01-01

28

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

Code of Federal Regulations, 2012 CFR

...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...

2012-10-01

29

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

Code of Federal Regulations, 2010 CFR

...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...

2010-10-01

30

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

Code of Federal Regulations, 2011 CFR

...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...

2011-10-01

31

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

Code of Federal Regulations, 2013 CFR

...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...

2013-10-01

32

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

NASA Astrophysics Data System (ADS)

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 1012 cm-2, and the hole mobility was up to 6.5 cm2 V-1 s-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.

Choi, Wookjin; Miyakai, Tomoyo; Sakurai, Tsuneaki; Saeki, Akinori; Yokoyama, Masaaki; Seki, Shu

2014-07-01

33

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

PubMed

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

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

2014-01-01

34

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

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.

Rehak, P.; Gatti, E.

1984-02-24

35

Criticality of surface topology for charge-carrier transport characteristics in two-dimensional borocarbonitrides: design principles for an efficient electronic material.  

PubMed

We have studied the effect of the spatial distribution of B, N and C domains in 2-dimensional borocarbonitrides and its influence on carrier mobility, based on density functional theory coupled with the Boltzmann transport equation. Two extreme features of C-domains in BN-rich B2.5CN2.5, namely, BCN-I (random) and BCN-II (localized), have been found to exhibit an electron (hole) mobility of ?10(6) cm(2) V(-1) s(-1) (?10(4) cm(2) V(-1) s(-1)) and ?10(3) cm(2) V(-1) s(-1) (?10(6) cm(2) V(-1) s(-1)), respectively. We have ascertained the underlying microscopic mechanisms behind such an extraordinarily large carrier mobility and the reversal of conduction polarity. Finally, we have derived the principle underlying the maximization of mobility and for obtaining a particular (electron/hole) conduction polarity of this nanohybrid in any stoichiometric proportion. PMID:25283315

Banerjee, Swastika; Pati, Swapan K

2014-10-24

36

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

Code of Federal Regulations, 2012 CFR

...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...

2012-10-01

37

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

Code of Federal Regulations, 2011 CFR

...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...

2011-10-01

38

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

Code of Federal Regulations, 2013 CFR

...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...

2013-10-01

39

Carrier transport in thin films of silicon nanoparticles  

NASA Astrophysics Data System (ADS)

The electrical and electroluminescence characteristics of heterostructure systems containing thin films of visibly emitting silicon nanoparticles are shown to be controlled by carrier transport through the nanoparticulate films. A conduction mechanism encompassing both geometric and electronic effects most effectively relates the high resistivity with structural properties of the films. Heterostructure devices are constructed with silicon nanoparticle active layers produced by pulsed laser ablation supersonic expansion. The observed temperature-dependent photoluminescence, electroluminescence, and I-V characteristics of the devices are consistent with a model in which carrier transport is controlled by space-charge-limited currents or tunneling through potential barriers on a percolating lattice.

Burr, T. A.; Seraphin, A. A.; Werwa, E.; Kolenbrander, K. D.

1997-08-01

40

Diffusion behaviour of charge carriers in thin films of phthalocyanines  

Microsoft Academic Search

Phthalocyanine (Pc) thin films were prepared by the vacuum-evaporating method. The diffusion behaviour of the charge carriers in these films was investigated by means of transient photovoltage (Dember effect) measurements. The experiments imply that the dominant charge carriers in phthalocyanines are electrons which diffuse from the surface closest to the light to the internal bulk. As a comparative system, photovoltic

He Tian; Kong-Chang Chen

1995-01-01

41

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

Code of Federal Regulations, 2010 CFR

...2010-10-01 false Per-minute carrier common line charge. 69.154 Section 69...COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES (CONTINUED) ACCESS...Carriers § 69.154 Per-minute carrier common line charge. (a) Local...

2010-10-01

42

Low-field carrier transport properties in biased bilayer graphene  

NASA Astrophysics Data System (ADS)

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.

Hu, Bo

2014-07-01

43

Carrier transport in high-density polyethylene  

Microsoft Academic Search

Current peaks due to transient SCLC were observed both in high-density polyethylene (HD-PE) and in oxidised HD-PE in the temperature range 50-90 degrees C. From the time at which the current peak occurs, carrier mobilities ranging from 10-11 to 10-9 cm2 V-1 s-1 were obtained. The mobility values obtained agree well with those evaluated from surface-charge decay measurements. They strongly

T. Mizutani; M. Ieda

1979-01-01

44

Electronic and ionic carrier transport in discotic liquid crystalline photoconductor  

NASA Astrophysics Data System (ADS)

We have investigated the negative charge carrier transport in discotic columnar phases of triphenylene derivatives, 2,3,6,7,10,11-hexapentyloxytriphenylene (H5T) and its related derivatives such as H4T and H6T, by time-of-flight experiments. We observed a fast transit for negative charge carriers in the discotic hexagonal columnar phase (Dh) of H5T, which corresponded to a high mobility of 10-3cm2V-1s-1 comparable to its hole mobility, in addition to a slow transit corresponding to the mobility of 10-5cm2V-1s-1 reported previously. We observed two transits in H4T and H6T as well, in which the fast mobility was on the order of 10-2 and 10-4cm2V-1s-1 in H4T and H6T, respectively, while the slow mobility was almost the same (3-4×10-5cm2V-1s-1) in both H4T and H6T. Through dilution experiments with n -dodecane, we found that these fast and slow transits were attributable to the electronic and ionic conduction, respectively, and that the latter was caused by negatively ionized impurity molecules trapping photogenerated electrons. We discuss that there exist two distinct carrier transport channels for electronic and ionic charges in the intrinsic nature of discotic columnar phases.

Iino, Hiroaki; Hanna, Jun-Ichi; Haarer, Dietrich

2005-11-01

45

Charge transport in disordered organic field-effect transistors  

Microsoft Academic Search

In this thesis we study charge transport in organic semiconductors. We do this by focusing on the physical characterization of disordered organic field-effect transistors. It will be made clear that the disorder in the polymer films is crucial for the interpretation of the data. The field-effect transistor geometry allows variation of the charge carrier density in the semiconductor, without the

E. J. Meijer

2003-01-01

46

Assessing charge carrier trapping in silicon nanowires using picosecond conductivity measurements.  

PubMed

Free-standing semiconductor nanowires on bulk substrates are increasingly being explored as building blocks for novel optoelectronic devices such as tandem solar cells. Although carrier transport properties, such as mobility and trap densities, are essential for such applications, it has remained challenging to quantify these properties. Here, we report on a method that permits the direct, contact-free quantification of nanowire carrier diffusivity and trap densities in thin (?25 nm wide) silicon nanowires-without any additional processing steps such as transfer of wires onto a substrate. The approach relies on the very different terahertz (THz) conductivity response of photoinjected carriers within the silicon nanowires from those in the silicon substrate. This allows quantifying both the picosecond dynamics and the efficiency of charge carrier transport from the silicon nanowires into the silicon substrate. Varying the excitation density allows for quantification of nanowire trap densities: for sufficiently low excitation fluences the diffusion process stalls because the majority of charge carriers become trapped at nanowire surface defects. Using a model that includes these effects, we determine both the diffusion constant and the nanowire trap density. The trap density is found to be orders of magnitude larger than the charge carrier density that would be generated by AM1.5 sunlight. PMID:22738182

Ulbricht, Ronald; Kurstjens, Rufi; Bonn, Mischa

2012-07-11

47

Anisotropic dynamics of charge carriers in graphene  

NASA Astrophysics Data System (ADS)

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.

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

2012-03-01

48

Nanoscale Charge Transport in Excitonic Solar Cells  

SciTech Connect

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.

Venkat Bommisetty, South Dakota State University

2011-06-23

49

Scattering of charge carriers and phonons in thermoelectric devices  

Microsoft Academic Search

We investigate the effects of the scattering of charge carriers and phonons on the figure of merit of thermoelectric devices. Despite many efforts devoted to the optimization of the figure of merit ZT, the commercial diffusion of such systems is still limited due to their low efficiency. The main problem behind the engineering of ZT is the interdependency between the

Giuseppe Romano; Lee Joo-Hyoung; Jeffrey Grossman

2011-01-01

50

Mechanism of charge transport in self-organizing organic materials  

NASA Astrophysics Data System (ADS)

Currently there is great interest in the use of organic materials as the active component in opto-electronic devices such as field-effect transistors, light-emitting diodes, solar cells and in nanoscale molecular electronics. Device performance is to a large extent determined by the mobility of charge carriers, which strongly depends on material morphology. Therefore, a fundamental understanding of the relation between the mechanism of charge transport and chemical composition and supramolecular organization of the active organic material is essential for improvement of device performance. Self-assembling materials are of specific interest, since they have the potential to form well defined structures in which molecular ordering facilitates efficient charge transport. This review gives an overview of theoretical models that can be used to describe the mobility of charge carriers, including band theory for structurally ordered materials, tight-binding models for weakly disordered systems and hopping models for localized charges in strongly disordered materials. It is discussed how the charge transport parameters needed in these models; i.e. charge transfer integrals, site energies and reorganization energies, can be obtained from quantum chemical calculations. Illustrative examples of application of the theoretical methods to charge transport in self-assembling materials are discussed: columns of discotic molecules, stacks of oligo(phenylene-vinylene) molecules and strands of DNA base pairs. It is argued that the mobility of charge carriers along stacks of triphenylene and oligo(phenylene-vinylene) molecules can be significantly enhanced by improvement of molecular organization. According to calculations, the mobility of charge carriers along DNA strands is strongly limited by the large charge induced structural reorganization of the nucleobases and the surrounding water.

Grozema, Ferdinand C.; Siebbeles, Laurens D. A.

51

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

SciTech Connect

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.

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

52

High charge-carrier mobility enables exploitation of carrier multiplication in quantum-dot films  

PubMed Central

Carrier multiplication, the generation of multiple electron–hole pairs by a single photon, is of great interest for solar cells as it may enhance their photocurrent. This process has been shown to occur efficiently in colloidal quantum dots, however, harvesting of the generated multiple charges has proved difficult. Here we show that by tuning the charge-carrier mobility in quantum-dot films, carrier multiplication can be optimized and may show an efficiency as high as in colloidal dispersion. Our results are explained quantitatively by the competition between dissociation of multiple electron–hole pairs and Auger recombination. Above a mobility of ~1?cm2?V?1?s?1, all charges escape Auger recombination and are quantitatively converted to free charges, offering the prospect of cheap quantum-dot solar cells with efficiencies in excess of the Shockley–Queisser limit. In addition, we show that the threshold energy for carrier multiplication is reduced to twice the band gap of the quantum dots. PMID:23974282

Sandeep, C. S. Suchand; Cate, Sybren ten; Schins, Juleon M.; Savenije, Tom J.; Liu, Yao; Law, Matt; Kinge, Sachin; Houtepen, Arjan J.; Siebbeles, Laurens D. A.

2013-01-01

53

Charge transport in desolvated DNA  

NASA Astrophysics Data System (ADS)

The conductivity of DNA in molecular junctions is often probed experimentally under dry conditions, but it is unclear how much of the solvent remains attached to the DNA and how this impacts its structure, electronic states, and conductivity. Classical MD simulations show that DNA is unstable if the solvent is removed completely, while a micro-hydrated system with few water molecules shows similar charge transport properties as fully solvated DNA does. This surprising effect is analyzed in detail by mapping the density functional theory-based electronic structure to a tight-binding Hamiltonian, allowing for an estimate of conductivity of various DNA sequences with snapshot-averaged Landauer's approach. The characteristics of DNA charge transport turn out to be determined by the nearest hydration shell(s), and the removal of bulk solvent has little effect on the transport.

Wolter, Mario; Elstner, Marcus; Kuba?, Tomáš

2013-09-01

54

Charge transport in desolvated DNA.  

PubMed

The conductivity of DNA in molecular junctions is often probed experimentally under dry conditions, but it is unclear how much of the solvent remains attached to the DNA and how this impacts its structure, electronic states, and conductivity. Classical MD simulations show that DNA is unstable if the solvent is removed completely, while a micro-hydrated system with few water molecules shows similar charge transport properties as fully solvated DNA does. This surprising effect is analyzed in detail by mapping the density functional theory-based electronic structure to a tight-binding Hamiltonian, allowing for an estimate of conductivity of various DNA sequences with snapshot-averaged Landauer's approach. The characteristics of DNA charge transport turn out to be determined by the nearest hydration shell(s), and the removal of bulk solvent has little effect on the transport. PMID:24089807

Wolter, Mario; Elstner, Marcus; Kuba?, Tomáš

2013-09-28

55

Charge Transport in Synthetic Metals  

SciTech Connect

The phenomenology of charge transport in synthetic metals is reviewed. It is argued that the conventional quasiparticle picture and Boltzmann transport theory do not apply to these materials. The central ideas of Fermi liquid theory are reviewed, and the significant corrections produced by quasiparticle scattering from ferromagnetic spin fluctuations in liquid {sup 3}He are described. It is shown that Sr{sub 2}RuO{sub 4} does not display the symptoms of a nearly-ferromagnetic Fermi liquid, so the source of its odd angular momentum pairing remains to be understood. The solution of an assisted-tunneling model of charge transport in quasi-one dimensional materials is described. This model has a quantum critical point and gives a resistivity that is linear in temperature or frequency, whichever is greater.

Emery, V. J.; Kivelson, S. A.; Muthukumar, V. N.

1999-01-15

56

Carrier transport in magnesium diboride: Role of nano-inclusions  

NASA Astrophysics Data System (ADS)

Anisotropic-gap and two-band effects smear out the superconducting transition (Tc) in literature reported thermal conductivity of MgB2, where large electronic contributions also suppress anomaly-manifestation in their negligible phononic-parts. Present thermal transport results on scarcely explored specimens featuring nano-inclusions exhibit a small but clear Tc-signature, traced to relatively appreciable phononic conduction, and its dominant electronic-scattering. The self-formed MgO as extended defects strongly scatter the charge carriers and minutely the phonons with their longer-mean-free-path near Tc. Conversely, near room temperature, the shorter-dominant-wavelength phonon's transport is hugely affected by these nanoparticles, undergoing ballistic to diffusive crossover and eventually entering the Ioffe-Regel mobility threshold regime.

Awasthi, A. M.; Bhardwaj, S.; Awana, V. P. S.; Figini Albisetti, A.; Giunchi, G.; Narlikar, A. V.

2013-09-01

57

Charge Transport in Reactive Mesogens and Liquid Crystal Polymer Networks  

NASA Astrophysics Data System (ADS)

Understanding the mechanisms of charge transport in organic semiconductor electronic devices is paramount to optimising performance. This chapter aims to provide an insight into methods of measuring and analysing charge transport with specific focus on cross-linkable systems, i.e., reactive mesogens (RMs) and liquid crystalline (LC) polymer networks. When cross-linked in a mesophase, RMs form solid layers which preserve the mesophase charge transport properties over extended temperature ranges. In contrast, liquid crystalline polymer networks form solid layers but continue to undergo thermotropic transitions as in the original system and carrier mobilities can be enhanced compared to the liquid crystal. Here we examine how the versatility of these compounds brings about such complex behaviour. We see that chemical factors such as reactive end groups and method of cross-linking affect the hole and electron transport characteristics separately and that physical changes in morphology and phase also significantly change the charge transport properties.

Kreouzis, T.; Whitehead, K. S.

58

Band filling with free charge carriers in organometal halide perovskites  

NASA Astrophysics Data System (ADS)

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.

Manser, Joseph S.; Kamat, Prashant V.

2014-09-01

59

Carrier Transport and Sensing in Compound Semiconductor Nanowires  

NASA Astrophysics Data System (ADS)

Experiments and analysis in this thesis advance the understanding of critical issues in the carrier transport properties of InAs and InAs/GaAs core/shell heterostructure nanowires (diameter 30-60 nm) grown by molecular beam epitaxy. Effects of robust sub-band quantization structure on the gate-voltage dependence of conductance are observed up to 77 K in a single InAs nanowire with diameter 34+/-2 nm. Electronic field effect mobility at 300 K and 30 K are typically 2000-4000 cm2V-1s -1 and 10000-20000 cm2V-1s-1 . Strain induced by lattice mismatch in epitaxial core/shell InAs/GaAs heterostructure nanowires is found to relax by formation of dislocations, correlated with nearly one order of magnitude suppression of room temperature field effect mobility compared with bare InAs nanowires. The carrier transport properties of Mn-doped ZnO nanowires were also investigated, where despite the large bandgap, conductivity is not thermally activated, and carrier mobility is consistent with strong degeneracy of the electron gas at 10 K. A novel method was developed providing the first experimental characterization of the quasi-equilibrium gate-voltage dependent surface potential in nanowire field-effect transistors, based on statistics of charging/discharging of a single Coulomb impurity evident in a random telegraph signal, which succeeds in nanostructures with tiny (attofarad) gate capacitance, where similar capacitance-voltage methods are challenging or impossible. We find that the evolution of channel potential with gate voltage is suppressed in the transistor's accumulation regime due to the screening effects of surface states with D ss = 1-- 2 x 1012 cm-2 eV-1. The gate voltage dependence of the random telegraph signals were used as a novel probe to spectroscopically study strong carrier reflection by single Coulomb impurities in nanowires. Reflection probabilities R = 0.98 -- 0.999 approach unity for an electron gas with density n = 30 -- 10 /mum in 30 nm diameter, 1 mum long InAs nanowires at 30 K. Results were compared with microscopic theory of electron scattering by Coulomb impurities in nanowires with dielectric confinement, i.e low dielectric constant surroundings. The latter, which is known to enhance the bare Coulomb interaction and excitonic binding energy, is an essential ingredient for the strong scattering in this regime, and in small diameter nanowires causes a breakdown in linear screening. Extending this, we show that InAs nanowires can operate is extremely sensitive charge sensors with sensitivity 60 mueHz-1/2 at high temperatures (200 K), a combination of characteristics that is not achieved by existing technology. Strong electrostatic coupling of a single charge to the conducting electron gas in the nanowire is enabled by miniaturization of nanowire diameter, operation in a regime of carrier density where the electronic screening length exceeds the nanowire diameter, and dielectric confinement. Finally, single ZnSe nanowire photodetectors are fabricated and studied. Peak responsivity at 2.0 V bias is 20 A/W at room temperature, similar to that of the best epitaxial ZnSe photodetectors. The high responsivity is due to a photoconductive gain g ? 500, the ratio of carrier lifetime to carrier transit time. The former is enhanced at room temperature due to rapid selective trapping of one species of excited carriers by surface states.

Salfi, Joseph R.

60

Carrier Transport in Thin Silicon Films  

Microsoft Academic Search

Films of p-type and n-type silicon 1–2 ? thick have been epitaxially grown on single-crystal sapphire. The Hall mobilities of films with carrier concentrations varying between 1013?cc to mid-1020?cc have been measured. For carrier concentrations above 1017?cc the mobility decreased with increasing carrier concentration similar to the drop in mobility observed in bulk silicon, indicating the dominance of impurity scattering

D. J. Dumin; P. H. Robinson

1968-01-01

61

Effects of nanofiller loading on the molecular motion and carrier transport in polyamide  

Microsoft Academic Search

Effects of nanofiller loading on the molecular motion and carrier transport in polyamide-6\\/mica nanocomposites were discussed by analyzing their complex permittivity spectra. As a result, the following four dielectric polarization processes were observed; space charge polarization, interfacial polarization at crystalline\\/amorphous boundaries, alpha relaxation due to dipolar orientation, and beta relaxation due to rotation of amide groups bonded with water molecules.

Norikazu Fuse; Hiroki Sato; Yoshimichi Ohki; Toshikatsu Tanaka

2009-01-01

62

Spectroscopy of Charge Carriers and Traps in Field-Doped Organic Semiconductors  

SciTech Connect

This research project aims to achieve quantitative and molecular level understanding of charge carriers and traps in field-doped organic semiconductors via in situ optical absorption spectroscopy, in conjunction with time-resolved electrical measurements. During the funding period, we have made major progress in three general areas: (1) probed charge injection at the interface between a polymeric semiconductor and a polymer electrolyte dielectric and developed a thermodynamic model to quantitatively describe the transition from electrostatic to electrochemical doping; (2) developed vibrational Stark effect to probe electric field at buried organic semiconductor interfaces; (3) used displacement current measurement (DCM) to study charge transport at organic/dielectric interfaces and charge injection at metal/organic interfaces.

Zhu, Xiaoyang; Frisbie, C Daniel

2012-08-13

63

Charge transport in nanoscale junctions.  

PubMed

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

Albrecht, Tim; Kornyshev, Alexei; Bjørnholm, Thomas

2008-09-01

64

Charge Carrier Field Emission Determines the Number of Charges on Native State Proteins in Electrospray Ionization  

PubMed Central

Although multiple charging in electrospray ionization (ESI) is essential to protein mass spectrometry, the underlying mechanism of multiple charging has not been explicated. Here, we present a new theory to describe ESI of native-state proteins and predict the number of excess charges on proteins in ESI. The theory proposes that proteins are ionized as charged residues in ESI, as they retain residual excess charges after solvent evaporation and do not desorb from charged ESI droplets. However, their charge state is not determined by the Rayleigh limit of a droplet of similar size to the protein; rather, their final charge state is determined by the electric field-induced emission of small charged solute ions and clusters from protein-containing ESI droplets. This theory predicts that the number of charges on a protein in ESI should be directly proportional to the square of the gas-phase protein diameter and to E*, the critical electric field strength at which ion emission from droplets occurs. This critical field strength is determined by the properties of the excess charge carriers (i.e., the solute) in droplets. Charge-state measurements of native-state proteins with molecular masses in the 5–76 kDa range in ammonium acetate and triethyl ammonium bicarbonate are in excellent agreement with theoretical predictions and strongly support the mechanism of protein ESI proposed here. PMID:18461930

Hogan, Christopher J.; Carroll, James A.; Rohrs, Henry W.; Biswas, Pratim; Gross, Michael L.

2008-01-01

65

Charge transport in single crystal organic semiconductors  

NASA Astrophysics Data System (ADS)

Organic electronics have engendered substantial interest in printable, flexible and large-area applications thanks to their low fabrication cost per unit area, chemical versatility and solution processability. Nevertheless, fundamental understanding of device physics and charge transport in organic semiconductors lag somewhat behind, partially due to ubiquitous defects and impurities in technologically useful organic thin films, formed either by vacuum deposition or solution process. In this context, single-crystalline organic semiconductors, or organic single crystals, have therefore provided the ideal system for transport studies. Organic single crystals are characterized by their high chemical purity and outstanding structural perfection, leading to significantly improved electrical properties compared with their thin-film counterparts. Importantly, the surfaces of the crystals are molecularly flat, an ideal condition for building field-effect transistors (FETs). Progress in organic single crystal FETs (SC-FETs) is tremendous during the past decade. Large mobilities ~ 1 - 10 cm2V-1s-1 have been achieved in several crystals, allowing a wide range of electrical, optical, mechanical, structural, and theoretical studies. Several challenges still remain, however, which are the motivation of this thesis. The first challenge is to delineate the crystal structure/electrical property relationship for development of high-performance organic semiconductors. This thesis demonstrates a full spectrum of studies spanning from chemical synthesis, single crystal structure determination, quantum-chemical calculation, SC-OFET fabrication, electrical measurement, photoelectron spectroscopy characterization and extensive device optimization in a series of new rubrene derivatives, motivated by the fact that rubrene is a benchmark semiconductor with record hole mobility ~ 20 cm2V-1s-1. With successful preservation of beneficial pi-stacking structures, these rubrene derivatives form high-quality single crystals and exhibit large ambipolar mobilities. Nevertheless, a gap remains between the theory-predicted properties and this preliminary result, which itself is another fundamental challenge. This is further addressed by appropriate device optimization, and in particular, contact engineering approach to improve the charge injection efficiencies. The outcome is not only the achievement of new record ambipolar mobilities in one of the derivatives, namely, 4.8 cm2V-1s-1 for holes and 4.2 cm2V-1s-1 for electrons, but also provides a comprehensive and rational pathway towards the realization of high-performance organic semiconductors. Efforts to achieve high mobility in other organic single crystals are also presented. The second challenge is tuning the transition of electronic ground states, i.e., semiconducting, metallic and superconducting, in organic single crystals. Despite an active research area since four decades ago, we aim to employ the electrostatic approach instead of chemical doping for reversible and systematic control of charge densities within the same crystal. The key material in this study is the high-capacitance electrolyte, such as ionic liquids (ILs), whose specific capacitance reaches ~ ?F/cm2, thus allowing accumulation of charge carrier above 1013 cm-2 when novel transport phenomena, such as insulator-metal transition and superconductivity, are likely to occur. This thesis addresses the electrical characterization, device physics and transport physics in electrolyte-gated single crystals, in the device architecture known as the electrical double layer transistor (EDLT). A detailed characterization scheme is first demonstrated for accurate determination of several key parameters, e.g., carrier mobility and charge density, in organic EDLTs. Further studies, combining both experiments and theories, are devoted to understanding the unusual charge density dependent channel conductivity and gate-to-channel capacitance behaviors. In addition, Hall effect and temperature-dependent measurements are employed for more in-depth unders

Xie, Wei

66

Collective bulk carrier delocalization driven by electrostatic surface charge accumulation.  

PubMed

In the classic transistor, the number of electric charge carriers--and thus the electrical conductivity--is precisely controlled by external voltage, providing electrical switching capability. This simple but powerful feature is essential for information processing technology, and also provides a platform for fundamental physics research. As the number of charges essentially determines the electronic phase of a condensed-matter system, transistor operation enables reversible and isothermal changes in the system's state, as successfully demonstrated in electric-field-induced ferromagnetism and superconductivity. However, this effect of the electric field is limited to a channel thickness of nanometres or less, owing to the presence of Thomas-Fermi screening. Here we show that this conventional picture does not apply to a class of materials characterized by inherent collective interactions between electrons and the crystal lattice. We prepared metal-insulator-semiconductor field-effect transistors based on vanadium dioxide--a strongly correlated material with a thermally driven, first-order metal-insulator transition well above room temperature--and found that electrostatic charging at a surface drives all the previously localized charge carriers in the bulk material into motion, leading to the emergence of a three-dimensional metallic ground state. This non-local switching of the electronic state is achieved by applying a voltage of only about one volt. In a voltage-sweep measurement, the first-order nature of the metal-insulator transition provides a non-volatile memory effect, which is operable at room temperature. Our results demonstrate a conceptually new field-effect device, extending the concept of electric-field control to macroscopic phase control. PMID:22837001

Nakano, M; Shibuya, K; Okuyama, D; Hatano, T; Ono, S; Kawasaki, M; Iwasa, Y; Tokura, Y

2012-07-26

67

47 CFR 51.907 - Transition of price cap carrier access charges.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false Transition of price cap carrier access charges. 51.907 Section...Pricing § 51.907 Transition of price cap carrier access charges. (a) Notwithstanding...Commission's rules, on December 29, 2011, a Price Cap Carrier shall cap the rates for...

2013-10-01

68

Transport of elliptic intense charged -particle beams  

E-print Network

The transport theory of high-intensity elliptic charged-particle beams is presented. In particular, the halo formation and beam loss problem associated with the high space charge and small-aperture structure is addressed, ...

Zhou, J. (Jing), 1978-

2006-01-01

69

Transport in disordered monolayer MoS2 nanoflakes—evidence for inhomogeneous charge transport  

NASA Astrophysics Data System (ADS)

We study charge transport in a monolayer MoS2 nanoflake over a wide range of carrier density, temperature and electric bias. We find that the transport is best described by a percolating picture in which the disorder breaks translational invariance, breaking the system up into a series of puddles, rather than previous pictures in which the disorder is treated as homogeneous and uniform. Our work provides insight to a unified picture of charge transport in monolayer MoS2 nanoflakes and contributes to the development of next-generation MoS2-based devices.

Lo, Shun-Tsung; Klochan, O.; Liu, C.-H.; Wang, W.-H.; Hamilton, A. R.; Liang, C.-T.

2014-09-01

70

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

NASA Astrophysics Data System (ADS)

We investigated the structural influences on the charge carrier dynamics in zinc phthalocyanine/fullerene (ZnPc/C60) 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/C60 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/C60 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.

Wang, Zhiping; Miyadera, Tetsuhiko; Saeki, Akinori; Zhou, Ying; Seki, Shu; Shibata, Yosei; Yamanari, Toshihiro; Matsubara, Koji; Yoshida, Yuji

2014-07-01

71

Charge transport in Si nanocrystal/SiO2 superlattices  

NASA Astrophysics Data System (ADS)

Size-controlled silicon nanocrystals in silicon oxynitride matrix were prepared using plasma-enhanced chemical vapor deposition following the superlattice approach. A combination of current transport and charge trapping studies is carried out on a number of samples with varied structural configuration. We demonstrate that at low electric fields, trapping of injected carriers dominates, if the coupling between the silicon nanocrystals is strong. In contrast, we show that at higher electric fields, the charge distribution within the films is essentially governed by charge separation within the superlattice. This effect can be well explained by a two-step electric field ionization of silicon nanocrystals that proceeds via defect-assisted band-to-band tunneling of silicon valence electrons to the conduction band and is mediated by silicon surface dangling bonds. The defects are dominating the charge transport even if the defect density is reduced to a minimum by efficient hydrogen passivation.

Gutsch, S.; Laube, J.; Hartel, A. M.; Hiller, D.; Zakharov, N.; Werner, P.; Zacharias, M.

2013-04-01

72

Microscopic Simulations of Charge Transport in Disordered Organic Semiconductors  

PubMed Central

Charge carrier dynamics in an organic semiconductor can often be described in terms of charge hopping between localized states. The hopping rates depend on electronic coupling elements, reorganization energies, and driving forces, which vary as a function of position and orientation of the molecules. The exact evaluation of these contributions in a molecular assembly is computationally prohibitive. Various, often semiempirical, approximations are employed instead. In this work, we review some of these approaches and introduce a software toolkit which implements them. The purpose of the toolkit is to simplify the workflow for charge transport simulations, provide a uniform error control for the methods and a flexible platform for their development, and eventually allow in silico prescreening of organic semiconductors for specific applications. All implemented methods are illustrated by studying charge transport in amorphous films of tris-(8-hydroxyquinoline)aluminum, a common organic semiconductor. PMID:22076120

2011-01-01

73

Microscopic Simulations of Charge Transport in Disordered Organic Semiconductors.  

PubMed

Charge carrier dynamics in an organic semiconductor can often be described in terms of charge hopping between localized states. The hopping rates depend on electronic coupling elements, reorganization energies, and driving forces, which vary as a function of position and orientation of the molecules. The exact evaluation of these contributions in a molecular assembly is computationally prohibitive. Various, often semiempirical, approximations are employed instead. In this work, we review some of these approaches and introduce a software toolkit which implements them. The purpose of the toolkit is to simplify the workflow for charge transport simulations, provide a uniform error control for the methods and a flexible platform for their development, and eventually allow in silico prescreening of organic semiconductors for specific applications. All implemented methods are illustrated by studying charge transport in amorphous films of tris-(8-hydroxyquinoline)aluminum, a common organic semiconductor. PMID:22076120

Rühle, Victor; Lukyanov, Alexander; May, Falk; Schrader, Manuel; Vehoff, Thorsten; Kirkpatrick, James; Baumeier, Björn; Andrienko, Denis

2011-10-11

74

Interface recombination influence on carrier transport  

NASA Astrophysics Data System (ADS)

A theory of interface recombination in the semiconductor-semiconductor junction is developed. The interface recombination rate dependence on the nonequilibrium carrier densities is derived on the basis of a model in which the interface recombination occurs through the mechanism of trapping. The general relation between the interface recombination parameters at small carrier density deviation from the equilibrium ones is obtained. The validity of this relation is proved considering the generation of the Hall electric field in the extrinsic semiconductor sample. The anomalous Hall electromotive force in a weak magnetic field was investigated and interpreted by means of a new interface recombination model. The experimental data corroborate the developed theory.

Konin, A.

2013-02-01

75

Extracting the charge carrier mobility from the nanosecond photocurrent response of organic solar cells and photodiodes  

NASA Astrophysics Data System (ADS)

We present two simple methods to estimate the effective mobility of the faster charge carrier species from the transient nanosecond photoresponse of an organic solar cell or photodiode. In combination with detailed numerical drift-diffusion simulations in the framework of the multiple-trapping model, we identify the energetic relaxation of the charge carriers and hence a decrease of the effective charge carrier mobility while drifting towards the electrodes. From the characteristic shape of the transient current density, the temperature as well as the nonlinear voltage dependence of the charge carrier transit time, we can quantify an exponential trap distribution. In addition, the nonlinearity of the transit time, as also known from comparable time-of-flight measurements, can be explained by charge carrier relaxation processes in the presence of trap states. The effective charge carrier mobility is shown to be field independent but highly temperature dependent.

Christ, Nico; Kettlitz, Siegfried W.; Mescher, Jan; Lemmer, Uli

2014-02-01

76

Mechanisms of carrier transport induced by a microswimmer bath  

E-print Network

Recently, it was found that a wedgelike microparticle (referred to as "carrier") which is only allowed to translate but not to rotate exhibits a directed translational motion along the wedge cusp if it is exposed to a bath of microswimmers. Here we model this effect in detail by resolving the microswimmers explicitly using interaction models with different degrees of mutual alignment. Using computer simulations we study the impact of these interactions on the transport efficiency of V-shaped carrier. We show that the transport mechanisms itself strongly depends on the degree of alignment embodied in the modelling of the individual swimmer dynamics. For weak alignment, optimal carrier transport occurs in the turbulent microswimmer state and is induced by swirl depletion inside the carrier. For strong aligning interactions, optimal transport occurs already in the dilute regime and is mediated by a polar cloud of swimmers in the carrier wake pushing the wedge-particle forward. We also demonstrate that the optimal shape of the carrier leading to maximal transport speed depends on the kind of interaction model used.

Andreas Kaiser; Andrey Sokolov; Igor S. Aranson; Hartmut Löwen

2014-08-08

77

Local charge carrier mobility in disordered organic field-effect transistors  

Microsoft Academic Search

In conventional field-effect transistors, the extracted mobility does not take into account the distribution of charge carriers. However, in disordered organic field-effect transistors, the local charge carrier mobility decreases from the semiconductor\\/insulator interface into the bulk, due to its dependence on the charge carrier density. It is demonstrated that the conventional field-effect mobility is a good approximation for the local

C. Tanase; E. J. Meijer; P. W. M. Blom; D. M. de Leeuw

2003-01-01

78

Fractal spectrum of charge carriers in quasiperiodic graphene structures.  

PubMed

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

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

2010-11-24

79

Transient effects controlling the charge carrier population of organic field effect transistor channels  

NASA Astrophysics Data System (ADS)

We present device simulations exploring the effects of traps during transient processes in the conducting channel of organic field effect transistors (OFETs). The device structure explored resembles a typical organic thin-film transistor with one of the channel contacts removed. However, the channel length is much longer than in typical OFETs in order to increase the transit time. By measuring the displacement current in these long-channel capacitors, transient effects in the carrier transport in organic semiconductors may be studied. When carriers are injected into the device, a conducting channel is established while traps, which are initially empty, are being populated. The filling of the traps then modifies the transport characteristics of the injected charge carriers. In contrast, dc experiments as they are typically performed to characterize the transport properties of organic semiconductor channels investigate a steady state with traps partially filled. Numerical and approximate analytical models for the formation of the conducting channel and the resulting displacement current are discussed here. The temperature dependence of the effective mobility arising from the temperature dependence of the trap emission rate is explored, and calculated results are compared with experimental data. We show that displacement current measurements on OFET structures provide unique opportunities for the study of trap dynamics involving a wide range of time scales.

Chang, Hsiu-Chuang; Ruden, P. Paul; Liang, Yan; Frisbie, C. Daniel

2010-05-01

80

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

NASA Astrophysics Data System (ADS)

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.

Zubarev, A.; Dragoman, D.

2014-10-01

81

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

NASA Astrophysics Data System (ADS)

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.

Monobe, Hirosato; Shimizu, Yo

2014-01-01

82

The Self-Consistent Charge Method: A Numerical Approach to Radiation-Induced Charge Transport Phenomena  

Microsoft Academic Search

Reconsidering the numerous conceptions as they have been developed in atomic physics (self-consistent field), heat and charge transport theory (carrier-enhanced and radiation-induced conductivity) and many other related fields for iteratively solving the corresponding integro-differential equation systems we come now to propose a new approach to the subject addressed in the title. This method has been implemented in a FORTRAN code,

E. Hartmann; H.-R. Döring; J. Leonhardt

1990-01-01

83

Imaging ultrafast carrier transport in nanoscale field-effect transistors.  

PubMed

In the present study, we visualize ultrafast carrier dynamics in one-dimensional nanoscale devices, such as Si nanowire and carbon nanotube transistors using femtosecond photocurrent microscopy. We investigate transit times of ultrashort carriers that are generated near one metallic electrode and subsequently transported toward the opposite electrode based on drift and diffusion motions. Conversely, pure diffusion motion is observed when the pump pulse is located in the middle of the nanowires. Carrier dynamics have been addressed for various working conditions, in which we found that the carrier velocity and pulse width can be manipulated by the external electrodes. In particular, the carrier velocities extracted from transit times increase for a larger negative gate bias because of the increased field strength at the Schottky barrier. PMID:25338294

Son, Byung Hee; Park, Jae-Ku; Hong, Jung Taek; Park, Ji-Yong; Lee, Soonil; Ahn, Yeong Hwan

2014-11-25

84

Fullerene–oligophenyleneethynylene?conjugates: relationships between charge-carrier mobility, photovoltaic characteristics and chemical structure  

Microsoft Academic Search

The charge-mobility properties of thin films prepared from different fullerene–oligophenyleneethynylene conjugates are reported. A direct relationship between the chemical structure, the charge-carrier mobility and the photovoltaic characteristics of these materials has been clearly evidenced.

J.-F. Nierengarten; T. Gu; T. Aernouts; W. Geens; J. Poortmans; G. Hadziioannou; D. Tsamouras

2004-01-01

85

75 FR 18255 - Passenger Facility Charge Database System for Air Carrier Reporting  

Federal Register 2010, 2011, 2012, 2013

...FAA-2010] Passenger Facility Charge Database System for Air Carrier Reporting AGENCY...the Passenger Facility Charge (PFC) database system to report PFC quarterly report...The FAA has developed a national PFC database system in order to more easily...

2010-04-09

86

Low temperature carrier transport properties in isotopically controlled germanium  

SciTech Connect

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.

Itoh, K.

1994-12-01

87

Low temperature carrier transport properties in isotopically controlled germanium  

NASA Astrophysics Data System (ADS)

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 Ge-75 and Ge-70 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 (Ge-74)/(Ge-70) 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.

Itoh, K.

1994-12-01

88

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

SciTech Connect

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.

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

89

41 CFR 301-10.105 - What are the basic requirements for using common carrier transportation?  

...requirements for using common carrier transportation? 301-10.105 Section 301-10...ALLOWANCES ALLOWABLE TRAVEL EXPENSES 10-TRANSPORTATION EXPENSES Common Carrier Transportation § 301-10.105 What are the...

2014-07-01

90

Electric Properties of Obsidian: Evidence for Positive Hole Charge Carriers  

NASA Astrophysics Data System (ADS)

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.

Nordvik, R.; Freund, F. T.

2012-12-01

91

Electron and molecular dynamics: Penning ionization and molecular charge transport  

NASA Astrophysics Data System (ADS)

An understanding of fundamental reaction dynamics is an important problem in chemistry. In this work, experimental and theoretical methods are combined to study the dynamics of fundamental chemical reactions. Molecular collision and dissociation dynamics are explored with the Penning ionization of amides, while charge transfer reactions are examined with charge transport in organic thin film devices. Mass spectra from the Penning ionization of formamide by He*, Ne*, and Ar* were measured using molecular beam experiments. When compared to 70eV electron ionization spectra, the He* and Ne* spectra show higher yields of fragments resulting from C--N and C--H bond cleavage, while the Ar* spectrum only shows the molecular ion, H-atom elimination, and decarbonylation. The differences in yields and observed fragments are attributed to the differences in the dynamics of the two ionization methods. Fragmentation in the Ar* spectrum was analyzed using quantum chemistry and RRKM calculations. Calculated yields for the Ar* spectrum are in excellent agreement with experiment and show that 15% and 50% of the yields for decarbonylation and H-atom elimination respectively are attributed to tunneling. The effects of defects, traps, and electrostatic interactions on charge transport in imperfect organic field effect transistors were studied using course-grained Monte Carlo simulations with explicit introduction of defect and traps. The simulations show that electrostatic interactions dramatically affect the field and carrier concentration dependence of charge transport in the presence of a significant number of defects. The simulations also show that while charge transport decreases linearly as a function of neutral defect concentration, it is roughly unaffected by charged defect concentration. In addition, the trap concentration dependence on charge transport is shown to be sensitive to the distribution of trap sites. Finally, density functional theory calculations were used to study how charge localization affects the orbital energies of positively charged bithiophene clusters. These calculations show that the charge delocalizes over at least seven molecules, is more likely to localize on "tilted" molecules due to polarization effects, and affects molecules anisotropically. These results suggest that models for charge transport in organic semiconductors should be modified to account for charge delocalization and intermolecular interactions.

Madison, Tamika Arlene

92

Charge generation, charge transport, and residual charge in the electrospinning of polymers: A review of issues and complications  

NASA Astrophysics Data System (ADS)

Electrospinning has become a widely implemented technique for the generation of nonwoven mats that are useful in tissue engineering and filter applications. The overriding factor that has contributed to the popularity of this method is the ease with which fibers with submicron diameters can be produced. Fibers on that size scale are comparable to protein filaments that are observed in the extracellular matrix. The apparatus and procedures for conducting electrospinning experiments are ostensibly simple. While it is rarely reported in the literature on this topic, any experience with this method of fiber spinning reveals substantial ambiguities in how the process can be controlled to generate reproducible results. The simplicity of the procedure belies the complexity of the physical processes that determine the electrospinning process dynamics. In this article, three process domains and the physical domain of charge interaction are identified as important in electrospinning: (a) creation of charge carriers, (b) charge transport, (c) residual charge. The initial event that enables electrospinning is the generation of region of excess charge in the fluid that is to be electrospun. The electrostatic forces that develop on this region of charged fluid in the presence of a high potential result in the ejection of a fluid jet that solidifies into the resulting fiber. The transport of charge from the charge solution to the grounded collection device produces some of the current which is observed. That transport can occur by the fluid jet and through the atmosphere surrounding the electrospinning apparatus. Charges that are created in the fluid that are not dissipated remain in the solidified fiber as residual charges. The physics of each of these domains in the electrospinning process is summarized in terms of the current understanding, and possible sources of ambiguity in the implementation of this technique are indicated. Directions for future research to further articulate the behavior of the electrospinning process are suggested.

Collins, George; Federici, John; Imura, Yuki; Catalani, Luiz H.

2012-02-01

93

Picosecond dynamics of free carrier populations, space- charge fields, and photorefractive nonlinearities in zincblende semiconductors  

NASA Astrophysics Data System (ADS)

Generally, nonlinear optics studies investigate optically-induced changes in refraction or absorption, and their application to spectroscopy or device fabrication. The photorefractive effect is a nonlinear optical effect that occurs in solids, where transport of an optically-induced free-carrier population results in an internal space-charge field, which produces an index change via the linear electrooptic effect. The photorefractive effect has been widely studied for a variety of materials and device applications, mainly because it allows large index changes to be generated with laser beams having only a few milliwatts of average power. Compound semiconductors are important photorefractive materials because they offer a near-infrared optical response, and because their carrier transport properties allow the index change to be generated quickly and efficiently. While many researchers have attempted to measure the fundamental temporal dynamics of the photorefractive effect in semiconductors using continuous-wave, nanosecond- and picosecond-pulsed laser beams, these investigations have been unsuccessful. However, studies with this goal are of clear relevance because they provide information about the fundamental physical processes that produce this effect, as well as the material's speed and efficiency limitations for device applications. In this dissertation, for the first time, we time-resolve the temporal dynamics of the photorefractive nonlinearities in two zincblende semiconductors, semi- insulating GaAs and undoped CdTe. While CdTe offers a lattice-match to the infrared material HgxCd1-xTe, semi-insulating GaAs has been widely used in optoelectronic and high- speed electronic applications. We use a novel transient- grating experimental method that allows picosecond temporal resolution and high sensitivity. Our results provide a clear and detailed picture of the picosecond photorefractive response of both materials, showing nonlinearities due to hot-carrier transport and the Dember space-charge field, and a long-lived nonlinearity that is due to the EL2 midgap species in GaAs. We numerically model our experimental results using a general set of equations that describe nonlinear diffraction and carrier transport, and obtain excellent agreement with the experimental results in both materials, for a wide variety of experimental conditions.

Stark, Thomas Spencer

94

Identifying the charge carriers of the quark-gluon plasma.  

PubMed

Charge correlations in lattice gauge calculations suggest that up, down, and strange charges move independently in the quark-gluon plasma, and that the density of such charges is similar to what is expected from simple thermal arguments. Here, we show how specific elements of the charge-charge correlation matrix in the quark-gluon plasma survive hadronization and become manifest in final-state charge-charge correlation measurements. PMID:23003245

Pratt, Scott

2012-05-25

95

Biological Contexts for DNA Charge Transport Chemistry  

E-print Network

The double helical structure adopted by B-form DNA, where a negatively charged sugar phosphate backbone surrounds a ?-stacked array of heterocyclic aromatic basepairs, allows it to serve as an efficient medium for long-range charge transport (CT) (1). This chemistry has now been well established as a property of DNA. DNA CT can be

unknown authors

96

Charge and spin transport in mesoscopic superconductors  

PubMed Central

Summary Background: Non-equilibrium charge transport in superconductors has been investigated intensely in the 1970s and 1980s, mostly in the vicinity of the critical temperature. Much less attention has been paid to low temperatures and the role of the quasiparticle spin. Results: We report here on nonlocal transport in superconductor hybrid structures at very low temperatures. By comparing the nonlocal conductance obtained by using ferromagnetic and normal-metal detectors, we discriminate charge and spin degrees of freedom. We observe spin injection and long-range transport of pure, chargeless spin currents in the regime of large Zeeman splitting. We elucidate charge and spin transport by comparison to theoretical models. Conclusion: The observed long-range chargeless spin transport opens a new path to manipulate and utilize the quasiparticle spin in superconductor nanostructures. PMID:24605283

Wolf, M J; Hübler, F; Kolenda, S

2014-01-01

97

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

ERIC Educational Resources Information Center

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…

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

98

Transport properties of carbon dioxide through amine functionalized carrier membranes  

Microsoft Academic Search

COâ facilitated transport was studied using a membrane with amine sites covalently bound to the polymer backbone and ion exchange membranes which have amine complexing agents (carrier) as counterions. The two types of membranes were compared, and several amine functionalities for the ion-exchange membrane were studied. Although the covalently bonded membranes had a larger absorption capacity than amine functionalized Nafion

Takeo Yamaguchi; Lars M. Boetje; Carl A. Koval; Richard D. Noble; Christopher N. Bowman

1995-01-01

99

41 CFR 301-10.100 - What types of common carrier transportation may I be authorized to use?  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false What types of common carrier transportation may I be authorized...EXPENSES 10-TRANSPORTATION EXPENSES Common Carrier Transportation § 301-10.100 What types of common carrier transportation may I be...

2010-07-01

100

Carrier transport, polarization matching, and efficiency droop in GaN-based visible LEDs  

NASA Astrophysics Data System (ADS)

Transport of electrons and holes in GaInN/GaN LEDs is known to be largely asymmetric, due to differences in carrier mobility and the ionization energy for donors and acceptors. Sheet charges at heterointerfaces of devices grown in the c-direction, which arise due to mismatch in spontaneous and piezoelectric polarization, further hinder transport by increasing barriers for carrier injection into quantum wells. The effect of these sheet charges upon capture of carriers by quantum wells is analyzed with a quantum-mechanical calculation of the dwell time of electrons and holes over quantum wells. Wavefunctions and dwell times are calculated using the k.p quantum transmitting boundary method with the wurtzite 8-band Hamiltonian with Burt-Foreman operator ordering. The effect of quantum well width upon dwell time is also considered. It is shown that both reduction of sheet charges by polarization matching and the increase of well width result in substantially longer dwell times, and therefore higher probability of capture. Experimental results of LEDs with polarization-matched active regions are presented. Such LEDs are shown to have improved efficiency throughout the entire range of forward currents. This indicates that a reduction in carrier density is not solely responsible for the improved efficiency, since reduced carrier density would also lead to a higher Shockley-Reed-Hall rate at low currents. The implications of this result are discussed in detail. Further, experimental results of LEDs with varying doping in the active region are presented. It is shown that a reduction in doping -- which has the effect of slowing electron transport -- results in an increase in efficiency at large forward currents. This result is explained in detail using modeling results.

Schubert, Martin

2010-03-01

101

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

Code of Federal Regulations, 2010 CFR

...carriers for 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,...

2010-07-01

102

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

Code of Federal Regulations, 2011 CFR

...carriers for 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,...

2011-07-01

103

Parametrization of extended Gaussian disorder models from microscopic charge transport  

E-print Network

-of-flight,11,12 field effect transistor,13­15 diode,3 microwave conductivity,16 or charge ex- traction,3 and field effect tran- sistors4 requires the improvement of the charge-carrier mobility, µ, of an organic semiconduc- tor, which depends on charge-carrier density, , external electric field, F

Schmidt, Volker

104

47 CFR 1.1154 - Schedule of annual regulatory charges and filing locations for common carrier services.  

Code of Federal Regulations, 2010 CFR

...Schedule of annual regulatory charges and filing locations for common carrier services. 1.1154 Section 1.1154 Telecommunication...Schedule of annual regulatory charges and filing locations for common carrier services. Radio facilities Fee amount...

2010-10-01

105

An alternative approach to charge transport in semiconducting electrodes  

NASA Technical Reports Server (NTRS)

The excess-carrier charge transport through the space-charge region of a semiconducting electrode is analyzed by a technique known as the flux method. In this approach reflection and transmission coefficients appropriate for a sheet of uniform semiconducting material describe its transport properties. A review is presented of the flux method showing that the results for a semiconductor electrode reduce in a limiting case to those previously found by Gaertner if the depletion layer is treated as a perfectly transmitting medium in which scattering and recombination are ignored. Then, in the framework of the flux method the depletion layer is considered more realistically by explicitly taking into account scattering and recombination processes which occur in this region.

Thomchick, J.; Buoncristiani, A. M.

1980-01-01

106

34 nm Charge Transport through DNA  

NASA Astrophysics Data System (ADS)

Long-range charge transport through DNA has broad-reaching implications due to its inherent biological recognition capabilities and unmatched capacity to be patterned into precise, nanoscale shapes. We have observed charge transport through 34 nm DNA monolayers (100 base pairs) using DNA-mediated electrochemistry. Cyclic voltammetry of multiplexed gold electrodes modified with 100mer DNAs reveal sizable peaks from distally-bound Nile Blue redox probes for well matched duplexes but highly attenuated redox peaks from 100mer monolayers containing a single base pair mismatch, demonstrating that the charge transfer is DNA-mediated. The 100mers on the gold surface are efficiently cleaved by the restriction enzyme RsaI. The 100mers in the DNA film thus adopt conformations that are readily accessible to protein binding and restriction. The ability to assemble well-characterized DNA films with these 100mers permits the demonstration of charge transport over distances surpassing most reports of molecular wires.

Slinker, Jason; Muren, Natalie; Renfrew, Sara; Barton, Jacqueline

2011-03-01

107

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

PubMed

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

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

2014-04-21

108

Nanocone Tip-Film Solar Cells with Efficient Charge Transport  

SciTech Connect

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.

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

2011-01-01

109

Charge transport anisotropy in n-type disk-shaped triphenylene-tris(aroyleneimidazole)s.  

PubMed

Two novel n-type disk-shaped molecules containing a triphenylene core and three fused naphthaleneimide imidazole or peryleneimide imidazole "arms" are synthesized and characterized. The n-type charge carrier mobilities of these molecules are evaluated by both field effect transistors and space-charge limited-current measurements, which exhibit drastically different mobility anisotropy. A strong correlation between film morphology and the charge transport behavior is established by X-ray scattering and atomic force microscopic analyses. PMID:22082278

Zhang, Yue; Hanifi, David; Alvarez, Steven; Antonio, Francisco; Pun, Andrew; Klivansky, Liana M; Hexemer, Alexander; Ma, Biwu; Liu, Yi

2011-12-16

110

Spin relaxation in materials lacking coherent charge transport  

NASA Astrophysics Data System (ADS)

We describe a broadly applicable theory of spin relaxation in materials with incoherent charge transport; examples include amorphous inorganic semiconductors, organic semiconductors, quantum dot arrays, and systems displaying trap-controlled transport or transport within an impurity band. The theory can incorporate many different relaxation mechanisms, so long as electron-electron correlations can be neglected. We focus primarily on spin relaxation caused by spin-orbit effects, which manifest through inhomogeneities in the g factor and non-spin-conserving carrier hops, scattering, trapping, or detrapping. Analytic and numerical results from the theory are compared in various regimes with Monte Carlo simulations. Our results should assist in evaluating the suitability of various disordered materials for spintronic devices.

Harmon, N. J.; Flatté, M. E.

2014-09-01

111

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

E-print Network

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 ...

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

2006-01-01

112

Mobility of delocalized charge carriers in an ideal homopolar glass as a function of temperature  

SciTech Connect

The relationship between temperature and the mobility of delocalized charge carriers for an intrinsic random field of a homopolar glass is investigated through application of a method of scattering amplitude calculation based on employing short-lived potential factorization.

Iskra, V.D.

1986-10-01

113

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

...system do in relation to common carrier transportation? 301-72.100 Section 301-72...RESPONSIBILITIES RELATED TO COMMON CARRIER TRANSPORTATION Accounting for Common Carrier Transportation § 301-72.100 What must my...

2014-07-01

114

41 CFR 301-72.200 - Under what conditions may we authorize cash payments for procuring common carrier transportation...  

Code of Federal Regulations, 2010 CFR

...we authorize cash payments for procuring common carrier transportation services? 301-72...72-AGENCY RESPONSIBILITIES RELATED TO COMMON CARRIER TRANSPORTATION Cash Payments for Procuring Common Carrier Transportation Services §...

2010-07-01

115

41 CFR 301-72.3 - What method of payment must we authorize for common carrier transportation?  

Code of Federal Regulations, 2010 CFR

...What method of payment must we authorize for common carrier transportation? 301-72.3 Section...RESPONSIBILITIES 72-AGENCY RESPONSIBILITIES RELATED TO COMMON CARRIER TRANSPORTATION Procurement of Common Carrier Transportation § 301-72.3...

2010-07-01

116

41 CFR 301-51.100 - What method of payment must I use to procure common carrier transportation?  

Code of Federal Regulations, 2010 CFR

...method of payment must I use to procure common carrier transportation? 301-51...51-PAYING TRAVEL EXPENSES Paying for Common Carrier Transportation § 301-51...method of payment must I use to procure common carrier transportation? You...

2010-07-01

117

Thickness dependence of surface morphology and charge carrier mobility in organic field-effect transistors  

Microsoft Academic Search

With the aim of understanding the relationships between organic small molecule field-effect transistors (FETs) and organic conjugated polymer FETs, we investigate the thickness dependence of surface morphology and charge carrier mobility in pentacene and regioregular poly (3-hexylthiophene) (RR-P3HT) field-effect transistors. On the basis of the results of surface morphologies and electrical properties, we presume that the charge carrier mobility is

Xue-Yan Tian; Zheng Xu; Su-Ling Zhao; Fu-Jun Zhang; Guang-Cai Yuan; Jing Li; Qin-Jun Sun; Yun Wang; Xu-Rong Xu

2010-01-01

118

CLASSIFICATION OF THE MGR CARRIER/CASK TRANSPORT SYSTEM  

SciTech Connect

The purpose of this analysis is to document the Quality Assurance (QA) classification of the Monitored Geologic Repository (MGR) carrier/cask transport system structures, systems and components (SSCs) performed by the MGR Safety Assurance Department. This analysis also provides the basis for revision of YMP/90-55Q, Q-List (YMP 1998). The Q-List identifies those MGR SSCs subject to the requirements of DOE/RW-0333P, ''Quality Assurance Requirements and Description'' (QARD) (DOE 1998).

S.E. Salzman

1999-08-30

119

Carrier transport in Ge nanowire/Si substrate heterojunctions  

NASA Astrophysics Data System (ADS)

Low impedance and negligible conductivity temperature dependence are found for micron-long Ge nanowires (NWs) grown on (p+)Si substrates. In contrast, Ge NW/(n+)Si substrate samples exhibit many orders of magnitude higher impedance, an exponential dependence of conductivity on temperature, current instabilities, and negative differential photoconductivity. Our experimental results are explained by a model that considers energy-band alignment and carrier transport in abrupt Ge NW/Si substrate heterojunctions.

Lee, E.-K.; Kamenev, B. V.; Tsybeskov, L.; Sharma, S.; Kamins, T. I.

2007-05-01

120

Intrinsic Charge Transport in Organic Field-Effect Transistors  

NASA Astrophysics Data System (ADS)

Organic field-effect transistors (OFETs) are essential components of modern electronics. Despite the rapid progress of organic electronics, understanding of fundamental aspects of the charge transport in organic devices is still lacking. Recently, the OFETs based on highly ordered organic crystals have been fabricated with innovative techniques that preserve the high quality of single-crystal organic surfaces. This technological progress facilitated the study of transport mechanisms in organic semiconductors [1-4]. It has been demonstrated that the intrinsic polaronic transport, not dominated by disorder, with a remarkably high mobility of ``holes'' ? = 20 cm^2/Vs can be achieved in these devices at room temperature [4]. The signatures of the intrinsic polaronic transport are the anisotropy of the carrier mobility and an increase of ? with cooling. These and other aspects of the charge transport in organic single-crystal FETs will be discussed. Co-authors are Etienne Menard, University of Illinois at Urbana Champaign; Valery Kiryukhin, Rutgers University; John Rogers, University of Illinois at Urbana Champaign; Michael Gershenson, Rutgers University. [1] V. Podzorov et al., Appl. Phys. Lett. 82, 1739 (2003); ibid. 83, 3504 (2003). [2] V. C. Sundar et al., Science 303, 1644 (2004). [3] R. W. I. de Boer et al., Phys. Stat. Sol. (a) 201, 1302 (2004). [4] V. Podzorov et al., Phys. Rev. Lett. 93, 086602 (2004).

Podzorov, Vitaly

2005-03-01

121

Electric field assisted charge carrier photogeneration in poly(spirobifluorene-co-benzothiadiazole)  

SciTech Connect

The dynamics of charge carrier generation in poly(spirobifluorene-co-benzothiadiazole) was investigated by electric field-induced fluorescence quenching and differential absorption measurements. Three different time domains of carrier generation have been identified: an ultrafast phase, a subnanosecond phase, and an entire lifetime phase. The charge generation efficiencies during the first and second phases were found to be almost independent of temperature, being about 25% and 10%, respectively, at an applied electric field of 1.3x10{sup 6} V/cm, while the generation efficiency during the third phase increases from 2% at 80 K to 10% at room temperature. The results of transient spectroscopy measurements and quantum chemical calculations suggest an intramolecular charge transfer for about 1 ps from the alkoxy-substituted fluorene side group to the benzothiadiazole subunit of the main chain. The formation and evolution of the resulting charge transfer states determine the way of charge carrier generation.

Devizis, A.; Serbenta, A.; Peckus, D. [Center for Physical Sciences and Technology, Savanoriu 231, LT-02300 Vilnius (Lithuania); Thiessen, A.; Alle, R.; Meerholz, K.; Hertel, D. [Department of Chemistry, Physical Chemistry, University of Cologne, Luxemburgerstr. 116, 50939 Cologne (Germany); Gulbinas, V. [Center for Physical Sciences and Technology, Savanoriu 231, LT-02300 Vilnius (Lithuania); Vilnius University, Sauletekio 9, LT-10220 Vilnius (Lithuania)

2010-10-28

122

Earthquake lights and the stress-activation of positive hole charge carriers in rocks  

USGS Publications Warehouse

Earthquake-related luminous phenomena (also known as earthquake lights) may arise from (1) the stress-activation of positive hole (p-hole) charge carriers in igneous rocks and (2) the accumulation of high charge carrier concentrations at asperities in the crust where the stress rates increase very rapidly as an earthquake approaches. It is proposed that, when a critical charge carrier concentration is reached, the p-holes form a degenerated solid state plasma that can break out of the confined rock volume and propagate as a rapidly expanding charge cloud. Upon reaching the surface the charge cloud causes dielectric breakdown at the air-rock interface, i.e. corona discharges, accompanied by the emission of light and high frequency electromagnetic radiation. ?? 2006 Elsevier Ltd. All rights reserved.

St-Laurent, F.; Derr, J.S.; Freund, F.T.

2006-01-01

123

Molecular Wires: Charge Transport, Mechanisms, and Control  

Microsoft Academic Search

By molecular wires, one generally means molecular structures that transmit a signal between two termini. We discuss some theoretical models and analysis for electron- ically conductive molecular wires in which a single molecule conducts charge between two electrodes. This situation resembles both intramolecular non-adiabatic electron transfer, in which electronic tunneling between donor and acceptor is seen, and mesoscopic quantum transport.

Mark A. Ratner; Bill Davis; Mathieu Kemp; Vladimiro Mujica; Adrian Roitberg; Sophia Yaliraki

1998-01-01

124

SINGLE CARRIER CHARGE COLLECTION IN SEMICONDUCTOR NUCLEAR DETECTORS (*)  

E-print Network

'efficacité de collection de photons 03B3. Des exemples de spectres enregistrés avec des compteurs CdTe et HgI2-rays, are shown. Examples of gamma spectra observed with hemispherical HgI2 and CdTe detectors contact configuration requires good col- lection efficiency of both carriers. With shperical contacts

Paris-Sud XI, Université de

125

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

NASA Astrophysics Data System (ADS)

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.

Ziabari, Ali Abdolahzadeh; Rozati, S. M.

2014-08-01

126

BALLISTIC CARRIER TRANSPORT IN SEMICONDUCTORS STUDIED BY ULTRAFAST LASER TECHNIQUES  

E-print Network

in several materials and structures are studied, including GaAs bulk, quantum wells, and germanium wafers. We observed the intrinsic inverse spin-Hall effect by time-resolving the ballistic spin and charge transport. We found that the Hall current appeared...

Werake, Lalani Kumari

2011-08-31

127

Energy Carrier Transport In Surface-Modified Carbon Nanotubes  

E-print Network

was converted from p-type to n-type with a large thermopower (58 ?V/K) by using polyethyleneimine (PEI) without vacuum or controlled environment. This transport behavior is believed to be from charge interactions resulted from the difference between the work...

Ryu, Yeontack

2012-11-30

128

Negative correlation between charge carrier density and mobility fluctuations in graphene  

NASA Astrophysics Data System (ADS)

By carrying out simultaneous longitudinal and Hall measurements in graphene, we find that the 1/f noise for the charge carrier density is negatively correlated to that of mobility, with a governing behavior that differs significantly from the relation between their mean values. The correlation in the noise data can be quantitatively explained by a single-parameter theory whose underlying physics is the trapping and detrapping of the fluctuating charge carriers by the oppositely charged Coulomb scattering centers. This can alter the effective density of long-range scattering centers in a transient manner, with the consequent fluctuating effect on the mobility.

Lu, Jianming; Pan, Jie; Yeh, Sheng-Shiuan; Zhang, Haijing; Zheng, Yuan; Chen, Qihong; Wang, Zhe; Zhang, Bing; Lin, Juhn-Jong; Sheng, Ping

2014-08-01

129

Photoexcitation, relaxation and control of charge carriers in metals through interferometric time-resolved photoemission  

NASA Astrophysics Data System (ADS)

The coherent response of metals to optical excitation is investigated by a newly developed technique, interferometric time-resolved two-photon photoemission spectroscopy.(S. Ogawa, H. Nagano, H. Petek and A. Heberle, Phys. Rev. Lett. 78, 1339 (1997).)(H. Petek, A. P. Heberle, W. Nessler, H. Nagano, S. Kubota, S. Matsunami, N. Moriya and S. Ogawa, Phys. Rev. Lett. 79, 4649 (1997).) Photoexcitation, relaxation, and control of charge carrier distributions are reported for the low index surfaces of copper. Two-photon photoemission (2PP) is excited by an identical pair of pump and probe pulses with a delay defined to a fraction of an optical cycle ( 0.05 fs). Interferometric two-pulse correlation measurements (I2PC), where the 2PP signal at a specific energy and momentum is recorded as a function of the pump probe delay, probe coherent (polarization) and incoherent (population) dynamics of the charge carriers. The time scale for the phase decay (dephasing) of the optically excited wavefunction, as a result of the deformation potential scattering, is deduced from the decay of interference fringes in the I2PC scans. Measurement of optical dephasing on 20 fs time scale in excitation of the occupied s,p-gap surface state on Cu(111) is in good agreement with photoemission linewidth analysis. I2PC also offers an unambiguous way to monitor the decay of the optically created hot-electron population due to e-e scattering and transport into the bulk. Finally, demonstration of long dephasing times in copper suggests a possibility of coherent control of electrons in metals. This is demonstrated with two simple excitation schemes.

Petek, Hrvoje

1998-03-01

130

Charge transport and injection in amorphous organic electronic materials  

NASA Astrophysics Data System (ADS)

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 materials, commonly used in organic electronic devices, are investigated by the means of carrier mobility measurements. Transient electroluminescence (EL) technique was used to evaluate the electron mobility of an electron transporting material--- tris(8-hydroxyquinoline) aluminum (Alq3). The results are in excellent agreement with independent time-of-flight (TOF) measurements. Then, the effect of dopants on electron transport was also examined. TOF technique was also used to examine the effects of tertiary-butyl (t-Bu) substitutions on anthracene derivatives (ADN). All ADN compounds were found to be ambipolar. As the degree of t-Bu substitution increases, the carrier mobilities decrease progressively. The reduction of carrier mobilities with increasing t-butylation can be attributed to a decrease in the charge-transfer integral or the wavefunction overlap. In addition, from TOF measurements, two naphthylamine-based hole transporters, namely, N,N'-diphenyl-N,N'-bis(1-naphthyl)(1,1'-biphenyl)-4,4'diamine (NPB) and 4,4',4"-tris(n-(2-naphthyl)-n-phenyl-amino)-triphenylamine (2TNATA) were found to possess electron-transporting (ET) abilities. An organic light-emitting diode that employed NPB as the ET material was demonstrated. The electron conducting mechanism of NPB and 2TNATA in relation to the hopping model will be discussed. Furthermore, the ET property of NPB applied in OLEDs will also be examined. Besides transient EL and TOF techniques, we also use dark-injection space-charge-limited current (DISCLC) to study the charge injection properties of three phenylamine-based (PA) compounds, MTDATA (4,4',4''-Tris(N-3-methylphenyl-N-phenyl-amino)triphenylamine), NPB, and TPD (N,N'-diphenyl-N,N'-bis(3-methyl phenyl) (1,1'-biphenyl)-4,4'diamine).Poly(3,4-ethylenedioxythiophene) doped with polystyrenesulphonic acid (PEDOT:PSS) was used as a hole-injecting anode in current-voltage (JV) and DISCLC. Clear DISCLC transient peaks were observed over a wide range of electric fields in all cases. For MTDATA and NPB, hole mobilities evaluated by DI experiments are in excellent agreement with mobilties deduced from TOF technique. It can be concluded that, for the purpose of JV and DI experiments, PEDOT:PSS forms an Ohmic contact with MTDATA and a quasi-Ohmic contact with NPB despite the relatively low-lying highest occupied molecular orbital of the later. In the case of TPD, hole injection from PEDOT:PSS deviates substantially from Ohmic injection, leading to a lower than expected DI-extracted hole mobility. Finally, a composite anode will be demonstrated to improve the hole injection efficiency.

Tse, Shing Chi

131

Low Temperature Carrier Transport Properties in Isotopically Controlled Germanium  

NASA Astrophysics Data System (ADS)

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 ^{74}Ge and ^{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 (^{74 }Ge) / (^{70}Ge) ratios of the starting Ge materials, respectively. This method also guarantees unprecedented doping uniformity. Using such samples we 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. We have also performed infrared absorption spectroscopy studies of compensated Ge samples, investigating the line broadening mechanism due to random electric fields arising from ionized impurity centers. In the study of neutral impurity scattering, we find excellent agreement between the low temperature experimental mobility and phase shift calculations for the hydrogen atom scaled to shallow impurities in semiconductors. In the ionized impurity scattering study, none of the theories we have tested so far explains our low temperature experimental mobilities in highly compensated Ge (K>0.3). We discuss possible problems associated with the theories, in particular, the treatment of the screening mechanism. In the study of low temperature hopping conduction, we show results of temperature dependent resistivity measurements as a function of both the net-carrier concentration and the compensation ratio. These results are compared with the theoretical prediction of variable range hopping conduction. A transport study of samples close to the metal -insulator transition allows us to probe the nature of this important phenomenon. Our NTD isotopically engineered samples with extreme dopant uniformity are ideal systems to re-examine some of the previously published results. Our results suggest that one of the most controversial findings reported recently is most likely an artifact arising from inhomogeneous dopant distribution. Lastly, we discuss low-temperature infrared absorption spectroscopy studies of p-type Ge:Ga,As samples as a function of the compensation ratio. The observed Ga impurity absorption peaks broaden linearly with the ionized impurity concentration due to the quadrupole interactions between Ga bound holes and the electric field gradients. Experimental linewidths are quantitatively compared to existing theories of electric field broadening. We find excellent agreement with the theory which is based on the correlated distribution of ionized impurity centers.

Itoh, Kohei

132

Effects of hole carrier injection and transport in organic light-emitting diodes  

SciTech Connect

In this paper, the authors examine the effects of hole carrier injection and mobility on both the electroluminescence (EL) quantum efficiency and the operating voltage of bilayer organic light-emitting diodes (OLED`s). They find that hole-injection is limited by the nature of the hole injecting interface and significantly affects the operating voltage, but not the quantum efficiency of the OLED. Hole mobility is found not to affect the device quantum efficiency. They demonstrate the characteristics of an ideal ohmic contact by measuring space-charge-limited currents in a trap-free hole transporting polymer layer.

Antoniadis, H.; Miller, J.N.; Roitman, D.B. [Hewlett-Packard Labs., Palo Alto, CA (United States)] [Hewlett-Packard Labs., Palo Alto, CA (United States); Campbell, I.H. [Los Alamos National Lab., NM (United States)] [Los Alamos National Lab., NM (United States)

1997-08-01

133

Novel macrocyclic carriers for proton-coupled liquid membrane transport  

SciTech Connect

The objective of our research program is to elucidate the chemical principles which are responsible for the cation selectivity and permeability of liquid membranes containing macrocyclic carriers. Several new macrocyclic carriers were synthesized during the last three year period, including selenium-containing macrocycles, new crown-4 structures, and several new crown structures containing nitrogen based heterocycles as substituents in the principal macrocyclic ring. The cation binding properties of these macrocycles were investigated by potentiometric titration, calorimetric titration, solvent extraction, and NMR techniques. In addition, hydrophobic macrocycles were incorporated into dual hollow fiber membrane systems to investigate their membrane performance, especially in the proton-coupled transport mode. It was found that the dual hollow fiber system maintains the cation selectivity and permeability of supported liquid membranes, while enhancing membrane stability. The diffusion limited transport model was expanded to account for membrane solvent effects. Furthermore, Eu{sup 2+} transport was found to be similar to that of strontium and much higher than that of the lanthanides, in supported liquid membrane systems.

Lamb, J.D.

1991-06-10

134

Determining the drift time of charge carriers in p-type point-contact HPGe detectors  

NASA Astrophysics Data System (ADS)

An algorithm to determine the drift time of charge carriers in p-type point contact (PPC) high-purity germanium (HPGe) detectors from the signals processed with a charge-sensitive preamplifier is introduced. It is demonstrated that the drift times can be used to estimate the distance of charge depositions from the point contact and to characterize losses due to charge trapping. A correction for charge trapping effects over a wide range of energies is implemented using the measured drift times and is shown to improve the energy resolution by up to 30%.

Martin, R. D.; Amman, M.; Chan, Y. D.; Detwiler, J. A.; Loach, J. C.; Looker, Q.; Luke, P. N.; Poon, A. W. P.; Qian, J.; Vetter, K.; Yaver, H.

2012-06-01

135

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

Federal Register 2010, 2011, 2012, 2013

...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...

2010-08-10

136

Transport in Charged Colloids Driven by Thermoelectricity  

E-print Network

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.

Alois Würger

2014-01-29

137

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

138

Coupling between local vibrations and charge transport in discotic materials  

NASA Astrophysics Data System (ADS)

Charge transport between molecular units is sensitive to coupling between thermal motion and the electronic structure of these units. The thermal motion of a short column of discotic molecules is simulated by a molecular dynamics simulation in order to provide the correct distribution of distorted molecular units, including the effects of the alkoxy tails. Ab initio calculations are then used to determine the electronic structure of the distorted triphenylene cores and the time dependence of the interaction between these. This goes beyond previous works that have calculated changes in charge transfer by finite displacement of rigid molecular units along translational and rotational coordinates. Two timescales and types of motion are distinguished: slow whole body motions of the disks, and internal vibrational modes of the aromatic cores. The effects of these motions are separated via their different timescales, and are found to be of equal importance in the interaction between the HOMOs of neighbouring molecules. Electron/phonon coupling from these small molecular distortions may be important not only for charge transport, but also for loss of carriers via relaxation of electronically excited states.

Kruglova, Olga; Mulder, Fokko M.; Siebbeles, Laurens D. A.; Kearley, Gordon J.

2006-11-01

139

41 CFR 301-72.1 - Why is common carrier presumed to be the most advantageous method of transportation?  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Why is common carrier presumed to be the most advantageous...RESPONSIBILITIES 72-AGENCY RESPONSIBILITIES RELATED TO COMMON CARRIER TRANSPORTATION Procurement of Common Carrier Transportation § 301-72.1...

2010-07-01

140

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

NASA Astrophysics Data System (ADS)

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.

Luo, Yan-Xiang; Shih, Chun-Hsing

2014-11-01

141

Charge carrier densities in chemically doped organic semiconductors verified by two independent techniques  

NASA Astrophysics Data System (ADS)

The charge carrier density of the p-type doped organic semiconductor 2,7-bis(9-carbazolyl)-9,9-spirobifluorene is determined for varied doping concentrations. As p-type dopant molybdenum trioxide is used. We determine the carrier density by measuring the polaron induced optical absorption and by a capacitance-voltage analysis. We show that both results are in excellent agreement. An almost linear dependence of the charge carrier density on the doping concentration is observed. Carrier densities on the order of 1018 cm-3 at a dopant concentration of 1 mol % can be achieved. Overall, a low doping efficiency on the order of 2%-4.5% is evidenced.

Lehnhardt, M.; Hamwi, S.; Hoping, M.; Reinker, J.; Riedl, T.; Kowalsky, W.

2010-05-01

142

Variational multiscale models for charge transport.  

PubMed

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

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

2012-01-01

143

Variational multiscale models for charge transport  

PubMed Central

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

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

2012-01-01

144

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

Code of Federal Regulations, 2013 CFR

...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,...

2013-07-01

145

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

Code of Federal Regulations, 2012 CFR

...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,...

2012-07-01

146

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

...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,...

2014-07-01

147

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

Code of Federal Regulations, 2010 CFR

...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...

2010-01-01

148

Two-dimensional charge transport in self-organized, high-mobility conjugated polymers  

Microsoft Academic Search

Self-organization in many solution-processed, semiconducting conjugated polymers results in complex microstructures, in which ordered microcrystalline domains are embedded in an amorphous matrix. This has important consequences for electrical properties of these materials: charge transport is usually limited by the most difficult hopping processes and is therefore dominated by the disordered matrix, resulting in low charge-carrier mobilities (<=10-5cm2V-1s-1). Here we use

H. Sirringhaus; P. J. Brown; R. H. Friend; M. M. Nielsen; K. Bechgaard; B. M. W. Langeveld-Voss; A. J. H. Spiering; R. A. J. Janssen; E. W. Meijer; PT Herwig; D. M. de Leeuw

1999-01-01

149

Charge Transport and Glassy Dynamics in Ionic Liquids  

SciTech Connect

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.

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

2012-01-01

150

Charge transport and glassy dynamics in ionic liquids.  

PubMed

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 Einstein-Smoluchowski 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. PMID:22082024

Sangoro, Joshua R; Kremer, Friedrich

2012-04-17

151

Phonon-driven carrier transport caused by short excitation pulses in semiconductors  

Microsoft Academic Search

We propose a simple model describing phonon-wind-driven transport of photoexcited carriers in bulk and in multiple-quantum-well (MQW) semiconductors. We take into account diffusion of carriers and primary acoustical phonons, generated at the final stage of the carrier's relaxation, and show that their simultaneous action gives fast (even supersonic at higher excitation intensities) transport of photoexcited carriers. The phonon retardation effects

A. E. Bulatov; S. G. Tikhodeev

1992-01-01

152

Electrical Transport of Spin Polarized Carriers in Disordered Ultrathin Films  

Microsoft Academic Search

Glass like behavior of electrical transport relaxation has been induced in quench-condensed ultrathin films of amorphous Bismuth by application of a parallel magnetic field. This effect is found in films well on the insulating side of the superconductor-insulator transition, and disappears as thickness is increased. We propose that this behavior is caused by space-charge-limited current flow, which is induced by

Anand Bhattacharya; Luis Hernandez; Kevin Parendo; Allen Goldman

2003-01-01

153

Dust Charging and Transport on Surfaces  

NASA Astrophysics Data System (ADS)

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.

Wang, X.; Robertson, S.; Horányi, M.

2011-11-01

154

Carriers  

MedlinePLUS

... has been caused by a single carrier. Carrier Testing A DNA test is the only way to ... races. Deciding whether or not to undergo genetic testing is highly personal, and we strongly recommend discussing ...

155

Tunable charge carriers and thermoelectricity of single-crystal Ba8Ga16Sn30  

Microsoft Academic Search

We have grown single crystals of the type-VIII intermetallic clathrate Ba8Ga16Sn30 from both Sn and Ga fluxes, evaluated their compositions through electron microprobe analysis and studied their transport properties through measurements on the temperature dependent resistivity, thermopower and Hall coefficient. Crystals grown in Sn flux show n-type carriers and those from Ga flux show p-type carriers, whereas all measured compositions

M. A. Avila; D. Huo; T. Sakata; K. Suekuni; T. Takabatake

2006-01-01

156

Recombination in liquid filled ionisation chambers with multiple charge carrier species: Theoretical and numerical results  

NASA Astrophysics Data System (ADS)

Liquid-filled ionisation chambers (LICs) are used in radiotherapy for dosimetry and quality assurance. Volume recombination can be quite important in LICs for moderate dose rates, causing non-linearities in the dose rate response of these detectors, and needs to be corrected for. This effect is usually described with Greening and Boag models for continuous and pulsed radiation respectively. Such models assume that the charge is carried by two different species, positive and negative ions, each of those species with a given mobility. However, LICs operating in non-ultrapure mode can contain different types of electronegative impurities with different mobilities, thus increasing the number of different charge carriers. If this is the case, Greening and Boag models can be no longer valid and need to be reformulated. In this work we present a theoretical and numerical study of volume recombination in parallel-plate LICs with multiple charge carrier species, extending Boag and Greening models. Results from a recent publication that reported three different mobilities in an isooctane-filled LIC have been used to study the effect of extra carrier species on recombination. We have found that in pulsed beams the inclusion of extra mobilities does not affect volume recombination much, a behaviour that was expected because Boag formula for charge collection efficiency does not depend on the mobilities of the charge carriers if the Debye relationship between mobilities and recombination constant holds. This is not the case in continuous radiation, where the presence of extra charge carrier species significantly affects the amount of volume recombination.

Aguiar, P.; González-Castaño, D. M.; Gómez, F.; Pardo-Montero, J.

2014-10-01

157

41 CFR 301-72.1 - Why is common carrier presumed to be the most advantageous method of transportation?  

...to be the most advantageous method of transportation? 301-72.1 Section 301-72...RESPONSIBILITIES RELATED TO COMMON CARRIER TRANSPORTATION Procurement of Common Carrier Transportation § 301-72.1 Why is common...

2014-07-01

158

Charge transport in holography with momentum dissipation  

NASA Astrophysics Data System (ADS)

In this work, we examine how charge is transported in a theory where momentum is relaxed by spatially dependent, massless scalars. We analyze the possible IR phases in terms of various scaling exponents and the (ir)relevance of operators in the IR effective holographic theory with a dilaton. We compute the (finite) resistivity and encounter broad families of (in)coherent metals and insulators, characterized by universal scaling behaviour. The optical conductivity at zero temperature and low frequencies exhibits power tails which can violate scaling symmetries, due to the running of the dilaton. At low temperatures, our model captures features of random-field disorder.

Goutéraux, B.

2014-04-01

159

Charge carrier dynamics in thiol capped CdTe quantum dots.  

PubMed

We report the ultrafast charge carrier relaxation dynamics of mercaptopropionic acid capped CdTe quantum dot (QD) using femtosecond transient absorption spectroscopy by exciting the particles with 400 nm laser light and monitoring the transients in the visible to near IR region. Cooling dynamics and population dynamics in different quantized states of the charge carriers were monitored by following the growth kinetics of the bleach at different excitonic positions. The cooling time second and first excitonic states were found to be 150 fs and 500 fs, respectively, which increases non-linearly with its size. Defect states of QD surface play an important role in the cooling dynamics of the charge carriers. Quenching studies have been carried out to find out cooling and trapping dynamics of the individual charge carriers. Electron and hole cooling time were measured to be 700 fs and 150 fs for the first excitonic state using quenchers. Trapping dynamics of electron and hole have been determined by monitoring transient signal at 1000 nm and by using hole and electron quencher, respectively. Electron and hole trapping times have been found to be 700 fs and 1 ps, respectively, in CdTe QD. PMID:20379514

Kaniyankandy, Sreejith; Rawalekar, Sachin; Verma, Sandeep; Palit, Dipak K; Ghosh, Hirendra N

2010-04-28

160

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

E-print Network

Localized Excited Charge Carriers Generate Ultrafast Inhomogeneous Strain in the Multiferroic Bi to monitor the lattice dynamics in a thin film of multiferroic BiFeO3 after above-band-gap photoexcitation.05.cp, 77.22.Ej, 78.47.J- Multiferroics have a great potential for application due to their possible

Evans, Paul G.

161

Local environment effects on a charge carrier injected into an Ising chain  

NASA Astrophysics Data System (ADS)

We present numerically exact results for the spectral function of a single charge carrier that is injected into an Ising chain at finite temperature T. Both ferromagnetic and antiferromagnetic coupling between the Ising spins are considered. The interaction between the carrier and the Ising spins is assumed to be on-site and of Ising type, as well. We find that the carrier's spectral function exhibits a distinctive fine structure of resonances that are due to the temporary entrapping of the carrier inside small magnetic domains. The connection to models of disordered binary alloys where similar effects can occur is explained. We use these results to construct an accurate (quasi)analytic approximation for low and medium-T spectral functions.

Möller, Mirko; Berciu, Mona

2014-08-01

162

Trap-Related Carrier Transports in p-Channel Field-Effect Transistor with Polycrystalline Si/HSiON Gate Stack  

NASA Astrophysics Data System (ADS)

A microscopic investigation of gate leakage behaviors in metal-oxide-semiconductor field-effect transistors (MOSFETs) with polycrystalline Si/HfSiON high-k gate stacks was carried out by an electron-beam-induced current (EBIC) technique. The transport mechanisms of electrons and holes in nonbreakdown MOSFETs were clarified. Carrier separated measurement revealed that hole transport in pFETs is significantly enhanced by charged traps, while electron transport in nFETs appears to be independent of such traps. A detailed investigation on the trap-related carrier transport in pFETs was carried out employing EBIC observations and gate bias and acceleration voltage dependences.

Chen, Jun; Sekiguchi, Takashi; Fukata, Naoki; Takase, Masami; Hasunuma, Ryu; Yamabe, Kikuo; Sato, Motoyuki; Nara, Yasuo; Yamada, Keisaku; Chikyo, Toyohiro

2009-04-01

163

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

SciTech Connect

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.

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

164

Charge Transport Anisotropy in n-Type Disk-Shaped Triphenylene-Tris(aroyleneimidazole)s  

NASA Astrophysics Data System (ADS)

Two novel n-type disk-shaped molecules containing a triphenylene core and three fused naphthaleneimide imidazole or peryleneimide imidazole ``arms'' are synthesized and characterized. Their optical and electronic properties are consistent with the pi-extended structural feature of the aromatic cores. The n-type charge carrier mobilities of these molecules are evaluated by both field effect transistors and space-charge limited-current measurements, which show drastically different mobility anisotropy. A strong correlation between film morphology and the charge transport behavior is established by X-ray scattering and atomic force microscopic analyses.

Alvarez, Steven; Zhang, Yue; Hanifi, David; Antonio, Francisco; Pun, Andrew; Klivansky, Liana; Hexemer, Alexander; Ma, Biwu; Liu, Yi

2012-02-01

165

49 CFR 375.705 - If a shipment is transported on more than one vehicle, what charges may I collect at delivery?  

Code of Federal Regulations, 2010 CFR

...vehicle, what charges may I collect at delivery? 375.705 Section 375.705...Transportation (Continued) FEDERAL MOTOR CARRIER SAFETY ADMINISTRATION, DEPARTMENT...CONSUMER PROTECTION REGULATIONS Delivery of Shipments § 375.705...

2010-10-01

166

The Kondo effect and carrier transport in amorphous Cr-doped In2O3 thin films  

NASA Astrophysics Data System (ADS)

Understanding the interaction between spin of the charge carriers and local magnetic moments in diluted magnetic oxide is an important issue for applications in spintronic devices. This study examines amorphous Cr-doped In2O3 diluted magnetic oxide thin films for the existence of the Kondo effect and a general s-d scattering effect on the magneto transport, as well as for the well known 3D weak localization effect that explains the low temperature transport behavior of transparent conducting oxides. The carrier transport behavior at low temperature can be accurately described and well fit by a combination of these effects. At temperatures lower than the minimum resistivity temperature, the Kondo effect dominates the magnetoresistance effect and is responsible for the enhancement of resistivity.

Lin, C. P.; Hsu, C. Y.; Sun, S. J.; Chou, H.

2012-12-01

167

Carrier Transport and Related Effects in Detectors of the Cryogenic Dark Matter Kyle Michael Sundqvist  

E-print Network

Carrier Transport and Related Effects in Detectors of the Cryogenic Dark Matter Search by Kyle Effects in Detectors of the Cryogenic Dark Matter Search Copyright 2012 by Kyle Michael Sundqvist #12;1 Abstract Carrier Transport and Related Effects in Detectors of the Cryogenic Dark Matter Search by Kyle

California at Berkeley, University of

168

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

DOEpatents

An ionization detector electrode and signal subtraction apparatus and method provides 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.

Luke, Paul (Castro Valley, CA)

1996-01-01

169

Structures of yeast mitochondrial ADP/ATP carriers support a domain-based alternating-access transport mechanism  

PubMed Central

The mitochondrial ADP/ATP carrier imports ADP from the cytosol and exports ATP from the mitochondrial matrix. The carrier cycles by an unresolved mechanism between the cytoplasmic state, in which the carrier accepts ADP from the cytoplasm, and the matrix state, in which it accepts ATP from the mitochondrial matrix. Here we present the structures of the yeast ADP/ATP carriers Aac2p and Aac3p in the cytoplasmic state. The carriers have three domains and are closed at the matrix side by three interdomain salt-bridge interactions, one of which is braced by a glutamine residue. Glutamine braces are conserved in mitochondrial carriers and contribute to an energy barrier, preventing the conversion to the matrix state unless substrate binding occurs. At the cytoplasmic side a second salt-bridge network forms during the transport cycle, as demonstrated by functional analysis of mutants with charge-reversed networks. Analyses of the domain structures and properties of the interdomain interfaces indicate that interconversion between states involves movement of the even-numbered ?-helices across the surfaces of the odd-numbered ?-helices by rotation of the domains. The odd-numbered ?-helices have an L-shape, with proline or serine residues at the kinks, which functions as a lever-arm, coupling the substrate-induced disruption of the matrix network to the formation of the cytoplasmic network. The simultaneous movement of three domains around a central translocation pathway constitutes a unique mechanism among transport proteins. These findings provide a structural description of transport by mitochondrial carrier proteins, consistent with an alternating-access mechanism. PMID:24474793

Ruprecht, Jonathan J.; Hellawell, Alex M.; Harding, Marilyn; Crichton, Paul G.; McCoy, Airlie J.; Kunji, Edmund R. S.

2014-01-01

170

Structures of yeast mitochondrial ADP/ATP carriers support a domain-based alternating-access transport mechanism.  

PubMed

The mitochondrial ADP/ATP carrier imports ADP from the cytosol and exports ATP from the mitochondrial matrix. The carrier cycles by an unresolved mechanism between the cytoplasmic state, in which the carrier accepts ADP from the cytoplasm, and the matrix state, in which it accepts ATP from the mitochondrial matrix. Here we present the structures of the yeast ADP/ATP carriers Aac2p and Aac3p in the cytoplasmic state. The carriers have three domains and are closed at the matrix side by three interdomain salt-bridge interactions, one of which is braced by a glutamine residue. Glutamine braces are conserved in mitochondrial carriers and contribute to an energy barrier, preventing the conversion to the matrix state unless substrate binding occurs. At the cytoplasmic side a second salt-bridge network forms during the transport cycle, as demonstrated by functional analysis of mutants with charge-reversed networks. Analyses of the domain structures and properties of the interdomain interfaces indicate that interconversion between states involves movement of the even-numbered ?-helices across the surfaces of the odd-numbered ?-helices by rotation of the domains. The odd-numbered ?-helices have an L-shape, with proline or serine residues at the kinks, which functions as a lever-arm, coupling the substrate-induced disruption of the matrix network to the formation of the cytoplasmic network. The simultaneous movement of three domains around a central translocation pathway constitutes a unique mechanism among transport proteins. These findings provide a structural description of transport by mitochondrial carrier proteins, consistent with an alternating-access mechanism. PMID:24474793

Ruprecht, Jonathan J; Hellawell, Alex M; Harding, Marilyn; Crichton, Paul G; McCoy, Airlie J; Kunji, Edmund R S

2014-01-28

171

Far-infrared response of free charge carriers localized in semiconductor nanoparticles  

NASA Astrophysics Data System (ADS)

A Monte Carlo method is employed to calculate the dynamical conductivity in the terahertz range of free charge carriers localized in semiconductor nanoparticles. The shape of the conductivity spectrum is essentially determined by the probability of carrier transition through interparticle boundaries and by the ratio of the nanoparticle size and carrier mean free path in the bulk. It is shown that the conductivity spectrum exhibits similar features as the classical extension of the Drude conductivity of electrons proposed by Smith [Phys. Rev. B 64, 155106 (2001)]. We find and discuss the link of this model to the results of our simulations which suggests an interpretation of the phenomenological parameters of the Drude-Smith model.

N?mec, Hynek; Kužel, Petr; Sundström, Villy

2009-03-01

172

Charge Carrier Dynamics of Quantum Confined Semiconductor Nanoparticles Analyzed via Transient Absorption Spectroscopy  

NASA Astrophysics Data System (ADS)

Semiconductor nanoparticles are tiny crystalline structures (typically range from 1 - 100 nm) whose shape in many cases can be dictated through tailored chemical synthesis with atomic scale precision. The small size of these nanoparticles often results in quantum confinement (spatial confinement of wave functions), which imparts the ability to manipulate band-gap energies thus allowing them to be optimally engineered for different applications (i.e., photovoltaics, photocatalysis, imaging). However, charge carriers excited within these nanoparticles are often involved in many different processes: trapping, trap migration, Auger recombination, non-radiative relaxation, radiative relaxation, oxidation / reduction, or multiple exciton generation. Broadband ultrafast transient absorption laser spectroscopy is used to spectrally resolve the fate of excited charge carriers in both wavelength and time, providing insight as to what synthetic developments or operating conditions will be necessary to optimize their efficiency for certain applications. This thesis outlines the effort of resolving the dynamics of excited charge carriers for several Cd and Si based nanoparticle systems using this experimental technique. The thesis is organized into five chapters and two appendices as indicated below. Chapter 1 provides a brief introduction to the photophysics of semiconductor nanoparticles. It begins by defining what nanoparticles, semiconductors, charge carriers, and quantum confinement are. From there it details how the study of charge carrier dynamics within nanoparticles can lead to increased efficiency in applications such as photocatalysis. Finally, the experimental methodology associated with ultrafast transient absorption spectroscopy is introduced and its power in mapping charge carrier dynamics is established. Chapter 2 (JPCC, 19647, 2011) introduces the first of the studied samples: water-solubilized 2D CdSe nanoribbons (NRs), which were synthesized in the Osterloh laboratory (UCD). The measured signals were decomposed into the constituent dynamics of three transient populations: hot tightly bound excitons, relaxed tightly bound excitons, and separated trapped carriers (holes and electrons). The influenes of three external factors affecting the observed dynamics were explored: (1) excitation wavelength, (2) excitation fluence, and (3) presence of the hole scavenger HS -. Both higher-energy excitation photons and higher-intensity excitation induce slower relaxation of charge carriers to the band edge due to the need to dissipate excess excitation energy. Nonlinear decay kinetics of the relaxed exciton population is observed and demonstrated to arise from bimolecular trapping of excitons with low-density trap sites located at CdSe NR surface sites instead of the commonly resolved multiparticle Auger recombination mechanism. This is supported by the observed linear excitation-fluence dependence of the trapped-carrier population that is n umerically simulated and found to deviate from the excitation fluence dependence expected of Auger recombination kinetics. Introducing hole scavenging HS- has a negligible effect on the exciton kinetics, including migration and dissociation, and instead passivates surface trap states to induce the rapid elimination of holes after exciton dissociation. This increases the lifetime of the reactive electron population and increases measured photocatalytic H2 generation activity. A broad (200 nm) and persistent (20 ps) stimulated emission observed in the tightly bound excitons suggests their potential use as broadband microlasers. In chapter 3 (JPCL, 2688, 2011), the photocatalytic H2O splitting activities of CdSe and CdSe/CdS core/shell quantum dots, which were also synthesized in the Osterloh laboratory (UCD) are contrasted. CdSe/CdS core/shell quantum dots constructed from 4.0 nm CdSe quantum dots are shown to be strongly active for visible-light-driven photocatalytic H2 evolution in 0.1M Na 2S/Na2SO3 solution with a turnover number of 9.94 after 5 h at 103.9 ?mol/h. CdSe quantum dots themselv

Thibert, Arthur Joseph, III

173

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

PubMed Central

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

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

2013-01-01

174

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

...false How are the charges calculated when a carrier charges a minimum weight, but the actual weight of HHG, PBP&E and temporary storage is less than the minimum weight charged? 302-7.103 Section 302-7.103 Public Contracts...

2014-07-01

175

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

...false How are the charges calculated when a carrier charges a minimum weight, but the actual weight of HHG, PBP&E and temporary storage is less than the minimum weight charged? 302-7.103 Section 302-7.103 Public Contracts...

2012-07-01

176

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, 2011 CFR

...false How are the charges calculated when a carrier charges a minimum weight, but the actual weight of HHG, PBP&E and temporary storage is less than the minimum weight charged? 302-7.103 Section 302-7.103 Public Contracts...

2011-07-01

177

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

... true How are the charges calculated when a carrier charges a minimum weight, but the actual weight of HHG, PBP&E and temporary storage is less than the minimum weight charged? 302-7.103 Section 302-7.103 Public Contracts...

2013-07-01

178

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

SciTech Connect

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.

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

179

Charge carrier mobility in organic molecular materials probed by electromagnetic waves.  

PubMed

Charge carrier mobility is an essential parameter providing control over the performance of semiconductor devices fabricated using a variety of organic molecular materials. Recent design strategies toward molecular materials have been directed at the substitution of amorphous silicon-based semiconductors; accordingly, numerous measurement techniques have been designed and developed to probe the electronic conducting nature of organic materials bearing extremely wide structural variations in comparison with inorganic and/or metal-oxide semiconductor materials. The present perspective highlights the evaluation methodologies of charge carrier mobility in organic materials, as well as the merits and demerits of techniques examining the feasibility of organic molecules, crystals, and supramolecular assemblies in semiconductor applications. Beyond the simple substitution of amorphous silicon, we have attempted to address in this perspective the systematic use of measurement techniques for future development of organic molecular semiconductors. PMID:24776977

Seki, Shu; Saeki, Akinori; Sakurai, Tsuneaki; Sakamaki, Daisuke

2014-06-21

180

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

E-print Network

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 ...

Difley, Seth

2010-01-01

181

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

PubMed

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

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

2013-02-27

182

Dynamic charge-carrier-mobility-mediated holography in thin layers of photoconducting polymers  

NASA Astrophysics Data System (ADS)

The dynamic holography technique is proposed for the measurement of the charge-carrier-mobility in thin layers of a photoconducting polymer, used in optically addressed liquid-crystal spatial light modulators. The photorefractive properties of these modulators are studied under short-pulse (20 ps, 532 nm) laser illumination conditions and the charge mobility in the photoconducting polymer (muh=10-7 cm2/V s) is obtained from the temporal evolution of intensity of the first-order diffracted beam. A mechanism responsible for the grating formation is proposed and discussed.

Bartkiewicz, S.; Miniewicz, A.; Sahraoui, B.; Kajzar, F.

2002-11-01

183

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

SciTech Connect

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.

Vukmirovic, Nenad; Wang, Lin-Wang

2009-11-10

184

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

PubMed

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

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

2014-08-01

185

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

Code of Federal Regulations, 2010 CFR

... 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...

2010-07-01

186

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

Code of Federal Regulations, 2012 CFR

... 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...

2012-07-01

187

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

Code of Federal Regulations, 2013 CFR

...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...

2013-07-01

188

Ambipolar blends of CuPc and C60: charge carrier mobility, electronic structure and its implications for solar cell applications  

E-print Network

Ambipolar transport has been realised in blends of the molecular hole conductor Cu-phthalocyanine (CuPc) and the electron conducting fullerene C60. Charge carrier mobilities and the occupied electronic levels have been analyzed as a function of the mixing ratio using field-effect transistor measurements and photoelectron spectroscopy. These results are discussed in the context of photovoltaic cells based on these materials.

W. Bruetting; M. Bronner; M. Goetzenbrugger; A. Opitz

2007-09-25

189

Polymer/Polymer Heterojunctions for Ambipolar Charge Transport in Organic Electronics  

NASA Astrophysics Data System (ADS)

Understanding of charge transport in polymer semiconductor heterojunctions is of basic interest in developing high-performance organic optoelectronic devices based on multicomponent polymer semiconductors. We report ambipolar charge transport in thin films of layered heterojunctions and bulk heterojunctions of solution-processable unipolar polymer semiconductors. Selective solubility of the polymer semiconductors, poly(thiazolothiazole)s and ladder-type poly(benzobisimidazo-benzophenanthroline), in organic and acidic solvents enabled the sequential deposition or blending of the polymer semiconductors. Charge carrier mobilities of 0.001-0.01 cm2/Vs were observed for both electrons and holes in the polymer/polymer heterojunction field-effect transistors. Thin film deposition and processing with various solvents are effective to improve charge-carrier mobilities by a factor of 100-1000. We have investigated the effects of the processing methods on morphology, and photophysical and charge transport properties of the polymer semiconductor heterojunctions. Integrated circuits and solar cells based on the polymer semiconductor heterojunctions are also demonstrated.

Kim, Felix; Subramaniyan, Selvam; Jenekhe, Samson

2011-03-01

190

Charge-carrier transport in amorphous organic semiconductors  

E-print Network

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 ...

Limketkai, Benjie, 1982-

2008-01-01

191

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

E-print Network

, 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-complementary organic field- effect transistors and organic photovoltaic cells. Many inves- tigations in the latter

Schreiber, Frank

192

Overall current-voltage characteristics of space charge controlled currents for thin films by a single carrier species  

NASA Astrophysics Data System (ADS)

The Mott-Gurney equation (Child's law) has been frequently applied to measure the mobility of carrier transport layers. One of the main assumption in the Mott-Gurney theory is ignoring the diffusive currents. It was not obvious, however, whether the diffusive currents can be ignored for thin carrier transport layers. We obtained the current-voltage relation using analytical solutions of drift-diffusion equation coupled with the Poisson's equation. The integration constants were numerically determined using nonlinear equations obtained from boundary conditions. A simple analytical relation between the voltage and current was also derived. The analytical equation improved over the Mott-Gurney equation when the voltage is between 0.1 and 2 (V) at room temperature. By using published data, we show that both the mobility and the layer thickness can be simultaneously obtained by applying the analytical expression. The effect of diffusion on the current-voltage relation is explained by the movement of the virtual electrode formed by space charge accumulation.

Seki, Kazuhiko

2014-08-01

193

41 CFR 301-72.2 - May we utilize methods of transportation other than common carrier (e.g., POVs, chartered...  

... false May we utilize methods of transportation other than common carrier (e.g...RESPONSIBILITIES RELATED TO COMMON CARRIER TRANSPORTATION Procurement of Common Carrier Transportation § 301-72.2 May we utilize...

2014-07-01

194

41 CFR 301-72.2 - May we utilize methods of transportation other than common carrier (e.g., POVs, chartered...  

Code of Federal Regulations, 2010 CFR

...utilize methods of transportation other than common carrier (e.g., POVs, chartered vehicles...RESPONSIBILITIES 72-AGENCY RESPONSIBILITIES RELATED TO COMMON CARRIER TRANSPORTATION Procurement of Common Carrier Transportation § 301-72.2...

2010-07-01

195

41 CFR 301-51.100 - What method of payment must I use to procure common carrier transportation?  

...must I use to procure common carrier transportation? 301-51.100 Section 301-51...EXPENSES Paying for Common Carrier Transportation § 301-51.100 What method...must I use to procure common carrier transportation? You must use a Government...

2014-07-01

196

Brownian dynamics determine universality of charge transport in ionic liquids  

SciTech Connect

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.

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

197

Nature and the Sign of Stress-Activated Electronic Charge Carriers in Rocks  

NASA Astrophysics Data System (ADS)

When rocks are subjected to increasing uniaxial stress, highly mobile charge carriers become activated, which have the remarkable ability to flow out of the stressed rock volume, spreading into and through adjacent less stressed or unstressed rocks. Two basic questions arise: (i) What is the nature - and the sign - of these charge carriers and (ii) How do they exist in the rocks before being activated by stress? A large body of evidence is available that points to a positive sign, consistent with defect electrons, which (in semiconductor parlance) are called 'holes'. Holes that reside in the oxygen anion sublattice, associated with O 2sp-type energy states at the upper edge of the valence band, are called 'positive holes'. The positive holes exist in rocks in form of dormant, electrically inactive peroxy defects. Ever so slight deformation, leading to grain-grain sliding, can break the peroxy bonds and activate positive holes. Electrons that are co-activated by the same process cannot flow out of the stressed rock volume into the unstressed rocks. This leads to charge separation and, hence, to a potential difference similar to a battery voltage. In order to experimentally confirm the positive sign of the positive hole charge carriers flowing out of a given stressed rock volume, certain rules have to be obeyed. If not, unreliable results may be obtained, even negative outflow currents, seemingly inconsistent with the postulated positive sign of the positive hole charge carriers. Such errors can be avoided by taking into account that the charge outflow occurs in response to a 'battery potential', V, rapidly evolving between stressed and unstressed or less stressed parts of the rock. The current I given by Ohm's Law, I=V/R, is then limited by the internal resistance R. A second complicating factor arises from the fact that, as the positive holes are stress-activated and begin to flow out, they simultaneously recombine, returning to the dormant state. The ensuing variations in the potential and outflow current can lead to misinterpretations. Hence, the study of stress-activated outflow currents has to be approached with proper understanding of the underlying physical principle.

Freund, F.

2013-12-01

198

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

NASA Astrophysics Data System (ADS)

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.

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

2009-12-01

199

DNA charge transport over 34 nm  

NASA Astrophysics Data System (ADS)

Molecular wires show promise in nanoscale electronics, but the synthesis of uniform, long conductive molecules is a significant challenge. Deoxyribonucleic acid (DNA) of precise length, by contrast, is synthesized easily, but its conductivity over the distances required for nanoscale devices has not been explored. Here we demonstrate DNA charge transport (CT) over 34 nm in 100-mer monolayers on gold. Multiplexed gold electrodes modified with 100-mer DNA yield sizable electrochemical signals from a distal, covalent Nile Blue redox probe. Significant signal attenuation upon incorporation of a single base-pair mismatch demonstrates that CT is DNA-mediated. Efficient cleavage of these 100-mers by a restriction enzyme indicates that the DNA adopts a native conformation accessible to protein binding. Similar electron-transfer rates measured through 100-mer and 17-mer monolayers are consistent with rate-limiting electron tunnelling through the saturated carbon linker. This DNA-mediated CT distance of 34 nm surpasses that of most reports of molecular wires.

Slinker, Jason D.; Muren, Natalie B.; Renfrew, Sara E.; Barton, Jacqueline K.

2011-03-01

200

Charge transport in single photochromic molecular junctions  

NASA Astrophysics Data System (ADS)

Recently, photoswitchable molecules, i.e. diarylethene, gained significant interest due to their applicability in data storage media, as optical switches, and in novel logic circuits [1]. Diarylethene-derivative molecules are the most promising candidates to design electronic functional elements, because of their excellent thermal stability, high fatigue resistance, and negligible change upon switching [1]. Here, we present the preferential conductance of specifically designed sulfur-free diarylethene molecules [2] bridging the mechanically controlled break-junctions at low temperatures [3]. The molecular energy levels and electrode couplings are obtained by evaluating the current-voltage characteristics using the single-level model [4]. The charge transport mechanism of different types of diarylethene molecules is investigated, and the results are discussed within the framework of novel theoretical predictions. [4pt] [1] M. Del Valle etal., Nat Nanotechnol 2, 176 (2007) S. J. van der Molen etal., Nano. Lett. 9, 76 (2009).[0pt] [2] D. Sysoiev etal., Chem. Eur. J. 17, 6663 (2011).[0pt] [3] Y. Kim etal., Phys. Rev. Lett. 106, 196804 (2011).[0pt] [4] Y. Kim etal., Nano Lett. 11, 3734 (2011). L. Zotti etal., Small 6, 1529 (2010).

Kim, Youngsang; Pietsch, T.; Scheer, Elke; Hellmuth, T.; Pauly, F.; Sysoiev, D.; Huhn, T.; Exner, T.; Groth, U.; Steiner, U.; Erbe, A.

2012-02-01

201

Defect states and disorder in charge transport in semiconductor nanowires  

NASA Astrophysics Data System (ADS)

We present a comprehensive investigation into disorder-mediated charge transport in InP nanowires in the statistical doping regime. At zero gate voltage, transport is well described by the space charge limited current model and hopping transport, but positive gate voltage (electron accumulation) reveals a previously unexplored regime of nanowire charge transport that is not well described by existing theory. The ability to continuously tune between these regimes provides guidance for the extension of existing models and directly informs the design of next-generation nanoscale electronic devices.

Ko, Dongkyun; Zhao, X. W.; Reddy, Kongara M.; Restrepo, O. D.; Mishra, R.; Lemberger, T. R.; Beloborodov, I. S.; Trivedi, Nandini; Padture, Nitin P.; Windl, W.; Yang, F. Y.; Johnston-Halperin, E.

2013-07-01

202

Measurement of Minority Charge Carrier Diffusion Length in Gallium Nitride Nanowires Using Electron Beam Induced Current (EBIC).  

National Technical Information Service (NTIS)

Electron Beam Induced Current (EBIC) measurements were performed on GaN nanowires to determine minority charge carrier diffusion length, Ld. Although EBIC has been used to characterize bulk and thin film materials, very little is known about near contact ...

C. P. Ong

2009-01-01

203

Measurement of charge-carrier concentration in indium phosphide by means of an electrolyte-semiconductor contact  

SciTech Connect

An electrolyte-semiconductor contact is used to study the conductivity of epitaxial layers and single crystals of n-type indium phosphide obtained by gas transport. Some of the specimens were alloyed with tin and sulfur. The volt-farad characteristics are used to find the potentials of planar zones, which amount to 0.8-1.3 V for different electrolytes. Values of concentration of charge carriers calculated from measured values of capacitance of the electrolyte-indium-phosphide contact showed good agreement with measurements of the Hall effect on single crystals in the range 10/sup 16/-10/sup 18/ cm/sup -3/. The use of measurements of the capacitance of the electrolyte-semiconductor contact with simultaneous etching of a local region made it possible to study the electron distribution in epitaxial layers of indium phosphide.

Asanov, O.M.; Gaman, V.I.; Zorkal'tseva, N.N.; Korableva, T.V.; Petrova, N.G.

1987-11-01

204

User charges in international air transportation  

E-print Network

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 ...

Seagrave, Norman P.

1979-01-01

205

Hot Carrier Transport and Photocurrent Response in Graphene  

E-print Network

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 ...

Song, Justin Chien Wen

206

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

Code of Federal Regulations, 2011 CFR

...Aeronautics and Space OFFICE OF THE SECRETARY, DEPARTMENT OF TRANSPORTATION (AVIATION PROCEEDINGS) ECONOMIC REGULATIONS AIRLINE SERVICE QUALITY PERFORMANCE REPORTS § 234.13 Reports by air carriers on incidents involving animals during air...

2011-01-01

207

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

Code of Federal Regulations, 2012 CFR

...Aeronautics and Space OFFICE OF THE SECRETARY, DEPARTMENT OF TRANSPORTATION (AVIATION PROCEEDINGS) ECONOMIC REGULATIONS AIRLINE SERVICE QUALITY PERFORMANCE REPORTS § 234.13 Reports by air carriers on incidents involving animals during air...

2012-01-01

208

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

Code of Federal Regulations, 2013 CFR

...Aeronautics and Space OFFICE OF THE SECRETARY, DEPARTMENT OF TRANSPORTATION (AVIATION PROCEEDINGS) ECONOMIC REGULATIONS AIRLINE SERVICE QUALITY PERFORMANCE REPORTS § 234.13 Reports by air carriers on incidents involving animals during air...

2013-01-01

209

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

...Aeronautics and Space OFFICE OF THE SECRETARY, DEPARTMENT OF TRANSPORTATION (AVIATION PROCEEDINGS) ECONOMIC REGULATIONS AIRLINE SERVICE QUALITY PERFORMANCE REPORTS § 234.13 Reports by air carriers on incidents involving animals during air...

2014-01-01

210

Electron transport and charge induction in cadmium zinc telluride detectors with space charge build up under intense x-ray irradiation  

SciTech Connect

Under intense x-ray irradiation, wide band gap semiconductor radiation detectors fabricated from crystals with low hole transport properties develop a steady-state space charge distribution that results from a dynamic equilibrium between charge carrier dynamics and the incident photon field. At a high enough x-ray flux, this space charge can collapse the electric field within the detector, resulting in the paralyzation of photon counting (i.e., high-flux polarization). However, well before polarization causes a catastrophic device failure, there can be enough space charge present to significantly modify the electric field. A modified field affects the electron transport and, therefore, signal generation within the sensor, which can ultimately degrade the performance of high-rate photon counting electronics. In this study, we analytically solve the fundamental equation of charge conservation to derive the modified electron transport in the presence of an exponential space charge distribution that results from the incident x-rays. We use these space-time solutions to calculate and study the time dependence of the resulting charge-induced signals. The predicted induced signals are compared throughout with numerical solutions of the full charge transport equation. In addition, we present analogous closed-form signals for a uniform distribution relevant to a broader class of {gamma}-ray applications. Finally, we use these solutions to derive a two-parameter family of modified Hecht curves that naturally predict a voltage offset that appears due to the space charge.

Bale, Derek S.; Szeles, Csaba [eV Microelectronics, a division of Endicott Interconnect Technologies Inc., Saxonburg, Pennsylvania 16056 (United States)

2010-06-15

211

Functional interactions between arginine-133 and aspartate-88 in the human reduced folate carrier: evidence for a charge-pair association.  

PubMed Central

The human reduced folate carrier (hRFC) is an integral membrane protein that mediates cellular uptake of reduced folates and antifolates. hRFC contains several highly conserved charged residues predicted to lie in the transmembrane domains (TMDs). To explore the possible roles of the conserved arginine-133, located in TMD 4, in hRFC structure and function, this residue was systematically mutagenized to histidine, leucine, lysine and glutamate. When transfected into transport-impaired K562 cells, the mutant hRFC constructs were expressed at high levels; however, only lysine-133 hRFC was able to transport methotrexate and (6S)-5-formyl tetrahydrofolate. Substitution of aspartate-453 (in hRFC TMD 12) by valine largely preserved transport activity for both substrates. Although mutagenesis of aspartate-88 (in TMD 2) to leucine completely abolished transport activity in transfected cells, substitution with a glutamate preserved low levels ( approximately 12%) of transport. To assess the possibility that arginine-133 and aspartate-88 may form a charge-pair to stabilize hRFC tertiary structure, both charges were neutralized (by substituting leucine and valine, respectively) in the same construct. In contrast to the singly mutated hRFCs, the double mutant exhibited high levels of transport with both methotrexate and 5-formyl tetrahydrofolate. These results strongly suggest that arginine-133 and aspartate-88 form a charge-pair and that TMD 4 lies next to TMD 2 in the hRFC tertiary structure. PMID:11513752

Liu, X Y; Matherly, L H

2001-01-01

212

Basal localization of the presumptive auxin transport carrier in pea stem cells.  

PubMed

By means of an indirect immunofluorescence technique with the use of monoclonal antibodies, the location of the presumptive auxin transport carrier of pea stem tissue was identified in the plasma membranes at the basal ends of parenchyma cells sheathing the vascular bundles. The results represent what is believed to be the first direct evidence for the hypothesized basal efflux carrier conferring polarity to auxin transport in plant stems. PMID:17769371

Jacobs, M; Gilbert, S F

1983-06-17

213

Transport behaviors of photo-carriers across the aligned carbon nanotubes and silicon interface.  

PubMed

Transport of photo-carriers across the aligned carbon nanotubes and silicon (CNT/Si) interface determines cell performance. It is revealed that S-shaped current-voltage characters are generated due to the mismatch between the generation and transportation of photo-carriers, which can be eliminated by tuning the light intensity and CNT coverage on the Si surface, with the power conversion efficiency enhanced up to 121%. PMID:25178095

Li, Ru; Li, Hongfang; Zou, Jingyun; Zhang, Xiaohua; Li, Qingwen

2014-10-21

214

Temperature dependent investigation of carrier transport, injection, and densities in 808 nm AlGaAs multi-quantum-well active layers for VCSELs  

NASA Astrophysics Data System (ADS)

The electro-optical efficiency of semiconductor vertical-cavity surface-emitting lasers (VCSELs) strongly depends on the efficient carrier injection into the quantum wells (QWs) in the laser active region. However, carrier injection degrades with increasing temperature which limits the VCSEL performance particularly in high power applications where self heating imposes high temperatures in operation. By simulation we investigate the transport of charge carriers in 808 nm AlGaAs multi-quantum-well active layers with special attention to the temperature dependence of carrier injection into the QWs. Experimental reference data was extracted from oxide-confined, top-emitting VCSELs. The transport simulations follow a drift-diffusion-model complemented by a customized, energy-resolved, semi-classical carrier capture theory. QW gain was calculated in the screened Hartree-Fock approximation with band structures from 8x8 k.p-theory. Using the gain data and by setting losses and the optical confinement factor according to experimental reference results, the appropriate threshold condition and threshold carrier densities in the QWs for a VCSEL are established in simulation for all transport considerations. With the combination of gain and transport model, we can explain experimental reference data for the injection efficiency and threshold current density. Our simulations show that the decreasing injection efficiency with temperature is not solely due to increased thermionic escape of carriers from the QWs. Carrier injection is also hampered by state filling in the QWs initiated from higher threshold carrier densities with temperature. Consequently, VCSEL properties not directly related to the active layer design like optical out-coupling or internal losses link the temperature dependent carrier injection to VCSEL mirror design.

Engelhardt, Andreas P.; Kolb, Johanna S.; Römer, Friedhard; Weichmann, Ulrich; Moench, Holger; Witzigmann, Bernd

2014-05-01

215

Selective Monosaccharide Transport through Lipid Bilayers Using Boronic Acid Carriers  

E-print Network

boronate, which is the major complexed structure in bulk, aqueous solution. At the bilayer surface and sucrose were not transported to any significant degree. Facilitated transport was demonstrated at present about the molecular mechanism of glucose transport or the transport of any solute across

Smith, Bradley D.

216

Ultrafast Charge Carrier Recombination and Trapping in Hematite Photoanodes under Applied Bias  

PubMed Central

Transient absorption spectroscopy on subpicosecond to second time scales is used to investigate photogenerated charge carrier recombination in Si-doped nanostructured hematite (?-Fe2O3) photoanodes as a function of applied bias. For unbiased hematite, this recombination exhibits a 50% decay time of ?6 ps, ?103 times faster than that of TiO2 under comparable conditions. Anodic bias significantly retards hematite recombination dynamics, and causes the appearance of electron trapping on ps??s time scales. These ultrafast recombination dynamics, their retardation by applied bias, and the associated electron trapping are discussed in terms of their implications for efficient water oxidation. PMID:24950057

2014-01-01

217

Exchange splitting and charge carrier spin polarization in EuO.  

PubMed

High quality thin films of the ferromagnetic semiconductor EuO have been prepared and were studied using a new form of spin-resolved spectroscopy. We observed large changes in the electronic structure across the Curie and metal-insulator transition temperature. We found that these are caused by the exchange splitting of the conduction band in the ferromagnetic state, which is as large as 0.6 eV. We also present strong evidence that the bottom of the conduction band consists mainly of majority spins. This implies that doped charge carriers in EuO are practically fully spin polarized. PMID:11801161

Steeneken, P G; Tjeng, L H; Elfimov, I; Sawatzky, G A; Ghiringhelli, G; Brookes, N B; Huang, D-J

2002-01-28

218

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

SciTech Connect

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.

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

219

Recombination of charge carriers in the GaAs-based p-i-n diode  

SciTech Connect

It is established that the radiative recombination of charge carriers plays a substantial role in the GaAs-based p-i-n diodes at high densities of the forward current. It is shown experimentally that the diodes operating in microwave integrated circuits intensely emit light in the IR range with wavelengths from 890 to 910 nm. The obtained results indicate the necessity of taking into account the features of recombination processes in the GaAs-based microwave p-i-n diodes.

Ayzenshtat, G. I., E-mail: ayzen@mail.tomsknet.ru [Tomsk State University (Russian Federation); Yushenko, A. Y. [Tomsk State University of Control Systems and Radioelectronics (Russian Federation); Gushchin, S. M. [OAO Research Institute of Semiconductor Devices (Russian Federation); Dmitriev, D. V.; Zhuravlev, K. S.; Toropov, A. I. [Russian Academy of Sciences, Institute of Semiconductor Physics (Russian Federation)

2010-10-15

220

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

PubMed

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

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

221

Space charge effects in carrier escape from single quantum well structures  

NASA Astrophysics Data System (ADS)

Recently published data on the variation with applied bias and temperature of steady-state photoluminescence and photoconductivity from a series of GaAs/AlGaAs single quantum well p-i-n structures are subjected to detailed theoretical analysis, using phenomenological variables introduced in connection with these results. The data are interpreted as revealing the presence in the well of a space charge, which causes band bending and hence indirectly modifies carrier escape lifetimes. It is shown that the thermionic escape of holes can affect the electron tunneling escape lifetime so that the latter displays a thermal activation energy which is quantitatively similar to the hole well depth.

McFarlane, S. C.; Barnes, J.; Barnham, K. W. J.; Tsui, E. S. M.; Button, C.; Roberts, J. S.

1999-11-01

222

Charge transport in organic semiconductors: Assessment of the mean field theory in the hopping regime  

NASA Astrophysics Data System (ADS)

The performance of the mean field theory to account for charge transfer rate in molecular dimers and charge transport mobility in molecular stacks with small intermolecular electronic coupling and large local electron-phonon coupling (i.e., in the hopping regime) is carefully investigated against various other approaches. Using Marcus formula as a reference, it is found that mean field theory with system-bath interaction and surface hopping approaches yield fully consistent charge transfer rates in dimers. However, in contrast to the dimer case, incorporating system-bath interaction in the mean field approach results in a completely wrong temperature dependence of charge carrier mobility in larger aggregates. Although the mean field simulation starting from the relaxed geometry of a charged molecule and neglecting system-bath interaction can reproduce thermally activated transport, it is not able to characterize properly the role of additional nonlocal electron-phonon couplings. Our study reveals that the mean field theory must be used with caution when studying charge transport in the hopping regime of organic semiconductors, where the surface hopping approach is generally superior.

Wang, Linjun; Beljonne, David

2013-08-01

223

Minority carrier transport in p-ZnO nanowires  

NASA Astrophysics Data System (ADS)

In this work, we explore the minority carrier diffusion length in zinc oxide nanowires, using the electron beam-induced current technique. Systematic measurements as a function of temperature were performed on p-type, Sb-doped ZnO film, containing a 4 ?m thick nanowire layer. The minority carrier diffusion length exhibits a thermally activated increase with the energy of 74±5 meV. Electron beam irradiation also causes the diffusion length increase with the activation energy of 247±10 meV, likely related to SbZn-2VZn acceptor-complex.

Lin, Y.; Shatkhin, M.; Flitsiyan, E.; Chernyak, L.; Dashevsky, Z.; Chu, S.; Liu, J. L.

2011-01-01

224

Hot carrier diffusion in graphene  

E-print Network

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...

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

2010-11-01

225

Charge Transport Asymmetry in Cryogenic High Purity Germanium  

NASA Astrophysics Data System (ADS)

The SuperCDMS experiment relies on detection of free charges generated in high purity germanium (HPGe) crystals by particle interactions. To better understand long-term trapping effects which make carriers unavailable for such rapid ionization measurements, we used infrared LEDs ( = 940 nm) to create electron-hole pairs near each face of a HPGe SuperCDMS detector operated under applied electric field at 400 mK. By alternating the polarity of an applied electric field, we were able to study propagation of each carrier through the crystal separately. Asymmetry in the resulting current transients revealed differences in trapping characteristics between electrons and holes at these low temperatures.

Shank, B.; Nagasawa, D. Q.; Cabrera, B.; Cherry, M.; Young, B. A.

2014-08-01

226

Charge Transport in Amorphous Polythiophene-Fullerene Blends  

NASA Astrophysics Data System (ADS)

Energy-filtered transmission electron microscopy studies revealed that amorphous mixed phases are ubiquitous within mesostructured polythiophene/fullerene mixtures. Nevertheless, the role of mixing within nanophases on charge transport of organic semiconductor mixtures is not fully understood. We have examined the electron mobility in amorphous blends of poly(3-hexylthiophene) and phenyl-C61-butyric acid methyl ester. Our studies reveal that the miscibility of the components strongly affects electron transport within amorphous blends. Immiscibility promotes efficient electron transport by promoting percolating pathways within organic semiconductor mixtures. As a consequence, partial miscibility may be important for efficient charge transport in polythiophene/fullerene mixtures and organic solar cell performance.

Vakhshouri, Kiarash; Kozub, Derek; Wang, Chenchen; Salleo, Alberto; Gomez, Enrique

2012-02-01

227

Ultrafast charge carrier dynamics and photoelectrochemical properties of ZnO nanowires decorated with Au nanoparticles  

NASA Astrophysics Data System (ADS)

This study was designed to examine the possible photosensitization effect of zinc oxide (ZnO) nanowires (NWs) by Au nanoparticles (AuNPs) by directly monitoring the charge carrier lifetime in AuNP-decorated ZnO NWs. ZnO-Au nanocomposite structures showed reduced photocurrent compared to pristine ZnO NWs due to the combined effect of ZnO etching during the AuNPs growth and competitive absorption/scattering effects from AuNPs of incident UV photons. Ultrafast transient pump-probe spectroscopy was utilized to characterize the charge carrier dynamics. The bleach recovery of ZnO indicates electron-hole recombination on the 150 ps time scale attributed to shallow donor recombination. The AuNP-decorated ZnO NWs exhibit a fast decay of 3 ps in addition to the decays observed for ZnO NWs. This fast decay is similar to the hot electron relaxation lifetime observed for AuNPs in solution. Overall, the dynamics features for AuNP-decorated ZnO NWs appear as a simple sum of those from AuNPs and ZnO NWs alone. There is no evidence of photosensitization of the ZnO NWs by AuNPs investigated in this study.

Cooper, Jason K.; Ling, Yichuan; Li, Yat; Zhang, Jin Z.

2011-10-01

228

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

NASA Astrophysics Data System (ADS)

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.

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

2007-11-01

229

Calixarene derivative as the neutral carrier in silver ion-selective electrode and liquid membrane transport  

Microsoft Academic Search

The performances of calixarene derivative containing nitrogen atom used as a neutral carrier for silver polymeric membrane electrode and in metal ions transport by bulk liquid membrane were investigated. The faster transport rates were found by the soft heavy metal ions such as Ag+, Hg2+ in the bulk liquid membrane system. The silver ion-selective electrode based on calixarene derivative gave

Langxing Chen; Xiwen He; Bangtun Zhao; Yu Liu

2000-01-01

230

Dependence of nonproportionality in scintillators on diffusion of excitons and charge carriers  

NASA Astrophysics Data System (ADS)

The dipole-dipole and free-carrier Auger quenching processes that are generally regarded to be at the root of nonproportionality depend respectively on the 4th or 6th power of the electron track radius if modeled as cylindrical. In an initial time interval ? when nonlinear quenching and diffusion compete to reduce the density of excited states, the track radius expands as (Deff?)1/2 where Deff is the effective diffusion coefficient for the mixture of excitons and charge carriers. The range of Deff across semiconductor and scintillator radiation detectors is large, illustrated by 8 decades between mobilities of self-trapped holes in CsI:Tl and holes in high purity Ge. We present the functional form of nonlinear quenching predicted by diffusive track dilution and show that the simple model provides a surprisingly good fit of empirical nonproportionality across a wide range of semiconductor and oxide radiation detectors. We also show how diffusion drives nonlinear branching between excitons and free carriers in the track when electron and hole mobilities are unequal, and that this nonlinear branching coupled with linear trapping on defects can produce the "halide hump" seen in electron yield data for activated halide scintillators. Picosecond time-resolved spectroscopy in alkali halides, as well as quantitative comparison of recently measured 2nd order quenching rate constants K2 and results of K-dip spectroscopy, provide experimental benchmarks for consideration of carrier thermalization and the initial track or cluster radius r0 from which (nearly thermalized) diffusion is assumed to commence. The ratio of initial rate of 2nd order quenching to that of dilution by diffusion in a cylindrical track is proportional to K2/Deff and does not depend on r0 in lowest order; however, the absolute rates of both processes decrease with increasing r0.

Williams, R. T.; Li, Qi; Grim, Joel Q.; Ucer, K. B.

2011-09-01

231

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

NASA Astrophysics Data System (ADS)

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.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. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr00733f

Sato, Keisuke; Dutta, Mrinal; Fukata, Naoki

2014-05-01

232

An acoustic charge transport imager for high definition television applications  

NASA Technical Reports Server (NTRS)

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.

Hunt, William D.; Brennan, Kevin F.; Summers, Chris J.

1992-01-01

233

Charge Transport in Molecular Catalysis in a Heterogeneous Phase  

Microsoft Academic Search

This chapter focuses on the fundamental aspects in controlling charge transport (CT) processes through molecules in energy\\u000a conversion systems. The central reactions involved in the energy conversion are the charge separation and charge transfer\\u000a processes along the reaction coordinates from reactant molecules, assisted by the catalyst active sites. In some cases the\\u000a polymer medium plays an important role in the

M. Kaneko; T. Okada

234

Charge transport studies of polymeric photovoltaic thin films with an electron blocking and trapping layer  

NASA Astrophysics Data System (ADS)

The transport properties of two photovoltaic polymers, poly(3-hexylthiophene) (P3HT) and poly(2,7-carbazole) derivative (PCDTBT), and their polymer:fullerene bulk heterojunction (BHJ) are studied by space-charge-limited current (SCLC), dark-injection space-charge-limited current (DI-SCLC), and admittance spectroscopy(AS). For a nominally hole-only device, electrons leakage occurs. This results in a current larger than the theoretical SCLC and ill-defined DI-SCLC and AS signals. In order to prevent electron leakage, a hole-transporting but electron blocking/trapping thin layer is added between active layer and Au. The layer composed of copper phthalocyanine (CuPc) doped into an amine-based small molecule. Using this interlayer, well-defined carrier transit time can be obtained for mobility extraction. With a suitable interlayer to suppress undesirable carrier injection and transport, these techniques should find broad applications in the transport characterization of narrow gap photovoltaic polymers and BHJ blends.

Lee, Harrison K. H.; Chan, Kevin K. H.; So, S. K.

2012-06-01

235

Contactless Probing of the Carrier Transport in Carbon Nanotubes Using Dielectric Force Microscopy  

NASA Astrophysics Data System (ADS)

We have developed a scanning probe microscopy (SPM) based technique which is named as dielectric force microscopy (DFM) to manipulate and probe the majority carriers in 1-dimentional nanoelectronic materials. We have demonstrated its success in distinguishing semiconducting single-walled carbon nanotubes (SWNTs) from metallic ones, locating semiconducting-metallic junction in SWNTs, determining the majority carrier types in SWNTs and ZnO nanowires, and detecting the electronic doping of SWNTs by gaseous ammonia. To achieve a quantitative measure of the intrinsic carrier transport, we have performed DFM measurement on individual SWNTs, fabricated field effect transistor devices with the individual SWNT serving as the channel, and carried out electrical transport experiment. The results from DFM and transport measurements are quantitatively correlated in an almost perfect fashion allowing the extraction of intrinsic carrier transport properties especially carrier mobility from DFM data without making metal contacts. Furthermore, we have successfully detected the location and behavior of local transport barriers in SWNTs utilizing the nanometer scale resolution feature of DFM.

Li, Yize; Ge, Jun; Liu, Jia; Zhang, Jie; Lu, Wei; Chen, Liwei

2013-03-01

236

Electron spin resonance of charge carriers in chlorophyll a/water micelles  

SciTech Connect

Chlorophyll a/water micelles (P740) prepared in hydrocarbon media have been shown by small-angle neutron scattering to consist of hollow cylinders whose surface is formed of a monolayer of chlorophyll crosslinked by water. The micelles can be reversibly oxidized or reduced to generate highly mobile holes or electrons that undergo rapid, one-dimensional transport along the chains of chlorophyll macrocycles comprising the surface of the micelles. Large ..pi..-..pi.. overlap within the chains facilitates the one-dimensional charge transport and is expected to do the same for energy transport. Structural defects in the micelle surface act as boundaries for charge transport, confining the spins to one-dimensional domains of approximately 200 macrocycles. The one-dimensional transport within the limited domains results in motionally narrowed electron spin resonance lines with some residual inhomogeneous broadening. Although the chlorophyll a incorporated in micelles is more easily oxidized than is monomeric chlorophyll a, it is much more resistant to chemical alteration.

Bowman, M.K.; Michalski, T.J.; Tyson, R.L.; Worcester, D.L.; Katz, J.J.

1988-03-01

237

Carrier Transport in InGaN MQWs of Aquamarine and Green-Laser Diodes  

Microsoft Academic Search

We studied experimentally and theoretically the substrate-orientation impact on carrier transport and capture in InGaN multiple quantum well (MQW) laser diodes (LDs) with emission in the aquamarine-green spectral range. A new simula- tion approach was developed to analyze this behavior of LEDs and LDs emitting at these wavelengths. We show that due to deep carrier confinement, the thermal escape from

Dmitry S. Sizov; Rajaram Bhat; Aramais Zakharian; Kechang Song; Donald E. Allen; Sean Coleman; Chung-en Zah

2011-01-01

238

Transport of Sugars and Amino Acids in the Intestine: Evidence for a Common Carrier  

Microsoft Academic Search

D-Galactose, L-arginine, and their respective actively transported analogs are partially competitive inhibitors of the active transport of neutral amino acids in the small intestine of hamsters. Since the aforesaid classes of compounds are all transported by similar, sodium-ion-dependent mechanisms and elicit countertransport of each other, all may share a common, polyfunctional carrier in which a series of separate binding sites,

Francisco Alvarado

1966-01-01

239

Charge transfer and charge transport on the double helix N. P. Armitage*  

E-print Network

a ruthenium intercalator to end of a single DNA strand and a rhodium intercalator to a comple- mentary stand present a short review of various experiments that measure charge transfer and charge transport in DNA measurements performed by our group on the millimeter wave response of DNA. By measur- ing over a wide range

Gruner, George

240

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

Code of Federal Regulations, 2010 CFR

...a commercial carrier for transporting a mobile home? 302-10.402 Section 302-10... 10-ALLOWANCES FOR TRANSPORTATION OF MOBILE HOMES AND BOATS USED AS A PRIMARY RESIDENCE...a commercial carrier for transporting a mobile home? The costs you must pay a...

2010-07-01

241

Charge-carrier mobilities in binary mixtures of discotic triphenylene derivatives as a function of temperature  

Microsoft Academic Search

The pulse-radiolysis time-resolved microwave conductivity technique was used to study charge transport in three binary mixtures of triphenylene derivatives and in three of these components separately. In the liquid-crystalline mesophase the hole mobilities in the mixtures are found to be an order of magnitude higher than those in the separate components. This is partly due to the more stable columnar

B. R. Wegewijs; L. D. A. Siebbeles; N. Boden; R. J. Bushby; B. Movaghar; O. R. Lozman; Q. Liu; A. Pecchia; L. A. Mason

2002-01-01

242

Charge Transport and Electroluminescence in Novel Heterocyclic Liquid Crystals  

NASA Astrophysics Data System (ADS)

Start your abstract by replacing this line with your text. We have investigated charge transport in a family of novel liquid crystals containing five member ring heterocycles (oxadiazoles, thiadiazoles, etc.). Efficient electron transport was observed in the smectic phase. The electric field and temperature dependence of the electron mobility was studied. Apart from being able to simultaneously function as liquid crystals and charge transport agents, these materials are highly fluorescent, allowing the fabrication of organic light emitting diodes. Their electroluminescent properties in devices with various electrode materials were studied.

Fan, Rong; Malliaras, George; Sukhomlinova, L.; Gu, S.; Twieg, R. J.

2000-03-01

243

Charge accumulation due to spin transport in magnetic multilayers  

NASA Astrophysics Data System (ADS)

Starting with the Valet-Fert theory of the current-perpendicular-to-plane giant magnetoresistance, we studied the charge accumulation due to spin transport in magnetic multilayers by solving Poisson's equation analytically. Our results show that, in ferromagnetic layers, the charge accumulation has two exponential terms with opposite signs and different decaying lengths: the Thomas-Fermi screening length (on the order of angstrom) and the spin diffusion length (tens of nm in 3d ferromagnetic metals). The charge accumulation on the scale of the screening length is spin-unpolarized and also present in spin-independent transport in nonmagnetic multilayers. However, the charge accumulation on the scale of the spin diffusion length is spin-polarized and shows up only in ferromagnetic layers. Our analysis also provides new insights into the widely used quasi-neutrality approximation, which neglects the charge accumulation.

Zhu, Yao-Hui; Xu, Deng-Hui; Geng, Ai-Cong

2014-08-01

244

Measurement of carrier transport and recombination parameter in heavily doped silicon  

NASA Technical Reports Server (NTRS)

The minority carrier transport and recombination parameters in heavily doped bulk silicon were measured. Both Si:P and Si:B with bulk dopings from 10 to the 17th and 10 to the 20th power/cu cm were studied. It is shown that three parameters characterize transport in bulk heavily doped Si: the minority carrier lifetime tau, the minority carrier mobility mu, and the equilibrium minority carrier density of n sub 0 and p sub 0 (in p-type and n-type Si respectively.) However, dc current-voltage measurements can never measure all three of these parameters, and some ac or time-transient experiment is required to obtain the values of these parameters as a function of dopant density. Using both dc electrical measurements on bipolar transitors with heavily doped base regions and transients optical measurements on heavily doped bulk and epitaxially grown samples, lifetime, mobility, and bandgap narrowing were measured as a function of both p and n type dopant densities. Best fits of minority carrier mobility, bandgap narrowing and lifetime as a function of doping density (in the heavily doped range) were constructed to allow accurate modeling of minority carrier transport in heavily doped Si.

Swanson, Richard M.

1986-01-01

245

Studying of hot-carrier effect in floating body SOI MOSFETs by the transient charge pumping technique  

Microsoft Academic Search

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

Mikhail Nagoga; Serguei Okhonin; Pierre Fazan

2004-01-01

246

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

PubMed

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

Sato, Keisuke; Dutta, Mrinal; Fukata, Naoki

2014-06-01

247

Carrier transport simulation in a model liquid crystalline system with the biaxial Gay-Berne potential  

NASA Astrophysics Data System (ADS)

In this paper, we performed carrier transport simulation to understand the unusual temperature dependence of the carrier mobility observed in nematic liquid crystals. For this purpose, we made a model liquid crystalline system consisting of biaxial Gay-Berne particles, and then we simulated hopping transport between these particles. The hopping rate was formulated suitably for the biaxial Gay-Berne particles based on the investigation of the electronic overlaps between actual aromatic molecules. The carrier transport simulation was performed by master equation method on the model system prepared by N-P-T ensemble Monte Carlo simulation. We reproduced gradual mobility increase in the nematic phase as a result of the change in the short range molecular order.

Goto, Masanao; Takezoe, Hideo; Ishikawa, Ken

2010-02-01

248

Effect of Cooling Rate on Microstructure and Charge Transport in Semiconducting Polymer Thin Films  

NASA Astrophysics Data System (ADS)

Thermal annealing of polymer thin films often enhances charge carrier mobility which can be attributed to self-healing of the film morphology. We have investigated the effect of cooling rate following the annealing treatment on the thin film microstructure and the charge transport properties using a high performance semiconducting polymer, poly(2,5-bis(3-alkylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT). The cooling rate plays a key role in determining the microstructure and performance of polymer thin films. Differential scanning calorimeter measurement shows that fast cooling suppresses the crystallization process. The microstructure of thin films is investigated by using 2D X-ray diffraction and atomic force microscopy. Slow cooling results in well-connected large domains with enhanced three dimensional ordering whereas fast cooling leads to misalignment of small domains with relatively rough surface. Transport characteristics at various temperatures show increase in the charge carrier mobility and decrease in the activation energy when the cooling rate is slowed. This change in the mobility and activation energy becomes saturated with cooling rate below 15 C/min.

Kang, Evan; Kim, Eunseong

2011-03-01

249

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

PubMed

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 cm(2) 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. PMID:25367432

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

2014-12-21

250

Charge transport study of high mobility polymer thin-film transistors based on thiophene substituted diketopyrrolopyrrole copolymers.  

PubMed

In this paper, we report on the device physics and charge transport characteristics of high-mobility dual-gated polymer thin-film transistors with active semiconductor layers consisting of thiophene flanked DPP with thienylene-vinylene-thienylene (PDPP-TVT) alternating copolymers. Room temperature mobilities in these devices are high and can exceed 2 cm(2) V(-1) s(-1). Steady-state and non-quasi-static measurements have been performed to extract key transport parameters and velocity distributions of charge carriers in this copolymer. Charge transport in this polymer semiconductor can be explained using a Multiple-Trap-and-Release or Monroe-type model. We also compare the activation energy vs. field-effect mobility in a few important polymer semiconductors to gain a better understanding of transport of DPP systems and make appropriate comparisons. PMID:23673383

Ha, Tae-Jun; Sonar, Prashant; Dodabalapur, Ananth

2013-06-28

251

Normal-State magnetic scattering of charge carriers in YNi_2B_2C single crystals  

NASA Astrophysics Data System (ADS)

Normal-state magnetic scattering in YNi_2B_2C single crystals are reported. The resistivity as a function of temperature clearly follows Matthiessen's rule implying the existence of impurity scattering at low temperatures. In addition, magnetoresistivity is positive and negative in low and high temperature respectively. The sign change occurs at various magnetic fields for different temperatures. Such unusual behavior can be understood qualitatively based on spin-orbit coupling of charge carriers and magnetic ions. However, it is plausible that such change of magnetoresistance is due to the geometric features of the Fermi surfaces. Comparisons will be made regarding these possible scenarios. aps397

Chu, Rambis K.; Chen, Quark Y.; Ting, S. T.; Chu, Wei-Kan

1998-03-01

252

Quantifying charge carrier concentration in ZnO thin films by Scanning Kelvin Probe Microscopy  

NASA Astrophysics Data System (ADS)

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.

Maragliano, C.; Lilliu, S.; Dahlem, M. S.; Chiesa, M.; Souier, T.; Stefancich, M.

2014-02-01

253

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

NASA Astrophysics Data System (ADS)

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.

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

2012-02-01

254

Surface charge transport and decay in dielectric barrier discharges  

NASA Astrophysics Data System (ADS)

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.

Wild, R.; Benduhn, J.; Stollenwerk, L.

2014-10-01

255

Tuning optoelectronic properties and understanding charge transport in nanocrystal thin films of earth abundant semiconducting materials  

NASA Astrophysics Data System (ADS)

With the capability of producing nearly 600 TW annually, solar power is one renewable energy source with the potential to meet a large fraction of the world's burgeoning energy demand. To make solar technology cost-competitive with carbon-based fuels, cheaper devices need to be realized. Solution-processed solar cells from nanocrystal inks of earth abundant materials satisfy this requirement. Nonetheless, a major hurdle in commercializing such devices is poor charge transport through nanocrystal thin films. The efficiency of charge transport through nanocrystal thin films is strongly dependent on the quality of the nanocrystals, as well as their optoelectronic properties. Therefore, the first part of this dissertation is focused on synthesizing high quality nanocrystals of Cu2ZnSnS4, a promising earth abundant photovoltaic absorber material. The optoelectronic properties of the nanocrystals were tuned by altering the copper to zinc ratio, as well as by introducing selenium to create Cu2ZnSn(S1-xSe x)4 solid solutions. Photoelectrochemical characterization was used to test the Cu2ZnSnS4 and Cu2ZnSn(S 1-xSex)4 nanocrystal thin films. The results identify minority carrier diffusion and recombination via the redox shuttle as the major loss mechanisms hindering efficient charge transport through the nanocrystal thin films. One way to solve this issue is to sinter the nanocrystals together, creating large grains for efficient charge transport. Although this may be quick and effective, it can lead to the formation of structural defects, among other issues. To this end, using a different copper-based material, namely Cu2Se, and simple surface chemistry treatments, an alternative route to enhance charge transport through nanocrystals thin films is proposed.

Riha, Shannon C.

256

Charged-particle calculations using Boltzmann transport methods  

SciTech Connect

Several aspects of radiation damage effects in fusion reactor neutron and ion irradiation environments are amenable to treatment by transport theory methods. In this paper, multigroup transport techniques are developed for the calculation of charged particle range distributions, reflection coefficients, and sputtering yields. The Boltzmann transport approach can be implemented, with minor changes, in standard neutral particle computer codes. With the multigroup discrete ordinates code, ANISN, determination of ion and target atom distributions as functions of position, energy, and direction can be obtained without the stochastic error associated with atomistic computer codes such as MARLOWE and TRIM. With the multigroup Monte Carlo code, MORSE, charged particle effects can be obtained for problems associated with very complex geometries. Results are presented for several charged particle problems. Good agreement is obtained between quantities calculated with the multigroup approach and those obtained experimentally or by atomistic computer codes.

Hoffman, T.J.; Dodds, H.L. Jr.; Robinson, M.T.; Holmes, D.K.

1981-01-01

257

Influence of electron trapping on minority carrier transport properties of wide band gap semiconductors  

NASA Astrophysics Data System (ADS)

Minority carrier transport properties and the effects of electron irradiation/injection were studied in GaN and ZnO containing dopants known to form acceptor states deep within the materials' bandgap. Minority carrier diffusion length and lifetime changes were investigated using Electron Beam Induced Current (EBIC) method, cathodoluminescence spectroscopy, spectral photoresponse and persistent photoconductivity measurements. It is shown that electron irradiation by the beam of a scanning electron microscope results in a significant increase of minority carrier diffusion length. These findings are supported by the cathodoluminescence measurements that demonstrate the decay of near-band-edge intensity as a consequence of increasing carrier lifetime under continuous irradiation by the electron beam. Temperature-dependent measurements were used to determine the activation energies for the electron irradiation-induced effects. The latter energies were found to be consistent with the involvement of deep acceptor states. Based on these findings, the effects of electron irradiation are explained via the mechanism involving carrier trapping on these levels. Solid-state electron injection was also shown to result in a similar increase of minority carrier lifetime and diffusion length. Solid-state injection was carried out by applying the forward bias to a ZnO homojunction and resulted in a significant improvement of the peak photoresponse of the junction. This improvement was unambiguously correlated with the increase of the minority carrier diffusion length due to electron injection.

Tirpak, Olena Lopatiuk

258

Charge carrier and spin doping in ZnO thin films D.P. Norton a,*, M. Ivill a  

E-print Network

Charge carrier and spin doping in ZnO thin films D.P. Norton a,*, M. Ivill a , Y. Li a , Y.W. Kwon, United States Available online 30 September 2005 Abstract Recent efforts on doping ZnO films for charge that is stabilized via epitaxial film growth. Epitaxial wurtzite Zn1Ã?xMgxO thin films have been realized with x

Hebard, Arthur F.

259

Hepatocellular uptake of peptides by bile acid transporters: relationship of carrier-mediated transport of linear peptides with renin-inhibiting activity to multispecific bile acid carriers.  

PubMed

The uptake of a linear peptide with renin-inhibiting activity (code number EMD 51921) was characterized in isolated rat liver cells. Isolated hepatocytes take up EMD 51921 in a time-, concentration-, energy- and temperature-dependent manner. Transport of the peptide follows mixed-type kinetics. Diffusion occurs at a rate of 8.123 x 10(-6) cm/sec at 6 degrees C. For the saturable part of uptake, a Km of 2.0 microM and a Vmax of 160 pmol/mg per min were calculated. Various substrate analogues inhibit the uptake of EMD 51921. Absence of oxygen or decreased cellular ATP content (e.g., by metabolic inhibitors or xylulose) blocks hepatocellular uptake of EMD 51921. Temperatures above 20 degrees C accelerate the uptake. The activation energy was calculated to be 58.3 kJ/mol. The apparently active uptake of EMD 51921 was not sodium dependent. The membrane potential is a driving force for the accumulation of EMD 51921. Mutual competitive transport inhibition of EMD 51921, cholate and taurocholate is indicative of a common transport system. Benzamidotaurocholate and a cyclosomatostatin analog 008, not phalloidin and iodipamide, however, considerably decrease the uptake of EMD 51921. AS 30D ascites hepatoma cells, unable to accumulate bile acids and certain cyclopeptides, also fail to transport EMD 51921. BSP, a foreign substrate of the bilirubin carrier, noncompetitively inhibits the transport of EMD 51921. The inhibition of the uptake of EMD 51921 by rifampicin, a further substrate of the bilirubin carrier, is mixed: competitive at high EMD 51921 concentrations and uncompetitive at low EMD 51921 concentrations. The uptake of rifampicin into isolated rat liver cells, however, is not influenced by EMD 51921. Substrates of the transport systems for cations, amino acids, long chain fatty acids and hexoses did not influence the transport of EMD 51921. PMID:2001417

Bertrams, A; Ziegler, K

1991-02-19

260

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

SciTech Connect

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.

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

261

Cost models for coal transportation by common carrier. Appendix 1: User's Manual. Final report  

Microsoft Academic Search

This manual provides the technical information needed to operate the computerized transportation cost models developed in EA--675, Cost Models for Coal Transportation by Common Carrier, prepared for the Electric Power Research Institute by Manalytics, Inc., March 1979. Three models were developed: one for rail; one for inland river, Great Lakes, and coastal ocean waterways; and one for origin\\/destination loading\\/unloading and

S. J. White; J. P. Hynes

1980-01-01

262

Grain Boundary Effect on Charge Transport in Pentacene Thin Films  

NASA Astrophysics Data System (ADS)

We report on charge transport properties of polycrystalline pentacene films with variable average grain size in the range from 0.1 to 0.3 µm controlled by the preparation technology. We illustrate with the organic field-effect transistors decrease of the effective mobility and presence of traps with decrease of the grain size. Analysis of the charge transfer excitons reveals decrease of the mobile charge density and the steady-state voltammetry showed significant increase of oxygen- and hydrogen-related defects. We also briefly discuss accumulation of the defects on the grain boundary and show relation between the defect density and grain boundary length.

Weis, Martin; Gmucová, Katarína; Nádaždy, Vojtech; Majková, Eva; Haško, Daniel; Taguchi, Dai; Manaka, Takaaki; Iwamoto, Mitsumasa

2011-04-01

263

Efficient organic electroluminescent device using a single bipolar carrier transport layer  

NASA Astrophysics Data System (ADS)

An electroluminescent device was developed in which a single bipolar transport layer is used. High efficiencies can be obtained from this device by judiciously selecting a dopant that enhances the radiant recombination probability of carrier pairs and spaces this recombination zone away from the cathode.

Littman, Jon; Martic, Peter

1992-09-01

264

Alloy scattering limited transport of two-dimensional carriers in strained Si, -,Ge, quantum wells  

E-print Network

Alloy scattering limited transport of two-dimensional carriers in strained Si, -,Ge, quantum wells, demonstrating the etlect of strong alloy disorder scattering. This was confirmed by the relatively weaker effects in the standard two-dimensional alloy scattering model, an effective scattering potential V&,=0

265

FACILITATED TRANSPORT OF HNO3 THROUGH A SUPPORTED LIQUID MEMBRANE CONTAINING A TERTIARY AMINE AS CARRIER  

Microsoft Academic Search

The facilitated transport of HN03 through a supported liquid membrane consisting of a porous polypropylene film containing a solution of trllaurylamine 1n diethyl benzene as carrier was studied as a function of the stirring speed of the aqueous solutions and the membrane composition. A physico-chemical model which takes Into account diffusion through an aqueous boundary layer, a fast Interfaclal chemical

C. Cianetti; P. R. Danesi

1983-01-01

266

Molecular engineering to improve the balance of charge carrier in single-layer silole-based OLEDs.  

E-print Network

Molecular engineering to improve the balance of charge carrier in single-layer silole-based OLEDs = 0.8 cd/A at 7 V. Introduction15 Organic light-emitting diodes (OLEDs) using small molecules OLEDs structures11 . Nevertheless, this approach suffers of some drawbacks due to a large number

Paris-Sud XI, Université de

267

High-field charge transport on the surface of Bi2Se3  

NASA Astrophysics Data System (ADS)

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 [Costache et al., Phys. Rev. Lett. 112, 086601 (2014), 10.1103/PhysRevLett.112.086601]. 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.

Weng, M. Q.; Wu, M. W.

2014-09-01

268

14 CFR 382.21 - May carriers limit access to transportation on the basis that a passenger has a communicable...  

Code of Federal Regulations, 2010 CFR

...carriers limit access to transportation on the basis that a passenger has a communicable disease...REGULATIONS NONDISCRIMINATION ON THE BASIS OF DISABILITY IN AIR TRAVEL Nondiscrimination...carriers limit access to transportation on the basis that a passenger has a communicable...

2010-01-01

269

Highly selective transport of silver ion through a supported liquid membrane using calix[4]pyrroles as suitable ion carriers  

Microsoft Academic Search

Facilitated transport of silver ion across a supported liquid membrane (SLM) by calix[4]pyrroles, as selective ion carriers, dissolved in kerosene has been investigated. The influences of fundamental parameters affecting the transport of silver ion including ion carrier concentration in the membrane phase, thiosulfate concentration in strip phase, picric acid concentration in the feed phase, stirring speed of aqueous phases, type

Ali Asghar Amiri; Afsaneh Safavi; Ali Reza Hasaninejad; Hashem Shrghi; Mojtaba Shamsipur

2008-01-01

270

Quadrimolecular recombination kinetics of photogenerated charge carriers in the composites of regioregular polythiophene derivatives and soluble fullerene  

NASA Astrophysics Data System (ADS)

Light-induced electron spin resonance (LESR) measurements have been performed on the composites of regioregular polythiophene derivatives and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) in order to study the recombination kinetics of photogenerated charge carriers. We adopt two regioregular polymers with different side chains; head-to-tail poly(3-hexylthiophene) (RR-P3HT) and head-to-head poly(3-dodecynylthiophene-2,5-diyl) [HH-P3(C?CDec)Th]. In both systems, two LESR signals due to positive polarons on the polymer (g ˜2.002) and fullerene radical anions (g ˜2.000) have been observed. Quadrimolecular recombination (QR) kinetics, previously reported for RR-P3HT/C60 composites, where two positive polarons and two radical anions recombine simultaneously, has been confirmed in both systems by the observation of Iex0.25 dependence of the LESR intensity on the excitation light intensity (Iex) and the decay curve of the LESR intensity. This process implies the formation of doubly-charged states such as bipolarons or polaron pairs on the polymer to attract two radical anions. Temperature dependence of the QR rate constant, ?, in both systems has exhibited a crossover of the transport mechanism from low temperature tunneling to high temperature hopping process, as in the case of RR-P3HT/C60 composites. In the RR-P3HT/PCBM composites, ? has exhibited marked dependencies on the PCBM concentration or annealing, which may be related to the change of the crystallinity of the phase-separated polymer and fullerene domains as well as their interface structures, affecting the carrier mobilities or the trap states at the interface. Associated change of the molecular orientation of RR-P3HT crystalline domains with the lamellar structure has been further confirmed from the anisotropic LESR signals of the cast films on the substrates, exhibiting a qualitative agreement with the reported x-ray or optical analyses. In the HH-P3(C?CDec)Th/PCBM composite, ? has been smaller than those in the RR-P3HT/PCBM composites, reflecting the difference of local structures due to the different molecular structure. Furthermore, the hyperfine-determined LESR linewidth of the positive polaron has exhibited a smaller value than those in the RR-P3HT composite, implying the larger extension of the polaron wave function on the polymer chain, which is consistent with the highly coplanar structure of this polymer.

Tanaka, Hisaaki; Yokoi, Yuki; Hasegawa, Naoki; Kuroda, Shin-ichi; Iijima, Takayuki; Sato, Takao; Yamamoto, Takakazu

2010-04-01

271

?-Isopropylmalate, a Leucine Biosynthesis Intermediate in Yeast, Is Transported by the Mitochondrial Oxalacetate Carrier*  

PubMed Central

In Saccharomyces cerevisiae, ?-isopropylmalate (?-IPM), which is produced in mitochondria, must be exported to the cytosol where it is required for leucine biosynthesis. Recombinant and reconstituted mitochondrial oxalacetate carrier (Oac1p) efficiently transported ?-IPM in addition to its known substrates oxalacetate, sulfate, and malonate and in contrast to other di- and tricarboxylate transporters as well as the previously proposed ?-IPM transporter. Transport was saturable with a half-saturation constant of 75 ± 4 ?m for ?-IPM and 0.31 ± 0.04 mm for ?-IPM and was inhibited by the substrates of Oac1p. Though not transported, ?-ketoisocaproate, the immediate precursor of leucine in the biosynthetic pathway, inhibited Oac1p activity competitively. In contrast, leucine, ?-ketoisovalerate, valine, and isoleucine neither inhibited nor were transported by Oac1p. Consistent with the function of Oac1p as an ?-IPM transporter, cells lacking the gene for this carrier required leucine for optimal growth on fermentable carbon sources. Single deletions of other mitochondrial carrier genes or of LEU4, which is the only other enzyme that can provide the cytosol with ?-IPM (in addition to Oac1p) exhibited no growth defect, whereas the double mutant ?OAC1?LEU4 did not grow at all on fermentable substrates in the absence of leucine. The lack of growth of ?OAC1?LEU4 cells was partially restored by adding the leucine biosynthetic cytosolic intermediates ?-ketoisocaproate and ?-IPM to these cells as well as by complementing them with one of the two unknown human mitochondrial carriers SLC25A34 and SLC25A35. Oac1p is important for leucine biosynthesis on fermentable carbon sources catalyzing the export of ?-IPM, probably in exchange for oxalacetate. PMID:18682385

Marobbio, Carlo M. T.; Giannuzzi, Giulia; Paradies, Eleonora; Pierri, Ciro L.; Palmieri, Ferdinando

2008-01-01

272

Charge transport in porous nanocrystalline titanium dioxide  

NASA Astrophysics Data System (ADS)

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.

Eppler, Anuradha M.; Ballard, Ian M.; Nelson, Jenny

2002-04-01

273

[Intracellular protein transport--the cell as a mail carrier].  

PubMed

The eukaryotic cell has a highly developed machinery for routing proteins to their correct intra- or extra-cellular locations. Short stretches of amino acids ("signal peptides") serve as address labels that are recognized by receptors on the surface of the appropriate organelle, where-upon translocation across one or more membranes ensues. Premature folding of the nascent protein is prevented by cytoplasmic "chaperones", i.e. proteins that bind to unfolded or partially folded nascent chains. After import into the organelle, other chaperones are required for catalyzing the final folding of the protein, and for promoting its correct assembly into oligomeric protein complexes. Transport along the secretory pathway (endoplasmic reticulum to Golgi to trans-Golgi to plasma membrane) is mediated by vesicles that bud from a donor compartment and fuse with an acceptor compartment. PMID:2280633

Von Heijne, G

1990-12-12

274

Photoconductivity and charge transporting properties of metal-containing poly(p-phenylenevinylene)s  

NASA Astrophysics Data System (ADS)

A novel type of poly(p-phenylenevinylene)s which contain (bis(2,2':6',2''-terpyridine) ruthenium (II) complexes has been developed. The absorption of the polymers at 500 nm was strongly enhanced by the metal complexes due to the presence of the metal-ligand charge transfer transition. The charge transportation is dispersive with hole carrier mobilities and activation energy of ˜7×10-5 cm2 V-1 s-1 and 0.20 eV, respectively, depending on the concentration of the metal complex. A log ? vs E1/2 plot shows that hole mobilities decrease with increasing field, which suggests the presence of off-diagonal disorder in the hopping sites.

Chan, Wai Kin; Gong, Xiong; Ng, Wai Yue

1997-11-01

275

Charge-carrier mobilities in binary mixtures of discotic triphenylene derivatives as a function of temperature  

NASA Astrophysics Data System (ADS)

The pulse-radiolysis time-resolved microwave conductivity technique was used to study charge transport in three binary mixtures of triphenylene derivatives and in three of these components separately. In the liquid-crystalline mesophase the hole mobilities in the mixtures are found to be an order of magnitude higher than those in the separate components. This is partly due to the more stable columnar structure in the mixtures and partly due to efficient ``alloy band formation.'' In the crystalline phase the mobility in the mixtures is only a few times lower than that of the separate components. The ionization energies of the components as measured by cyclic voltammetry are up to ~0.5 eV apart. It turns out that this energy difference is easily compensated by the relatively large charge-transfer integrals for hole transport in the binary mixtures, which was obtained from ab initio Hartree Fock calculations. The mobilities estimated theoretically for ordered systems largely exceed the experimental values. This is most likely due to structural disorder along the columns in the material. Theoretical estimations of the hole mobility suggest that mobilities in excess of 1 cm2/V s could be attainable in well-ordered crystalline triphenylene samples.

Wegewijs, B. R.; Siebbeles, L. D.; Boden, N.; Bushby, R. J.; Movaghar, B.; Lozman, O. R.; Liu, Q.; Pecchia, A.; Mason, L. A.

2002-06-01

276

On the Structure of the Fixed Charge Transportation Problem  

ERIC Educational Resources Information Center

This work extends the theory of the fixed charge transportation problem (FCTP), currently based mostly on a forty-year-old publication by Hirsch and Danzig. This paper presents novel properties that need to be considered by those using existing, or those developing new methods for optimizing FCTP. It also defines the problem in an easier way,…

Kowalski, K.

2005-01-01

277

Carriers transport properties in GaInP solar cells grown by molecular beam epitaxy  

NASA Astrophysics Data System (ADS)

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.

Dai, P.; Lu, S. L.; Arimochi, M.; Uchida, S.; Watanabe, T.; Luo, X. D.; Yang, H.

2014-12-01

278

Two-dimensional Au lattices featuring unique carrier transport preference and wide forbidden gap.  

PubMed

Large-scale 2D Au lattices with honeycomb-like structure are fabricated on Si(111)-7 × 7 surface at room temperature. The growth pattern investigated by reflection high-energy electron diffraction and in situ scanning tunneling microscopy indicates that the 2D Au lattices are composed of two interfacial distinct layers that are completely formed one after another with a close-packed structure. A unique wide forbidden gap of 4.1 eV is measured around the Fermi level of the 2D Au lattices by scanning tunneling spectroscopy. Bias-dependent STM images and theoretical simulations suggest that the in-plane quantum coupling and carrier transport behavior are responsible for the novel electronic properties. In addition to local electronic states, the electronic structures of 2D Au lattices are further modulated by the carrier transport preference that is determined by carrier energy and symmetry of 2D lattices. These findings will provide some references for the controlled fabrication and for routing the carrier transport behavior of low-dimensional metal structures. PMID:25037748

Zhang, Chunmiao; Wu, Yaping; Zhou, Yinghui; Gao, Na; Guo, Fei; Chen, Xiaohang; Jiang, Baofeng; Hu, Wei; Kang, Junyong

2014-09-01

279

Glucose transport carrier of human erythrocytes. Radiation target size measurement based on flux inactivation  

SciTech Connect

Intact human erythrocytes frozen in the presence of cryoprotective reagents and irradiated with an electron beam retained their diffusion barrier to L-glucose. The carrier-mediated flux of D-glucose, on the other hand, was inactivated as a simple exponential function of the radiation dose. Classical target size analysis of this data yielded a molecular size of 185,000 daltons for the carrier. This represents the first measurement of the functional size of a transport protein based directly on flux inactivation.

Cuppoletti, J.; Jung, C.Y.; Green, F.A.

1981-02-10

280

Charge transport in 4H-SiC detector structures under conditions of a high electric field  

SciTech Connect

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.

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

281

Storage of charge carriers on emitter molecules in organic light-emitting diodes  

NASA Astrophysics Data System (ADS)

Organic light-emitting diodes (OLEDs) using the red phosphorescent emitter iridium(III)bis(2-methyldibenzo[f,h]quinoxaline) (acetylacetonate) [Ir(MDQ)2(acac)] are studied by time-resolved electroluminescence measurements. A transient overshoot after voltage turn-off is found, which is attributed to electron accumulation on Ir(MDQ)2(acac) molecules. The mechanism is verified via impedance spectroscopy and by application of positive and negative off-voltages. We calculate the density of accumulated electrons and find that it scales linearly with the doping concentration of the emitter. Using thin quenching layers, we locate the position of the emission zone during normal OLED operation and after voltage turn-off. In addition, the transient overshoot is also observed in three-color white-emitting OLEDs. By time- and spectrally resolved measurements using a streak camera, we directly attribute the overshoot to electron accumulation on Ir(MDQ)2(acac). We propose that similar processes are present in many state-of-the-art OLEDs and believe that the quantification of charge carrier storage will help to improve the efficiency of OLEDs.

Weichsel, Caroline; Burtone, Lorenzo; Reineke, Sebastian; Hintschich, Susanne I.; Gather, Malte C.; Leo, Karl; Lüssem, Björn

2012-08-01

282

On the advancement of quantum dot solar cell performance through enhanced charge carrier dynamics  

NASA Astrophysics Data System (ADS)

The quantum dot solar cell is one of the few solar technologies which promises to compete with fossil fuels, but work is still needed to increase its performance. Electron transfer kinetics at interfaces and limitations of the redox couple within the cell, are responsible for lowering power conversion efficiency. Several techniques which are able to increase electron transfer within the working electrode and at the counter electrode/electrolyte interface are discussed in this dissertation. Trap sites on the surface of CdSe quantum dots are created when mercaptopropionic acid (MPA) is added to the suspension. The trap sites are emissive creating a loss pathway for photogenerated charges which will manifest as reduced photocurrent. MPA displaces amines on the surface of CdSe creating Se vacancies. Emission properties are controlled by the concentration of MPA. Because trap sites are generated, a more successful method to sensitize TiO2 films is the SILAR technique which directly grows quantum dots on the desired surface. Anodically etched TiO2 nanotubes yield photocurrents 20% greater than TiO2 nanoparticles because of longer electron diffusion lengths. Peak incident photon to charge carrier efficiencies of TiO2 nanotube samples show a doubling of photocurrent in the visible region compared to nanoparticles. The TiO2 substrates are sensitized with CdS by the SILAR process which is found to utilize both the inside and outside surfaces of the TiO2 nanotubes. Etched TiO2 nanotubes are removed from the underlying titanium foil in order to use spectroscopic techniques. Ultrafast transient absorption shows the extremely fast nature of charge injection from SILAR CdS into TiO 2 nanotubes. Surface area analysis of TiO2 nanotube powder gives an area of 77m2/g, a value 1.5 times larger than traditional TiO2 nanoparticles. By isolating the counter electrode with a salt bridge the effect of the polysulfide electrolyte is found to act as an electron scavenger on the working electrode. Though activity at the platinum counter electrode increases with the presence of polysulfides, the activity is too low to counteract scavenging at the working electrode. Cu2S, CoS and PbS electrochemically show promise as alternatives to platinum. Cu2S and CoS produce higher photocurrents and fill factors, greatly improving cell performance.

Baker, David R.

283

Pore network model of electrokinetic transport through charged porous media.  

PubMed

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

Obliger, Amaël; Jardat, Marie; Coelho, Daniel; Bekri, Samir; Rotenberg, Benjamin

2014-04-01

284

Vertical carrier transport in InGaAsP multiple-quantum-well laser structures: effect of p-doping  

Microsoft Academic Search

Carrier transport across p-doped quantum wells (QWs) has been measured by time-resolved photoluminescence for a number of InGaAsP multiple-quantum-well (MQW) laser structures with different structural parameters. The transport times are found to be of the order of tens of picoseconds. This shows that the interwell carrier transport is a limiting factor in high-speed laser modulation schemes. Modeling of the experiments

Nir Tessler; S. Marcinkevicius; U. Olin; C. K. V. Silfvenius; B. F. Stalnacke; G. Landgren

1997-01-01

285

Mixed quantum-classical simulations of charge transport in organic materials: Numerical benchmark of the Su-Schrieffer-Heeger model  

SciTech Connect

The electron-phonon coupling is critical in determining the intrinsic charge carrier and exciton transport properties in organic materials. In this study, we consider a Su-Schrieffer-Heeger (SSH) model for molecular crystals, and perform numerical benchmark studies for different strategies of simulating the mixed quantum-classical dynamics. These methods, which differ in the selection of initial conditions and the representation used to solve the time evolution of the quantum carriers, are shown to yield similar equilibrium diffusion properties. A hybrid approach combining molecular dynamics simulations of nuclear motion and quantum-chemical calculations of the electronic Hamiltonian at each geometric configuration appears as an attractive strategy to model charge dynamics in large size systems ''on the fly,'' yet it relies on the assumption that the quantum carriers do not impact the nuclear dynamics. We find that such an approximation systematically results in overestimated charge-carrier mobilities, with the associated error being negligible when the room-temperature mobility exceeds {approx}4.8 cm{sup 2}/Vs ({approx}0.14 cm{sup 2}/Vs) in one-dimensional (two-dimensional) crystals.

Wang Linjun; Beljonne, David [Laboratory for Chemistry of Novel Materials, University of Mons, Place du Parc 20, B-7000 Mons (Belgium); Chen Liping; Shi Qiang [State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Zhongguancun, 100190 Beijing (China)

2011-06-28

286

Modeling carrier transport and electric field evolution in Gaussian disordered organic field-effect transistors  

NASA Astrophysics Data System (ADS)

Stimulated by the time resolved microscopic optical second-harmonic generation (TRM-SHG) experiment, we model the carriers transport and electric field evolution in the channel of three-dimensional Gaussian disordered organic field-effect transistors (OFETs) by the coupled time-dependent master equation and Poisson equation. We show that this model with the Miller-Abrahams rate can satisfactorily account for the experimental observations that include different profiles of the electric field in the channel and the diffusionlike migration of the field peaks with respect to time. Particularly, we find that the dynamic mobility proposed by us earlier is distinct from the standard one in the presence of a typical disorder, which is attributed to the uncompleted energy relaxation of the carriers in the transport process.

Liu, Fei; Lin, Jack; Manaka, Takaaki; Iwamoto, Mitsumasa

2011-05-01

287

Correlated conformation and charge transport in multiwall carbon nanotube-conducting polymer nanocomposites  

NASA Astrophysics Data System (ADS)

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.

Choudhury, Paramita Kar; Ramaprabhu, S.; Ramesh, K. P.; Menon, Reghu

2011-07-01

288

Development of a maritime transportation planning support system for car carriers based on genetic algorithm  

Microsoft Academic Search

Recently, the port logistics market is rapidly expanding, along with the active maritime trade. To adjust to this trend and\\u000a gain a competitive advantage, competition among shipping companies at home and abroad has intensified, and many efforts are\\u000a being made for the improvement of customer services and cost saving. In particular, car carriers transporting more than 80%\\u000a of total car

Moo Hong Kang; Hyung Rim Choi; Hyun Soo Kim; Byung Joo Park

289

Targeting carrier-mediated transport to improve the blood-brain barrier permeation of paclitaxel  

E-print Network

TARGETING CARRIER-MEDIATED TRANSPORT TO IMPROVE THE BLOOD-BRAIN BARRIER PERMEATION OF PACLITAXEL Kelly E. Desino1, Kenneth L. Audus1, Haibo Ge2, Gunda I. Georg2, Jariat Oyetunji2, Jared T. Spletstoser2, and Brandon J. Turunen2 University of Kansas..., Department of Pharmaceutical Chemistry1 and Department of Medicinal Chemistry2, Lawrence, KS 66047 ABSTRACT Purpose: Paclitaxel is a chemotherapeutic used for a variety of cancers; however, it cannot be used for cancers of the CNS. The permeation...

Desino, Kelly Elizabeth; Audus, Kenneth L.; Ge, Haibo; Georg, Gunda I.; Oyetunji, Jariat; Spletstoser, J. T.; Turunen, B. J.

2006-10-27

290

Determination of the charge carrier compensation mechanism in Te-doped GaAs by scanning tunneling microscopy  

NASA Astrophysics Data System (ADS)

We identified the charge carrier compensation mechanism in Te-doped GaAs with atomically resolved scanning tunneling microscopy. Three types of defects were found: tellurium donors (TeAs), Ga vacancies (VGa), and Ga vacancy-donor complexes (VGa-TeAs). We show quantitatively that the compensation in Te-doped bulk GaAs is exclusively caused by vacancy-donor complexes in contrast to Si-doped GaAs. This is explained with the Fermi-level effect as the universal mechanism leading to Ga vacancy formation in n-doped GaAs, and a Coulomb interaction leading to the formation of the complexes. The quantification of the carrier compensation yields a -3e charge state of VGa in bulk GaAs.

Gebauer, J.; Weber, E. R.; Jäger, N. D.; Urban, K.; Ebert, Ph.

2003-03-01

291

Effect of temperature and rare-earth doping on charge-carrier mobility in indium-monoselenide crystals  

SciTech Connect

In the temperature range T = 77-600 K, the dependence of the charge-carrier mobility ({mu}) on the initial dark resistivity is experimentally investigated at 77 K ({rho}d{sub 0}), as well as on the temperature and the level (N) of rare-earth doping with such elements as gadolinium (Gd), holmium (Ho), and dysprosium (Dy) in n-type indium-monoselenide (InSe) crystals. It is established that the anomalous behavior of the dependences {mu}(T), {mu}({rho}d{sub 0}), and {mu}(N) found from the viewpoint of the theory of charge-carrier mobility in crystalline semiconductors is related, first of all, to partial disorder in indium-monoselenide crystals and can be attributed to the presence of random drift barriers in the free energy bands.

Abdinov, A. Sh., E-mail: abdinov-axmed@yandex.ru [Baku State University (Azerbaijan); Babayeva, R. F., E-mail: Babaeva-Rena@yandex.ru [Azerbaijan State Economic University (Azerbaijan); Amirova, S. I.; Rzayev, R. M. [Baku State University (Azerbaijan)] [Baku State University (Azerbaijan)

2013-08-15

292

Comparison of majority carrier charge transfer velocities at Si/polymer and Si/metal photovoltaic heterojunctions  

SciTech Connect

Two sets of silicon (Si) heterojunctions with either Au or PEDOT:PSS contacts have been prepared to compare interfacial majority carrier charge transfer processes at Si/metal and Si/polymer heterojunctions. Current-voltage (J-V) responses at a range of temperatures, wavelength-dependent internal quantum yields, and steady-state J-V responses under illumination for these devices are reported. The cumulative data suggest that the velocity of majority carrier charge transfer, v{sub n}, is several orders of magnitude smaller at n-Si/PEDOT:PSS contacts than at n-Si/Au junctions, resulting in superior photoresponse characteristics for these inorganic/organic heterojunctions.

Price, Michelle J.; Foley, Justin M. [Applied Physics Program, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109-1040 (United States); May, Robert A. [Department of Chemistry and Biochemistry, University of Texas at Austin, 1 University Station A5300, Austin, Texas 78712-0165 (United States); Maldonado, Stephen [Applied Physics Program, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109-1040 (United States); Department of Chemistry, University of Michigan, 930 N University, Ann Arbor, Michigan 48109-1055 (United States)

2010-08-23

293

41 CFR 301-10.309 - What will I be reimbursed if I am authorized to use common carrier transportation and I use a POV...  

Code of Federal Regulations, 2010 CFR

...be reimbursed if I am authorized to use common carrier transportation and I use a POV...be reimbursed if I am authorized to use common carrier transportation and I use a POV...constructive cost of the authorized method of common carrier transportation plus per...

2010-07-01

294

Reduction and transition in thermal activation for charge transport through electrolyte-gated polythiophene thin films with high hole densities  

NASA Astrophysics Data System (ADS)

We investigate the activation energy for electrical charge transport through a polythiophene thin film. The results are particularly obtained under high hole density (5.9 × 1020 holes/cm3) through electrolyte-gating and are compared with previous results attained from the same polymer film but with low induced carrier densities. Comparative analyses show that introducing high hole densities into the polymer results in (i) suppression of the transport activation energy and (ii) reduction of the temperature that yields transition in the activation energy. These results are explained based on the formation of bipolaron states, which are generated at such high hole densities.

Lee, Jiyoul; Cho, Boeun; Won Chung, Jong; Sung Kang, Moon

2013-10-01

295

Computational investigation of charge injection and transport properties of a series of thiophene-pyrrole based oligo-azomethines.  

PubMed

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

Sahu, Harikrishna; Panda, Aditya N

2014-05-14

296

Charge Migration in DNA: Ion-Gated Transport  

NASA Astrophysics Data System (ADS)

Electron hole (radical cation) migration in DNA, where the quantum transport of an injected charge is gated in a correlated manner by the thermal motions of the hydrated counterions, is described here. Classical molecular dynamics simulations in conjunction with large-scale first-principles electronic structure calculations reveal that different counterion configurations lead to formation of states characterized by varying spatial distributions and degrees of charge localization. Stochastic dynamic fluctuations between such ionic configurations can induce correlated changes in the spatial distribution of the hole, with concomitant transport along the DNA double helix. Comparative ultraviolet light-induced cleavage experiments on native B DNA oligomers and on ones modified to contain counterion (Na+)-starved bridges between damage-susceptible hole-trapping sites called GG steps show in the latter a reduction in damage at the distal step. This reduction indicates a reduced mobility of the hole across the modified bridge as predicted theoretically.

Barnett, Robert N.; Cleveland, Charles L.; Joy, Abraham; Landman, Uzi; Schuster, Gary B.

2001-10-01

297

Charge carrier mobilities in the crystalline solid and discotic mesophases of hexakis-hexylthio and hexakis-hexyloxy triphenylene  

Microsoft Academic Search

The radiation-induced conductivities of bulk samples of hexakis-hexylthio and hexakis-hexyloxy triphenylene, HHTT and HHOT, have been studied from 0 to +100°C using the pulse-radiolysis time-resolved microwave conductivity (PR-TRMC) technique. The one-dimensional, intracolumnar mobility, ??c, of charge carriers in the various phases is estimated and compared with values obtained using the time-of-flight technique. Temperature independent values of ??c, of 0.4×10?4 and

Anick M. van de Craats; Matthijs P. de Haas; John M. Warman

1997-01-01

298

Physical Properties, Charge Carrier Mobility, and Photovoltaic Performance of Dendritic Oligothiophene Bearing Naphthalene Bis(dicarboximide) Groups  

NASA Astrophysics Data System (ADS)

Dendritic oligothiophene having naphthalene bis(dicarboximide) (NDI) was synthesized, and its physical properties were investigated by ultraviolet-visible (UV-vis) spectroscopy and cyclic voltammetry. The charge carrier mobility measurements by organic field-effect transistor devices and flash-photolysis time-resolved microwave conductivity measurements revealed p-channel behavior. The photovoltaic performance of the dendritic oligothiophene-NDI dyad with PCBM exhibited a power conversion efficiency of 0.14%.

Ie, Yutaka; Uto, Toshihiko; Honsho, Yoshihito; Seki, Shu; Karakawa, Makoto; Aso, Yoshio

2010-01-01

299

Charge Transport and Transfer at the Nanoscale Between Metals and Novel Conjugated Materials  

NASA Astrophysics Data System (ADS)

Organic semiconductors (OSCs) and graphene are two classes of conjugated materials that hold promise to create flexible electronic displays, high speed transistors, and low-cost solar cells. Crucial to understanding the behavior of these materials is understanding the effects metallic contacts have on the local charge environment. Additionally, characterizing the charge carrier transport behavior within these materials sheds light on the physical mechanisms behind transport. The first part of this thesis examines the origin of the low-temperature, high electric field transport behavior of OSCs. Two chemically distinct OSCs are used, poly-3(hexylthiophene) (P3HT) and 6,13-bis(triisopropyl-silylethynyl) (TIPS) pentacene. Several models explaining the low-temperature behavior are presented, with one using the Tomonaga-Luttinger liquid (TLL) insulator-to-metal transition model and one using a field-emission hopping model. While the TLL model is only valid for 1-dimensional systems, it is shown to work for both P3HT (1D) and TIPS-pentacene (2D), suggesting the TLL model is not an appropriate description of these systems. Instead, a cross-over from thermally-activated hopping to field-emission hopping is shown to explain the data well. The second part of this thesis focuses on the interaction between gold and platinum contacts and graphene using suspended graphene over sub-100 nanometer channels. Contacts to graphene can strongly dominate charge transport and mobility as well as significantly modify the charge environment local to the contacts. Platinum electrodes are discovered to be strong dopants to graphene at short length scales while gold electrodes do not have the same effect. By increasing the separation distance between the electrodes, this discrepancy is shown to disappear, suggesting an upper limit on charge diffusion from the contacts. Finally, this thesis will discuss a novel technique to observe the high-frequency behavior in OSCs using two microwave sources and an organic transistor as a mixer. A theoretical model motivating this technique is presented which suggests the possibility of retrieving gigahertz charge transport phenomena at kilohertz detection frequencies. The current state of the project is presented and discrepancies between devices made with gold and platinum electrodes measured in the GHz regime are discussed.

Worne, Jeffrey Howard

300

Transport of charged particles in the earth's magnetosphere  

NASA Technical Reports Server (NTRS)

A review of recent data on and conceptions of processes in which high energy particles are transported across magnetic shells in the earth's magnetosphere is presented. The processes discussed include adiabatic processes (with conservation of all three adiabatic invariants of charged particle motion in the magnetic field), diffusion processes (with violation of only the third or third and second invariants), and the so-called fast nonadiabatic processes, which appear to result from the action of strong electric fields.

Shalimov, V. P.

1974-01-01

301

Charge pulse studies of transport phenomena in bilayer membranes  

Microsoft Academic Search

Summary The charge-pulse technique is applied to a study of valinomycin-mediated potassium transport across glycerol monooleate (GMO) bilayers. The theory, based on the Läuger-Stark model, is developed for the steady-state domain. The voltage dependences of the surface complexation reactions are also considered. The analysis of the data yields the following values for the rate constants:\\u000a$$\\\\begin{array}{*{20}c} {k'_R = 2.6 \\\\times

Stephen W. Feldberg; Hisamitsu Nakadomari

1977-01-01

302

Carrier Injection and Transport in Blue Phosphorescent Organic Light-Emitting Device with Oxadiazole Host  

PubMed Central

In this paper, we investigate the carrier injection and transport characteristics in iridium(III)bis[4,6-(di-fluorophenyl)-pyridinato-N,C2?]picolinate (FIrpic) doped phosphorescent organic light-emitting devices (OLEDs) with oxadiazole (OXD) as the bipolar host material of the emitting layer (EML). When doping Firpic inside the OXD, the driving voltage of OLEDs greatly decreases because FIrpic dopants facilitate electron injection and electron transport from the electron-transporting layer (ETL) into the EML. With increasing dopant concentration, the recombination zone shifts toward the anode side, analyzed with electroluminescence (EL) spectra. Besides, EL redshifts were also observed with increasing driving voltage, which means the electron mobility is more sensitive to the electric field than the hole mobility. To further investigate carrier injection and transport characteristics, FIrpic was intentionally undoped at different positions inside the EML. When FIrpic was undoped close to the ETL, driving voltage increased significantly which proves the dopant-assisted-electron-injection characteristic in this OLED. When the undoped layer is near the electron blocking layer, the driving voltage is only slightly increased, but the current efficiency is greatly reduced because the main recombination zone was undoped. However, non-negligible FIrpic emission is still observed which means the recombination zone penetrates inside the EML due to certain hole-transporting characteristics of the OXD. PMID:22837713

Chiu, Tien-Lung; Lee, Pei-Yu

2012-01-01

303

Physical origin of nonlinear transport in organic semiconductor at high carrier densities  

NASA Astrophysics Data System (ADS)

The charge transport in some organic semiconductors exhibits nonlinear properties and further universal power-law scaling with both bias and temperature. The physical origin of this behavior is investigated here by using variable-range hopping theory. The results indicate that this nonlinear behavior can be well explained by variable-range hopping theory. In the high temperature regime, charge transport is thermally activated. However, for the low temperature case, field-assisted tunneling will be dominant, which is responsible for the nonlinear characteristics observed by experiment. The comparison between the theoretical calculation and recent experimental data is also presented.

Li, Ling; Lu, Nianduan; Liu, Ming

2014-10-01

304

Carrier transport and bandgap shift in n-type degenerate ZnO thin films: The effect of band edge nonparabolicity  

NASA Astrophysics Data System (ADS)

Contribution of band edge nonparabolicity to the charge carrier transport in degenerate n-type zinc oxide thin films has been investigated theoretically in order to understand the fundamental aspects of electron scattering in such thin films regardless of precise details of the preparation procedure. To conduct this, the theoretical evaluated results have been compared to the experimental values taken from literatures. The results indicate that the nonparabolicity (introducing through effective mass of charge carriers) has a strong effect on the total mobility of carriers in zinc oxide films so that a satisfactory agreement with experimental data is fulfilled. The dependence of nonparabolicity on bandgap shift is also discussed. Studying the optoelectronic properties of numerous moderately and heavily doped samples revealed that their optical bandgap has lower blueshift than the theoretical value obtained from the well-known Burstein-Moss effect. So, the observed bandgap shift was dependent on the carrier concentration and the total shift of bandgap was evaluated by combining the Burstein-Moss and bandgap narrowing effects. Two different cases were also examined; parabolic and nonparabolic (modified) Burstein-Moss effects. The results show that the modified Burstein-Moss effect leads to great agreement with experimental data.

Abdolahzadeh Ziabari, A.; Rozati, S. M.

2012-12-01

305

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

Code of Federal Regulations, 2011 CFR

...Public Contracts and Property Management 4 2011-07-01 2011-07-01...false What must my travel accounting system do in relation to...Public Contracts and Property Management Federal Travel Regulation...COMMON CARRIER TRANSPORTATION Accounting for Common Carrier...

2011-07-01

306

Charge transport under illumination in mesoporous continuous films  

NASA Astrophysics Data System (ADS)

Recent developments in the preparation of surfactant-templated mesostructured sol-gel silica materials have extended the morphology from the originally discovered powders, with particle sizes on the order of microns, to mesoporous continuous thin films. These films could find applications in membrane-based separations, selective catalysis and sensors. Particularly, sodium dodecyl sulfate (SDS)- templated sol-gel films formed by the rapid dip-coating sol-gel method possess highly ordered lamellar phase structure. The interest in the potential applications of these films and the introduction of new properties lead to the research of their chemical modifications. The improvement of their photorefractive response requires knowledge of the microscopic processes, such as the charge transport mechanism. The photoconductivity technique provides information about that mechanism, and it allows for measuring the transport parameters. Mesoporous continuous films were prepared by the dip-coating method on glass substrates. The films were doped with SDS, carbazole (SiK) and dispersed red one (DR1) at 1:20:20 molar concentration. Photoconductivity studies were done on them at different illumination wavelengths in order to know the transport mechanism and surfactant influence. The electric field versus current density plot shows a linear behavior, i.e. an ohmic response. The conductivity slope dependence with the polarization time shows a Gaussian behavior. And there is an exponential decay from the absorption coefficient with the accumulated polarization time. Interpretation of these results is presented and the obtained charge transport parameters are reported.

Garcia-Macedo, Jorge A.; Cruz, Daniel; Valverde, Guadalupe; Zink, Jeffrey I.; Hernandez, Raquel; Minoofar, Payam

2002-02-01

307

Proton-associated sucrose transport of mammalian solute carrier family 45: an analysis in Saccharomyces cerevisiae.  

PubMed

The members of the solute carrier 45 (SLC45) family have been implicated in the regulation of glucose homoeostasis in the brain (SLC45A1), with skin and hair pigmentation (SLC45A2), and with prostate cancer and myelination (SLC45A3). However, apart from SLC45A1, a proton-associated glucose transporter, the function of these proteins is still largely unknown, although sequence similarities to plant sucrose transporters mark them as a putative sucrose transporter family. Heterologous expression of the three members SLC45A2, SLC45A3 and SLC45A4 in Saccharomyces cerevisiae confirmed that they are indeed sucrose transporters. [14C]Sucrose-uptake measurements revealed intermediate transport affinities with Km values of approximately 5 mM. Transport activities were best under slightly acidic conditions and were inhibited by the protonophore carbonyl cyanide m-chlorophenylhydrazone, demonstrating an H+-coupled transport mechanism. Na+, on the other hand, had no effect on sucrose transport. Competitive inhibition assays indicated a possible transport also of glucose and fructose. Real-time PCR of mouse tissues confirmed mRNA expression of SLC45A2 in eyes and skin and of SLC45A3 primarily in the prostate, but also in other tissues, whereas SLC45A4 showed a predominantly ubiquitous expression. Altogether the results provide new insights into the physiological significance of SLC45 family members and challenge existing concepts of mammalian sugar transport, as they (i) transport a disaccharide, and (ii) perform secondary active transport in a proton-dependent manner. PMID:25164149

Bartölke, Rabea; Heinisch, Jürgen J; Wieczorek, Helmut; Vitavska, Olga

2014-12-01

308

Monte Carlo simulations of carrier transport in AlGaInP laser diodes  

Microsoft Academic Search

A self-consistent ensemble Monte Carlo simulation of charge transport in AlGaInP multiple quantum well lasers has been devised in an effort to understand why the light output from these lasers is reduced at high temperatures

G. C. Crow; R. A. Abram

1996-01-01

309

Ring-Containing Conjugated Polymers: Charge Transport and Electroluminiscence  

NASA Astrophysics Data System (ADS)

Conjugated polymers have been studied extensively in the last decade both in the doped conducting state and the undoped semiconducting or insulating form. For the doped conducting polymers, the nature of the metallic state upon doping and the dimensionality of the system have been a hot issue, with improvements in chemical processing playing the key role in clarifying them. For the undoped polymers, particularly the luminescent polymers, the nature of the electronic and optical processes occurring upon charge injection or photoexcitation have been under intense study because they reflect the underlying physics in conjugated polymer based light-emitting (electroluminescent) devices. In this dissertation, both issues are studied. In the conducting state, systematic charge transport and structural studies were performed on hydrochloric and camphor sulfonic acid doped polyaniline and its methyl derivative poly(o-toluidine) (POT) fibers to investigate the role of chemical processing and the nature of the metallic state in conducting polymers. The study shows that the charge transport properties are controlled by the local microstructural order whose formation is very sensitive to chemical processing conditions such as processing temperature, dopant and solvent used. The solvent, or the so-called secondary dopant, has been shown to play a critical role in improving the charge transport properties. As a result of improved chemical processing, high quality camphor sulfonic acid doped poly(o-toluidine) (POT-CSA) fibers have been prepared from m-cresol, enabling a direct experimental test of the random-dimer model (RDM), one of the models proposed to account for the metallic state in polyaniline. The results of the charge transport studies on the POT-CSA fibers and the dielectric response studies of the POT-CSA solutions in formic acid are clearly inconsistent with the RDM. In the semiconducting/insulating states, pyridine-based fluorescent polymers were used to study the electroluminescent processes and properties. Light -emitting diodes based on these polymers were fabricated and characterized in various device configurations. In addition, a new type of electroluminescent device, the symmetrically configured AC light-emitting (SCALE) device, is described. The mechanism for the SCALE device operation is discussed with the emphasis on the role of the interfaces.

Wang, Yunzhang

310

49 CFR 369.3 - Classification of carriers-motor carriers of passengers.  

Code of Federal Regulations, 2011 CFR

... false Classification of carriers-motor carriers of passengers. 369.3 ...Transportation (Continued) FEDERAL MOTOR CARRIER SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION FEDERAL MOTOR CARRIER SAFETY REGULATIONS...

2011-10-01

311

49 CFR 369.3 - Classification of carriers-motor carriers of passengers.  

Code of Federal Regulations, 2010 CFR

... false Classification of carriers-motor carriers of passengers. 369.3 ...Transportation (Continued) FEDERAL MOTOR CARRIER SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION FEDERAL MOTOR CARRIER SAFETY REGULATIONS...

2010-10-01

312

49 CFR 369.3 - Classification of carriers-motor carriers of passengers.  

Code of Federal Regulations, 2012 CFR

... false Classification of carriers-motor carriers of passengers. 369.3 ...Transportation (Continued) FEDERAL MOTOR CARRIER SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION FEDERAL MOTOR CARRIER SAFETY REGULATIONS...

2012-10-01

313

49 CFR 369.3 - Classification of carriers-motor carriers of passengers.  

Code of Federal Regulations, 2013 CFR

... false Classification of carriers-motor carriers of passengers. 369.3 ...Transportation (Continued) FEDERAL MOTOR CARRIER SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION FEDERAL MOTOR CARRIER SAFETY REGULATIONS...

2013-10-01

314

Charge Localization and Transport in Lithiated Olivine Phosphate Materials  

SciTech Connect

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.

Yu, Jianguo; Rosso, Kevin M.; Liu, Jun

2011-11-10

315

Selective contacts drive charge extraction in quantum dot solids via asymmetry in carrier transfer kinetics  

NASA Astrophysics Data System (ADS)

Colloidal quantum dot solar cells achieve spectrally selective optical absorption in a thin layer of solution-processed, size-effect tuned, nanoparticles. The best devices built to date have relied heavily on drift-based transport due to the action of an electric field in a depletion region that extends throughout the thickness of the quantum dot layer. Here we study for the first time the behaviour of the best-performing class of colloidal quantum dot films in the absence of an electric field, by screening using an electrolyte. We find that the action of selective contacts on photovoltage sign and amplitude can be retained, implying that the contacts operate by kinetic preferences of charge transfer for either electrons or holes. We develop a theoretical model to explain these experimental findings. The work is the first to present a switch in the photovoltage in colloidal quantum dot solar cells by purposefully formed selective contacts, opening the way to new strategies in the engineering of colloidal quantum dot solar cells.

Mora-Sero, Ivan; Bertoluzzi, Luca; Gonzalez-Pedro, Victoria; Gimenez, Sixto; Fabregat-Santiago, Francisco; Kemp, Kyle W.; Sargent, Edward H.; Bisquert, Juan

2013-08-01

316

Carrier of Wingless (Cow), a Secreted Heparan Sulfate Proteoglycan, Promotes Extracellular Transport of Wingless  

PubMed Central

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

Chang, Yung-Heng; Sun, Yi Henry

2014-01-01

317

Pathway annotation and analysis with Reactome: The solute carrier class of membrane transporters  

PubMed Central

Reactome is an expert-authored, peer-reviewed knowledge base of human reactions and pathways that functions as a data-mining resource and electronic textbook. Its current release covers approximately 23 per cent of the complete human proteome from UniProt. The pathway browser, search and data-mining tools facilitate searching and visualising pathway data and the analysis of user-supplied high-throughput datasets. A catalogue of all the solute-carrier (SLC) class of transporters which have known ligands has been annotated in Reactome. Reactome provides a detailed and interactive view of this set of transport reactions. Using the example of the SLC class of transporters, we show how they can be overlaid with protein-protein interaction, protein-drug interaction and gene expression data and compared with equivalent pathways in other species, to facilitate over-representation, expression and other pathway analyses. PMID:21712192

2011-01-01

318

Influence of humidity on the electrostatic charge and aerosol performance of dry powder inhaler carrier based systems.  

PubMed

To investigate the influence of storage relative humidity (RH) on the aerosolisation efficiency and tribo-electrification of carrier based dry powder inhaler (DPI) formulations using the next generation impactor (NGI) in vitro methodology and the electrostatic low pressure impactor (ELPI). Micronised salbutamol (d (0.5) 1.48 +/- 0.03 microm) was blended with 63-90 microm sieve fractioned alpha-lactose monohydrate carrier and stored at a range of humidities (0-84% RH). The aerosolisation efficiency after storage for 24 h periods was investigated using the NGI. The same experiment was conducted using the ELPI, with corona charger switched off, to measure the net charge vs. mass deposition profile. Significant variations in the aerosolisation efficiency of the formulation were observed with respect to storage RH. In general, the fine particle fraction aerosol performance measured by NGI and ELPI (fraction with mass median aerodynamic diameter <4.46 and 4.04 microm, respectively) followed a positive parabola with aerosol performance increasing over the range 0-60% RH before decreasing >60% RH. Analysis of the ELPI charge data suggested that the micronised salbutamol sulphate had an electronegative charge when aerosolised from lactose based carriers, which was most electronegative at low RH. Increased storage RH resulted in a reduction in net charge to mass ratio with the greatest reduction at RH >60%. The aerosol performance of this binary system is dependent on both electrostatic and capillary forces. The use of the ELPI allows a degree of insight into how these forces affect formulation performances after storage at different RH. PMID:17377746

Young, Paul M; Sung, Adrian; Traini, Daniela; Kwok, Philip; Chiou, Herbert; Chan, Hak-Kim

2007-05-01

319

Activation of hole charge carriers and generation of electromotive force in gabbro blocks subjected to nonuniform loading  

NASA Astrophysics Data System (ADS)

study verifies the activation of hole charge carriers in gabbro under nonuniform loading, which has been proposed as the possible source of the stress-induced electromotive force in dry rocks without piezoelectric effect. When one end of vacuum-dried gabbro blocks was subjected to uniaxial loading, the unloaded end became electronically positive (+80 mV at 50 MPa). The Seebeck coefficient of the loaded volume decreased from ~15.8 mV/K to ~14.9 mV/K when loaded, while the Seebeck coefficient of the unloaded end did not change remarkably (~15.6 mV/K). This means that this gabbro originally included a small number of hole charge carriers and the carriers in the loaded volume increased when loaded. From the viewpoint of the fundamental band model of solid state, the most reasonable mechanism of the increment is the decrease of the energy gap between the acceptors and the valence band top. Based on this idea, a generation model of the stress-induced electromotive force is proposed. Since this model is expected to be universally applicable to various types of rocks, similar electromotive forces in the crustal scale may be induced by seismic, volcanic, and tidal activities.

Takeuchi, Akihiro; Nagao, Toshiyasu

2013-03-01

320

Improved understanding of the electronic and energetic landscapes of perovskite solar cells: high local charge carrier mobility, reduced recombination, and extremely shallow traps.  

PubMed

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

Oga, Hikaru; Saeki, Akinori; Ogomi, Yuhei; Hayase, Shuzi; Seki, Shu

2014-10-01

321

Charge and energy transport in one-dimensional nanomaterials  

NASA Astrophysics Data System (ADS)

This dissertation is comprised of two parts: Charge transport in DNA hair-pins and light transport in linear arrays of dielectric spherical particles. Experimental results suggest specific charge (hole) migration kinetics for stilbene-capped DNA hair-pins of the form Sa(AT)nSd, where Sa and Sd denote the acceptor and donor stilbene respectively and (AT) n a bridge of adenine-thymine base pairs of length n = 1 -- 7. Kinetics equations are derived from experimental data for both charge separation and recombination. Counterion binding to the radicalized stilbene ions is considered a significant contributor to charge migration kinetics. In the second part, bound modes infinite linear chains of dielectric particles of various lengths and particle materials are investigated. Through a unique application of the multisphere Mie scattering formalism, numerical methods are developed to calculate eigen-optical modes for various arrays of particles. Eigenmodes with the highest quality factor are identified by the application of a modified version of the Newton-Raphson algorithm. Convergence is strong using this algorithm for linear chains of up to several hundred particles. By comparing the dipolar approach with the more complex approach utilizing a combination of both dipolar and quadrupolar approaches, the dipolar approach is shown to have an accuracy of approximately 99%. The quality factor increases with the cubed value of the number of particles in agreement with previously developed theory. The effects of disordering of particle sizes and inter-particle distances as well as interference of guiding modes in "traffic circle" waveguide configurations will be discussed.

Blaustein, Gail S.

322

Charge transport mechanisms and memory effects in amorphous TaNx thin films  

PubMed Central

Amorphous semiconducting materials have unique electrical properties that may be beneficial in nanoelectronics, such as low leakage current, charge memory effects, and hysteresis functionality. However, electrical characteristics between different or neighboring regions in the same amorphous nanostructure may differ greatly. In this work, the bulk and surface local charge carrier transport properties of a-TaNx amorphous thin films deposited in two different substrates are investigated by conductive atomic force microscopy. The nitride films are grown either on Au (100) or Si [100] substrates by pulsed laser deposition at 157 nm in nitrogen environment. For the a-TaNx films deposited on Au, it is found that they display a negligible leakage current until a high bias voltage is reached. On the contrary, a much lower threshold voltage for the leakage current and a lower total resistance is observed for the a-TaNx film deposited on the Si substrate. Furthermore, I-V characteristics of the a-TaNx film deposited on Au show significant hysteresis effects for both polarities of bias voltage, while for the film deposited on Si hysteresis, effects appear only for positive bias voltage, suggesting that with the usage of the appropriate substrate, the a-TaNx nanodomains may have potential use as charge memory devices. PMID:24134740

2013-01-01

323

Charge transport studies of proton and ion conducting materials  

NASA Astrophysics Data System (ADS)

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.

Versek, Craig Wm

324

Reduction of Effective Carrier Density and Charge Collection Efficiency in SiC Devices Due to Radiations  

NASA Astrophysics Data System (ADS)

6H-Silicon Carbide (SiC) diodes were fabricated and irradiated with Co-60 gamma-rays, 1 MeV electrons, and 65 MeV protons. After the radiation damage was introduced in devices, the Charge Collection Efficiency (CCE) was evaluated by using the Transient Ion Beam Induced Current (TIBIC) system. The effective carrier density was also estimated from Capacitance-Voltage (C-V) characteristics. It was found that both the CCE and the effective carrier density decrease with increase in the fluence. We discuss whether Non-Ionizing Energy Loss (NIEL) analysis can estimate the degradation in these parameters. Results from this study suggest that the damage factors of these parameters in SiC can be scaled by the NIEL.

Onoda, Shinobu; Iwamoto, Naoya; Hirao, Toshio; Kawano, Katsuyasu; Kojima, Kazuhisa; Ohshima, Takeshi

2009-03-01

325

Extrinsic limiting factors of carrier transport in organic field-effect transistors  

Microsoft Academic Search

Extrinsic factors to disturb the carrier transport in pentacene field-effect transistors (FETs), as a representative of the\\u000a high-mobility organic FETs (OFETs), have been comprehensively analyzed by using atomic-force-microscope potentiometry (AFMP),\\u000a microscopic four-point-probe field-effect transistor (MFPP-FET) measurement, and other techniques. In the first part, by mainly\\u000a using AFMP as a powerful tool to reveal the potential distribution in working OFETs, we

Masakazu Nakamura; Hirokazu Ohguri; Naoyuki Goto; Hiroshi Tomii; Mingsheng Xu; Takashi Miyamoto; Ryousuke Matsubara; Noboru Ohashi; Masaaki Sakai; Kazuhiro Kudo

2009-01-01

326

Transport of 3D space charge dominated beams  

NASA Astrophysics Data System (ADS)

In this paper we present the theoretical analysis and the computer code design for the intense pulsed beam transport. Intense beam dynamics is a very important issue in low-energy high-current accelerators and beam transport systems. This problem affects beam transmission and beam qualities. Therefore, it attracts the attention of the accelerator physicists worldwide. The analysis and calculation for the intense beam dynamics are very complicated, because the state of particle motion is dominated not only by the applied electromagnetic fields, but also by the beam-induced electromagnetic fields (self-fields). Moreover, the self fields are related to the beam dimensions and particle distributions. So, it is very difficult to get the self-consistent solutions of particle motion analytically. For this reason, we combine the Lie algebraic method and the particle in cell (PIC) scheme together to simulate intense 3D beam transport. With the Lie algebraic method we analyze the particle nonlinear trajectories in the applied electromagnetic fields up to third order approximation, and with the PIC algorithm we calculate the space charge effects to the particle motion. Based on the theoretical analysis, we have developed a computer code, which calculates beam transport systems consisting of electrostatic lenses, electrostatic accelerating columns, solenoid lenses, magnetic and electric quadruples, magnetic sextupoles, octopuses and different kinds of electromagnetic analyzers. The optimization calculations and the graphic display for the calculated results are provided by the code.

Lü, Jian-Qin

2013-10-01

327

Trapping of charge carriers into InAs/AlAs quantum dots at liquid-helium temperature  

SciTech Connect

The problem of how the probability of trapping of charge carriers into quantum dots via the wetting layer influences the steady-state and time-dependent luminescence of the wetting layer and quantum dots excited via the matrix is analyzed in the context of some simple models. It is shown that the increase in the integrated steady-state luminescence intensity of quantum dots with increasing area fraction occupied by the quantum dots in the structure is indicative of the suppression of trapping of charge carriers from the wetting layer into the quantum dots. The same conclusion follows from the independent decays of the time-dependent luminescence signals from the wetting layer and quantum dots. The processes of trapping of charge carriers into the InAs quantum dots in the AlAs matrix at 5 K are studied experimentally by exploring the steady-state and time-dependent photoluminescence. A series of structures with different densities of quantum dots has been grown by molecular-beam epitaxy on a semi-insulating GaAs (001) substrate. It is found that the integrated photoluminescence intensity of quantum dots almost linearly increases with increasing area occupied with the quantum dots in the structure. It is also found that, after pulsed excitation, the photoluminescence intensity of the wetting layer decays more slowly than the photoluminescence intensity of the quantum dots. According to the analysis, these experimental observations suggest that trapping of excitons from the wetting layer into the InAs/AlAs quantum dots at 5 K is suppressed.

Abramkin, D. S., E-mail: demid@thermo.isp.nsc.ru; Zhuravlev, K. S.; Shamirzaev, T. S.; Nenashev, A. V.; Kalagin, A. K. [Russian Academy of Sciences, Institute of Semiconductor Physics, Siberian Branch (Russian Federation)

2011-02-15

328

Railway transport of low temperature heat from large power stations by means of alternative heat carriers and water  

NASA Astrophysics Data System (ADS)

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 as heat carriers. Of these, three ammonia compounds are considered as promising. Considering, however, that complicated and expensive facilities are needed for heat transfer to and from ammonia, water is identified as the better choice. Results, based on 1975 transport prices, show that railway heat transport becomes competitive for heat loads above 50 to 100 MW and transport distances over 20 km.

Luchtman, G.; Bracke, T.

1981-11-01

329

Is There an Intrinsic Limit to the Charge-Carrier-Induced Increase of the Curie Temperature of EuO?  

NASA Astrophysics Data System (ADS)

Rare earth doping is the key strategy to increase the Curie temperature (TC) of the ferromagnetic semiconductor EuO. The interplay between doping and charge carrier density (n), and the limit of the TC increase, however, are yet to be understood. We report measurements of n and TC of Gd-doped EuO over a wide range of doping levels. The results show a direct correlation between n and TC, with both exhibiting a maximum at high doping. On average, less than 35% of the dopants act as donors, raising the question about the limit to increasing TC.

Mairoser, T.; Schmehl, A.; Melville, A.; Heeg, T.; Canella, L.; Böni, P.; Zander, W.; Schubert, J.; Shai, D. E.; Monkman, E. J.; Shen, K. M.; Schlom, D. G.; Mannhart, J.

2010-12-01

330

Is there an intrinsic limit to the charge-carrier-induced increase of the Curie temperature of EuO?  

PubMed

Rare earth doping is the key strategy to increase the Curie temperature (T(C)) of the ferromagnetic semiconductor EuO. The interplay between doping and charge carrier density (n), and the limit of the T(C) increase, however, are yet to be understood. We report measurements of n and T(C) of Gd-doped EuO over a wide range of doping levels. The results show a direct correlation between n and T(C), with both exhibiting a maximum at high doping. On average, less than 35% of the dopants act as donors, raising the question about the limit to increasing T(C). PMID:21231624

Mairoser, T; Schmehl, A; Melville, A; Heeg, T; Canella, L; Böni, P; Zander, W; Schubert, J; Shai, D E; Monkman, E J; Shen, K M; Schlom, D G; Mannhart, J

2010-12-17

331

Charge migration in DNA: ion-gated transport  

NASA Astrophysics Data System (ADS)

A new microscopic mechanism of electron-hole (radical cation) migration in DNA, where the quantum transport of an injected charge is gated in a correlated manner by the thermal motions of the hydrated counterions, is described [1]. Classical molecular dynamics simulations in conjunction with large-scale first-principles electronic structure calculations reveal that different counterion configurations lead to formation of states characterized by varying spatial distributions and degrees of charge-localization. Stochastic dynamic fluctuations between such ionic configurations can induce correlated changes in the spatial distribution of the hole, with concomitant transport along the DNA double helix. Comparative UV light-induced cleavage experiments on native B-DNA oligomers and on ones modified to contain counterion (sodium) - starved bridges between damage-susceptible hole-trapping sites (GG steps), show in the latter a reduction in damage at the distal step, indicating a reduced mobility of the hole across the modified bridge in correspondence with theoretical prediction. In addition, we discuss first-principles studies of DNA base sequence and hydration effects on the electronic properties and on the energetics and spatial distribution of the ionization hole in certain DNA oligomers, and investigations of the structure and bonding mechanism of certain intercalants to DNA. [1] R.N. Barnett, C.L. Cleveland, A. Joy, U. landman, G.B. Schuster, Science 294, 567 (2001).

Landman, Uzi

2003-03-01

332

Flow Potentials for Transport of Charged Species in Clay Soils  

NASA Astrophysics Data System (ADS)

Clay particles frequently have a charged surface which strongly influence the transport of ions. In turn, the ion concentration and pH affect the swelling and shrinking of particular clay soils. The coupling of these phenomenon and its effect on transport is complicated and governing flow equations cannot be heuristically derived. In this talk, recent results obtained using Hybrid Mixture Theory (HMT), an approach based on fundamental thermodynamic principles, are discussed. The resulting governing equations are found to be generalized versions of what is standardly used (i.e. Darcy's law) in order to account for the charges and swelling nature of clay. Hybrid mixture theory consists of classical mixture theory applied to a multiphase system with volume averaged field equations. Averaging each field equation (e.g. conservation of mass, momentum balance, energy balance, and entropy inequality) produces macroscopic variables which are precisely defined in terms of their microscopic counterparts. A two-phase porous medium (e.g. solid and fluid) with N constituents per phase is thus viewed as 2N overlaying continua with each macroscopic variable for each constituent of each phase defined spatially everywhere. Constitutive restrictions and near-equilibrium expressions are obtained by exploiting the entropy inequality using the Coleman and Noll method.

Bennethum, L. S.; Cushman, J. H.

2001-12-01

333

Controlling Polymer Translocation and Ion Transport via Charge Correlations.  

PubMed

We develop a correlation-corrected transport theory in order to predict ionic and polymer transport properties of membrane nanopores under physical conditions where mean-field electrostatics breaks down. The experimentally observed low KCl conductivity of open ?-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 to 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. PMID:25310861

Buyukdagli, Sahin; Ala-Nissila, T

2014-11-01

334

DNA-mediated Charge Transport in Redox Sensing and Signaling  

PubMed Central

The transport of charge through the DNA base pair stack offers a route to carry out redox chemistry at a distance. Here we describe characteristics of this chemistry that have been elucidated and how this chemistry may be utilized within the cell. The shallow distance dependence associated with these redox reactions permits DNA-mediated signaling over long molecular distances in the genome and facilitates the activation of redox-sensitive transcription factors globally in response to oxidative stress. The long-range funneling of oxidative damage to sites of low oxidation potential in the genome also may provide a means of protection within the cell. Furthermore, the sensitivity of DNA charge transport to perturbations in base pair stacking, as may arise with base lesions and mismatches, may be used as a route to scan the genome for damage as a first step in DNA repair. Thus, the ability of double helical DNA, in mediating redox chemistry at a distance, provides a natural mechanism for redox sensing and signaling in the genome. PMID:20047321

Genereux, Joseph C.; Boal, Amie K.

2010-01-01

335

Controlling polymer translocation and ion transport via charge correlations  

E-print Network

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.

Sahin Buyukdagli; Tapio Ala-Nissila

2014-08-19

336

IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 17, NO. 9, SEPTEMBER 2005 1779 The Role of Carrier Transport on the Current Injection  

E-print Network

, and Nelson Tansu Abstract--A theoretical and experimental study demonstrates that the current injection of a theoretical and experimental study on the impact of carrier transport on for InGaAsN QW lasers, providing of hole transport on the temperature dependence of the external differential quantum efficiency and above

Gilchrist, James F.

337

Charge transport and electroluminescence of silicon nanocrystals/SiO2 superlattices  

NASA Astrophysics Data System (ADS)

Charge transport and electroluminescence mechanisms in Si-rich Si oxynitride/silicon oxide (SRON/SiO2) superlattices deposited on p-type Si substrate are reported. The superlattice structures were deposited by plasma-enhanced chemical-vapor deposition and subsequently annealed at 1150 °C to precipitate and crystallize the Si excess into Si nanocrystals. The dependence of the electrical conduction on the applied voltage and temperature was found to be well described by a Poole-Frenkel transport mechanism over a wide voltage range. On the other hand, the observed dependence of the electroluminescence on the SRON layer thickness is a clear proof of quantum confinement and was attributed to an excitonic radiative recombination taking place in the confined states within the Si quantum dots. A model is proposed based on thermal hopping of electrons between the quantum dots acting as trap states (Poole-Frenkel). A correlation between carrier transport and electroluminescence has been established considering impact ionization of high-kinetic energy electrons on the Si quantum dots.

López-Vidrier, J.; Berencén, Y.; Hernández, S.; Blázquez, O.; Gutsch, S.; Laube, J.; Hiller, D.; Löper, P.; Schnabel, M.; Janz, S.; Zacharias, M.; Garrido, B.

2013-10-01

338

Dioxin mediates downregulation of the reduced folate carrier transport activity via the arylhydrocarbon receptor signalling pathway  

SciTech Connect

Dioxins such as 2,3,7,8-tetrachlordibenzo-p-dioxin (TCDD) are common environmental contaminants known to regulate several genes via activation of the transcription factor aryl hydrocarbon receptor (AhR) associated with the development of numerous adverse biological effects. However, comparatively little is known about the molecular mechanisms by which dioxins display their toxic effects in vertebrates. The 5' untranslated region of the hepatocellular Reduced folate carrier (Rfc1; Slc19a1) exhibits AhR binding sites termed dioxin responsive elements (DRE) that have as yet only been found in the promoter region of prototypical TCDD target genes. Rfc1 mediated transport of reduced folates and antifolate drugs such as methotrexate (MTX) plays an essential role in physiological folate homeostasis and MTX cancer chemotherapy. In order to determine whether this carrier represents a target gene of dioxins we have investigated the influence of TCDD on functional Rfc1 activity in rat liver. Pre-treatment of rats with TCDD significantly diminished hepatocellular Rfc1 uptake activity in a time- and dose-dependent manner. In further mechanistic studies we demonstrated that this reduction was due to TCDD-dependent activation of the AhR signalling pathway. We additionally showed that binding of the activated receptor to DRE motifs in the Rfc1 promoter resulted in downregulation of Rfc1 gene expression and reduced carrier protein levels. As downregulation of pivotal Rfc1 activity results in functional folate deficiency associated with an elevated risk of cardiovascular diseases or carcinogenesis, our results indicate that deregulation of this essential transport pathway represents a novel regulatory mechanism how dioxins display their toxic effects through the Ah receptor.

Halwachs, Sandra, E-mail: halwachs@vetmed.uni-leipzig.d [Institute of Pharmacology, Pharmacy and Toxicology, Faculty of Veterinary Medicine, University of Leipzig, Leipzig (Germany); Lakoma, Cathleen [Institute of Pharmacology, Pharmacy and Toxicology, Faculty of Veterinary Medicine, University of Leipzig, Leipzig (Germany); Gebhardt, Rolf [Institute of Biochemistry, Faculty of Medicine, University of Leipzig, Leipzig (Germany); Schaefer, Ingo; Seibel, Peter [Molecular Cell Therapy, Center for Biotechnology and Biomedicine, Faculty of Medicine, University of Leipzig, Leipzig (Germany); Honscha, Walther [Institute of Pharmacology, Pharmacy and Toxicology, Faculty of Veterinary Medicine, University of Leipzig, Leipzig (Germany)

2010-07-15

339

Capture of charge carriers and output power of a quantum well laser  

SciTech Connect

The effect of noninstantaneous carrier capture by a nanoscale active region on the power characteristics of a semiconductor laser is studied. A laser structure based on a single quantum well is considered. It is shown that delayed carrier capture by the quantum well results in a decrease in the internal differential quantum efficiency and sublinearity of the light-current characteristic of the laser. The main parameter of the developed theoretical model is the velocity of carrier capture from the bulk (waveguide) region to the two-dimensional region (quantum well). The effect of the capture velocity on the dependence of the following laser characteristics on the pump current density is studied: the output optical power, internal quantum efficiency of stimulated emission, current of stimulated recombination in the quantum well, current of spontaneous recombination in the optical confinement layer, and carrier concentration in the optical confinement layer. A decrease in the carrier capture velocity results in a larger sublinearity of the light-current characteristic, which results from an increase in the injection current fraction expended to parasitic spontaneous recombination in the optical confinement layer and, hence, a decrease in the injection current fraction expended to stimulated recombination in the quantum well. A comparison of calculated and experimental light-current characteristics for a structure considered as an example shows that good agreement between them (up to a very high injection current density of 45 kA/cm{sup 2}) is attained at a capture velocity of 2 Multiplication-Sign 10{sup 6} cm/s. The results of this study can be used to optimize quantum well lasers for generating high optical powers.

Sokolova, Z. N., E-mail: Zina.Sokolova@mail.ioffe.ru; Tarasov, I. S. [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation); Asryan, L. V. [Virginia Polytechnic Institute and State University (United States)

2011-11-15

340

An appraisal of the one-flux method for treating carrier transport in modern semiconductor devices  

NASA Astrophysics Data System (ADS)

McKelvey's one-flux method, which has recently been used to investigate transport in short-base bipolar transistors and to specify the carrier mobility in a forward-biased barrier, is put into perspective by a comparison with the usual continuity and drift-diffusion equations. For a bulk semiconductor region in which a small electric field is present, and under typical operating conditions, it is shown that the use of the time-dependent flux method is equivalent to solving the usual continuity and drift-diffusion equations under low-level injection. It is the shown that recent one-flux analyses of short-base transport, for both d.c. and a.c. conditions, are equivalent to solving the continuity and drift-diffusion equations with appropriate boundary conditions. It is pointed out that the use of the flux method to resolve the long-standing issue of specifying the carrier mobility within a forward-biased barrier is impeded by a lack of knowledge of the required backscattering coefficients. Recent suggestions for these backscattering coefficients are carefully examined; the physical basis for the choices made, and hence the resulting values of mobility and diffusivity, are questioned.

Vaidyanathan, M.; Pulfrey, D. L.

1996-06-01

341

Dependence of growth temperature on carrier gas velocity in open tube transport  

NASA Astrophysics Data System (ADS)

The apparent supercooling ( ?T ? Ts - Te, where Ts is the saturation temperature and Te is the equilibr ium growth temperature) of ZnTe crystals was measured in an open tube transport experiment as a function of carrier gas velocity. For four growth tubes with diameters from 0.1 to 0.84 cm, a minimum in ? T of ˜ 0 °C is observed at a Reynolds number of about 50. At lower Reynolds numbers the temperatures required for nucleation and growth were as much as 100 °C below Ts, although it might have been expected that equilibrium would be approached most closely at the lowest gas velocities. At higher Reynolds numbers growth also occurs many degrees below Ts. On the other hand, crystals sometimes grow near the axis of the growth tube at temperatures above Ts. It is suggested that these unexpected results may be due to concentration gradients in the gas phase resulting from thermal diffusion of the heavier atoms and molecules to the cooler regions of the system. Whatever the explanation, the carrier gas velocity performs an important role in crystal growth by open tube transport.

Reed, T. B.; Lafleur, W. J.

1972-12-01

342

Novel macrocyclic carriers for proton-coupled liquid membrane transport. Final report  

SciTech Connect

The objective of this research program is to elucidate the chemical principles which are responsible for the cation selectivity and permeability of liquid membranes containing macrocyclic carriers. Several new macrocyclic carriers were synthesized during the last three year period. In addition, new, more convenient synthetic routes were achieved for several nitrogen-containing bicyclic and tricyclic macrocycles. The cation binding properties of these macrocycles were investigated by potentiometric titration, calorimetric titration, solvent extraction and NMR techniques. In addition, hydrophobic macrocycles were incorporated into dual hollow fiber and other membrane systems to investigate their membrane performance, especially in the proton-coupled transport mode. A study of the effect of methoxyalkyl macrocycle substituents on metal ion transport was completed. A new calorimeter was constructed which made it possible to study the thermodynamics of macrocycle-cation binding to very high temperatures. Measurements of thermodynamic data for the interaction of crown ethers with alkali and alkaline earth cations were achieved to 473 K. Molecular modeling work was begun for the first time on this project and fundamental principles were identified and developed for the establishment of working models in the future.

Lamb, J.D.; Izatt, R.M.; Bradshaw, J.S.; Shirts, R.B.

1996-08-24

343

Scale-Free Networks and Commercial Air Carrier Transportation in the United States  

NASA Technical Reports Server (NTRS)

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.

Conway, Sheila R.

2004-01-01

344

Monte Carlo simulations of carrier transport in AlGaInP laser diodes  

Microsoft Academic Search

A self-consistent ensemble Monte Carlo simulation of charge transport in AlGaInP quantum-well (QW) lasers has been developed in an effort to understand the temperature sensitivity of these devices. In particular, the lasing capability of a three-well design has been studied at 300 and 360 K. Although the electron and hole leakage currents are found to increase with the temperature, this

G. C. Crow; R. A. Abram

1997-01-01

345

Electrical Transport of Spin-Polarized Carriers in Disordered Ultrathin Films  

Microsoft Academic Search

Slow, nonexponential relaxation of electrical transport accompanied by memory effects has been induced in quench-condensed ultrathin amorphous Bi films by the application of a parallel magnetic field. This behavior, which is very similar to space-charge limited current flow, is found in extremely thin films well on the insulating side of the thickness-tuned superconductor-insulator transition. It may be the signature of

L. M. Hernandez; A. Bhattacharya; Kevin A. Parendo; A. M. Goldman

2003-01-01

346

Direct Observation of Anisotropic Carrier Transport in Organic Semiconductor by Time-Resolved Microscopic Optical Second-Harmonic Imaging  

NASA Astrophysics Data System (ADS)

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.

Manaka, Takaaki; Matsubara, Kohei; Abe, Kentaro; Iwamoto, Mitsumasa

2013-10-01

347

Charge carrier photogeneration and recombination in ladder-type poly(para-phenylene): Interplay between impurities and external electric field  

NASA Astrophysics Data System (ADS)

Charge carrier generation and decay in m -LPPP polymer films were examined by means of femtosecond transient absorption spectroscopy in the time window of 100fs-15ns . Two modes of polaron formation with distinct behavior were identified, impurity induced in the absence of an external electric field and electric field induced in pristine film. While field induced charge generation is relatively slow, occurring throughout the excited state lifetime, the rate of impurity induced charge generation is much faster and depends on excitation wavelength; it occurs on the several hundred femtosecond time scale under excitation within the main absorption band, but excitation into the red wing of the absorption band results in charge generation within less than 100fs . Polaron decay through geminate electron-hole recombination occurs with widely distributed lifetimes, from ˜0.8ns to microseconds; the polarons characterized by the shortest decay time have a redshifted absorption spectrum (as compared to more long-lived polarons) and are attributed to tightly bound polaron pairs.

Gulbinas, V.; Hertel, D.; Yartsev, A.; Sundström, V.

2007-12-01

348

Carrier-mediated transport of monocarboxylic acids in BeWo cell monolayers as a model of the human trophoblast  

E-print Network

relevance due to the fact that nutrients, hormones, as well as, drugs and drugs of abuse can be transported across the placental barrier by these mechanisms.7 Carrier-mediated transport mechanisms for monocarboxylic acids exist in many cell types.8.... In addition to the transport of lactic acid,11,14,15 a MCT at the placental barrier presents a potential mechanism by which monocarboxylic acid drugs and drugs of abuse may readily distribute between maternal and fetal compartments. Therefore, the Utoguchi...

Utoguchi, Naoki; Magnusson, Malin; Audus, Kenneth L.

1999-01-01

349

Towards a unified description of the charge transport mechanisms in conductive atomic force microscopy studies of semiconducting polymers  

NASA Astrophysics Data System (ADS)

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

Moerman, D.; Sebaihi, N.; Kaviyil, S. E.; Leclère, P.; Lazzaroni, R.; Douhéret, O.

2014-08-01

350

The Carrier's Liability for Damage Caused by Delay in International Air Transport  

NASA Technical Reports Server (NTRS)

Delay in the air transport occurs when passengers, baggage or cargo do not arrive at their destination at the time indicated in the contract of carriage. The causes of delay in the carriage of passengers are booking errors or double booking, delayed departure of aircraft, incorrect information regarding the time of departure, failure to land at the scheduled destination and changes in flight schedule or addition of extra landing stops. Delay in the carriage of baggage or cargo may have different causes: no reservation, lack of space, failure to load the baggage or cargo at the right place, or to deliver the covering documents at the right place. The Montreal Convention of 1999 Article 19 provides that 'The carrier is liable for damage occasioned by delay in the carriage by air of passengers, baggage or cargo. Nevertheless, the carder shall not be liable for damage occasioned by delay if it proves that it and its servants and agents took all measures that could reasonably be required to avoid the damage or that it was impossible for it or them to take such measures'. The Montreal Convention Article 22 provides liability limits of the carrier in case of delay for passengers and their baggage and for cargo. In the carriage of persons, the liability of the carrier for each passenger is limited to 4,150 SDR. In the carriage of baggage, the liability of the carrier is limited to 1,000 SDR for each passenger unless a special declaration as to the value of the baggage has been made. In the carriage of cargo, the liability of the carrier is limited to 17 SDR per kilogram unless a special declaration as to the value of the cargo has been made. The Montreal Convention Article 19 has shortcomings: it is silent on the duration of the liability for carriage,andit does not make any distinction between persons and good. It does not give any indication concerning the circumstances to be taken into account in cases of delay, and about the length of delay. In conclusion, it is desirable to define the period of carriage with accuracy, and to insert the word 'unreasonable' in Article 19.

Lee, Kang Bin

2003-01-01

351

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

...when a commercial carrier transports my mobile home overland or over water? 302-10... 10-ALLOWANCES FOR TRANSPORTATION OF MOBILE HOMES AND BOATS USED AS A PRIMARY RESIDENCE...when a commercial carrier transports my mobile home overland or over water?...

2010-07-01

352

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

...when a commercial carrier transports the mobile home? 302-10.300 Section 302-10... 10-ALLOWANCES FOR TRANSPORTATION OF MOBILE HOMES AND BOATS USED AS A PRIMARY RESIDENCE...when a commercial carrier transports the mobile home? Yes, you may receive an...

2010-07-01

353

Effect of Column Disorder on Carrier Transport in Columnar Discotic Liquid Crystal Evaluated by Applying Precisely Controlled Shear Stress  

NASA Astrophysics Data System (ADS)

The effect of column disorder on carrier drift mobility in columnar discotic liquid crystals has been investigated by applying a precisely controlled oscillating shear stress. Drift mobilities on the order of 10-1 cm2.V-1.s-1 were confirmed for positive and negative carriers in the columnar phase of 1,4,8,11,15,18,22,25-octahexylphthalocyanine in a well-aligned homeotropic geometry, in which the columnar axis was perfectly perpendicular to substrates with an electrode. A slight tilt of the columnar axis upon applying shear stress led to a marked decrease in electronic carrier mobility from 10-1 to less than 10-6 cm2.V-1.s-1, and transport was only confirmed for positive ion carriers. This result indicates that a uniform shear stress blocks the carrier transport path in the entire area of the electrode, and one-dimensional carrier transport path along the columns is easily hindered in columnar discotic liquid crystals.

Kim, Jaeki; Yamasaki, Naoyuki; Hayashi, Takeshi; Katayama, Mitsuyoshi; Yoshida, Hiroyuki; Moritake, Hiroshi; Fujii, Akihiko; Ozaki, Masanori

2013-10-01

354

Charge transport in cancer-related genes and early carcinogenesis  

NASA Astrophysics Data System (ADS)

The electronic transmission properties of DNA molecules are believed to play a significant role in many physical phenomena taking place in living organisms (Chakraborty, 2007) [1]. Here we study the charge transport (CT) properties of cancer-related genes, including some of the most important tumor suppressors. We find that the changes in averaged CT around the sites of pathogenic and cancerous mutations are statistically smaller than those on sites where pathogenic mutations have not been observed. The results suggest that CT might be an indicator to discriminate between pathogenic and non-pathogenic mutations at an early stage. Mutations which cause little change in CT may be more likely to occur, or more likely to be missed by damage-repair enzymes which probe CT, and are therefore more likely to persist and cause disease.

Shih, Chi-Tin; Cheng, Yun-Yin; Wells, Stephen A.; Hsu, Ching-Ling; Römer, Rudolf A.

2011-01-01

355

Perovskite solar cells employing organic charge-transport layers  

NASA Astrophysics Data System (ADS)

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.

Malinkiewicz, Olga; Yella, Aswani; Lee, Yong Hui; Espallargas, Guillermo Mínguez; Graetzel, Michael; Nazeeruddin, Mohammad K.; Bolink, Henk J.

2014-02-01

356

Charge transport properties in CdZnTe detectors grown by the vertical Bridgman technique  

SciTech Connect

Presently, a great amount of effort is being devoted to the development of CdTe and CdZnTe (CZT) detectors for a large variety of applications such as medical, industrial, and space research. We present the spectroscopic properties of some CZT crystals grown by the standard vertical Bridgman method and by the boron oxide encapsulated vertical Bridgman method, which has been recently implemented at IMEM-CNR (Parma, Italy). In this technique, the crystal is grown in an open quartz crucible fully encapsulated by a thin layer of liquid boron oxide. This method prevents contact between the crystal and the crucible, thereby allowing larger single grains with a lower dislocation density to be obtained. Several mono-electrode detectors were realized, with each having two planar gold contacts. The samples are characterized by an active area of about 7 mm x 7 mm and thicknesses ranging from 1 to 2 mm. The charge transport properties of the detectors have been studied by mobility-lifetime ({mu} x {tau}) product measurements, carried out at the European Synchrotron Radiation Facility (Grenoble, France) in the planar transverse field configuration, where the impinging beam direction is orthogonal to the collecting electric field. We have performed several fine scans between the electrodes with a beam spot of 10 {mu}m x 10 {mu}m at various energies from 60 to 400 keV. In this work, we present the test results in terms of the ({mu} x {tau}) product of both charge carriers.

Auricchio, N.; Caroli, E. [INAF/IASF-Bologna, Bologna, 40129 (Italy); Marchini, L.; Zappettini, A. [IMEM-CNR, Parma, 43100 (Italy); Abbene, L. [DIFI, University of Palermo, Palermo, 90128 (Italy); Honkimaki, V. [European Synchrotron Radiation Facility, Grenoble, 38000 (France)

2011-12-15

357

Nanoscale investigation of charge transport at the grain boundaries and wrinkles in graphene film  

NASA Astrophysics Data System (ADS)

The influence of grain boundaries and mechanical deformations in graphene film on the electric charge transport is investigated at nanoscale with conductive atomic force microcopy. Large area monolayer graphene samples were prepared by the chemical vapor deposition technique. Field emission scanning electron microscopy confirmed the formation of grain boundaries and the presence of wrinkles. The presence of the D-band in the Raman spectrum also indicated the existence of sharp defects such as grain boundaries. Extremely low conductivity was found at the grain boundaries and the wrinkled surface was also more resistive in comparison to the plain graphene surface. Many samples were experimented with to justify our findings by selecting different areas on the graphene surface. Uniform conductivity was found on grain boundary and wrinkle free graphene surfaces. We made channels of varied lengths by local anodic oxidation to confine the charge carrier to the smallest dimensions to better confirm the alteration in current due to grain boundaries and wrinkles. The experimental findings are discussed with reference to the implementation of graphene as transparent conductive electrode.

Ahmad, Muneer; An, Hyosub; Kim, Yong Seung; Lee, Jae Hong; Jung, Jongwan; Chun, Seung-Hyun; Seo, Yongho

2012-07-01

358

Metal Complexes for DNA-Mediated Charge Transport  

PubMed Central

In all organisms, oxidation threatens the integrity of the genome. DNA-mediated charge transport (CT) may play an important role in the generation and repair of this oxidative damage. In studies involving long-range CT from intercalating Ru and Rh complexes to 5?-GG-3? sites, we have examined the efficiency of CT as a function of distance, temperature, and the electronic coupling of metal oxidants bound to the base stack. Most striking is the shallow distance dependence and the sensitivity of DNA CT to how the metal complexes are stacked in the helix. Experiments with cyclopropylamine-modified bases have revealed that charge occupation occurs at all sites along the bridge. Using Ir complexes, we have seen that the process of DNA-mediated reduction is very similar to that of DNA-mediated oxidation. Studies involving metalloproteins have, furthermore, shown that their redox activity is DNA-dependent and can be DNA-mediated. Long range DNA-mediated CT can facilitate the oxidation of DNA-bound base excision repair proteins to initiate a redox-active search for DNA lesions. DNA CT can also activate the transcription factor SoxR, triggering a cellular response to oxidative stress. Indeed, these studies show that within the cell, redox-active proteins may utilize the same chemistry as that of synthetic metal complexes in vitro, and these proteins may harness DNA-mediated CT to reduce damage to the genome and regulate cellular processes. PMID:21643528

Barton, Jacqueline K.; Olmon, Eric D.; Sontz, Pamela A.

2010-01-01

359

Charge Transport Mechanism in Thin Cuticles Holding Nandi Flame Seeds  

PubMed Central

Metal-sample-metal sandwich configuration has been used to investigate DC conductivity in 4??m thick Nandi flame [Spathodea campanulata P. Beauv.] seed cuticles. J-V characteristics showed ohmic conduction at low fields and space charge limited current at high fields. Charge mobility in ohmic region was 4.06 × 10?5??(m2V?1s?1). Temperature-dependent conductivity measurements have been carried out in the temperature range 320?K < T > 450?K. Activation energy within a temperature of 320?K–440?K was about 0.86?eV. Variable range hopping (VRH) is the main current transport mechanism at the range of 330–440?K. The VRH mechanism was analyzed based on Mott theory and the Mott parameters: density of localized states near the Fermi-level N(EF) ? 9.04 × 1019??(eV?1cm?3) and hopping distance R ? 1.44 × 10?7?cm, while the hopping energy (W) was in the range of 0.72?eV–0.98?eV. PMID:20130799

Kipnusu, Wycliffe K.; Katana, Gabriel; Migwi, Charles M.; Rathore, I. V. S.; Sangoro, Joshua R.

2009-01-01

360

Charge transport mechanism in thin cuticles holding nandi flame seeds.  

PubMed

Metal-sample-metal sandwich configuration has been used to investigate DC conductivity in 4 mum thick Nandi flame [Spathodea campanulata P. Beauv.] seed cuticles. J-V characteristics showed ohmic conduction at low fields and space charge limited current at high fields. Charge mobility in ohmic region was 4.06 x 10(-5) (m(2)V(-1)s(-1)). Temperature-dependent conductivity measurements have been carried out in the temperature range 320 K < T > 450 K. Activation energy within a temperature of 320 K-440 K was about 0.86 eV. Variable range hopping (VRH) is the main current transport mechanism at the range of 330-440 K. The VRH mechanism was analyzed based on Mott theory and the Mott parameters: density of localized states near the Fermi-level N(E(F)) approximately 9.04 x 10(19) (eV(-1)cm(-3)) and hopping distance R approximately 1.44 x 10(-7) cm, while the hopping energy (W) was in the range of 0.72 eV-0.98 eV. PMID:20130799

Kipnusu, Wycliffe K; Katana, Gabriel; Migwi, Charles M; Rathore, I V S; Sangoro, Joshua R

2009-01-01

361

Mass and charge transport in arbitrarily shaped microchannels  

NASA Astrophysics Data System (ADS)

We consider laminar flow of incompressible electrolytes in long, straight channels driven by pressure and electro-osmosis. We use a Hilbert space eigenfunction expansion to address the problem of arbitrarily shaped cross sections and obtain general results in linear-response theory for the mass and charge transport coefficients which satisfy Onsager relations [1,2]. In the limit of non-overlapping Debye layers the transport coefficients are simply expressed in terms of parameters of the electrolyte as well as half the hydraulic diameter R=2 A/P with A and P being the cross- sectional area and perimeter, respectively. In particular, we consider the limits of thin non-overlapping as well as strongly overlapping Debye layers, respectively, and calculate the corrections to the hydraulic resistance due to electro- hydrodynamic interactions.[1] N. A. Mortensen, F. Okkels, and H. Bruus, Phys. Rev. E 71, 057301 (2005) [2] N. A. Mortensen, L. H. Olesen, and H. Bruus, New J. Phys. 8, 37 (2006)

Bruus, Henrik; Asger Mortensen, Niels; Okkels, Fridolin; Hoejgaard Olesen, Laurits

2006-11-01

362

Ring-shaped spatial pattern of exciton luminescence formed due to the hot carrier transport in a locally photoexcited electron-hole bilayer  

SciTech Connect

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.

Paraskevov, A. V., E-mail: avp.workbox@yandex.ru [National Research Center 'Kurchatov Institute,' (Russian Federation)

2012-06-15

363

The exocyst complex contributes to PIN auxin efflux carrier recycling and polar auxin transport in Arabidopsis.  

PubMed

In land plants polar auxin transport is one of the substantial processes guiding whole plant polarity and morphogenesis. Directional auxin fluxes are mediated by PIN auxin efflux carriers, polarly localized at the plasma membrane. The polarization of exocytosis in yeast and animals is assisted by the exocyst: an octameric vesicle-tethering complex and an effector of Rab and Rho GTPases. Here we show that rootward polar auxin transport is compromised in roots of Arabidopsis thaliana loss-of-function mutants in the EXO70A1 exocyst subunit. The recycling of PIN1 and PIN2 proteins from brefeldin-A compartments is delayed after the brefeldin-A washout in exo70A1 and sec8 exocyst mutants. Relocalization of PIN1 and PIN2 proteins after prolonged brefeldin-A treatment is largely impaired in these mutants. At the same time, however, plasma membrane localization of GFP:EXO70A1, and the other exocyst subunits studied (GFP:SEC8 and YFP:SEC10), is resistant to brefeldin-A treatment. In root cells of the exo70A1 mutant, a portion of PIN2 is internalized and retained in specific, abnormally enlarged, endomembrane compartments that are distinct from VHA-a1-labelled early endosomes or the trans-Golgi network, but are RAB-A5d positive. We conclude that the exocyst is involved in PIN1 and PIN2 recycling, and thus in polar auxin transport regulation. PMID:23163883

Drdová, Edita Janková; Synek, Lukáš; Pe?enková, Tamara; Hála, Michal; Kulich, Ivan; Fowler, John E; Murphy, Angus S; Zárský, Viktor

2013-03-01

364

Charge transport properties of a partially reduced V{sub 2}O{sub 5} xerogel intercalated with a polymer electrolyte  

SciTech Connect

Recently, there has been considerable interest in advanced materials and processing techniques for practical applications. V{sub 2}O{sub 5} xerogels have generated much attention because they are layered materials that undergo reversible redox intercalation with lithium. The sol-gel process has been used to intercalate V{sub 2}O{sub 5} xerogels with the polymer electrolyte, oxymethylene linked poly(ethylene oxide)-lithium triflate[(a-PEO){sub n}(LiCF{sub 3}SO{sub 3})]. The resulting nanocomposite is a mixed ionic-electronic conductor in which the ionic charge carriers in the polymer electrolyte are in intimate contact with the electronic charge carriers in the V{sub 2}O{sub 5} xerogel. Variable-temperature electronic conductivity and thermoelectric power measurements have been performed to examine the charge transport properties.

Thomas, J.A.; Kloster, G.M.; Shriver, D.; Kannewurf, C.R. [Northwestern Univ., Evanston, IL (United States)

1995-12-31

365

Global seamless network demonstrator: carrier grade automatic switched transport network implementation in realistic telecom field environment  

NASA Astrophysics Data System (ADS)

The Global Seamless Network (GSN) Demonstrator is presented, a joint effort of system vendors and Deutsche Telekom Group R&D to demonstrate network functions and management integration and enable, for the first time, experiences with a carrier grade Automatically Switched Transport Network (ASTN) implementation and the envisaged main ASTN clients, IP and Ethernet. For end-to-end monitoring capability, integrating the view on the ASTN and Ethernet-MAN configuration, an UMS (Upper Monitoring System) is being developed. Furthermore broadband application were implemented to visualise the network functions. The ASTN backbone consists of four cross connects and an ULH-WDM system with 3x 10Gbit/s channels (OCh) between Berlin and Darmstadt, whereby each OCh is treated as a virtual fibre.

Foisel, Hans-Martin; Hanik, Norbert; Braun, Ralf-Peter; Lehr, Georg; Gladisch, Andreas

2004-04-01

366

Charge carrier dynamics of vapor-deposited small-molecule/fullerene organic solar cells.  

PubMed

Although small-molecule organic solar cells (SMOSCs) have shown increasingly promising prospects as a source of solar power, there have been few studies concerning the photophysics of these systems. Here, we report the time scale and efficiency of charge separation and recombination in a vapor-deposited SMOSC material that produces 5.81% power conversion efficiency. Transient absorption and time-resolved photoluminescence (trPL) studies of thin film blends comprising DTDCTB, a narrow-band gap electron donor, and either C60 or C70 as an electron acceptor show that charge separation occurs in ~100 fs, while charge recombination takes place over sub-ns and ns time scales. trPL indicates a donor electron-hole pair lifetime of ~33 ps in the neat film and reveals that ~20% of donors fail to charge separate in donor-acceptor mixed films, likely owing to some spatially extended donor-rich regions that interact poorly with acceptors. Our results suggest that morphological manipulations of this material could further improve device efficiency. PMID:23718234

Chang, Angela Y; Chen, Yi-Hong; Lin, Hao-Wu; Lin, Li-Yen; Wong, Ken-Tsung; Schaller, Richard D

2013-06-19

367

Charge transport in hexagonal columnar liquid crystals self-organized from supramolecular cylinders based on acene-functionalized dendrons  

NASA Astrophysics Data System (ADS)

We report measurements of time-of-flight charge carrier mobility and thermal optical polarized microscopy on a new class of hexagonal columnar (?h) liquid crystals (LC) self-organized from supramolecular cylinders self-assembled from acene functionalized dendrons. We discuss the temperature and electric field-independent high hole mobility of 1 3.5×10-3 cm2/V s of fluorinated tapered first generation dendrons that contain pyrene and naphthalene groups in their core and self-assemble into supramolecular nanocylinders. The anomalous temperature behavior of the mobility is consistent with polaron transport mechanisms. Studies of time-of-flight transients, which reveal evidence for dynamic defects with lifetimes in the range of 10-6 s, are presented as aspects of charge generation and recombination kinetics.

Shiyanovskaya, I.; Singer, K. D.; Percec, V.; Bera, T. K.; Miura, Y.; Glodde, M.

2003-01-01

368

Interplay of nanoscale domain purity and size on charge transport and recombination dynamics in polymer solar cells.  

PubMed

Charge transport and bimolecular recombination dynamics were correlated with nanomorphology in polymer solar cells. The morphology of poly(diketopyrrolopyrrole-terthiophene) (PDPP3T) and phenyl-C61-butyric acid methyl ester (PC60BM) blend films was modified using different solvent additives namely 1-chloronaphthalene (CN), 1,8-diiodooctane (DIO) and 1,8-octanedithiol (ODT) and their role on steady state and transient optoelectronic properties was investigated. The energy filtered transmission electron microscopy (EFTEM) images showed that additives (e.g. CN and DIO) improved the domain purity which leads to significantly higher short circuit current densities (Jsc). However when the cells were processed with the ODT additive, the fill factor (FF) and open circuit voltage (Voc) decreased dramatically. Films processed with the ODT additive showed a smaller domain size but were more connected compared to films processed using CN and DIO additives. Transient photocurrent analysis indicates faster charge collection in the case of CN and DIO processed solar cells and the slowest charge collection in ODT processed solar cells. Interestingly devices processed with the ODT additive also showed the longest charge carrier recombination lifetime and lowest bimolecular recombination coefficient. This is attributed to the smaller donor domains that are connected with each other to provide a more interconnected and efficient charge transport matrix but longer pathways in ODT films. Such a matrix helped the charge to escape from the donor-acceptor interfaces and thus reduces the bimolecular recombination, while the longer pathway increases the charge collection time. Further insight is provided into the selection of processing conditions to achieve an ideal active layer morphology consisting of domains with higher polymer purity and optimal size that lead to higher Jsc and FF. PMID:24292406

Venkatesan, Swaminathan; Adhikari, Nirmal; Chen, Jihua; Ngo, Evan C; Dubey, Ashish; Galipeau, David W; Qiao, Qiquan

2014-01-21

369

Correlated evolution of barrier capacitance charging, generation, and drift currents and of carrier lifetime in Si structures during 25 MeV neutrons irradiation  

SciTech Connect

The in situ examination of barrier capacitance charging, of generation and drift currents, and of carrier lifetime in Si structures during 25 MeV neutrons irradiation has been implemented to correlate radiation induced changes in carrier recombination, thermal release, and drift characteristics and to clarify their impact on detector performance. It has been shown that microwave probed photo-conductivity technique implemented in contact-less and distant manner can be a powerful tool for examination in wide dynamic range of carrier lifetime modified by radiation defects and for rather precise prediction of detector performance.

Gaubas, E.; Ceponis, T.; Jasiunas, A.; Uleckas, A.; Vaitkus, J. [Vilnius University, Institute of Applied Research, Vilnius LT-10222 (Lithuania); Cortina, E. [Center for Cosmology, Particle Physics and Phenomenology, Universite catholique de Louvain, Louvain la Neuve B-1348 (Belgium); Militaru, O. [Cyclotron Research Center, Universite catholique de Louvain, Louvain la Neuve B-1348 (Belgium)

2012-12-03

370

The role of electron-electron interaction in the process of charge-carrier capture in deep quantum wells  

SciTech Connect

The role of electron-electron interaction in the process of electron capture to a deep quantum well is investigated. Using two-level and three-level quantum wells as examples, the basic electron-capture mechanisms, i.e., the interaction with optical phonons and the Coulomb electron-electron interaction, are considered, and the corresponding capture probabilities and electron lifetimes are calculated. The effect of Auger recombination on the charge-carrier distribution in a quantum well is also taken into account. With this taken into consideration, a set of rate equations is solved for a nonsteady-state mode, and the time dependences of the electron concentration at the ground energy level in the quantum well are found. The contributions of each of the recombination processes under consideration are shown.

Danilov, L. V., E-mail: danleon84@mail.ru; Zegrya, G. G. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)] [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)

2013-10-15

371

Electronic properties of meso-superstructured and planar organometal halide perovskite films: charge trapping, photodoping, and carrier mobility.  

PubMed

Solution-processed organometal trihalide perovskite solar cells are attracting increasing interest, leading to high performances over 15% in thin film architectures. Here, we probe the presence of sub gap states in both solid and mesosuperstructured perovskite films and determine that they strongly influence the photoconductivity response and splitting of the quasi-Fermi levels in films and solar cells. We find that while the planar perovskite films are superior to the mesosuperstructured films in terms of charge carrier mobility (in excess of 20 cm(2) V(-1) s(-1)) and emissivity, the planar heterojunction solar cells are limited in photovoltage by the presence of sub gap states and low intrinsic doping densities. PMID:24949826

Leijtens, Tomas; Stranks, Samuel D; Eperon, Giles E; Lindblad, Rebecka; Johansson, Erik M J; McPherson, Ian J; Rensmo, Håkan; Ball, James M; Lee, Michael M; Snaith, Henry J

2014-07-22

372

Charge carrier localization induced by excess Fe in the Fe1+y(Te1-xSex) superconductor system  

NASA Astrophysics Data System (ADS)

Iron chalcogenide Fe1+y(Te1-xSex) is the simplified version of Fe-based superconductors. Its non-superconducting parent compound Fe1+yTe exhibits an AFM structure distinct from those seen in undoped FeAs compounds. Understanding of the superconducting properties of this system has been considered critical. We have investigated the effect of Fe nonstoichiometry on properties of the Fe1+y(Te1-xSex) superconductor system by means of resistivity, Hall coefficient, magnetic susceptibility, and specific heat measurements. We find that the excess Fe at interstitial sites of the (Te, Se) layers not only suppresses superconductivity, but also results in a weakly localized electronic state. Together with neutron scattering studies and recent DFT calculations, our results suggest that such weak charge carrier localization originates from the magnetic coupling between the excess Fe and the adjacent Fe square planar sheets.

Hu, Jin; Liu, Tijiang; Ke, Xianglin; Bin, Qian; Fobes, David; Vehstedt, Erin; Pham, Huy; Yang, Jinhu; Fang, Minghu; Spinu, Leonard; Schiffer, Peter; Liu, Ying; Mao, Zhiqiang

2010-03-01

373

Redox-active charge carriers of conducting polymers as a tuner of conductivity and its potential window  

PubMed Central

Electric conductivity of conducting polymers has been steadily enhanced towards a level worthy of being called its alias, “synthetic metal”. PEDOT:PSS (poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonate)), as a representative conducting polymer, recently reached around 3,000?S cm?1, the value to open the possibility to replace transparent conductive oxides. The leading strategy to drive the conductivity increase is solvent annealing in which aqueous solution of PEDOT:PSS is treated with an assistant solvent such as DMSO (dimethyl sulfoxide). In addition to the conductivity enhancement, we found that the potential range in which PEDOT:PSS is conductive is tuned wider into a negative potential direction by the DMSO-annealing. Also, the increase in a redox-active fraction of charge carriers is proposed to be responsible for the enhancement of conductivity in the solvent annealing process. PMID:23949091

Park, Han-Saem; Ko, Seo-Jin; Park, Jeong-Seok; Kim, Jin Young; Song, Hyun-Kon

2013-01-01

374

Solar-induced direct biomass-to-electricity hybrid fuel cell using polyoxometalates as photocatalyst and charge carrier  

NASA Astrophysics Data System (ADS)

The current polymer-exchange membrane fuel cell technology cannot directly use biomass as fuel. Here we present a solar-induced hybrid fuel cell that is directly powered with natural polymeric biomasses, such as starch, cellulose, lignin, and even switchgrass and wood powders. The fuel cell uses polyoxometalates as the photocatalyst and charge carrier to generate electricity at low temperature. This solar-induced hybrid fuel cell combines some features of solar cells, fuel cells and redox flow batteries. The power density of the solar-induced hybrid fuel cell powered by cellulose reaches 0.72?mW?cm-2, which is almost 100 times higher than cellulose-based microbial fuel cells and is close to that of the best microbial fuel cells reported in literature. Unlike most cell technologies that are sensitive to impurities, the cell reported in this study is inert to most organic and inorganic contaminants present in the fuels.

Liu, Wei; Mu, Wei; Liu, Mengjie; Zhang, Xiaodan; Cai, Hongli; Deng, Yulin

2014-02-01

375

Electron-hole separation distance during the charge carrier photogeneration in conjugated polymer  

NASA Astrophysics Data System (ADS)

Charge separation dynamics in a Ladder-Type Methyl substituted Poly(Para-Phenylene) (m-LPPP) was investgiated by means of electric filed modulated femtosecond pump-probe absorption spectroscopy. The Stark shift of the absorption band modified by created excitons and electron-hole pairs provided information about the average intrapair charge separation distance. The electron and hole initially separated by ca. 7 Å moved away from each other to more than 30 Å during 600 ps and later the separation rate decreased. Neither the initial separation distance, nor that obtained at 600 ps were found to depend on the applied electric field, only the separation rate at stronger field was slightly faster.

Gulbinas, Vidmantas; Baussler, H.; Yartsev, A.; Zaushitsyn, Y.; Sundstroem, V.

2003-08-01

376

Poly(p-phenylenevinylene) light-emitting diodes: Enhanced electroluminescent efficiency through charge carrier confinement  

NASA Astrophysics Data System (ADS)

We have fabricated light-emitting diodes with poly(p-phenylenevinylene) as the emissive layer, and with an electron-transporting layer formed from a solid state dispersion of 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole in poly(methyl methacrylate), placed between this and the negative electrode. These structures show typically a tenfold improvement in efficiency in the low-voltage regime and an eightfold improvement in the high-voltage regime over devices without the electron-transporting layer. Typical efficiencies are about 0.8% photons/electron. We consider that the role of the electron-transport layer is to confine holes to the emissive layer.

Brown, A. R.; Bradley, D. D. C.; Burroughes, J. H.; Friend, R. H.; Greenham, N. C.; Burn, P. L.; Holmes, A. B.; Kraft, A.

1992-12-01

377

Parasitic-free study of carrier transport in asymmetric 1.55 {micro}m MQW laser structures  

SciTech Connect

The authors have measured the carrier transport times in asymmetrically confined InGaAs/InGaAlAs MQW laser structures. Taking advantage of their optical modulation method, the authors have been able to determine effective transport times of carriers from both confinement layers into the quantum wells. These two different transport times are directly identified as being caused by the two different widths of the confinement layer on both sides of the quantum wells. The transport times are found to stem from a purely diffusive process and are responsible for a considerable different in modulation bandwidth of both types of lasers. The authors find an ambipolar diffusion constant of 3.2 cm{sup 2}/s in excellent agreement with published mobilities for quaternary InGaAlAs.

Zimmermann, M.; Kraemer, S.; Hangleiter, A. [Univ. Stuttgart (Germany). Physikalisches Inst.; Steinhagen, F.; Hillmer, H.; Burkhard, H. [Deutsche Telekom AG, Darmstadt (Germany). Forschungs- und Technologiezentrum

1996-12-31

378

Simulation and modelling of charge transport in dye-sensitized solar cells based on carbon nano-tube electrodes  

NASA Astrophysics Data System (ADS)

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.

Gacemi, Yahia; Cheknane, Ali; Hilal, Hikmat S.

2013-03-01

379

Carrier Transport in Volatile Memory Device with SnO2 Quantum Dots Embedded in a Polyimide Layer  

NASA Astrophysics Data System (ADS)

Carrier transport in a volatile memory device utilizing self-assembled tin dioxide quantum dots (SnO2 QDs) embedded in a polyimide (PI) layer was investigated. Current-voltage (I-V) curves showed that the Ag/PI/SnO2 QDs/PI/indium-tin-oxide (ITO) device memory device had the ability to write, read, and refresh the electric states under various bias voltages. The capacitance-voltage (C-V) curve for Ag/PI/SnO2 QDs/PI/p-Si capacitor exhibited a counterclockwise hysteresis, indicative of the existence of sites occupied by carriers. The origin of the volatile memory effect was attributed to holes trapping in the shallow traps formed between QD and PI matrix, which determines the carrier transport characteristics in the hybrid memory device.

Wu, Chaoxing; Li, Fushan; Guo, Tailiang; Kim, Tae Whan

2011-09-01

380

Determination of thermal and electronic carrier transport properties of SnS thinfilms using photothermal beam deflection technique  

SciTech Connect

Graphical abstract: Display Omitted Highlights: ? Determination of carrier transport properties of SnS thin films non-destructively. ? SnS thin films were deposited by chemical spray pyrolysis technique. ? Photothermal beam deflection technique is used for film analysis. ? Optimization of film deposition parameters. ? Photothermal imaging of SnS films. -- Abstract: Photothermal beam deflection technique is an efficient tool for non-destructive evaluation of thin films. Thin films of tin mono sulphide, which find application as absorber layer in photovoltaic cells, were deposited by chemical spray pyrolysis technique and their carrier transport properties were determined using photothermal beam deflection technique. Thermal diffusivity, minority carrier lifetime, mobility and surface recombination velocity of these films fabricated under different spray conditions like varying spray rate, Sn/S ratio and substrate temperature were determined. Photothermal beam deflection technique was also employed for constructing the thermal images of these films to evaluate the film uniformity.

Warrier, Anita R., E-mail: anitawarrier2@gmail.com [Cochin University of Science and Technology, Cochin 682 022 (India); Sajeesh, T.H.; Kartha, C. Sudha; Vijayakumar, K.P. [Cochin University of Science and Technology, Cochin 682 022 (India)] [Cochin University of Science and Technology, Cochin 682 022 (India)

2012-11-15

381

Microscopic modeling of charge transport in sensing proteins  

NASA Astrophysics Data System (ADS)

Sensing proteins (receptors) are nanostructures that exhibit very complex behaviors (ions pumping, conformational change, reaction catalysis, etc). They are constituted by a specific sequence of amino acids within a codified spatial organization. The functioning of these macromolecules is intrinsically connected with their spatial structure, which modifications are normally associated with their biological function. With the advance of nanotechnology, the investigation of the electrical properties of receptors has emerged as a demanding issue. Beside the fundamental interest, the possibility to exploit the electrical properties for the development of bioelectronic devices of new generations has attracted major interest. From the experimental side, we investigate three complementary kinds of measurements: (1) current-voltage (I-V) measurements in nanometric layers sandwiched between macroscopic contacts, (2) I-V measurements within an AFM environment in nanometric monolayers deposited on a conducting substrate, and (3) electrochemical impedance spectroscopy measurements on appropriate monolayers of self-assembled samples. From the theoretical side, a microscopic interpretation of these experiments is still a challenging issue. This paper reviews recent theoretical results carried out within the European project, Bioelectronic Olfactory Neuron Device, which provides a first quantitative interpretation of charge transport experiments exploiting static and dynamic electrical properties of several receptors. To this purpose, we have developed an impedance network protein analogue (INPA) which considers the interaction between neighboring amino acids within a given radius as responsible of charge transfer throughout the protein. The conformational change, due to the sensing action produced by the capture of the ligand (photon, odour), induces a modification of the spatial structure and, thus, of the electrical properties of the receptor. By a scaling procedure, the electrical change of the receptor when passing from the native to the active state is used to interpret the macroscopic measurement obtained within different methods. The developed INPA model is found to be very promising for a better understanding of the role of receptor topology in the mechanism responsible of charge transfer. Present results point favorably to the development of a new generation of nano-biosensors within the lab-on-chip strategy.

Reggiani, Lino; Millithaler, Jean-Francois; Pennetta, Cecilia

2012-06-01

382

Charge carrier formation in polythiophene/fullerene blend films studied by transient absorption spectroscopy.  

PubMed

We report herein a comparison of the photophysics of a series of polythiophenes with ionization potentials ranging from 4.8 to 5.6 eV as pristine films and when blended with 5 wt % 1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]C61 (PCBM). Three polymers are observed to give amorphous films, attributed to a nonplanar geometry of their backbone while the other five polymers, including poly(3-hexylthiophene), give more crystalline films. Optical excitation of the pristine films of the amorphous polymers is observed by transient absorption spectroscopy to give rise to polymer triplet formation. For the more crystalline pristine polymers, no triplet formation is observed, but rather a short-lived (approximately 100 ns), broad photoinduced absorption feature assigned to polymer polarons. For all polymers, the addition of 5 wt % PCBM resulted in 70-90% quenching of polymer photoluminescence (PL), indicative of efficient quenching of polythiophene excitons. Remarkably, despite this efficient exciton quenching, the yield of dissociated polymer+ and PCBM- polarons, assayed by the appearance of a long-lived, power-law decay phase assigned to bimolecular recombination of these polarons, was observed to vary by over 2 orders of magnitude depending upon the polymer employed. In addition to this power-law decay phase, the blend films exhibited short-lived decays assigned, for the amorphous polymers, to neutral triplet states generated by geminate recombination of bound radical pairs and, for the more crystalline polymers, to the direct observation of the geminate recombination of these bound radical pairs to ground. These observations are discussed in terms of a two-step kinetic model for charge generation in polythiophene/PCBM blend films analogous to that reported to explain the observation of exciplex-like emission in poly(p-phenylenevinylene)-based blend films. Remarkably, we find an excellent correlation between the free energy difference for charge separation (deltaG(CS)rel) and yield of the long-lived charge generation, with efficient charge generation requiring a much larger deltaG(CS)rel than that required to achieve efficient PL quenching. We suggest that this observation is consistent with a model where the excess thermal energy of the initially formed polaron pairs is necessary to overcome their Coulombic binding energy. This observation has important implications for synthetic strategies to optimize organic solar cell performance, as it implies that, at least devices based on polythiophene/PCBM blend films, a large deltaG(CS)rel (or LUMO level offset) is required to achieve efficient charge dissociation. PMID:18278911

Ohkita, Hideo; Cook, Steffan; Astuti, Yeni; Duffy, Warren; Tierney, Steve; Zhang, Weimin; Heeney, Martin; McCulloch, Iain; Nelson, Jenny; Bradley, Donal D C; Durrant, James R

2008-03-12

383

Charge-selective transport of organic and protein analytes through synthetic nanochannels  

Microsoft Academic Search

We present an experimental demonstration of a synthetic nanoporous membrane suitable for charge-selective transport of ionic species. The surfaces and walls of synthetic nanochannels, fabricated in heavy ion-tracked polyethylene terephthalate membranes are negatively charged due to the presence of carboxylate moieties. These nanofilters discriminate and gate the transport of cations while inhibiting the passage of anions. The permselectivity of these

Quoc Hung Nguyen; Mubarak Ali; Veronika Bayer; Reinhard Neumann; Wolfgang Ensinger

2010-01-01

384

Analysis of charge transport during lightning using balloon-borne electric field sensors and Lightning  

E-print Network

Analysis of charge transport during lightning using balloon-borne electric field sensors a lightning flash have been obtained by a balloon-borne electric field sonde or Esonde. This paper develops, and W. L. Boeck (2007), Analysis of charge transport during lightning using balloon-borne electric field

Hager, William

385

Complexity in charge transport for multiwalled carbon nanotube and poly(methyl methacrylate) composites  

E-print Network

) composites Heon Mo Kim, Mahn-Soo Choi, and Jinsoo Joo* Department of Physics and Institute for Nano Science of the charge transport mechanism of the composites of multiwalled carbon nanotubes MWCNTs and poly methylComplexity in charge transport for multiwalled carbon nanotube and poly(methyl methacrylate

Choi, Mahn-Soo

386

Effects of Bilayer Surface Charge Density on Molecular Adsorption and Transport across Liposome Bilayers  

E-print Network

Effects of Bilayer Surface Charge Density on Molecular Adsorption and Transport across Liposome the adsorption of malachite green (MG), a positively charged organic dye, onto liposomes of different lipid compositions, and the transport kinetics of MG across the liposome bilayer in real time. We found that the dye

Eisenthal, Kenneth B.

387

A Boltzmann-weighted hopping model of charge transport in organic semicrystalline films  

E-print Network

A Boltzmann-weighted hopping model of charge transport in organic semicrystalline films Joe J with experimental data, we use the model to characterize the effects of defects in these films. Our findings support Optimization of charge transport in organic films remains a pressing challenge in the development of organic

Straight, Aaron

388

Effect of interface roughness on the carrier transport in germanium MOSFETs investigated by Monte Carlo method  

NASA Astrophysics Data System (ADS)

Interface roughness strongly influences the performance of germanium metal-organic-semiconductor field effect transistors (MOSFETs). In this paper, a 2D full-band Monte Carlo simulator is used to study the impact of interface roughness scattering on electron and hole transport properties in long- and short- channel Ge MOSFETs inversion layers. The carrier effective mobility in the channel of Ge MOSFETs and the in non-equilibrium transport properties are investigated. Results show that both electron and hole mobility are strongly influenced by interface roughness scattering. The output curves for 50 nm channel-length double gate n and p Ge MOSFET show that the drive currents of n- and p-Ge MOSFETs have significant improvement compared with that of Si n- and p-MOSFETs with smooth interface between channel and gate dielectric. The 82% and 96% drive current enhancement are obtained for the n- and p-MOSFETs with the completely smooth interface. However, the enhancement decreases sharply with the increase of interface roughness. With the very rough interface, the drive currents of Ge MOSFETs are even less than that of Si MOSFETs. Moreover, the significant velocity overshoot also has been found in Ge MOSFETs.

Du, Gang; Liu, Xiao-Yan; Xia, Zhi-Liang; Yang, Jing-Feng; Han, Ru-Qi

2010-05-01

389

Substitution Behavior and Stable Charge Carrier Species in Long-Bond Length Layered Cuprates  

E-print Network

, the transport properties, and the defect structures of the layered, quadruple perovskite La2Ba2Cu2Sn2O11 have-temperature electrical conductivity and thermopower measurements. The in-plane copper-oxygen bond lengths, in cooperation

Poeppelmeier, Kenneth R.

390

Transport of oppositely charged lipophilic probe ions in lipid bilayer membranes having various structures  

Microsoft Academic Search

Summary A comparative study of the charge transport kinetics of oppositely charged lipophilic probe ions in lipid bilayer membranes of varying composition was carried out by using the charge pulse technique. The ions investigated were the chemical analogs tetraphenylborate, tetraphenylarsonium and tetraphenylphosphonium. Membrane structural aspects investigated were the type of solvent used in membrane formation, sterol content, and the nature

Arnold D. Pickar; Roland Benz

1978-01-01

391

Spatial charge configuration regulates nanoparticle transport and binding behavior in vivo  

PubMed Central

Detailed Charge arrangements: A new set of zwitterionic quantum dots were synthesized and used to study the influence of microscopic charge arrangements on the in vivo behavior of nanoparticles. Experiments using cultured cells and live mice demonstrate that the microscopic arrangement of surface charges strongly influence nonspecific binding, clearance behavior, and in vivo transport of nanoparticles. PMID:23255143

Han, Hee-Sun; Martin, John D.; Lee, Jungmin; Harris, Daniel K.; Fukumura, Dai; Jain, Rakesh K.; Bawendi, Moungi

2013-01-01

392

Charge transport-mediated recruitment of DNA repair enzymes  

E-print Network

Damaged or mismatched bases in DNA can be repaired by Base Excision Repair (BER) enzymes that replace the defective base. Although the detailed molecular structures of many BER enzymes are known, how they colocalize to lesions remains unclear. One hypothesis involves charge transport (CT) along DNA [Yavin, {\\it et al.}, PNAS, {\\bf 102}, 3546, (2005)]. In this CT mechanism, electrons are released by recently adsorbed BER enzymes and travel along the DNA. The electrons can scatter (by heterogeneities along the DNA) back to the enzyme, destabilizing and knocking it off the DNA, or, they can be absorbed by nearby lesions and guanine radicals. We develop a stochastic model to describe the electron dynamics, and compute probabilities of electron capture by guanine radicals and repair enzymes. We also calculate first passage times of electron return, and ensemble-average these results over guanine radical distributions. Our statistical results provide the rules that enable us to perform implicit-electron Monte-Carlo simulations of repair enzyme binding and redistribution near lesions. When lesions are electron absorbing, we show that the CT mechanism suppresses wasteful buildup of enzymes along intact portions of the DNA, maximizing enzyme concentration near lesions.

Pak-Wing Fok; Chin-Lin Guo; Tom Chou

2008-11-18

393

Controllable spin-charge transport in strained graphene nanoribbon devices  

NASA Astrophysics Data System (ADS)

We theoretically investigate the spin-charge transport in two-terminal device of graphene nanoribbons in the presence of a uniform uniaxial strain, spin-orbit coupling, exchange field, and smooth staggered potential. We show that the direction of applied strain can efficiently tune strain-strength induced oscillation of band-gap of armchair graphene nanoribbon (AGNR). It is also found that electronic conductance in both AGNR and zigzag graphene nanoribbon (ZGNR) oscillates with Rashba spin-orbit coupling akin to the Datta-Das field effect transistor. Two distinct strain response regimes of electronic conductance as function of spin-orbit couplings magnitude are found. In the regime of small strain, conductance of ZGNR presents stronger strain dependence along the longitudinal direction of strain. Whereas for high values of strain shows larger effect for the transversal direction. Furthermore, the local density of states shows that depending on the smoothness of the staggered potential, the edge states of AGNR can either emerge or be suppressed. These emerging states can be determined experimentally by either spatially scanning tunneling microscope or by scanning tunneling spectroscopy. Our findings open up new paradigms of manipulation and control of strained graphene based nanostructure for application on novel topological quantum devices.

Diniz, Ginetom S.; Guassi, Marcos R.; Qu, Fanyao

2014-09-01

394

Thermoelectric and other phenomena in structures with nonequilibrium charge carriers and nanoparticles  

Microsoft Academic Search

The results of investigations of thermoelectric and other physical phenomena in semiconductor structures with n-p junctions are presented for the conducting direction. The direction of the heat transport is opposite to that observed for\\u000a the “conventional” Peltier effect, and its magnitude is much higher. The possible parameters of thermoelectric cooling devices\\u000a based on this effect are estimated. The sizes of

V. I. Stafeev

2009-01-01

395

Organic thin-film transistors for circuits in a foundry: process, charge transport phenomena and device library  

NASA Astrophysics Data System (ADS)

For the development of circuits consisting of organic thin film transistors (OTFT) with satisfying yield, a stable and reliable process is necessary. This can be achieved by eliminating failure mechanisms and understanding the charge transport phenomena in the individual device. Following the way of a charge through the device, we start with the investigation of the influence of the Schottky barrier height and contact morphology on the device performance by finite-elements simulations. It could be verified that the charge injection limiting contact resistance can be decreased by two orders of magnitude by reducing the thin oxide layer at the source and drain contacts and improving the semiconductor layer morphology at their vicinity. Second, we present an analytical closed-form solution of the OTFT channel potential used for Monte-Carlo charge transport simulations and compute current-voltage and transient response characteristics out of it. In a next step, the influence of the deposition process on the layer interface is investigated. Therefore, velocity distribution measurements of the charge carriers lead to a simulation model with varying disorder, depending on the layer surfaces and deposition techniques. Afterwards, leakage currents through the gate dielectric can be described by a poor conducting semiconductor model in the finite-elements framework. Leakage currents increase power consumption in circuits and, what is more critical, can lead to a total failure of the OTFT. However, they can be influenced by the number of deposited dielectric layers and charge injection supporting self-assembled monolayers at the source and drain contacts. These findings lead to circuit building blocks for an organic device library whereupon still existing performance fluctuations can be coped with Monte-Carlo circuit simulations.

Pankalla, Sebastian; Ganz, Simone; Spiehl, Dieter; Dörsam, Edgar; Glesner, Manfred

2013-09-01

396

Viologens as charge carriers in a polymer-based battery anode.  

PubMed

Viologens, either as anions in solution or as pendant substituents to pyrrole, were incorporated as dopants to electrodeposited films of polypyrrole. The resulting polymer films exhibited redox activity at -0.5 V vs Ag/AgCl. The film consisting of polypyrrole with pendant viologens exhibited the best charge-discharge behavior with a maximum capacity of 55 mAh/g at a discharge current of 0.25 mA/cm(2). An anode consisting of polypyrrole (pPy) doped with viologen (V) was coupled to a cathode consisting of pPy doped with 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) to yield a polymer-based battery with a cell electromotive force (emf) of 1.0 V, maximum capacity of 16 mAh/g, and energy density of 15 Wh/kg. PMID:23927403

Sen, Sujat; Saraidaridis, James; Kim, Sung Yeol; Palmore, G Tayhas R

2013-08-28

397

Charge transport and signal generation in CdTe pixel detectors  

Microsoft Academic Search

The current and charge signals on individual pixels of CdTe ?-ray cameras are calculated. The time and position dependent free carrier densities following the absorption of a ?-ray in the detector are first calculated by solving the continuity equations. These density distributions are then combined with the physical electric field and the pixel weighting field to provide the current induced

Louis-André Hamel; Sébastien Paquet

1996-01-01

398

Dynamics of charge carrier recombination and capture in laser nanostructures with InGaAsSb/AlGaAsSb quantum wells  

SciTech Connect

Time dynamics of photoluminescence intensity was studied in InGaAsSb/AlGaAsSb quantum wells with different compositions of the barrier solid solution and with different width of the quantum wells. The time of charge carrier capture in quantum wells, the energy relaxation times, lifetime related to resonant Auger recombination were estimated.

Vinnichenko, Maxim Ya.; Vorobjev, Leonid E.; Firsov, Dmitry A.; Mashko, Marina O.; Sofronov, Anton N. [St. Petersburg State Polytechnical University, 195251, Polytechnicheskaya str. 29, St. Petersburg (Russian Federation); Shterengas, Leon; Belenky, Gregory [Department of Electrical and Computer Engineering, State University of New York at Stony Brook, New York 11794 (United States)

2013-12-04

399

Ultrasonic coupling to optically generated charge carriers in CdS: Physical phenomena and applications. Ph.D. Thesis - Washington Univ., Saint Louis, Mo.  

NASA Technical Reports Server (NTRS)

Phonon-charge carrier interactions are studied as well as ultrasonic resonators. Sensitivity enhancement factors predicted by one dimensional resonator theory are verified and several sensitive ultrasonic experimental techniques are developed. Measurements are reported of an anomalous sign reversal of the acoustoelectric voltage in a CdS resonator. Applications of CdS as an ultrasonic power detector are described.

Heyman, J. S.

1975-01-01

400

Simulating the transport of heavy charged particles through trabecular spongiosa  

NASA Astrophysics Data System (ADS)

As planning continues for manned missions far beyond Low Earth Orbit, a paramount concern remains the flight crew's exposure to galactic cosmic radiation. When humans exit the protective magnetic field of Earth, they become subject to bombardment by highly-reactive heavy charged (HZE) particles. A possible consequence of this two- to three-year-long mission is the onset of radiation-induced leukemia, a disorder with a latency period as short as two to three years. Because data on risk to humans from exposure to HZE particles is non-existent, studies of leukemia in animals are now underway to investigate the relative effectiveness of HZE exposures. Leukemogenesis can result from energy depositions occurring within marrow contained in the trabecular spongiosa. Trabecular spongiosa is found in flat bones and within the ends of long bones, and is characterized by an intricate matrix of interconnected bone tissue forming cavities that house marrow. The microscopic internal dimensions of spongiosa vary between species. As radiation traverses this region, interface-induced dose perturbations that occur at the interfaces between bone and marrow affect the patterns of energy deposition within the region. An aim of this project is to determine the extent by which tissue heterogeneity and microscopic dimensions have on patterns of energy deposition within the trabecular spongiosa. This leads to the development of PATHFIT, a computer code capable of generating simple quadric-based geometric models of trabecular spongiosa for both humans and mice based on actual experimentally-determined internal dimensions of trabecular spongiosa. Following the creation of spongiosa models, focus is placed on the development of HITSPAP, a hybrid Monte Carlo (MC) radiation transport code system that combines capabilities of the MC code PENELOPE and MC code PARTRAC. This code is capable of simulating the transport of HZE particles through accurate models of trabecular spongiosa. The final and principal aim of this project is the analysis of differences in patterns of energy deposition between humans and mice following the simulated irradiation of human and mice spongiosa models with electrons and HZE particles ranging from alpha particles to bare iron ions.

Gersh, Jacob A.

401

HOMOGENIZATION OF THE POISSON-NERNST-PLANCK EQUATIONS FOR ION TRANSPORT IN CHARGED POROUS  

E-print Network

to ion transport in porous electrodes, separators, membranes, ion-exchange resins, soils, porous rocks impulse propagation in the porous intracellular matrix of an axon [84], selective ion transport through delivery and medical diagnostics [83]. In chemical engineering, the selective transport of ions and charged

Bazant, Martin Z.

402

Study of tunneling transport of carriers in structures with an InGaN/GaN active region  

SciTech Connect

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.

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

403

Charge delocalization upon chloride ion binding in ClC chloride ion channels/transporters  

NASA Astrophysics Data System (ADS)

Density functional theory calculations were carried out employing a set of truncated model systems for the EcClC Cl - transport protein and mutants. Geometry optimizations implied a possible additional binding site near the residue R147. Analysis based on the Löwdin and Natural charge models showed that significant (about 30%) charges on the bound Cl - ions were smeared out among the solvation shells and the gating residue E148, whose delocalized pi bonds provide good accommodations for the transferred charges. The extensive anion-pi charge transfer along the Cl - translocation path might help to smooth/level the energy profiles for Cl - transport.

Smith, Mia; Lin, Hai

2011-01-01

404

Involvement of carrier-mediated transport in the retinal uptake of clonidine at the inner blood-retinal barrier.  

PubMed

In the present study, the blood-to-retina transport across the inner BRB was investigated for clonidine, a compound which is expected to exhibit a neuroprotective effect for the treatment of severe retinal diseases. In the in vivo study, the integration plot analysis for [(3)H]clonidine exhibited an apparent influx permeability clearance of 457 ?L/(min·g retina) in the retina. The in vivo inhibition study suggests that the blood-to-retina transport of clonidine at the BRB is organic cation-sensitive since clonidine, pyrilamine, and propranolol, at a concentration of 40 mM, significantly reduced the retinal uptake index (RUI) of [(3)H]clonidine, and an inhibitory effect on the RUI was also exhibited by verapamil, at a concentration of 3 mM. The in vitro study with TR-iBRB2 cells, an in vitro model cell line of the inner BRB, suggests that carrier-mediated transport is involved in the blood-to-retina transport of clonidine at the inner BRB since the results obtained demonstrated time-, temperature-, pH-, and concentration-dependent [(3)H]clonidine uptake, with a Km of 286 ?M. In the in vitro inhibition study, the [(3)H]clonidine uptake was significantly reduced by several organic cations, such as clonidine, verapamil, pyrilamine, and propranolol, and was competitively inhibited by 200 ?M verapamil, in spite of slight or no significant alteration being produced with organic anions. Furthermore, the typical substrates and inhibitors of well-known organic cation transporters had no significant effect on the uptake of [(3)H]clonidine to suggest the involvement of novel transporter molecules in the transport of clonidine across the inner BRB. These results suggest that the blood-to-retina transport of clonidine across the inner BRB involves a carrier-mediated transport manner, suggesting the contribution of a novel organic cation transporter expressed by the retinal capillary endothelial cells. PMID:25222277

Kubo, Yoshiyuki; Tsuchiyama, Ai; Shimizu, Yoshimi; Akanuma, Shin-Ichi; Hosoya, Ken-Ichi

2014-10-01

405

Relaxation of stored charge carriers in a Zn sub 0. 3 Cd sub 0. 7 Se mixed crystal  

SciTech Connect

Persistent photoconductivity (PPC) has been investigated in detail in a Zn{sub 0.3}Cd{sub 0.7}Se mixed crystal. Two different temperature conductivity states have been observed. Relaxation of stored charge carriers, which contribute to PPC, has been studied at different conditions. We find that the decay of PPC follows the stretched-exponential'' function that is usually observed in a wide class of disordered materials. At {ital T}{lt}220 K, the relaxation time increases with increase of temperature. At a constant temperature, the relaxation time increases with increase of excitation photon dose, which is a consequence of the presence of the two different conductivity states. However, at a constant temperature, the decay exponent is excitation-photon-dose independent, while the characteristic decay time constant depends on excitation photon dose. The PPC observed here thus exhibits characteristic phenomena of disordered systems, which suggests that the random local-potential fluctuations, which arise from the compositional fluctuations, are responsible for PPC. PPC-decay behavior is also analyzed for some of the previously published data on other materials. We find that the stretched-exponential function describes the PPC decay in various materials at low temperatures.

Lin, J.Y.; Jiang, H.X. (Department of Physics, Kansas State University, Cardwell Hall, Manhattan, Kansas 66506-2601 (USA))

1990-03-15

406

Electron Transfer Dissociation Mass Spectrometry of Peptides Containing Free Cysteine Using Group XII Metals as a Charge Carrier.  

PubMed

Electron transfer dissociation (ETD) has been used for peptide sequencing. Since ETD preferentially produces the c'/z(•) fragment pair, peptide sequencing is generally performed by interpretation of mass differences between series of consecutive c' and z(•) ions. However, the presence of free cysteine residues in a precursor promotes peptide bond cleavage, hindering interpretation of the ETD spectrum. In the present study, the divalent group XII metals, such as Zn(2+), Cd(2+) and Hg(2+), were used as charge carriers to produce metal-peptide complexes. The thiol group is deprotonated by complexation with the group XII metal. The formation of b and y' ions was successfully suppressed by using the zinc-peptide complex as a precursor, indicating Zn(2+)-aided ETD to be a useful method for sequencing of cysteine-containing peptides. By contrast, ETD of Cd(2+)- and Hg(2+)-peptide complexes mainly led to SH2 loss and radical cation formation, respectively. These processes were mediated by recombination energy between the metal cation and an electron. The presence of monovalent cadmium and neutral mercury in ETD products was confirmed by MS(3) analysis with collision-induced dissociation. PMID:25271566

Asakawa, Daiki; Wada, Yoshinao

2014-10-30

407

Effect of surface charge on the brain delivery of nanostructured lipid carriers in situ gels via the nasal route.  

PubMed

The aim of this study was to investigate the influence of the nanocarrier surface charge on brain delivery of a model hydrophilic drug via the nasal route. Anionic and cationic nanostructured lipid carriers (NLCs) were prepared and optimized for their particle size and zeta potential. The optimum particles were incorporated in poloxamer in situ gels and their in vivo behavior was studied in the plasma and brain after administration to rats. Optimum anionic and cationic NLCs of size <200 nm and absolute zeta potential value of ? 34 mV were obtained. Toxicity study revealed mild to moderate reversible inflammation of the nasal epithelium in rats treated with the anionic NLCs (A7), and destruction of the lining mucosal nasal epithelium in rats treated with the cationic NLCs (C7L). The absolute bioavailability of both drug loaded anionic and cationic NLCs in situ gels was enhanced compared to that of the intranasal solution (IN) of the drug with values of 44% and 77.3%, respectively. Cationic NLCs in situ gel showed a non significant higher Cmax (maximum concentration) in the brain compared to the anionic NLCs in situ gel. Anionic NLCs in situ gel gave highest drug targeting efficiency in the brain (DTE%) with a value of 158.5 which is nearly 1.2 times that of the cationic NLCs in situ gel. PMID:25062866

Gabal, Yasmine M; Kamel, Amany O; Sammour, Omaima A; Elshafeey, Ahmed H

2014-10-01

408

Lateral charge transport from heavy-ion tracks in integrated circuit chips  

NASA Technical Reports Server (NTRS)

A 256K DRAM has been used to study the lateral transport of charge (electron-hole pairs) induced by direct ionization from heavy-ion tracks in an IC. The qualitative charge transport has been simulated using a two-dimensional numerical code in cylindrical coordinates. The experimental bit-map data clearly show the manifestation of lateral charge transport in the creation of adjacent multiple-bit errors from a single heavy-ion track. The heavy-ion data further demonstrate the occurrence of multiple-bit errors from single ion tracks with sufficient stopping power. The qualitative numerical simulation results suggest that electric-field-funnel-aided (drift) collection accounts for single error generated by an ion passing through a charge-collecting junction, while multiple errors from a single ion track are due to lateral diffusion of ion-generated charge.

Zoutendyk, J. A.; Schwartz, H. R.; Nevill, L. R.

1988-01-01

409

Evidence for Carrier-mediated Transport of Unconjugated Bilirubin Across Plasma Membrane Vesicles from Human Placental Trophoblast  

Microsoft Academic Search

Unconjugated bilirubin (UCB) is currently believed to cross the placenta only by passive diffusion. To assess whether carrier-mediated transport might be involved, the uptake of [3H]-UCB by basal (bTPM) and apical (aTPM) plasma membrane vesicles from human placental trophoblast at term was investigated. In both types of vesicles, the uptake of [3H]-UCB into an osmotically sensitive space was temperature-dependent, independent

M. A. Serrano; J. E. Bayón; L. Pascolo; C. Tiribelli; J. D. Ostrow; J. Gonzalez-Gallego; J. J. G. Marin

2002-01-01

410

Intrinsic dielectric properties and charge transport in oligomers of organic semiconductor copper phthalocyanine  

E-print Network

in the experimentally detected dielectric response of organic semi- conductor copper phthalocyanine. While a giantIntrinsic dielectric properties and charge transport in oligomers of organic semiconductor copper. Huang and Q. M. Zhang Electrical Engineering Department and Materials Research Institute

Bobnar, Vid

411

ADIABATIC CHARGE TRANSPORT AND THE KUBO FORMULA FOR LANDAU TYPE HAMILTONIANS  

E-print Network

ADIABATIC CHARGE TRANSPORT AND THE KUBO FORMULA FOR LANDAU TYPE HAMILTONIANS ALEXANDER ELGART response Kubo­ Ÿ Streda formula. The proof relies on the expansion of Nenciu, some generalized phase space

412

38 CFR 12.9 - Rights of designate; sales instruction; transportation charges.  

Code of Federal Regulations, 2010 CFR

...designate; sales instruction; transportation charges. 12.9 Section 12.9 Pensions, Bonuses, and Veterans' Relief DEPARTMENT...Absence, and of Funds and Effects Found on Facility § 12.9 Rights of designate; sales instruction;...

2010-07-01

413

Numerical design of electron guns and space charge limited transport systems  

SciTech Connect

This paper describes the capabilities and limitations of computer programs used to design electron guns and similarly space-charge limited transport systems. Examples of computer generated plots from several different types of gun problems are included.

Herrmannsfeldt, W.B.

1980-10-01

414

Inhomogeneous Carrier Transport at Contact/GaN Interfaces and Thermal Instability of Vertical Light-Emitting Diodes.  

PubMed

The carrier-transport behavior at the interface of a contact and n-type GaN was investigated for group III nitride vertical light-emitting diodes (LEDs). Three types of samples were investigated including dry-etched flat Ga-polar n-GaN (GA), dry-etched flat N-polar n-GaN (NF), and wet-etched roughened N-polar n-GaN (NR). Schottky diodes fabricated using a palladium contact revealed that carrier transport at the contact/GaN interface could be understood in terms of the barrier inhomogeneity model, in which the local shallow barriers dominated the overall carrier transport. Kelvin probe force microscopy showed that the peculiar crystallographic structures and native defects (acting as the local shallow barriers) led to the largest tunneling probability of the NR samples. The study was followed up by forming a TiN/Al contact on the NR surfaces to study the thermal instability of the vertical LEDs, revealing that the vertical LEDs were degraded after a thermal annealing process. This could be related to the n-contact size, indicating that the degradation of vertical LEDs was likely due to the failure of Ohmic patches (contacts formed on the defects and/or the tip/edge of hexagonal cones) at elevated temperature. PMID:25302936

Choi, Yunju; Jung, Eunjin; Kim, Yangsoo; Oh, Sejong; Yoo, Myung-Cheol; Kim, Hyunsoo

2014-11-12

415

49 CFR 375.217 - How must I collect charges upon delivery?  

Code of Federal Regulations, 2010 CFR

... How must I collect charges upon delivery? 375.217 Section 375.217...Transportation (Continued) FEDERAL MOTOR CARRIER SAFETY ADMINISTRATION, DEPARTMENT... How must I collect charges upon delivery? (a) You must specify...

2010-10-01

416

Influence of nanoparticle shape on charge transport and recombination in polymer/nanocrystal solar cells.  

PubMed

A key consideration for the efficient operation of hybrid solar cells based upon conjugated polymers and inorganic semiconductor nanocrystals is charge transport in the nanocrystal phase. Here we report the results of a study into the charge transport kinetics of polymer/nanocrystal solar cells based on blends poly(3-hexylthiophene) (P3HT) with either CdSe nano-dots or CdSe nano-tetrapods. Transient photocurrent measurements reveal significant differences in the charge transport kinetics of nano-dot and nano-tetrapod hybrid cells, with the charge collection of the P3HT/CdSe nano-dot device severely limited by charge trapping. In comparison the nano-tetrapod cell exhibits significantly reduced charge trapping compared to the nano-dot cell accounting for the improved fill-factor and overall device efficiency. Transient photovoltage measurements have also been employed that demonstrate slower recombination rates in the P3HT/CdSe tetrapod device compared to the P3HT/CdSe dot device. These observations directly identify nanoparticle shape as a critical factor influencing the charge transport and hence recombination in this benchmark hybrid system, confirming the hypothesis that the use of tetrapods improves device performance through an improvement in electron transport in the nanocrystal phase. PMID:24781139

Li, Zhe; Wang, Weiyuan; Greenham, Neil C; McNeill, Christopher R

2014-12-21

417

Plasma physics, and transportation and use of positively charged particle beams  

Microsoft Academic Search

The invention pertains to plasma physics, and in particular to and transportation and use of positively charged particle beams. Particle beams of positively charged atoms have potentially a number of useful applications, among which are thin film deposition, semiconductor doping, use as a general laboratory tool, a source of pulsed neutrons (i.e., by impacting a suitable target), shock hardening of

Steven P. Slinker; Richard F. Hubbard; Glenn Joyce

1991-01-01

418

Lipid phosphate phosphatase 3 participates in transport carrier formation and protein trafficking in the early secretory pathway.  

PubMed

The inhibition of phosphatidic acid phosphatase (PAP) activity by propanolol indicates that diacylglycerol (DAG) is required for the formation of transport carriers at the Golgi and for retrograde trafficking to the ER. Here we report that the PAP2 family member lipid phosphate phosphatase 3 (LPP3, also known as PAP2b) localizes in compartments of the secretory pathway from ER export sites to the Golgi complex. The depletion of human LPP3: (i) reduces the number of tubules generated from the ER-Golgi intermediate compartment and the Golgi, with those formed from the Golgi being longer in LPP3-silenced cells than in control cells; (ii) impairs the Rab6-dependent retrograde transport of Shiga toxin subunit B from the Golgi to the ER, but not the anterograde transport of VSV-G or ssDsRed; and (iii) induces a high accumulation of Golgi-associated membrane buds. LPP3 depletion also reduces levels of de novo synthesized DAG and the Golgi-associated DAG contents. Remarkably, overexpression of a catalytically inactive form of LPP3 mimics the effects of LPP3 knockdown on Rab6-dependent retrograde transport. We conclude that LPP3 participates in the formation of retrograde transport carriers at the ER-Golgi interface, where it transitorily cycles, and during its route to the plasma membrane. PMID:23591818

Gutiérrez-Martínez, Enric; Fernández-Ulibarri, Inés; Lázaro-Diéguez, Francisco; Johannes, Ludger; Pyne, Susan; Sarri, Elisabet; Egea, Gustavo

2013-06-15

419

41 CFR 302-7.100 - How are the charges of transporting HHG, and temporary storage calculated?  

Code of Federal Regulations, 2010 CFR

...charges of transporting HHG, and temporary storage calculated? 302-7.100 Section 302-7...RELOCATION ALLOWANCES TRANSPORTATION AND STORAGE OF PROPERTY 7-TRANSPORTATION AND TEMPORARY STORAGE OF HOUSEHOLD GOODS AND PROFESSIONAL...

2010-07-01

420

Effects of variation of ion and methylation of carrier on the rate constants of macrotetralide-mediated ion transport in lipid bilayers  

Microsoft Academic Search

Summary The effects of methylation on the rate constants of carrier-mediated ion transport have been studied on monooleindecane bilayers with K+, Rb+, NH4+, and TI+ ions, using the series of homologue carriers, nonactin, monactin, dinactin, trinactin, and tetranactin, each member of the series differing from the previous one by only one methyl group. Measurements of the amplitude and time constant

Raynald Laprade; François Grenier; Jean-Yves Lapointe; Sylvic Asselin

1982-01-01

421

Examining Information Needs for Efficient Motor Carrier Transportation by Investigating Travel Time Characteristics and Logistics.  

National Technical Information Service (NTIS)

This report presents both survey results and field data analysis investigating information needs for motor carrier logistics. Relevant research in the area of estimating travel time characteristics is presented. Survey results of trucking companies and tr...

L. R. Rilett, W. L. Eisele

2002-01-01

422

Charge Transporting Properties and Output Characteristics in Polythiophene:Fullerene Derivative Solar Cells  

NASA Astrophysics Data System (ADS)

The carrier mobility (µ) and lifetime (?) of polymer solar cells based on the active layer with various compositions of regioregular poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) have been investigated through photoinduced charge carrier extraction by linearly increasing voltage measurement. Increase in the PCBM content resulted in the increase in the mobility up to one order of magnitude and the highest performance was attained at the composition of P3HT:PCBM (3:2), which corresponds to the bending point of mobility and lifetime. Furthermore, the mobility-lifetime product µ? was almost constant with various weight ratios of P3HT and PCBM. This result implies that the composition does not affect the charge correction efficiency before recombination. A semiconducting thin-film optics simulator was applied for prediction of the photovoltaic performance. Theoretical and experimental cell performance results were in good agreement with each other.

Tsai, Yueh-Tsung; Goto, Kensuke; Yoshikawa, Osamu; Mori, Shogo; Sagawa, Takashi; Yoshikawa, Susumu

2011-01-01

423

Charge-carrier mobilities in Cd(0.8)Zn(0.2)Te single crystals used as nuclear radiation detectors  

NASA Technical Reports Server (NTRS)

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. The hole mobility displayed a T exp -2.0 dependence in the same temperature range, with a room-temperature mobility of 120 sq cm/V s. Cd(0.8)Zn(0.2)Te appears to be a very favorable material for a room-temperature electronic nuclear radiation detector.

Burshtein, Z.; Jayatirtha, H. N.; Burger, A.; Butler, J. F.; Apotovsky, B.; Doty, F. P.

1993-01-01