Effect of excessive pressure on the drift mobility of charge carriers in poly(diphenylene phthalide) films

The electron-hole transport in poly(diphenylene phthalide) films has been investigated. The dependence of the drift mobility of charge carriers on the excessive mechanical pressure has been studied using the time-of-flight method. It has been revealed that, with an increase in the thickness of the polymer film, the dispersive transport of charge carries gives way to the quasi-dispersive transport. In thin films in the prethreshold range (i.e., before switching of the samples to the highly conductive state under excessive pressure), the electron mobility increases and exceeds the hole mobility. The experimental results have been discussed in the framework of the model describing the transport through the channels formed by metastable electron-hole pairs.     

Experimental determination of the transport coefficients of bismuth in the range 1·5–50 K

A method has been developed for the simultaneous measurement of several different transport coefficients on a sample. Experiments were performed on a Bi single crystal at temperatures 1·5–50 K. Six transport properties were measured, including the electrical resistivity, thermal conductivity and thermopower. A set of quantities related to transport integrals of the phenomenological transport theory has been determined from experimental data. All the possible transport coefficients can be calculated from them. The possibilities of the determination from experiments of the full tensorial transport integrals for an anisotropic material like Bi are discussed.     

Angular momentum transport produced by shear flow driven drift waves in a collisional magnetoplasma

A shear flow instability in a nonuniform partially ionized magnetoplasma has been investigated and the angular momentum transport of charged particles caused by drift waves has been estimated. The angular momentum transport of the electrons and ions is not equal because the system is not conservative. The present investigation should help to understand the origin of fluctuations and associated parallel momentum transport of charged particles in nonuniform laboratory and astrophysical plasmas with sheared ion flow.     

Numerical simulation of the transport properties of indium antimonide

A systematic investigation of the behavior of the transport coefficients of n-InSb over wide ranges of temperatures and concentrations of dopant atoms has been performed using the numerical solution of the Boltzmann transport equation. The thermoelectric characteristics of indium antimonide have been analyzed. The influence of different mechanisms of scattering of charge carriers on the transport coefficients and efficiency of thermoelectric energy conversion has been considered. The nature of the specific features of the temperature and concentration dependence of the transport and thermoelectric properties of n-InSb has been revealed.     

Turbulent scalar flux transport in head-on quenching of turbulent premixed flames: a direct numerical simulations approach to assess models for Reynolds averaged Navier Stokes simulations

The statistical behaviour and the modelling of turbulent scalar flux transport have been analysed using a direct numerical simulation (DNS) database of head-on quenching of statistically planar turbulent premixed flames by an isothermal wall. A range of different values of Damköhler, Karlovitz numbers and Lewis numbers has been considered for this analysis. The magnitudes of the turbulent transport and mean velocity gradient terms in the turbulent scalar flux transport equation remain small in comparison to the pressure gradient, molecular dissipation and reaction-velocity fluctuation correlation terms in the turbulent scalar flux transport equation when the flame is away from the wall but the magnitudes of all these terms diminish and assume comparable values during flame quenching before vanishing altogether. It has been found that the existing models for the turbulent transport, pressure gradient, molecular dissipation and reaction-velocity fluctuation correlation terms in the turbulent scalar flux transport equation do not adequately address the respective behaviours extracted from DNS data in the near-wall region during flame quenching. Existing models for transport equation-based closures of turbulent scalar flux have been modified in such a manner that these models provide satisfactory prediction both near to and away from the wall.     

New bipartition model of neutral particle transport in the HL-2A divertor region

A new bipartition neutral transport model has been developed for simulation of the hydrogenic neutral particle transport in the vicinity of HL-2A divertor target plate. The numerical calculation results on the basis of this model are fairly consistent with the results obtained with the “multi-generation method”. One possible application of this model is to provide a source term originating from neutral transport calculation for any other edge plasma transport code, for instance, B-2 code, which has been used to simulate edge plasma transport of the HL-2A divertor configuration. Especially it can be utilized to quickly classify the plasma in divertor region as high or low recycling regime.     

Detailed electrical measurements on sago starch biopolymer solid electrolyte

The biopolymer solid electrolyte has been synthesized and characterized. Potassium iodide (KI) has been added in polymer matrix to develop solid polymer electrolyte. Relationships between electrical, ionic transport parameter and mechanism have been studied in detail. Impedance spectroscopy reveals the detailed electrical studies and ion transport mechanism. The ion dissociation factor is compared with a measured dielectric constant at a fixed frequency. The dielectric data are calculated which support the ionic conductivity data.     

Effects of Weak Localization and Electron–Electron Interaction in GaAs–AlGaAs Heterostructures

The influence of the processes of weak localization and electron–electron interaction in an inhomogeneous two-dimensional electron gas of a single GaAs–AlGaAs heterojunction on the low-temperature transport characteristics in the case of occupation of two quantum subbands has been investigated. The transport characteristics have been interpreted from the viewpoint of a two-layer model taking into account the existence of two bypass conduction channels corresponding to the two-dimensional and three-dimensional electron gas. Both the electrical and optical measurements point to the existence of large-scale fluctuations of the potential, which determine the dependence of the conduction and the Hall resistance of the heterostructures on the magnetic field. It has been established that the weak localization determines the charge transport in a weak magnetic field, and the electron–electron interaction determines this transport in a strong magnetic field.     

贝利相与非线性输运

电子输运现象包含一系列很重要的材料性质,并可以用来提供关于载体物理系统的很多信息。在 最近的二三十年,人们逐渐认识到除了电子能谱之外,电子在布里渊区的几何性质,比如贝利曲率和 轨道磁矩,会在电子输运中起到关键性的作用。在线性输运现象中的此种关联已引起广泛的兴趣并得 到深入的研究。然而,在非线性输运现象中的电子几何性质的作用的研究最近才逐渐起步。此种关联 可以大大加深对各种非线性输运现象的认识,并对如何从材料控制上调节非线性现象的强度提供有价 值的研究视角和指导原则。基于此背景,本文试图引入研究输运现象的半经典理论框架,并在几种输 运现象中举例说明贝利相的作用。     

贝利相与非线性输运

电子输运现象包含一系列很重要的材料性质,并可以用来提供关于载体物理系统的很多信息。在 最近的二三十年,人们逐渐认识到除了电子能谱之外,电子在布里渊区的几何性质,比如贝利曲率和 轨道磁矩,会在电子输运中起到关键性的作用。在线性输运现象中的此种关联已引起广泛的兴趣并得 到深入的研究。然而,在非线性输运现象中的电子几何性质的作用的研究最近才逐渐起步。此种关联 可以大大加深对各种非线性输运现象的认识,并对如何从材料控制上调节非线性现象的强度提供有价 值的研究视角和指导原则。基于此背景,本文试图引入研究输运现象的半经典理论框架,并在几种输 运现象中举例说明贝利相的作用。     

Advection of an impurity in percolation media with a finite correlation length

The impurity transport regimes in percolation media with a finite correlation length, which are caused by advection and diffusion mechanisms, have been analyzed. It has been shown that the change in the transport characteristics of a medium from the self-similar type to the statistically homogeneous type occurs through two stages because of the structural features of percolation clusters (presence of a backbone and dead ends). As a result, new anomalous transport regimes appear in the system. The quasi-isotropic and moderately and strongly anisotropic media have been considered.     

The role of the wide-band-gap polymer layer for the existence of conductivity switching in the valve structure

The effect of electronic switching of the conductivity by a magnetic field lower than 500 mT has been implemented in the spin-valve structure in the “current perpendicular to plane” geometry with a transport layer of a wide-band-gap polymer to 1200 nm thick. The problem of spin transfer through the polymer layer has been discussed in the model of ballistic charge transport over nanoscale conducting channels.     

Control of one-dimensional transport in multi-wall carbon nanotubes by wall destruction

We have investigated the damage in multi-wall carbon nanotubes (MWNTs) destroyed by electrical breakdown and focused ion beam bombardment (FIBB). The transport properties of a MWNT destroyed by electrical breakdown have been compared with those of a MWNT destroyed by FIBB. Also the Tomonaga–Luttinger transport (TLT) model has been applied to each type of destroyed MWNT. The MWNT destroyed by FIBB showed TLT behavior because of the weak destruction of the remaining walls. However, in the case of MWNTs destroyed by electrical breakdown, three-dimensional variable-range hopping (VRH) was observed in the low temperature transport. This suggests that the local damage has been caused by strong breakdown. There exists a clear difference between the effects of electrical breakdown and FIBB. Wall destruction by FIBB could be applied to control the one-dimensional transport of MWNTs.     

Subband mobilities and dingle temperatures within a two-subband model in the presence of localized states

The transport time and the single-particle relaxation times in a two subband system of a two-dimensional electron gas have been calculated. Screening and density of states effects have been taken into account under the assumption that disorder leads to localized states in both subbands. It has been found that the single-particle relaxation time of the second subband is always larger than that for the first subband. The transport time of the second subband can be smaller or larger than the transport time of the first subband. The text was submitted by the authors in English.     

New model of heat transport across the metal-insulator interface by the example of boundaries in a diamond-copper composite

A model of heat transport from an insulator (diamond) to a metal (copper) has been proposed taking into account energy transport to the oscillations inherent in the insulator but having frequencies much higher than the frequencies inherent in the fundamental oscillations of the metal. This problem is solved exactly in the one-dimensional case and in the one-constant approximation of bonding at the interface. It has been established that energy transport occurs in a thin layer near the metal boundary.     

Electrical transport mechanism in Al/V2O5/Al microdevices

The current-voltage characteristics of metal-insulator-metal microdevices fabricated with electron-beam evaporated vanadium pentoxide films have been studied in order to understand the electrical transport mechanism in these films. The dependence of transport properties on various factors such as film thickness, substrate temperature, and applied field, has been established. The results revealed that the electrical transport follows a Schottky-type mechanism at lower electrical fields and a Poole-Frenkel-type at higher electrical fields than 2×10⁶ V/m.     

On the transistor effect in a vertical structure with a nonconjugated polymer as a transport layer

The charge carrier transport in a multilayer film structure based on a nonconjugated polymer has been studied. The conditions under which the charge carrier transport can be controlled by an electric field due to variations in the potential at the control electrode have been established. The results obtained are discussed within the model of passage of charge particles through a multibarrier system.     

Simulation of single-electron transport processes in thin granulated chromium films

The results of the numerical simulation of the single-electron transport in two-dimensional granulated chromium films at low temperatures are reported. A theoretical model has been developed in which the granulated film is represented as a two-dimensional matrix of conducting metallic granules (islands), which are weakly coupled with each other through slightly transparent tunnel barriers, ensuring the transport of single electrons localized on the islands. The recently measured current-voltage characteristics of submicron rectangular chromium samples have been explained by taking into account the inhomogeneities in the nanometer sizes of the islands and their effective electron temperature depending on the flowing current. A transition from the two-dimensional regime to the quasi-one-dimensional regime of the single-electron transport leading to the experimentally observed hysteresis has been revealed in the simulated system.     

Surface acoustic wave propagation and acoustoelectric interaction in multilayered piezoelectric semiconductors

In the past years, the acoustoelectric interaction has been used in a number of different devices such as acoustic amplifiers, acoustoelectric convolvers and acoustic coupled transport devices. Recent developments in synthesized semiconductor superlattices with high quality heterostructures have been found to be useful in a new generation of high performance devices such as the High Electron Mobility Transistor. The objective of this paper is to extend the use of these superlattices to acoustoelectric devices. A complete theory of acoustoelectric interaction in layered piezoelectric semiconductor has been developed. The acoustic propagation equations have been solved together with the continuity, transport and Poisson equations. The free carrier transport properties are accounted for using a mobility tensor to describe the two-dimensional behavior. The acoustical and electrical boundary conditions have been used to obtain mechanical displacement and electric field expressed in terms of Bloch functions. The effect of longitudinal D.C. applied field on SAW attenuation or amplification is also considered.