Transport of excess charge carriers in liquid and solid hydrogen

The temperature dependence of the drift mobility of excess charge carriers in liquid and solid hydrogen has been investigated. Both negative and positive carriers are observed in the liquid with mobilities ～ 5 × 10^-3 cm² V^-1 sec^-1 at 15 K; the mobile carriers in the solid are believed to be negatively Charged with a mobility ～ 6 × 10^-6 cm² V^-1 sec^-1 at 13 K. The mechanisms of charge localization and transport are discussed.     

Drift mobility of photogenerated current carriers in Bi12GeO20 crystals

The drift mobility of photogenerated electrons and holes in Bi₁₂GeO₂₀ crystals with different degrees of doping is investigated experimentally. Fiz. Tverd. Tela (St. Petersburg) 40, 2054–2055 (November 1998)     

Drift mobility of electrons in TlSbS2

The time-of-flight technique has been used to study the transport of electrons in TlSbS₂ in the perpendicular direction with respect to the cleavage planes. The transport of electrons is non-dispersive and can be considered an activated process with an activation energy of 0·40 eV. The value of 1·68 eV has been found for the energy gap of TlSbS₂ at room temperature.     

The mobility of charge carriers in a size-quantized coated semiconductor wire

Within the framework of a staircase infinitely deep potential well model, the mobility of charge carriers is calculated for scattering on impurity centers located on the axis of a size-quantized semiconducting coated wire. Calculations are done for the dielectric constant mismatch of the wire, coating and surrounding environment, taking into account the difference of the effective masses in the wire and coating. The effect of a longitudinal magnetic field on mobility is also considered. Numerical results are presented for the GaAs–Ga_1−xAl_xAs system at different values of the wire and coating radii, the alloy concentration x, and magnetic field.     

Quantum transport of slow charge carriers in quasicrystals and correlated systems

We show that the semiclassical model of conduction breaks down if the mean free path of charge carriers is smaller than a typical extension of their wave function. This situation is realized for sufficiently slow charge carriers and leads to a transition from a metalliclike to an insulatinglike regime when scattering by defects increases. This explains the unconventional conduction properties of quasicrystals and related alloys. The conduction properties of some heavy fermions or polaronic systems, where charge carriers are also slow, present a deep analogy.     

In-crystal and surface charge transport of electric-field-induced carriers in organic single-crystal semiconductors

Gate-voltage dependence of carrier mobility is measured in high-performance field-effect transistors of rubrene single crystals by simultaneous detection of the longitudinal conductivity sigma(square) and Hall coefficient R(H). The Hall mobility mu(H) (identical with sigma(square)R(H)) reaches nearly 10 cm(2)/V s when relatively low-density carriers (<10(11) cm(-2)) distribute into the crystal. mu(H) rapidly decreases with higher-density carriers as they are essentially confined to the surface and are subjected to randomness of the amorphous gate insulators. The mechanism to realize high carrier mobility in the organic transistor devices involves intrinsic-semiconductor character of the high-purity organic crystals and diffusive bandlike carrier transport in the bulk.     

The mobility of charge carriers in molecularly doped polymer films with various thicknesses

The dependence of the mobility of charge carriers in molecularly doped polycarbonate on the thickness of the polymer was studied at two dopant DEH concentrations (30 and 50 wt %). The mobility of holes in the more concentrated polymer did decrease as the film thickness increased in close agreement with the predictions of the theory of weakly nonequilibrium transport with a dispersion parameter of 0.75. For films with a lower dopant concentration, such a categorical statement cannot be made, because mobility can either decrease as the film thickness increases or remain almost unchanged depending on the method for data processing. For this reason, it is not recommended to use the dependence of the time of flight on film thickness as a criterion for selecting the mechanism of the transport of charge carriers in molecularly doped polymers.     

Effect of adsorption on the surface mobility of charge carriers in a semiconductor substrate

The effect of adsorption on the carrier mobility in the near-surface region of a semiconductor substrate has been investigated within the framework of the Schrieffer model. The dependence of the carrier surface mobility on the concentration of adatoms has been determined. The systems chosen for the study are the gases adsorbed on the surface of semiconductor oxides. Empirical estimates of the surface mobility, which are based on modification of conventional volume scattering mechanisms, have been proposed.     

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

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.     

金属/掺杂聚合物/金属结构中载流子的注入与输运

基于紧束缚的Su-Schrieffer-Heeger模型，利用非绝热的动力学方法，研究了金属/聚合物/金属三明治结构中载流子注入与输运的动力学过程，其中，聚合物中含有一个掺杂离子. 电子波函数随时间的演化满足含时Schrdinger方程，晶格运动满足经典的牛顿运动方程. 研究发现，掺杂离子对注入到聚合物中的载流子的作用类似一个控制阀门，阀门的状态与电场的强度和偏压的大小密切相关.     

金属/掺杂聚合物/金属结构中载流子的注入与输运

基于紧束缚的Su-Schrieffer-Heeger模型,利用非绝热的动力学方法,研究了金属/聚合物/金属三明治结构中载流子注入与输运的动力学过程,其中,聚合物中含有一个掺杂离子. 电子波函数随时间的演化满足含时Schrdinger方程,晶格运动满足经典的牛顿运动方程. 研究发现,掺杂离子对注入到聚合物中的载流子的作用类似一个控制阀门,阀门的状态与电场的强度和偏压的大小密切相关. 关键词： 载流子输运 波包 非绝热动力学     

Drift mobility measurements in melt-grown baryum titanate

Drift mobility measurements in melt-grown BaTiO₃ single crystal have been performed using the Spear method. The mobility of (3 ± 1) × 10^?3 cm²V^?1 sec^?1 at room temperature is found to be thermally activated, with an activation energy of 0.15 ± 0.04 eV. Two interpretations are investigated to explain these results: trapping effects due to oxygen vacancies or small polaron hopping.     

Electronic transitions in mobility gap in glassy semiconductors

Electronic transitions in mobility gap in glassy semiconductors are considered. Energies characteristics of the transitions, including de-trapping and luminescence energies, are in a simple way related to both the gap width and each other. Basic types of luminescence centres and some types of radiationless centres, including centres of photo-structural changes, are revealed. Correlations of the luminescence and its fatigue with some other photoinduced transitions are discussed. Some features of the luminescence are presented, including those associated with the inverse- Arrhenius law.     

The effect of excess volume on molecular mobility and on the mode of failure of glassy poly(ethylene terephthalate)

To gain further understanding regarding the modes of molecular motion which contribute to the ductility and toughness of glassy polymers, and the factors that influence such molecular mobility, a study has been undertaken of the effect of the amount of excess volume in glassy poly(ethylene terephthalate) on the mode of failure observed in tensile tests and on the associated level of molecular motion. The results of tensile stress-strain studies on films annealed at temperatures below the glass transition temperature indicate that there is a relationship between the mode of failure and the level of excess volume trapped in the glassy polymer. From dynamic mechanical loss studies of the annealed films, however, it is evident that the modes of motion associated with the major subsidiary dynamic mechanical absorption, i.e., the γ-relaxation process, are relatively unaffected by the loss of free volume caused by the densification of the glassy polymer on annealing. Further, these studies suggest that the limited segmental mobility associated with the onset of the glass transition phenomenon may be significant with regard to the ductile behavior of the glassy polymer.     

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.     

Charge carriers and mobility of Cu-Ti ferrite

The concentration and drift mobility of charge carriers in Cu_1–x Ti _x Fe₂O₄ ferrite are calculated, over a wide range of temperatures (300–773 K), employing d.c. conductivity and thermoelectric power data. With increasing temperature the concentration of charge carriers decreases whilst the drift mobility exhibits an exponential increase. Over the above-mentioned temperature range, the obtained density of charge carriers varies between 10²¹ and 10²² cm^–3 whereas the drift mobility has values between 10^–8 and 10^–4 cm²/V s. The results are discussed on the basis of a small-polaron hopping conduction. The activation of the d.c. conductivity has been attributed to the thermal activation of the mobility.     

Drift mobility correlation in a simple cubic lattice

A Monte Carlo method is described for the calculation of the drift mobility of interacting ions on a simple cubic lattice in an electric field. This formalism provides a useful operational model for electromigration in interstitial solid solutions. The results, which show a correlation in the drift of the ions, can be interpreted either in terms of a deviation from the Nernst-Einstein relation in the sense of vacancy wind effects or as an intrinsic correlation effect in the diffusion coefficient of the charge carriers. It is also shown that the usual tracer correlation factor can be calculated upon subtracting the square of the average drifts from the average squared displacements.