The effect of inhomogeneity on electrostatic oscillations of multi-velocity electron streams

The dispersion relations for electrostatic oscillations of an inhomogeneous beam with a longitudinal velocity spread and of two counter-streaming inhomogeneous beams are investigated. In both cases the effect of the inhomogeneity is to extinguish the discrete spectrum entirely and to make the dispersion function a multivalued analytic function: a pair of branch points is created corresponding to each zero of the dispersion function of the associated homogeneous problem. The zeros themselves do not vanish but move on other sheets of the Riemannian surface of the dispersion function. The result is, physically, that the Landau damping is enhanced and the aperiodic two-beam instability becomes an over-stability.     

The temperature variation of low field electron mobility in n-GaAs

We have studied the effect of low temperatures on low field electron mobility, threshold electric field and peak to valley ratio for Gunn oscillations. The low field electron mobility increases slightly while the threshold field decreases with the lowering of the temperature. The peak to valley ratio of the current is found to increase with a decrease in temperature.     

Spin-dependent hot electron transport in Co/Cu thin films

Hot-electron transport in Co/Cu/Co trilayer films has been studied in the energy range from 1.0 to 2.0 eV using ballistic electron magnetic microscopy. Both the spin-dependent attenuation lengths of Co and the cumulative polarizing effects of spin-dependent tunneling and transmission across a Co/Cu interface have been determined. For very thin (a few A) Co layers, the latter effects result in a weakly majority-spin polarized electron beam above approximately 1.3 eV and a minority-spin polarized beam below approximately 1.2 eV. For thicker Co layers the transmitted beam is always majority-spin polarized.     

The effect of periodic magnetic-electric barriers on electron transport in a nanostructure

Using the transfer matrix method, the transmission probability, the spin polarization and the electron conductance of a ballistic electron are studied in detail in a nanostructure. We observe that these quantities sensitively depend on the number of periodic magnetic-electric barriers. As the number of periods increases, the resonance splitting increases, the number of the resonance peaks increases and the peaks become sharper as well as the spin polarization being enhanced. Surprisingly, a polarization of nearly 100% can be achieved by spin-dependent resonant tunneling in this structure, although the average magnetic field of the structure is zero.     

Role of hot electron transport in scintillators: A theoretical study

Despite recent intensive study on scintillators, several fundamental questions on scintillator properties are still unknown. In this work, we use ab‐initio calculations to determine the energy dependent group velocity of the hot electrons from the electronic structures of several typical scintillators. Based on the calculated group velocities and optical phonon frequencies, a Monte‐Carlo simulation of hot electron transport in scintillators is carried out to calculate the thermalization time and diffusion range in selected scintillators. Our simulations provide physical insights on a recent trend of improved proportionality and light yield from mixed halide scintillators. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Asymmetry of nonlinear transport and electron interactions in quantum dots

The symmetry properties of transport beyond the linear regime in chaotic quantum dots are investigated experimentally. A component of differential conductance that is antisymmetric in both applied source-drain bias V and magnetic field B, absent in linear transport, is found to exhibit mesoscopic fluctuations around a zero average. Typical values of this component allow a measurement of the electron interaction strength.     

飞秒激光固体靶相互作用中超热电子的输运特性

 实验研究了在100 TW掺钛宝石超短超强脉冲激光装置上完成的飞秒激光-固体靶相互作用中超热电子的输运特性,获得了超热电子的能谱、产额、注量及超热电子在靶内输运能量沉积范围。测量结果表明:超热电子的注量和总能量随靶厚度的增加而减少,超热电子约80％的能量主要沉积在靶内的前约一个激光脉冲宽度的范围内,且能量沉积范围随激光脉冲宽度的增加而增加,这主要是静电场的影响所致。     

飞秒激光固体靶相互作用中超热电子的输运特性

实验研究了在100 TW掺钛宝石超短超强脉冲激光装置上完成的飞秒激光-固体靶相互作用中超热电子的输运特性,获得了超热电子的能谱、产额、注量及超热电子在靶内输运能量沉积范围。测量结果表明:超热电子的注量和总能量随靶厚度的增加而减少,超热电子约80％的能量主要沉积在靶内的前约一个激光脉冲宽度的范围内,且能量沉积范围随激光脉冲宽度的增加而增加,这主要是静电场的影响所致。     

Hot electron distribution function with LO phonon kink in n-GaAs

LO phonon kink in the hot electron distribution function has been observed for the first time by photoluminescence measurement in n-GaAs. A detailed comparison between the experiment and the calculation is made on the distribution function and electron mean energy.     

Anisotropic effect of appearing superconductivity on the electron transport in FeSe

A theoretical model has been proposed to describe the conductivity of a layered anisotropic normal metal containing small superconducting inclusions at an arbitrary eccentricity of spheroidal superconducting islands. The electron transport and magnetic properties of FeSe single crystals have been measured. The results indicate the existence of superconductivity at temperatures much higher than the critical superconducting transition temperature corresponding to vanishing electrical resistance. Within the proposed model, quantitative agreement has been achieved between the volume fraction of superconducting inclusions and its temperature dependence determined from the transport and magnetic measurements.     

18.2 nm Schwarzschild microscope for diagnostics of hot electron transport

Schwarzschild microscope at 18.2 nm for diagnostics of hot electron transport in femtosecond laser-plasma interaction has been developed. Based on the third-order aberration theory the microscope is designed for numerical aperture of 0.1 and magnification of 10. Mo/Si multilayer films with peak throughput at 18.2 nm is designed and deposited by magnetron sputtering method. The 24 lp/mm copper mesh is imaged via Schwarzschild microscope, and resolutions of less than 3 μm are measured in 1.2 mm field. The diagnostics experiment of hot electron transport is performed on 286 TW SILEX-I laser facilities, and the spatial distribution of radiation caused by hot electron is imaged by Schwarzschild microscope.     

The effect of phonon focusing on the electron-phonon relaxation and electron transport in potassium crystals

The influence of anisotropy of elastic energy on electron-phonon relaxation and the role of shear waves in the electrical resistance of potassium crystals are investigated. It is shown that, at temperatures much lower than the Debye temperature (T<< θ_D), the contribution of slow quasi-transverse phonons to the electrical resistance of potassium crystals exceeds that of longitudinal phonons by an order of magnitude. Earlier, the Bloch-Grüneisen theory left aside this component under the above conditions. At the same time, at high temperatures(T>>θ_D), the contribution of longitudinal phonons to the electrical resistance turns out to be 4 times greater than the total contribution of electron relaxation by fast and slow transverse modes. The role of shear waves in the electrical resistance of potassium crystals is analyzed. It is shown that, at low temperatures, this mechanism provides 32% of the total electrical resistance. It is 4 times higher than the contribution of longitudinal phonons to the electrical resistance and should be taken into account when analyzing the electrical resistance of alkali metals. The distribution function of the most effective phonons for electrical resistance is defined, and the inelasticity of electron-phonon scattering is analyzed. It is shown that the calculated results of the electrical resistance of potassium in the temperature range from 40 to 400 K, taking into account the anisotropy of elastic energy, are in good agreement with the experimental data without the use of fitting parameters.     

Electron transport near the Mott transition in n-GaAs and n-GaN

In this paper, we study the temperature dependence of the conductivity and the Hall coefficient near the metal–insulator phase transition. A theoretical investigation is performed within the effective mass approximation. The variational method is used to calculate the eigenvalues and eigenfunctions of the impurity states. Unlike previous studies, we have included nonlinear corrections to the screened impurity potential, because the Thomas–Fermi approximation is incorrect for the insulator phase. It is also shown that near the phase transition the exchange interaction is essential. The obtained temperature dependencies explain several experimental measurements in gallium arsenide (GaAs) and gallium nitride (GaN).     

飞秒激光-固体靶相互作用中超热电子输运的实验研究

报道了在100TW超短脉冲掺钛宝石激光装置上,完成的飞秒激光-固体靶相互作用中超热电子在靶内输运的实验研究结果.获得了超热电子的产额、注量和总能量.结果表明,超热电子的注量和总能量随靶厚的增加而减少,超热电子约80%的能量主要沉积在靶内的前10(m,对以上形成的原因进行了分析指出,是由于静电场对超热电子输运影响所致.     

The effect of temperature on the electrical characteristics of Ti/n-GaAs Schottky diodes

Schottky diodes still attract researchers as they are used in various device applications. This study provides I–V characteristics of Ti/n-GaAs (80–300 K). Higher barrier height (Φ_B0) values were obtained for higher temperatures, whereas the ideality factor exhibited the opposite behavior. This was associated with a barrier inhomogeneity at the Ti/GaAs interface, which has a Gaussian distribution (GD). The mean barrier height values calculated from the modified Richardson and Φ_B0 - q/2 kT plots were found to be 0.584 eV and 0.575 eV in the temperature range of 80–160 K. They were found as 1.041 eV and 1.033 eV between 180 K and 300 K, respectively. The modified Richardson constant value, on the other hand, was calculated as 22.06 A cm⁻² K⁻² (80–160 K) and 13.167 A cm⁻² K⁻² (180–300 K). These values are higher than the theoretical value for n-GaAs, which is 8.16 A cm⁻² K⁻². This difference may stem from intense inhomogeneity at the Ti/n-GaAs interface.     

Summation of electrostatic interactions in quasi-two-dimensional simulations

An error in our previous paper (Clark, A. T., Madden, T. J. and Warren, P. B., 1996 Molec. Phys., 87, 1063) is corrected. This brings the results into agreement with the recent work of Grønbech-Jensen et al. (Grønbech-Jensen, N., Hummer, G. and Beardmore, K. M., Molec. Phys., 1997, 92, 941).