Single-electron tunneling in silicon-on-insulator nano-wire transistors

The gate bias dependent evolution of the Coulomb oscillations in a silicon-on-insulator nano-wire transistor is reported. Transport data obtained for a wide range of front- and back-gate bias strongly suggest that multiple quantum dots (QDs) with different potential depths are formed in the nano-wire channel. Our data can be clearly interpreted as arising from the turning on or off of one of these QDs as the back-gate bias is varied. Quantitative calculation based on the model of single-electron tunneling through two parallel QDs is in reasonable agreement with the measured data in the back-gate bias range where the third dot is not activated.     

Phase-shift analysis of electric conductance through nanostructure bridges

We present our theoretical studies of electric conductance through nanostructure bridges. A simple expression of the electric conductance is obtained by using the phase-shift analysis. The phase-shifts are given by solving the characteristic equation obtained by extending the method applied to the single impurity problem in the metal. It is shown that the importance of the effect due to multiple orbitals in nanostructures. The conductance of the chain consisting atoms with sp_z character such as Al is given.     

Investigation of AlGaN/GaN fluorine plasma treatment enhancement-mode high electronic mobility transistors by frequency-dependent capacitance and conductance analysis

This paper reports fluorine plasma treatment enhancement-mode HEMTs (high electronic mobility transistors) EHEMTs and conventional depletion-mode HEMTs DHEMTs fabricated on one wafer using separate litho-photography technology. It finds that fluorine plasma etches the AlGaN at a slow rate by capacitance--voltage measurement. Using capacitance--frequency measurement, it finds one type of trap in conventional DHEMTs with τ_T=(0.5-6) ms and D_T= (1 - 5) × 10¹³ cm^-2·eV^-1. Two types of trap are found in fluorine plasma treatment EHEMTs, fast with τ_T(f)=(0.2-2) μs and slow with τ_T(s)=(0.5-6) ms. The density of trap states evaluated on the EHEMTs is D_T(f)=(1 - 3) × 10¹² cm^-2·eV^-1 and D_T(s)=(2 - 6) × 10¹² cm^-2·eV^-1 for the fast and slow traps, respectively. The result shows that the fluorine plasma treatment reduces the slow trap density by about one order, but introduces a new type of fast trap. The slow trap is suggested to be a surface trap, related to the gate leakage current.     

光纤激光器自组织相干阵列的理论分析

分析了光纤激光器自相干阵列最简单的情况——两个光纤激光器之间的相位锁定过程。建立了该过程的数学模型,并对它的时间特性和输出光束的模式进行了理论和数值分析,讨论了运行频率差和耦合系数对锁相过程的影响。对于运行频率相等的两个光纤激光器,当两个光纤激光器初始相位差不为0时,相位锁定后的激光器阵列输出模式为异相模;对于运行频率不等的情形,给出了锁相运行对两个光纤激光器运行频率差的要求,并分析了降低这种要求的几种方法。     

光纤激光器自组织相干阵列的理论分析

 分析了光纤激光器自相干阵列最简单的情况——两个光纤激光器之间的相位锁定过程。建立了该过程的数学模型,并对它的时间特性和输出光束的模式进行了理论和数值分析,讨论了运行频率差和耦合系数对锁相过程的影响。对于运行频率相等的两个光纤激光器,当两个光纤激光器初始相位差不为0时,相位锁定后的激光器阵列输出模式为异相模;对于运行频率不等的情形,给出了锁相运行对两个光纤激光器运行频率差的要求,并分析了降低这种要求的几种方法。     

微通道板电子传输时间特性的理论分析

电子在微通道内传输过程可以采用解析法和蒙特卡罗模拟进行研究，解析法的优点是物理图像更清晰，但对电子渡越时间的弥散特性不能给出满意的解释。采用统计学的方法对电子在微通道内传输过程的时间分布特性进行了讨论，得到了电子渡越时间的分布函数表达式，并据此可以得到时间弥散度与二次倍增次数的关系，即整个二次电子的渡越时间呈指数分布，且在最可机时间内集中了大量的二次电子。此外，由于碰撞次数对电子渡越时间弥散度的影响，因此在作为高时间分辨元件时应该考虑适当增加通道板两端的电压，以减少碰撞次数，从而降低渡越时间的弥散度和提高整个器件的时间分辨率。     

Resonance split of ballistic conductance peaks in electric and magnetic superlattices

Resonant peak splitting for ballistic conductance in finite electric superlattices (ES) and magnetic superlattices (MS) was investigated theoretically. It is shown that, for electron tunneling through the ES (MS) of identical n electric (magnetic) barriers, the resonance split of the conductance peak is (n–1)-fold; while for electron tunneling through the ES (MS) made of two different barriers, one resonant window of the former splits into two subwindows, within each of which the resonance split is (m–1)-fold, where m is the number of the renormalized building blocks consisting of two different barriers of the latter. Received 15 February 2000     

Observation of hopping transitions for delocalized electrons by temperature-dependent conductance in silicon junctionless nanowire transistors

We demonstrate transitions of hopping behaviors for delocalized electrons through the discrete dopant-induced quantum dots in n-doped silicon junctionless nanowire transistors by the temperature-dependent conductance characteristics.There are two obvious transition platforms within the critical temperature regimes for the experimental conductance data,which are extracted from the unified transfer characteristics for different temperatures at the gate voltage positions of the initial transconductance gm peak in V_(g1) and valley in V_(g2). The crossover temperatures of the electron hopping behaviors are analytically determined by the temperature-dependent conductance at the gate voltages V_(g1) and V_(g2). This finding provides essential evidence for the hopping electron behaviors under the influence of thermal activation and long-range Coulomb interaction.     

Theoretical study of electric conductance through nanostructures in terms of the phase-shift

A simple expression of the electric conductance through a nanostructure connected to two electrodes is obtained by using the phase-shift analysis. The Green function theory applicable to the nonequilibrium system is employed to formulate the electric conductance. The 0 bias limit, i.e., the linear response approximation is taken. The relation between Green functions and phase-shifts is obtained by extending the method applied to the single impurity problem in the metal. It is shown that a channel does not contribute to the conductance if its phase-shift is an integer multiple of π. Also shown is the importance of the effect due to multiple orbitals in nanostructures. Some concrete examples leading to simpler forms are given.     

扩展目标光学特性的理论分析与研究

利用双向反射分布函数经验公式推导出激光主动照明条件下的目标反射截面表达式,给出了目标反射截面的一种近似计算方法,基于该方法计算了圆锥体目标反射截面。利用固体激光器和CMOS相机搭建实验系统,实际测量了目标反射截面随入射角度和不同目标体等参数变化时的变化情况,实验系统及数据同提出的方法计算得到的结果基本一致。结果表明,目标形状相同,入射角小于45时,目标反射截面随着无涂层、白色油漆、灰色油漆逐渐变小,大于45时白色油漆涂层目标反射截面最大;在目标表面特性相同的时候,目标反射截面随圆板、圆柱、圆锥渐次减小。     

扩展目标光学特性的理论分析与研究

利用双向反射分布函数经验公式推导出激光主动照明条件下的目标反射截面表达式,给出了目标反射截面的一种近似计算方法,基于该方法计算了圆锥体目标反射截面。利用固体激光器和CMOS相机搭建实验系统,实际测量了目标反射截面随入射角度和不同目标体等参数变化时的变化情况,实验系统及数据同提出的方法计算得到的结果基本一致。结果表明,目标形状相同,入射角小于45时,目标反射截面随着无涂层、白色油漆、灰色油漆逐渐变小,大于45时白色油漆涂层目标反射截面最大;在目标表面特性相同的时候,目标反射截面随圆板、圆柱、圆锥渐次减小。     

Rippling and the external electric field on conductance in corrugated graphene nanoribbons molecular device

Molecular devices constructed using corrugated graphene nanoribbons (GNRs) are proposed in the paper. Recursive Green's function calculations show that the intrinsic ripples in graphene and the external electric field energy play important roles on the electron transport properties. Negative differential resistance is observed in zigzag corrugated GNRs. With the wavelength of the ripples decreasing, both the zigzag and armchair corrugated GNRs exhibit ON/OFF characteristics. On applying external electric field, current decreases dramatically in zigzag corrugated GNRs. These findings show that corrugated GNRs can be used to design functional nanoscale devices.     

Spin Hall effect on edge magnetization and electric conductance of a 2D semiconductor strip

The intrinsic spin Hall effect on spin accumulation and electric conductance in a diffusive regime of a 2D electron gas has been studied for a 2D strip of a finite width. It is shown that the spin polarization near the flanks of the strip, as well as the electric current in the longitudinal direction, exhibit damped oscillations as a function of the width and strength of the Dresselhaus spin-orbit interaction. Cubic terms of this interaction are crucial for spin accumulation near the edges. As expected, no effect on the spin accumulation and electric conductance have been found in case of Rashba spin-orbit interaction.     

Measurement of the hall coefficient and the electric conductance of anisotropic semiconductor samples

The macroscopic theory of the Hall effect is considered in anisotropic semiconductor samples of rectangular form with low-resistivity electrodes. The shunting influence of the electrodes and the corresponding Hall currents on the magnitude of the Hall emf is considered. Simple relations are obtained and practical recommendations are given for computing the components of the tensor of the Hall coefficient and of the conductivity. The results are presented in a form convenient for practical use in analyzing anisotropic monocrystals and films.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 56–60, November, 1990.     

Theoretical study of electric conductance of atomic contact with the Friedel sum rule

We analyze the electric conductance through nanostructure bridges in terms of phase-shifts, which satisfy the Friedel sum rule. The phase-shifts are given by solving the eigenvalue equation obtained by extending the method applied to a single impurity problem in a metal. We introduce the charge neutrality condition through the Friedel sum rule. It is analytically shown that the electric conductance is quantized and can increase as the two electrodes separate under the condition in which the phase-shifts satisfy the Friedel sum rule.     

超短激光脉冲二倍频理论分析

采用快速傅里叶变换（FFT）算法和Rung-Kutta法对KDP晶体中超短激光脉冲二倍频过程作了研究。详细讨论了群速度失配、群速度色散和三阶非线性相位调制效应对倍频光脉冲波形、光谱及转换效率的影响。研究结果表明：在超短激光脉冲二倍频中，三阶非线性相位调制效应可使二倍频光脉冲形状发生畸变，光谱明显展宽且转换效率降低；当入射基频光功率密度大于100GW/cm2时，三阶非线性效应是影响倍频过程的主要因素。     

猫眼谐振腔氦氖激光器理论分析

猫眼逆向器作为谐振腔镜与一个凹面镜构成猫眼激光谐振腔.精确计算了三种猫眼逆向器(即理想猫眼逆向器和两种存在误差的猫眼逆向器)的逆向平行反射性，并对应用这三种猫眼逆向器的谐振腔中高斯光束的各项参数进行了深入分析，得出结论：对于高斯光束，凸透镜的焦距、凹面镜曲率半径、凸透镜与凹面镜间距三者相等的猫眼逆向器为理想逆向器，其逆向平行反射性最好，此时猫眼谐振腔处于理想状态，基模模体积最大，远场发散角最小，稳定性最好；在猫眼谐振腔的设计中，要尽量减小猫眼逆向器中凸透镜的焦距，增大凹面输出镜的曲率半径；猫眼逆向器存在误差时谐振腔的各项性能将受到影响.为猫眼谐振腔激光器的设计提供了理论依据.     

三谐振高压脉冲变压器理论分析与模拟

 介绍了一种基于空芯变压器的三谐振高压脉冲变压器。通过对三谐振脉冲变压器无损等效电路的理论分析,给出了在回路本征频率为1∶2∶3时,电路各参数的关系及输出电压解析表达式,由此可知在此条件下变压器次级高压绕组上的最大电压与负载电容上最大电压比为0.36∶1。根据理论结果,设计了一组参数进行了电路模拟,证明了理论分析结果的正确性,可用于三谐振脉冲变压器的设计。并模拟了变压器耦合系数、调谐电感、调谐电容、初级电容及负载电容等参数变化对装置输出电压及能量传输效率的影响。由模拟结果可知,调谐电感和调谐电容在-10%～10%范围,初级电容在0～10%范围以及负载电容在-10%～0范围内变化对装置的性能影响不大,该变压器较容易实现工程化。     

介质单边二次电子倍增的理论分析与数值模拟

 针对介质单边二次电子倍增现象,理论分析给出了其动力学方程、二次电子初始能量与角度分布,结合二次电子发射的材料特性,研究了二次电子倍增的理论预估敏感区间。利用蒙特卡罗方法抽样选取电子初始发射能量和角度,数值研究了二次电子倍增的敏感区间,并与理论结果进行了比对,给出了二次电子数目随时间的增长关系;采用固定时间步长并考虑电子束动态加载饱和效应的细致蒙特卡罗方法,研究了二次电子数目、直流场、射频场、介质表面沉积功率、电子放电功率、二次电子碰撞能量及电子渡越时间等二次电子倍增特性物理量的变化过程,并且讨论了初始电流及二次电子倍增工作点对二次电子倍增整个过程的影响作用,得出了二次电子倍增存在初始阈值发射电流密度的结论。