半导体量子器件物理讲座第四讲 共振隧穿器件及其电路应用

当一个电子的能量低于势垒高度时,它仍可以隧穿通过势垒,在一定条件下,双势垒结构中电子的隧穿几率甚至可以接近1,利用这种共振隧穿现象可以做成共振隧穿二极管,它的电流－电压特性曲线中会出现负微分电阻,利用这种负阻效应可以做成高频振荡器和倍频器等电子器件,双势垒结构与通常的双极晶体管结合可以做成共振隧穿双极晶体管,它们可以用来做成多态记忆器和模数转换器等器件。     

球谐振子径向算符r^2s的平均值的解析公式

获得了球谐振子径向算符r2s正偶次幂和负偶次幂平均值之间的一个递推关系,在-4s4情况下给出了平均值<nrl|r2s|nrl>的解析计算结果.     

负阻二阶动态电路的实验分析

对R≤0时的RLC串联二阶电路的动态过程进行了理论分析和实验验证,明确了RLC串联电路在负阻状态下电路动态过程的变化规律。     

Some Interesting Features for External Region of Spherical Symmetric Mass in New Theory of Gravitation VGM

This paper briefly discusses some interesting features for the external region of the spherical symmetric mass in the new theory of gravitation VGM, i.e. the theory of gravitation by considering the vector graviton field and the metric field, such as pseudo-singularity, curvature tensor, static limit, event horizon, and the radial motion of a particle. All these features are different from the corresponding features obtained from general relativity.     

一类推广的中曲率水平集的运动

研究了根据一个光滑曲面的主曲率函数的经典运动短时存在及唯一性,推广了Evans和Spruck的结果。     

Existing conditions of full bandgaps and absolute negative refraction in metallic-dielectric photonic crystal

This paper has theoretically studied the characteristic frequencies of band structures in two-dimensional metallic-dielectric photonic crystals. It is demonstrated that a large filling fraction benefits the existence of absolute photonic band gap, while a smaller filling fraction benefits an absolute negative refraction band. In addition, it also finds that the relation between the cut-off frequency of E-polarized wave and the filling fraction exceeding 10{\%} is content with a linear increasing function, whose coefficients are exponential to the normalized lattice constant. These investigations have significant implications for tuning the operational frequencies to desired applications and manufacturing photonic crystals.     

Tokamak resistive magnetohydrodynamic ballooning instability in the negative shear regime

Improved confinement of tokamak plasma with central negative shear is checked against the resistive ballooning mode. In the negative shear regime, the plasma is always unstable for purely growing resistive ballooning mode. For a simplest tokamak equilibrium model, the s--α model, characteristics of this kind of instability are fully clarified by numerically solving the high n resistive magnetohydrodynamic ballooning eigen-equation. Dependences of the growth rate on the resistivity, the absolute shear value, the pressure gradient are scanned in detail. It is found that the growth rate is a monotonically increasing function of α while it is not sensitive to the changes of the shear s, the initial phase \ta₀ and the resistivity parameter \va_R.     

浙江交通运输与经济发展的相关性分析

本文运用灰色系统建模理论和数量经济的方法对浙江省交通运输与经济发展之间的关系进行相关性分析,研究交通运输业内各重要指标对经济发展的内在联系.这对充分发挥交通运输对经济活动中的重要作用,研究交通运输与经济的协调发展都将提供必要的参考依据.     

Size Dependence of Electronic Excitation Energy in Linear C2nH and C2n－1N

The geometries, bondings, and vibrational frequencies of C2nH (n = 3—9) and C2n-1N(n= 3—9) were in-vestigated by means of density functional theory (DFT). The vertical excitation energies for the X^2Ⅱ→^2Ⅱ transitions of C2nH(n= 3—9) and for the X2∑→^2Ⅱ and the X^2Ⅱ→^2Ⅱ transitions of C2n-1N (n= 3—9) have been calculated by the time-dependent density functional theory(TD-DFT) approach. On the basis of present calculations, the explicit expression for the wavelengths of the excitation energies in linear carbon chains is suggested, namely, λ0 = [1240. 6A/(2 √-3n 6 - √-3n 3）] (1 — Be^Cn), where A = 3. 24463, B =0. 90742, and C=0. 07862 for C2nH, and A=2. 94714, B=0. 83929, and C=0. 08539 for C2n-1N. In consid-eration of a comparison of the theory with the experiment, both the expressions are modified as λ1 = 0. 92 (λ0 100) and λ1 =0. 95(λ0-90) for C2nH and C2n-1N, respectively.     

辉光放电对负偏压增强热丝化学气相沉积碳纳米管的准直生长作用研究

利用负偏压增强热丝化学气相沉积在不同的负偏压和压强下,在沉积有不同厚度NiFe膜的Si衬底上制备了碳纳米管,并用扫描电子显微镜研究了它们的生长.发现在无辉光放电的情况下,碳纳米管弯曲生长,而在辉光放电时,碳纳米管准直生长,表明辉光放电对碳纳米管的准直生长起到了重要的作用.由于辉光放电的产生,在衬底表面附近形成很强的电场.相对无辉光放电时的电场,场强提高了两个数量级.本工作详细地研究了辉光放电对碳纳米管的准直生长作用.