接触电势差

一、引言两种不同的金属接触,它們之間产生的电势差叫做接触电势差。关于接触电势差存在的地点,各种书上的說法有些不一致,例如,福里斯及节目利娃著的普通物理学中虽然并未明显指出哪两点間有接触电势差,但是,在解释接触电势差时,可以看出两种金属的接触电势差是存在于不同金属內部两点之間的。高等工业学校物理学編写組編的物理学中也是认为接触电势差处于不同金属內部接触面邻近的二点之間,如图1a、b两点间。另外,巴巴列克西著的物理学教程和布吉     

启事

半径不同的两个带电小球接触后有无电荷的转移取决于两小球之间是否存在有电势差．若有电势差，则有电荷的定向移动；若无电势差，则没有电荷的移动．     

量测电子管接触电势差的改进方法

接触电势差是电子管中的一个重要的物理现象,它对管特性有着一定的影响。在用氧化物阴极的管中,由于工艺过程复杂,栅极表面情况往往很难掌握,这就造成阴极和第一栅之间的接触电势差的不一致,也是产品中特性散布的原因之一。而在一个管的寿命过程中,因阴极活性物质的不断蒸发和管内残留气体的继续作用,接触电势差也经常改变,这就使特性不能稳定。所以在电子管的生产中,为了分析报废的原因和提高产品的质量,就要了解和控制接触电势差,因而也就首先要求一个直接地和快速地量测它的方法。     

霍尔效应法测磁场实验误差研究

从机理上研究了霍尔效应法测定螺线管磁场实验的主要误差来源,分析了误差因素的具体特点,导出了准确的计算公式,成功消除了主要误差,研究结果表明:霍尔效应附效应产生的电势差和接触电势差以及不对称因素导致的误差均可采用对称测量法予以消除,这为霍尔效应实验教学与研究提供了更为清晰的理论参考和更为精确的测量方法。     

接触电位差与光电效应实验──兼与吴永懋同志商榷

除专门研究光电发射理论和近代物理实验的有关文献和论蔟之外，多数基础物理教科书在描述光电效应实验时，忽略了光电管发射极和接收极之间存在接触电势差及其影响．这不仅与（实际的）实验事实不符，而且会导致光电流与接收极逸出电势无关的错误结论．只要考虑接触电位差的存在并正确应用确定Ｖ０的条件，就会使文献［２］与［３］的分歧得到统一．     

实验“静电场的描绘”探讨

实验“静电场的描绘”探讨禹学甫（西安电力学校７１００３２）过去，我校学生分组实验“静电场的描绘”，用“检流计”取代了“万用表”，用“等距离”取代了“等电势差”来测等势线．实际做与教材相差甚远．为了解决这个问题，我试着按教材要求的用万用表，用“等电势差...     

PN结正向伏安特性曲线随温度的变化

介绍了在不同温度下，PN结正向伏安特性曲线的自动测量方法。讨论了PN结伏安特性与温度的关系．由于正向结电压小于内建电势差，温度升高或正向结电压增加，正向结电流将增大，温度升高反向结电流也相应增加．当温度趋向OK时。正向结电压趋向内建电势差。     

霍尔效应测量中的不等位热扩散电势差

尽管常规换向直流法可消除已知副效应干扰并得到霍尔电压，但它掩盖了存在未知附加电势的实验事实。将4次换向测量归纳为磁场与样品电流同相组合和反相组合，根据在磁场中样品电流和热扩散电流具有相似物理行为，必须考虑不等位热扩散电势差的影响。这一方案不仅更清晰地解释4次换向测量平均的物理原理，还通过同相测量平均和反相测量平均之差与和得到不等位热扩散电势差与确定且可重复的霍尔电压。实验事实及分析结果表明，引入不等位热扩散电势差才能完整描述霍尔测量中所有副效应的贡献。     

人体神经系统中的电势差和电流

电势差和电流是电学中最基本的概念。人体细胞内部和外部具有不同的电势,细胞膜两侧的电势差源于细胞内外体液中离子浓度不同;电势差在神经细胞和肌肉细胞中尤为显著。在人体的神经系统中存在着电荷的流动,使我们能够感知外部的世界。本文以人体神经系统为例,详细介绍神经系统中神经细胞产生的电势差、神经脉冲信号的传递及其物理原理。     

圆柱形导体壳的霍尔效应

提出了一种同轴电缆结构的霍尔效应装置.若中心导体通电流,则在通电的导体壳内外表面之间产生霍尔电势差.讨论了导体壳电势差与中心导体的电流强度、导体壳的电流强度以及导体壳结构之间的关系,发现导体壳很薄时霍尔电势差最大.     

声子摩擦能量耗散机理研究

以界面摩擦为研究对象,分析了黏滑过程中的能量积累和耗散问题.基于晶格热动力学理论,通过分析界面原子在周期性势场中跳跃前后的势能差,推导了界面原子温升公式.理论表明,界面温升与摩擦系统的接触状态和材料特性有关,界面交互势能是其中影响较大的因素之一.在滑动阶段初期,由于界面原子处于非热平衡状态,晶格的热振动将通过激发出新声子而耗散能量,从而使得非热平衡向平衡状态转变.通过引入量子力学和热力学理论,分析了界面摩擦能量的耗散规律.结果表明,当声子振动频率较大时,黏着阶段存储于界面振子上的弹性势能在滑动阶段就很快完全耗散,耗散时间远小于滑动阶段的时间. 关键词： 界面摩擦 黏滑 声子 温升     

准静态颗粒介质的弹性势能弛豫分析

颗粒体系是典型的多体相互作用体系, 具有多重的能量亚稳态. 对于准静态颗粒体系, 引入构型颗粒温度T_c描述弹性势能涨落. 本文认为平衡的体系具有一定的构型颗粒温度T_a, 其量值反映了其结构特征. 当外界扰动激发的构型颗粒温度超出T_a时, 产生不可逆过程. 通过对应力松弛过程的分析, 发现(T_c-T_a)激发了弹性弛豫, 且(T_c-T_a)越大则松弛过程中应力变化越大, 最终构型颗粒温度T_c→T_a时,宏观应力松弛结束,体系达到新的能量亚稳态.     

Conversion of environmental heat to electric energy in the metal-dielectric-semiconductor-metal system

The basis of the proposed converter is a thermoelectric capacitor, which is the system of a metal-dielectric-semiconductor-metal. In such a system, non-zero conversion of the environmental heat into electrical energy without preliminarily creating a temperature gradient is possible. Charging of the thermoelectric capacitor takes place through the bottom electrode of the semiconductor substrate and discharging takes place through the near-surface layer enriched electrons formed during charging in the near-surface layer on the boundary with the dielectric. In this case, the amount of absorbed heat at the capacitor charging in the contact of the metal-semiconductor is greater than being allocated heat at the discharge. This is due to the fact that the contact difference between the bottom electrode and semiconductor is more than the contact difference between the metal and near-surface enriched layer in which the concentration of electrons is significantly more than in the volume of a semiconductor. As a result, the absorbed heat, which is not emitted, is converted into electrical energy at the discharge according to the law of conservation of energy.     

测定材料逸出功的一种新方法

本文报道了一种测定材料逸出功的新方法,二次电子发射-接触电位差法(简称SEE-CPD法)。用该法对Ni,Al,Au和Mo四种纯金属的逸出功进行了测量,并与Fowler等温法和Kelvin的接触电位差法比较,结果是一致的。表明SEE-CPD法在理论上是正确的,在实际应用中也是成功的。 关键词：     

Investigation into the effect of size of local metallization of <Emphasis Type="Italic">N</Emphasis>-GaAs surface on the character of surface potential distribution determined by atomic-force microscopy

The potential of the GaAs surface with locally deposited thin layers of gold is studied by atomic-force microscopy (AFM) using the Kelvin probe method (KPM). The results obtained show that the measured potential in the probe – metal system corresponds, on the whole, to the contact potential difference (CPD) in this system.     

Effects of single-electron charging in a tunnel structure with a metallic cluster

The effects of single-electron tunnel charging and Coulomb blockade in a cluster structure (molecular transistor) are studied theoretically with allowance for the quantization of the electronic levels in an island electrode. The electronic spectrum is calculated for small spherical and disk-shaped clusters. Under the assumption that the total energy of the system is conserved with inclusion of the contact potential difference, equations are derived for analyzing the current-voltage characteristic. Limitations associated with the Coulomb instability of a cluster and with electron relaxation are introduced into the theory. For single-electron transistors with small gold clusters, the current gap and the asymmetry in its position on the voltage axis are calculated. The current gap is shown to vary nonmonotonically with the cluster size.     

基底支撑刚度梯度变化对石墨烯层间摩擦力的影响

基于纳米摩擦能耗理论,利用分子动力学方法建立了公度接触下支撑刚度梯度变化的石墨烯层间摩擦力模型,分析了基底质心刚度和支撑刚度梯度变化对基底和薄片各接触区摩擦能耗的贡献.结果表明:软边界区始终贡献驱动力;硬边界区贡献的摩擦力最大,且随着支撑刚度的增大,硬边界区对总摩擦的贡献比也越高.各接触区的摩擦力是薄片和基底之间的褶皱势和接触区产生的法向变形差两部分的共同作用.前者是公度接触下阻碍滑移的界面势垒和刚度梯度方向上不同刚度支撑原子热振动引起的势梯度;后者是接触边界过渡区两侧原子的非对称变形和自由度约束突变引起的非平衡边界势垒相耦合的结果.本文对研究公度接触下刚度梯度支撑的纳米器件的相对运动规律有指导意义.     

Energy dissipation prediction in a line of colliding oscillators

In this paper the impact of a line of adjacent structures, or oscillators, is studied using an energy formulation. The energy exchange and dissipation from a collision of a pair of oscillators is studied by creating an equivalent oscillator pair, one has the energy of the in-phase motion and the other has the out-of-phase energy. It is found that the energy exchange between colliding oscillators is proportional to the initial kinetic energy difference of the oscillators and that work in the collision is proportional to the out-of-phase energy or difference energy. The kinetic energy at contact is then related to the mean oscillator energy, permitting a power balance equation to be written for each oscillator in line. The power balance equations have three independent variables for each pair of oscillators: the oscillator time averaged energies and the phase difference. This equation is run in a time-stepping procedure, with steps at the mean collision rate. The work in the collisions and internal oscillator dissipation is output as a function of time. A parameter study is conducted to see how the work changes with oscillator: separation, contact stiffness and contact damping.     

Effect of dielectric coating on the electron work function and the surface stress of a metal

The electron work function, contact potential difference, and surface stress of the elastically deformed faces of the metal covered by a dielectric are calculated by using the Kohn–Sham method and stabilized jellium model. Our calculations demonstrate the opposite deformation dependencies of the work function and contact potential difference. Dielectric coating leads to a negative change in the work function and a positive change in the contact potential difference. It is shown that the measurements of the contact potential difference of a deformed face by the Kelvin method give only the change in the value of the one-electron effective potential in the plane of a virtual image behind the surface, rather than the value of the electron work function. The obtained values of the electron work function and surface stress for Al, Au, Cu, and Zn are in agreement with the results of experiments for polycrystals.     

On the effect of deformation and dielectric coating on the electron work function in a metal

The surface tension, electron work function, and contact potential difference of elastically deformed faces of Al, Au, Cu, and Zn crystals are calculated in the stable jelly model with the help of the self-consistent Kohn-Sham method. Calculations demonstrate a decrease (increase) in the electron work function and an increase (decrease) in the contact potential difference upon axial extension (compression) of the metal crystal surface. Dielectric coating leads to a negative (positive) change in the work function (contact potential difference). It is shown that the measurement of the contact potential difference of a deformed face by the Kelvin method corresponds to a change not in the electron work function, but in the value of one-electron effective potential on the virtual image plane behind the surface. The calculated values are in conformity with experimental results for polycrystals and the results of ab initio calculations.