Mechanically tunable conductivity in piezoelectric semiconductors

压敏电阻器和二极管的独特电性能依赖于永久实现在器件中的掺杂和界面势垒。在这里，我们提供了一种全新的方法，面向压电半导体，其中界面静电势垒可以通过外部机械应力可逆地调谐。这一概念与压电电子学有关，但迄今为止，压电电子学一直专注于纳米纤维中的肖特基势垒，只产生了潜在势垒高度的微小变化。利用ZnO作为高压电系数的半导体，从根本上研究了这一新颖的概念。重点将放在单（ZnO/金属）和双（ZnO/ZnO）肖特基势垒上，利用ZnO单晶确定取向。然后利用ZnO的晶粒电导率、金属的功函数和由晶界取向偏差和界面掺杂剂决定的界面状态进行裁剪。额外的灵活性是由于在电加载过程中施加界面应力而产生的。与其他项目合作的电气特性将在不同频率和温度下的阻抗谱和I - V曲线方面研究电子态密度和电子迁移率。一个特殊的挑战在于应力调谐界面电荷和半导体电导率诱导电荷筛选的二分法。同时，该项目将提供多晶氧化锌，以帮助建模项目的验证，并提供氧化锌极化结构的机电表征。

The unique electrical properties in varistors and diodes rely on doping and interfacial potential barriers which are permanently implemented into the device. Here we provide a fundamentally new approach, geared towards piezoelectric semiconductors in which an interfacial electrostatic potential barrier can be reversibly tuned through external mechanical stress. The concept is related to piezotronics that so far has been focused, however, on Schottky barriers in nanofibers and yielded only small changes of potential barrier heights.This novel concept is fundamentally investigated using ZnO as semiconductor with high piezoelectric coefficient. The focus will be on single (ZnO/metal) and double (ZnO/ZnO) Schottky barriers with well determined orientations utilizing ZnO single crystals. Tailoring is then afforded using grain conductivity of the ZnO, work function of the metal and interface states determined by grain boundary misorientation and interface dopants. The additional flexibility arises due to the application of interfacial stresses during electric loading. Electrical characterisations in collaboration with other projects will be on density of electron states and electron mobility, in terms of impedance spectroscopy and I V curves at different frequency and temperature. A special challenge lies in the dichotomy of stress-tuned interfacial charge and semiconductor conductivity-enticed charge screening. At the same time, this project will provide polycrystalline ZnO to aid validation of modelling projects and affords electromechanical characterisation of polarisation texture of ZnO.