Mesoscopic models for the mechanically modulated electrical conductivity of piezoelectric semiconductors

压电半导体机械调制电导率的介观模型

基本信息

批准号：
317661385
负责人：
Privatdozent Dr. Erion Gjonaj
金额：
--
依托单位：
Institut für Teilchenbeschleunigung und Elektromagnetische Felder
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2016
资助国家：
德国
起止时间：
2015-12-31 至 2020-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/317661385?language=en
关键词：
Mesoscopic models mechanically modulated electrical

项目摘要

The piezoelectric polarisation induced by internal or applied mechanical stresses in oxide ceramic semiconductors is known to modify the potential barriers at grain boundaries and therefore the electrical conductivity across these boundaries. Besides this modification in the microscopic scale, the effective electrical conductivity of polycrystalline bulk material depends also on the microstructural disorder associated with stochastic variations in grain size, grain boundary properties, crystallographic orientation and the related stress field distribution. The effect of microstructural disorder is manifested in the current flow properties, in particular, in the current filamentation phenomenon consisting in the concentration of current density along a few low resistivity paths within the material. Thus, the effective conductivity of polycrystalline materials depends not only on the piezoelectric grain boundary modification but also on the mesoscopic scale current distribution within the material for different applied voltages and mechanical stress conditions. Both, microscopic and mesoscopic effects are closely connected and should be investigated as coupled phenomena within a common research platform.The project is dedicated to the numerical modeling and simulation of the mechanically modulated electrical conductivity of ZnO. Microscopic-scale charge transport models for bicrystals and multigrain arrangements taking into account drift-diffusion, thermionic emission at grain boundaries as well as the direct and inverse piezoelectric effects will be developed. These models will be incorporated into 3D mechanically informed mesoscopic current flow simulations for polycrystalline ZnO using accurate mechanical stress distributions and taking into account stochastic microstructural variations. The microscopic-scale approach will provide insight into the range of validity of mesoscopic current simulations based on equivalent network and finite element models. The proposed models will be employed in the simulation based electromechanical characterization of ZnO varistors. Furthermore, textured ZnO films with intentionally oriented polarity will be investigated. All proposed investigations will be performed in close cooperation with our project partners.

已知由氧化陶瓷半导体中的内部或施加的机械应力诱导的压电极化，可以改变晶界处的潜在屏障，从而改变这些边界的电导率。除了在微观范围内进行这种修饰外，多晶体体积材料的有效电导率还取决于与晶粒尺寸，晶界特性，晶体边界特性，晶体学方向和相关应力场分布的随机变化相关的微结构障碍。微结构障碍的作用在当前的流量特性中表现出来，特别是在当前的细丝现象中，该现象由沿材料内几个低电阻率路径的电流密度浓度组成。因此，多晶材料的有效电导率不仅取决于压电晶界的修饰，而且还取决于材料中不同施加的电压和机械应力条件的介质尺度电流分布。显微镜和介观效应都密切相关，应在共同的研究平台内作为耦合现象进行研究。该项目专门用于ZnO机械调制电导率的数值建模和模拟。考虑到漂移扩散，晶界的热电话发射以及直接和反向压电效应，将开发出微观尺度的电荷运输模型和多流晶序列。这些模型将使用准确的机械应力分布并考虑到随机的微结构变化，将这些模型纳入多晶ZnO的3D机械知情介观流模拟中。微观尺度方法将洞悉基于等效网络和有限元模型的介观流模拟的有效性范围。所提出的模型将用于基于仿真的ZnO变种机的机电表征。此外，将研究具有有意定向极性的质感ZnO膜。所有提议的调查将与我们的项目合作伙伴密切合作进行。