Field-Induced Point Defect Redistribution in Metal Oxides: Mesoscopic Length Scale Phenomena

金属氧化物中场致点缺陷的重新分布：介观长度尺度现象

• 批准号: 1132058
• 负责人: Elizabeth Dickey
• 金额: $ 48万
• 依托单位: North Carolina State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-15 至 2016-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1132058&HistoricalAwards=false
• 关键词: Field; Induced; Point; Defect; Redistribution

NON-TECHNICAL DESCRIPTION: Oxide materials are being used increasingly in electronic and memory devices, and the properties of this class of materials are strongly influenced by the material's stoichiometry and the concomitant defects in the material's crystalline lattice. The redistribution of defects under an applied voltage leads to failure of many capacitive devices, but the redistribution can also lead to unique material functionalities such as resistive switching, which is being explored as a future memory technology. This research program aims to understand fundamental issues of the point defect redistribution process under applied voltage, focusing on the interactions of point defects with higher dimensional lattice defects and the effects of the metallic electrodes. The program utilizes and trains students in a variety of state-of-the-art electron imaging and spectroscopy techniques to study the dynamic evolution of defects under applied bias and the implications for the material electrical properties. TECHNICAL DETAILS: The mobility of charged lattice defects under applied electrical bias can have far reaching ramifications for functional electroceramic devices. For example, the redistribution of point defects during prolonged DC biasing is responsible for leakage current enhancement in oxide-based capacitors. Conversely, electric-field-induced defect migration in oxides can give rise to useful device properties such as resistive switching, which is being explored aggressively for nonvolatile memory. The overall objective of the proposed research is to develop a phenomenological and kinetic understanding of point defect distribution at the mesoscopic length scale. The proposed methodology is to conduct studies on a well-controlled model material system, rutile TiO2, as a function of the initial defect chemistry state, electrode boundary conditions, dislocation concentration, and crystallographic orientation. The experimental approach couples electrical transport measurements with local-stoichiometry and atomic-structure analysis. The advancement of fundamental science in the proposed research is enabling to the development of next-generation functional ceramics, and the program trains both graduate and undergraduate students in state-of-the-art electron microscopy and materials research.

非技术描述：氧化物材料越来越多地用于电子和存储设备，这类材料的性能受到材料的化学计量和材料晶格中伴随的缺陷的强烈影响。在外加电压下缺陷的重新分配会导致许多电容器件失效，但这种重新分配也会导致独特的材料功能，如电阻开关，这正在被探索作为未来的存储技术。本研究项目旨在了解外加电压下点缺陷重分布过程的基本问题，重点研究点缺陷与高维晶格缺陷的相互作用以及金属电极的影响。该计划利用和训练学生在各种最先进的电子成像和光谱技术，研究应用偏压下缺陷的动态演变和对材料电性能的影响。技术细节：应用电偏压下带电晶格缺陷的迁移率对功能电陶瓷器件具有深远的影响。例如，在长时间的直流偏置过程中，点缺陷的重新分布是导致氧化物基电容器泄漏电流增强的原因。相反，电场诱导的氧化物缺陷迁移可以产生有用的器件特性，如电阻开关，这是正在积极探索非易失性存储器。提出的研究的总体目标是在介观长度尺度上发展点缺陷分布的现象学和动力学理解。所提出的方法是对一个控制良好的模型材料系统金红石TiO2进行研究，研究其与初始缺陷化学状态、电极边界条件、位错浓度和晶体取向的关系。实验方法将电输运测量与局部化学计量学和原子结构分析相结合。在拟议的研究中，基础科学的进步使下一代功能陶瓷的发展成为可能，该项目在最先进的电子显微镜和材料研究方面培养研究生和本科生。