缺陷行为对于二氧化铈忆阻转变机制影响的理论研究

忆阻器及材料是近年来的一个研究热点。稀土氧化物CeO2具有优异的储氧/放氧能力，其氧缺陷的快速形成与合并会导致材料导电性的变化，是一种十分有潜力的忆阻器材料。材料缺陷的微观行为是影响其忆阻转变效应的关键因素。然而，目前缺陷的电子结构及忆阻器的物理机制还不清楚。本项目将利用第一原理计算方法，系统研究CeO2中不同种类的缺陷（氧空位、极化子、铈空位、氢杂质等）以及缺陷团簇（氧空位-氧空位、氧空位-铈空位等）的物理特性与扩散过程。分析缺陷对于CeO2电子结构的影响，探讨分布在不同位置的缺陷（体内、晶界、表面）的微观行为，给出材料阻变效应的物理图像，为CeO2在阻变式存储器的实际应用做理论指导。

Memristor and related materials have received wide attention in recent years. Rare earth oxides, especially CeO2, exhibit high oxygen storage/release capability due to the facile oxygen vacancy formation and elimination. This leads to continuous change of conductance between a high-resistance state and a low-resistance state, i.e., the resistive switching behavior. Therefore, CeO2 is a promising material for memristive devices. Resistive switching behavior is closely related to the microscopic behavior of defects. However, the atomic physical mechanism underlying CeO2 based resistive switching device is still unclear. In this project, via first-principles calculations, we will perform a systematic study on effects of defects on the physical properties of CeO2. We will investigate the formation and diffusion behaviors of different types of defects (such as oxygen vacancies, polarons, cerium vacancies, and hydrogen), and the defect clusters (oxygen-vacancy cluster, oxygen-vacancy and cerium-vacancy clusters). The effects of defects on the electronic structures of CeO2 will be discussed in detail. Furthermore, we will explore defects distributed in the bulk, grain boundary, and surface of CeO2 to reveal their different contributions to the electronic properties. We expect this study to provide a microscopic picture of resistive switching mechanisms associated with defects, and shed light on future exploration and application of memristive devices.