钙钛矿氧化物界面电子结构和界面性质的物理机制研究

In recent years, emergent phenomena arising from transition metal oxide interface have been reported. The interfacial property and the controlling method have been the hot topics in condensed mater and material science fields. To find new electronic materials for actual application, it is necessary to understand the fundamental physics of the electronic structure and properties at oxide interface. In this proposal, based on our techniques on film fabricating, structure and property characterizing techniques like transmission electron microscopy, electron energy loss spectrocopy, superconducting quantum interfence device, physical property measurements system, etc., as well as the x-ray magnetic circular dichroism and x-ray absorption fine structure from Shanghai Synchrotron Radiation Facility, we will investigate the interfacial electronic structure, interfacial properties of perovskite YMnO3/LaFeO3, (La,Sr)MnO3/SrRuO3 heterostructures and superlattices, and interfacial conductivity of perovskite LaAlO3/SrTiO3, especially top BaTiO3 ferroelectric polarization on the interfacial conductivity. By further combining the experimental results and theoretical analysis, we hope we can probe the relationship between “fabricating-interfacial crystal structure-interfacial electronic structure and interfacial properties”. Hopefully, this proposal will be helpful not only for further understanding the coupling physics of oxide interface and finding a possible way to control the interfacial properties, but also for finding artificial heterostructure or superlattice materials for future actual applications.

近年来，过渡金属氧化物的界面性质及其调控已经成为凝聚态和材料科学领域的热点课题。深入理解氧化物在原子尺度上的界面电子结构、界面性质及其可控性，是寻找新型电子材料、促进新型电子器件的产生基础。本申请拟结合我们在钙钛矿氧化物异质结和超晶格的制备、结构和性质表征方面的积累和技术，及上海光源“x射线磁圆二色(XMCD)”、“x射线吸收精细结构(XAFS)”技术，系统研究钙钛矿过渡金属氧化物YMnO3/LaFeO3, (La,Sr)MnO3/SrRuO3的界面电子结构和界面磁性、及表面BaTiO3层的铁电极化对LaAlO3/SrTiO3界面电子结构和界面输运性质的影响。在实验基础上，结合理论分析，建立“材料制备-界面晶体结构-界面电子结构和界面性质”之间的关联规律，探索界面性质的调控方法，理解界面性质的物理机制。本申请还可能获得具有优良性质的氧化物异质结和超晶格人工微结构材料。

本项目针对人工结构氧化物异质结和超晶格所具有的丰富的物理性质，并根据项目研究计划，在SrTiO3等单晶衬底上，制备了并研究了一系列以Sr2CrWO6为代表的氧化物异质结和超晶格、以ReAlO3/SrTiO3为代表的多种氧化物异质结等。首次在双钙钛矿结构Sr2CrWO6异质结中获得达17200%的巨正磁电阻效应，研究了其厚度依赖性，提出了外加磁场打破长程反铁磁序导致自旋不联系的畴界产生，从而形成了正磁阻；系统研究了ReAlO3/SrTiO3异质结中，界面性质与制备条件、界面结构、元素种类等参数的关系，分析了原子序数与界面电荷转移的关系；人工设计不同氧化物的复合结构并制备了相应的微结构材料，实验上通过外加电场调控了复合结构中界面电荷的分布，实现了对材料铁电、介电、稀土发光等宏观性质的调控。