Tailoring interface functionality of complex oxide heterostructures - A neutron and x-ray study

复杂过渡金属氧化物异质结是一个新兴且迅速发展的领域，在自旋电子学、催化剂、太阳能电池等方面具有重要的科学价值和潜在的应用前景。在氧化物异质结中的不同材料的界面上会出现大量的新的物理现象，这些现象在主体成分中是不存在的。这个项目通过调整衬底的几何形状和表面取向来创造和操纵新的界面功能，从而研究过渡金属氧化物异质结构中的这种新现象。重要的是，该项目作为培训下一代中子和同步加速器x射线散射科学家的平台，有助于促进国家实验室尖端设施的用户群体。除了培训研究生和本科生外，该项目还支持吸引高中教师和K-12学生参与的科学研究活动，以及在密歇根州社区大学为学生开发和介绍讲习班的活动。技术摘要：该项目通过创造和操纵新的界面功能，研究了相关过渡金属氧化物异质结构中的量子现象。调整衬底的几何形状和表面取向会导致不同的极性表面终止、键连接和八面体扭曲，预计这将影响电子和轨道重建以及界面上的磁性和结构耦合。因此，这可以极大地改变生长在顶部的氧化物异质结构的物理性质，为新的物理和材料研究提供了一条途径。该项目利用两种独特和互补的技术，即偏振中子反射仪和偏振X射线吸收光谱，提供高深度分辨率和过渡金属元素的特征指纹，以确定界面磁性和电子态的性质。

Non-technical Abstract: Complex transition-metal oxide heterostructures represent an emerging and rapidly growing field with both significant scientific merits and potential applications in spintronics, catalysts, solar cells, etc. A plethora of novel physical phenomena can arise at the interface of dissimilar materials in oxide heterostructures that are not attainable in the bulk constituents. This project investigates such novel phenomena in transition-metal oxide heterostructures via creation and manipulation of novel interface functionalities by tuning the substrate geometry and surface orientation. Importantly, this project serves as a platform to train the next-generation neutron and synchrotron x-ray scattering scientists, helping to promote the user community of the cutting-edge facilities in national laboratories. In addition to training graduate and undergraduate students, this project also supports the scientific research activities engaging high school teachers and K-12 students, as well as the activities of developing and presenting workshops to students in community colleges in Michigan. Technical Abstract: The project investigates the emergent quantum phenomena in correlated transition-metal oxide heterostructures via creation and manipulation of novel interface functionalities. Tuning the substrate geometry and surface orientation gives rise to diverse polar surface terminations, bond connections, and octahedral distortions, which are anticipated to affect electronic and orbital reconstruction as well as magnetic and structural coupling at the interfaces. Consequently, this can drastically alter physical properties of oxide heterostructures grown atop, providing a pathway to new physics and materials research. This project utilizes two unique and complementary techniques, i.e., polarized neutron reflectometry and polarized x-ray absorption spectroscopy, which offer high depth resolution and characteristic fingerprint of transition-metal elements to decisively determine the nature of interfacial magnetic and electronic states.