CAREER: Octahedral Control of Electronic Properties in Semiconducting Perovskite Heterostructures

非技术描述：设计和控制材料的原子结构以获得所需的宏观性能的能力是材料研究的巨大挑战。 由于复杂氧化物的普遍存在、社会重要性以及结构对性能的强烈依赖性，它们是解决这一挑战的理想化合物家族。例如，已知包括磁性、铁电性、催化行为和电子传导性的性质直接与氧化物中的原子结构耦合。该项目旨在稳定非平衡原子结构的复合氧化物薄膜，以控制从太阳能转换到光电子学等应用相关的电子特性。该项目还将开展宣传和教育活动，特别强调材料结构/性能关系的重要性。技术支持：该项目的目标是通过强化非平衡原子结构来控制半导体钙钛矿薄膜的电子性能，如带隙和载流子迁移率。虽然在氧化物研究中的一个主导主题是发展对界面电荷转移的理解，但使用界面来微调局部结构和键合环境作为控制物理性质的手段还有待于充分探索。在ABO 3钙钛矿中，角连接的BO 6八面体的扭曲和旋转（其决定B-O键长和B-O-B角）已知直接耦合到电子结构。虽然控制块状钙钛矿中八面体行为的方法限于组成变化，但氧化物异质结构提供了独立于组成的工程八面体行为的新途径。在这个项目中，局部原子结构在等成分钙钛矿薄膜系统地通过应变或基板膜耦合变化。结构和电子性质探测使用同步辐射衍射，光谱学和电子输运测量的组合。通过直接比较八面体行为和电子性质，该项目将结构隔离为单个独立变量，并直接研究如何通过局部键环境控制迁移率和带隙。对这些原子结构/电子性质关系的基本认识可用于指导能量转换和氧化物电子学应用的材料设计。参与的研究生和本科生将接受先进材料合成和表征技术的实践培训，包括分子束外延和基于同步加速器的散射。

NON-TECHNICAL DESCRIPTION: The ability to design and control the atomic structure of materials in order to achieve a desired macroscopic property is a grand challenge of materials research. The complex oxides are an ideal family of compounds for addressing this challenge due to their ubiquity, societal importance, and strong dependence of structure on properties. For instance, properties including magnetism, ferroelectricity, catalytic behavior, and electronic conductivity are known to couple directly to atomic structure in oxides. This project aims to stabilize complex oxide thin films in non-equilibrium atomic structures in order to control electronic properties relevant to applications ranging from solar energy conversion to optoelectronics. Outreach and educational activities, with particular emphasis on the importance of structure/property relationships in materials, are incorporated in the project.TECHNICAL DETAILS: The goal of the project is to control electronic properties such as the band gap and carrier mobilities in semiconducting perovskite films by enforcing non-equilibrium atomic structures. While a dominant theme in oxide research has been to develop an understanding of interfacial charge transfer, the use of interfaces to finely tune local structure and bonding environments has yet to be fully explored as a means to control physical properties. In ABO3 perovskites, the distortions and rotations of the corner-connected BO6 octahedra, which determine the B-O bond lengths and B-O-B angles, are known to couple directly to electronic structure. While approaches to control octahedral behavior in bulk perovskites are limited to compositional changes, oxide heterostructures offer new routes to engineering octahedral behavior independent of composition. In this project, local atomic structure in isocompositional perovskite films is systematically varied via strain or substrate-film coupling. Structural and electronic properties are probed using a combination of synchrotron diffraction, spectroscopy, and electronic transport measurements. By directly comparing octahedral behavior and electronic properties, the project isolates structure as a single independent variable and provides a direct study of how mobility and band gap can be controlled by the local bond environment. The fundamental insights gained into these atomic structure/electronic properties relationships can be used to guide materials design for applications in energy conversion and oxide electronics. The participating graduate and undergraduate students receive hands-on training with advanced materials synthesis and characterization techniques, including molecular beam epitaxy and synchrotron-based scattering.