CAREER: Octahedral Control of Electronic Properties in Semiconducting Perovskite Heterostructures

职业：半导体钙钛矿异质结构中电子特性的八面体控制

• 批准号: 1151649
• 负责人: Steven May
• 金额: $ 50万
• 依托单位: Drexel University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-07-01 至 2017-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1151649&HistoricalAwards=false
• 关键词: CAREER; Octahedral; Control; Electronic; Properties

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.

非技术描述：设计和控制材料的原子结构以达到所需的宏观性能的能力是材料研究的一个重大挑战。复合氧化物是解决这一挑战的理想化合物家族，因为它们无处不在，具有重要的社会意义，而且结构对性质的依赖性很强。例如，已知磁性、铁电性、催化行为和电子导电性等性质直接与氧化物中的原子结构相耦合。该项目旨在稳定处于非平衡原子结构中的复合氧化物薄膜，以便控制与从太阳能转换到光电子学等应用相关的电子性质。技术细节：该项目的目标是通过实施非平衡原子结构来控制半导体钙钛矿薄膜中的电子性质，如带隙和载流子迁移率。尽管氧化物研究的一个主要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尚未得到充分探索。在ABO3型钙钛矿中，角连接的BO6八面体的扭曲和旋转决定了B-O键长和B-O-B角，它们直接与电子结构耦合。虽然控制块状钙钛矿中八面体行为的方法仅限于成分变化，但氧化物异质结构为设计与成分无关的八面体行为提供了新的途径。在本项目中，通过应变或衬底-薄膜耦合，系统地改变了等组分钙钛矿薄膜中的局域原子结构。使用同步加速器衍射、光谱和电子输运测量相结合的方法来探索结构和电子性质。通过直接比较八面体行为和电子性质，该项目将结构分离为单个自变量，并提供了如何通过局域键环境来控制迁移率和带隙的直接研究。对这些原子结构/电子性质关系的基本认识可以用来指导应用于能量转换和氧化物电子的材料设计。参与的研究生和本科生接受先进的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。