Collaborative Research: Revealing the Role of Structural Modulations on the Electronic Properties of Hexagonal Chalcogenide Perovskite Semiconductors

非技术描述：含硫、硒和碲的硫属化合物是功能半导体，在信息存储和处理以及能量转换方面有着广泛的应用。这些材料的一个子集具有六角形对称性，显示出强烈的光-物质相互作用，在传感和通信方面具有潜在的应用。本项目采用理论和实验相结合的方法建立公理，阐明这些材料中成分和结构的细微变化对电子性能的作用，并通过控制成分和结构来实现所需的光学各向异性等性能。研究生被训练使用理论和实验相结合的方法来解决材料科学和工程中的基本问题。教育活动的重点是培养研究生和本科生为实现先进能源和信息技术所需的劳动力。技术细节：该项目旨在揭示非化学计量学和结构调制对六方硫族钙钛矿电子结构的作用，并通过改变其组成和结构来控制其物理性质，包括光学各向异性和电子跃迁。采用气相输运单晶生长和脉冲激光沉积法制备硫系钙钛矿。x射线、中子和电子探针的组合用于在多个长度尺度上表征结构和成分。物理性质用光谱学和电输运研究表征。第一性原理电子结构计算用于确定实验观察到的性质的原子起源。教育方面包括训练研究生和本科生使用综合理论和实验方法来调查和设计材料。该项目支持原子尺度建模和功能材料原子-原子生长课程模块的开发，并在功能半导体和硫系钙钛矿的全国会议上组织专题讨论会。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

NON-TECHNICAL DESCRIPTION: Chalcogenides that contain sulfur, selenium, and tellurium are functional semiconductors with broad applications in information storage and processing, and in energy conversion. A subset of these materials with hexagonal symmetry demonstrate strong light-matter interactions with potential applications in sensing and communication. This project employs an integrated theoretical and experimental approach to establish axioms elucidating the role of subtle changes in composition and structure in these materials on electronic properties, and to achieve desired properties such as optical anisotropy by controlling composition and structure. Graduate students are being trained to use a mix of theory and experiments to address fundamental problems in materials science and engineering. Education activities focus on preparing graduate and undergraduate students for a workforce needed to realize advanced energy and information technologies. TECHNICAL DETAILS: The project seeks to unravel the role of non-stoichiometry and structural modulations on the electronic structure of hexagonal chalcogenides perovskites, and control their physical properties including optical anisotropy and electronic transitions, by changing their composition and structure. The research employs vapor-transport single crystal growth and pulsed laser deposition to grow chalcogenide perovskites. A combination of x-ray, neutron, and electron-based probes are used to characterize structure and composition at multiple length scales. Physical properties are characterized using optical spectroscopy and electrical transport studies. First-principles electronic structure calculations are used to establish atomic origins of the experimentally observed properties. Education aspects include training of graduate and undergraduate students to use an integrated theoretical and experimental approach to investigate and design materials. This project supports the development of course modules on atomic-scale modeling and atom-by-atom growth of functional materials, and the organization of symposia at national meetings on functional semiconductors and chalcogenide perovskites.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.