CAREER: Point Defects in Two-dimensional Material Systems: Fundamentals and New Perspectives

非技术描述：众所周知，通过去除原子或添加外来原子将缺陷或瑕疵引入晶体材料中可以改变材料的特性，并且这种方法已经导致许多突破性的应用，例如发光二极管，晶体管和传感器。今天，人们已经很好地理解了如何操纵这些缺陷，以实现传统半导体（如硅）的理想特性。然而，研究人员刚刚开始了解如何利用缺陷来操纵一种全新的材料：原子级薄的二维（2D）半导体，它具有一系列不寻常的特性，预计在某些方面比传统半导体表现得更好。该CAREER奖的研究部分是探索在2D材料中引入缺陷的创新方法，并研究缺陷如何改变2D材料的特性。其中一种方法是用高能粒子撞击材料来去除原子。或者，具有不同电荷的外来原子可以锚定在它们的位置。研究团队使用最先进的技术来可视化这些缺陷如何形成，它们如何反应以及它们如何影响材料特性。该项目还通过开放日活动和高中生夏令营，以及研究生和本科生积极参与研究，向公众介绍纳米科学和2D材料概念。该项目的研究结果通过期刊出版物，会议演示和公开访问的2D材料数据库进行传播，该团队正在与非营利组织MaterialsProject.org合作开发技术描述：该研究项目旨在揭示点缺陷的物理特性，特别是新兴的2D半导体材料，如WS2，GeSe，GaSe和InTe。研究小组使用先进的高分辨率光谱和显微镜技术来研究硫族元素空位，反位缺陷和替代。在生长期间或在生长之后通过α粒子照射以期望的缺陷浓度引入缺陷，以实现期望的材料性质。纳米光致发光、超快光谱和电子能量损失光谱测量允许确定缺陷的能量状态和缺陷对激子复合物、光学吸收和发射特性以及2D材料的电子结构的影响。透射电子显微镜（TEM）的研究有助于确定结构特征，弛豫动力学和缺陷的扩散速度。总体目标是测量，分析和确定点缺陷在确定选择的2D半导体材料的光学和电子特性中的作用，并探索新的途径来控制材料的性能。

Nontechnical Description: It is known that introducing defects or imperfections into a crystalline material, either by removing atoms or adding foreign atoms, can change material's properties, and this approach has led to many ground breaking applications such as light emitting diodes, transistors and sensors. Today, there is a good understanding of how to manipulate these imperfections to achieve the desired properties of traditional semiconductors such as silicon. However, researchers are just starting to understand how to use defects to manipulate a whole new class of materials: two-dimensional (2D) semiconductors that are atomically thin, which have an unusual set of properties and are expected to perform far better than traditional semiconductors in some regards. The research component of this CAREER award is to explore innovative ways to introduce defects in 2D materials and to study how defects change the 2D material's properties. One way this can be done is to remove atoms by striking the material with energetic particles. Alternatively, foreign atoms with different electrical charges can be anchored in their place. The research team uses state-of-the-art techniques to visualize how these imperfections form, how they react and how they impact the material properties. This project also brings nanoscience and 2D material concepts to the public through open house events and summer camps for high-school students, as well as participation of graduate and undergraduate students in active research. Findings from this project are disseminated through journal publications, conference presentations, and a publicly-accessible 2D materials database, which the team is developing in collaboration with a non-profit organization, MaterialsProject.org.Technical Description: This research project aims to uncover the physics of point defects, in particular those in emerging 2D semiconducting materials such as WS2, GeSe, GaSe, and InTe. The research team uses advanced high-resolution spectroscopy and microscopy techniques to investigate chalcogen vacancies, anti-site defects, and substitutionals. Defects are introduced at desired defect concentrations during growth or after growth by alpha-particle irradiation to achieve desired material properties. Nano-photoluminescence, ultra-fast spectroscopy, and electron energy loss spectroscopy measurements allow determination of energy states of defects and effects of defects on the excitonic complexes, optical absorption and emission characteristics, as well as electronic structure of 2D materials. Transmission electron microscopy (TEM) studies help to determine structural characteristics, relaxation dynamics, and diffusion speed of defects. The overarching goal is to measure, analyze, and establish the roles of point defects in determining the optical and electronic properties of select 2D semiconducting materials and explore new routes to control material properties on demand.