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，在晶体材料中引入缺陷或不完美，可以改变材料的性质，这种方法已经导致了许多突破性的应用，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利用这些缺陷来实现传统半导体（如硅）所需的特性。然而，研究人员刚刚开始了解如何利用缺陷来操纵一类全新的材料：具有原子厚度的二维（2D）半导体，它具有一系列不同寻常的特性，预计在某些方面比传统半导体性能要好得多。该职业奖的研究部分是探索在二维材料中引入缺陷的创新方法，并研究缺陷如何改变二维材料的特性。一种方法是用高能粒子撞击材料来去除原子。或者，带不同电荷的外来原子可以固定在它们的位置上。研究小组使用最先进的技术来可视化这些缺陷是如何形成的，它们是如何反应的，以及它们是如何影响材料性能的。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，将纳米科学和二维材料概念带给公众。该项目的研究成果通过期刊出版物、会议报告和一个可公开访问的二维材料数据库进行传播，该数据库是该团队与非营利组织materialsproject.org合作开发的。技术描述：该研究项目旨在揭示点缺陷的物理特性，特别是那些新兴的二维半导体材料，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化物空位、反位缺陷和取代。在生长过程中或生长后，通过α粒子辐照在所需的缺陷浓度下引入缺陷，以达到所需的材料性能。纳米光致发光、超快速光谱和电子能量损失光谱测量可以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二维材料的电子结构的影响。透射电子显微镜（TEM）研究有助于确定缺陷的结构特征、弛豫动力学和扩散速度。总体目标是测量、分析和确定点缺陷在确定选定的二维半导体材料的光学和电子特性中的作用，并探索按需控制材料特性的新途径。

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.