Visualizing nanoscale phenomena in layered chalcogenides with heavy elements

可视化重元素层状硫属化物中的纳米级现象

• 批准号: 1506618
• 负责人: Weida Wu
• 金额: $ 50.71万
• 依托单位: Rutgers University New Brunswick
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-06-15 至 2019-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1506618&HistoricalAwards=false
• 关键词: Visualizing; nanoscale; phenomena; layered; chalcogenides

Nontechnical Abstract Tremendous progress has been made on discovering various new materials with enhanced functionalities. The technological applications of functional materials, however, demand extreme control of composition and imperfections of functional materials. The control of defects, especially point defects is crucial for the performance of semiconductor devices, which are building blocks of all modern electronics such as computers, cell phones, etc. Yet it is notoriously difficult to directly probe and exam individual point defects in functional materials. Scanning tunneling microscope (STM) is one of the few tools that allow scientists to directly probe atomic scale phenomena, including point defects and responses of local electronic properties. This project investigates the impacts of point defects, either intentionally or unintentionally introduced to bulk materials during synthesis, on novel electronic materials called layered chalcogenides. Using STM to visualize interesting electronic phenomena at nanometer scale, the principle investigator aims to obtain fundamental understandings of the driving mechanisms and the control of point defects in these functional materials. Education and training of graduate and undergraduate students is seamlessly integrated to the research activities, which enable them to learn fundamental material science, to master advanced microscopic techniques, and more importantly, to learn independent thinking. This project also integrates education and training of under-representative undergraduate students through various programs such as Aresty Research Center research program and Research Experiences for Undergraduates program at Rutgers, and of high school students through the Partner in Science program of Liberty Science Center. Technical AbstractLayered chalcogenides have been the active playground for various correlated phenomena in condensed matter physics, ranging from charge density wave and superconductivity. Incorporating heavy elements in layered chalcogenides introduces additional twists of strong spin-orbital coupling or dimerization, leading to emergent phenomena such as topological insulators and dimerization induced stripe modulations. This project addresses the impact of point defects (either intrinsic or extrinsic) on these fascinating phenomena to gain fundamental understanding of their driving mechanisms. Topological insulators are new quantum states of matter where insulating bulk states are surrounded by conducting surface states because of nontrivial topology of electronic wave functions. Native defects in topological insulators are known to induce substantial bulk conduction, which is detrimental for the observation and technological applications of exotic phenomena related to topological surface states. The influence of chemical inhomogeneity is crucial for fundamental understanding of "topological phase transitions" induced by chemical doping. The goal of this project is to identify and to control native and/or extrinsic point defects in layered chalcogenide topological insulators such as Bi2Se3 and Sb2Te3. In addition, this project aims to achieve a comprehensive understanding of the mechanism of emergent multiple stripe modulations in the heavy di-chalcogenide IrTe2 which is closely related to devil's staircase phenomena due to competing interactions. Atomic-scale defects, electronic modulations and nanoscale inhomogeneity in these materials are visualized and examined using state-of-the-art scanning tunneling microscopy and spectroscopy. These research efforts are complimented by bulk probes, first-principle calculations and theoretical modeling via domestic and international collaborations.

非技术性摘要在发现具有增强功能的各种新材料方面已经取得了巨大的进展。 然而，功能材料的技术应用要求对功能材料的组成和缺陷进行极端控制。 缺陷，特别是点缺陷的控制对于半导体器件的性能至关重要，半导体器件是所有现代电子产品（如计算机，手机等）的构建模块，但众所周知，直接探测和检查功能材料中的单个点缺陷非常困难。扫描隧道显微镜（STM）是为数不多的允许科学家直接探测原子尺度现象的工具之一，包括点缺陷和局部电子特性的响应。 本项目研究点缺陷的影响，无论是有意或无意地引入到体材料在合成过程中，对新型电子材料称为层状硫属化物。利用STM在纳米尺度上可视化有趣的电子现象，主要研究者旨在获得对这些功能材料中的驱动机制和点缺陷控制的基本理解。研究生和本科生的教育和培训与研究活动无缝集成，使他们能够学习基础材料科学，掌握先进的微观技术，更重要的是，学习独立思考。该项目还通过罗格斯大学的Aresty研究中心研究项目和本科生研究经验项目等各种项目整合了代表性不足的本科生的教育和培训，并通过自由科学中心的科学合作伙伴项目整合了高中生的教育和培训。层状硫族化合物是凝聚态物理中各种相关现象的活跃场所，从电荷密度波到超导电性。在层状硫族化物中重元素的重化引入了强自旋轨道耦合或二聚化的额外扭曲，导致涌现的现象，如拓扑绝缘体和二聚化诱导的条纹调制。该项目解决了点缺陷（内在或外在）对这些迷人现象的影响，以获得对其驱动机制的基本了解。拓扑绝缘体是一种新的物质量子态，由于电子波函数的非平凡拓扑结构，绝缘体态被导电表面态包围。拓扑绝缘体中的本征缺陷会引起大量的体导电，这对于与拓扑表面态相关的奇异现象的观察和技术应用是不利的。化学不均匀性的影响是至关重要的基本理解的“拓扑相变”诱导的化学掺杂。 本项目的目标是识别和控制本机和/或外来的点缺陷分层硫属拓扑绝缘体，如Bi 2Se 3和Sb 2 Te 3。此外，本项目旨在实现一个全面的理解的机制，紧急多重条纹调制重二硫族化合物IrTe 2，这是密切相关的魔鬼的楼梯现象，由于竞争的相互作用。 原子尺度的缺陷，电子调制和纳米级的不均匀性，这些材料的可视化和检查使用国家的最先进的扫描隧道显微镜和光谱。这些研究工作通过国内和国际合作得到了大量探针，第一原理计算和理论建模的补充。