Epitaxial Growth and Doping of Topological Insulator Heterostructures

拓扑绝缘体异质结构的外延生长和掺杂

• 批准号: 1105839
• 负责人: Lian Li
• 金额: $ 49.98万
• 依托单位: University of Wisconsin-Milwaukee
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-07-01 至 2015-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1105839&HistoricalAwards=false
• 关键词: Epitaxial; Growth; Doping; Topological; Insulator

Technical: This project aims to advance the understanding of the epitaxial growth and doping of the Bi2X3 (X=Se, Te) topological insulators and their modulation-doped superlattices. The critical issue is to control impurity incorporation vs. intercalation during growth, with the goal to selectively designate the sites for desired properties. In-situ scanning tunneling microscopy/spectroscopy is carried out to study the surface morphology, atomic structure, and carrier scattering by steps and magnetic impurities, and to determine how the defining properties of topological insulators are affected by magnetic impurity doping, gap opening, and warping of the Dirac cone. Scanning tunneling microscopy is also used to investigate the transport properties of topological insulator films and heterostructures in situ. Element-specific electronic and magnetic properties of dopants are determined by x-ray absorption spectroscopy and magnetic circular dichroism, while structural characterization is carried out using x-ray diffraction, Raman spectroscopy, and transmission electron microscopy, and magnetic and transport properties by temperature- and field-dependent magnetization measurements and Hall effects. The experimental efforts are complemented by density functional theory calculations of the energetics of impurity adsorption and doping, the changes in the electronic band structure, the x-ray absorption spectroscopy and magnetic circular dichroism spectra, and scanning tunneling microscopy images, which helps to identify the most promising heterostructures to be synthesized and their experimental signatures.Nontechnical: The project addresses basic research issues in a topical area of materials science with high technological relevance. With precise control of composition and doping, molecular beam epitaxy facilitates the synthesis of topological insulator heterostructures congruent with existing semiconductor device fabrication infrastructure, which can potentially bring a new paradigm for the next generation electronics. Graduate students are trained in an interdisciplinary environment for materials growth, characterization, and modeling. The PIs' active involvement in an on-going Research Experience for Teachers outreach program continues to bring cutting-edge research on materials sciences to high school students to impact their perception of science and technology, and to inspire them to seek college degrees and careers in science and engineering.

技术：该项目旨在增进对 Bi2X3 (X=Se, Te) 拓扑绝缘体及其调制掺杂超晶格的外延生长和掺杂的理解。关键问题是控制生长过程中的杂质掺入与嵌入，目标是选择性地指定具有所需特性的位点。原位扫描隧道显微镜/光谱学用于研究表面形貌、原子结构以及阶梯和磁性杂质的载流子散射，并确定拓扑绝缘体的定义特性如何受到磁性杂质掺杂、间隙开口和磁性杂质的影响。狄拉克锥的扭曲。扫描隧道显微镜还用于原位研究拓扑绝缘体薄膜和异质结构的输运特性。掺杂剂的元素特定电子和磁性特性通过 X 射线吸收光谱和磁圆二色性确定，而结构表征则使用 X 射线衍射、拉曼光谱和透射电子显微镜进行，磁性和输运特性则通过温度-以及场相关磁化测量和霍尔效应。实验工作辅以杂质吸附和掺杂能量学的密度泛函理论计算、电子能带结构的变化、X射线吸收光谱和磁圆二色性光谱以及扫描隧道显微镜图像，这有助于识别最有希望合成的异质结构及其实验特征。非技术：该项目解决了具有高技术相关性的材料科学主题领域的基础研究问题。通过精确控制成分和掺杂，分子束外延有助于合成与现有半导体器件制造基础设施一致的拓扑绝缘体异质结构，这有可能为下一代电子产品带来新的范例。研究生在跨学科环境中接受材料生长、表征和建模的培训。 PI 积极参与正在进行的教师研究体验外展计划，继续为高中生带来材料科学的前沿研究，影响他们对科学和技术的看法，并激励他们寻求大学学位和职业生涯科学和工程。