Growth of Tensile Germanium Nanowires Embedded in a III-V Matrix

嵌入 III-V 族基体中的拉伸锗纳米线的生长

• 批准号: 1506371
• 负责人: Minjoo Lee
• 金额: $ 39万
• 依托单位: Yale University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-06-01 至 2017-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1506371&HistoricalAwards=false
• 关键词: Growth; Tensile; Germanium; Nanowires; Embedded

Non-technical Description:Many of the properties of electronic and photonic materials are determined by the length of and the angle between their chemical bonds. Stress and strain can slightly alter these bonds, but cause profound changes in the way that materials interact with both light and electrical charge. Germanium is particularly noteworthy in this regard. A 2% change in bond length enables it to emit light very efficiently while in its normal state, germanium is a poor light emitter. This project seeks to engineer the properties of germanium nanostructures by embedding them into a matrix that induces stress. Nanocomposites formed from Ge nanostructures embedded in a foreign host enable new optical and electrical properties. The research project is integrated with the education and outreach activities. Besides interdisciplinary research training provided at the graduate and undergraduate levels, the PI schedules regular meetings with junior faculty in engineering to discuss how K-12 outreach can improve work-life balance, a growing concern among academic scientists. Through these outreach activities, he uses his personal experience to encourage junior faculty members in developing innovative outreach activities. Another activity involves pre-college outreach to talented seniors at Wilbur Cross High School, a racially and economically diverse public high school in New Haven.Technical Description:This project aims to demonstrate novel nanocomposite materials consisting of tensile-strained Ge nanowires embedded in III-V matrices. Recent research has shown that the properties of Ge nanomembranes, nanowires, microdisks, and microbridges can be tuned using external stressors to apply large biaxial or uniaxial tensile strains. In this project, surface-mediated phase separation during molecular beam epitaxy growth is investigated as a new approach to grow epitaxial Ge nanostructures embedded in a III-V matrix with high tensile strain. Specifically, Task 1 seeks to draw connections between growth conditions, structure, and properties of Ge/III-V nanocomposites, including basic understanding of interfacial strain coupling; Task 2 focuses on the coupled effects of matrix composition and lattice constant on the kinetics of Ge phase separation and the resulting microstructures. Finally task 3 seeks to understand the changes in structure and properties when the nanowires are modulated into nanorods or quantum dots. The ability to design and grow Ge/III-V nanocomposites with previously unattainable strain states may lead to a range of unprecedented material properties for Ge, such as the indirect-gap to direct-gap conversion or even becoming a semi-metallic material. Moreover, the fundamental understanding of epitaxial nanocomposites could apply to a wide range of other material systems such as complex oxides, dilute magnetic semiconductors, and highly mismatched alloys.

非技术描述：电子和光子材料的许多特性是由它们的化学键的长度和角度决定的。应力和应变可以轻微改变这些键，但会导致材料与光和电荷相互作用的方式发生深刻变化。锗在这方面尤其值得注意。键长的2%变化使其能够非常有效地发光，而在正常状态下，锗是一种较差的发光体。该项目旨在通过将锗纳米结构嵌入诱导应力的基质中来设计锗纳米结构的特性。由嵌入在外来宿主中的Ge纳米结构形成的纳米复合材料使新的光学和电学特性成为可能。该研究项目与教育和外联活动相结合。除了在研究生和本科阶段提供跨学科研究培训外，PI还定期与工程专业的初级教师举行会议，讨论K-12外展如何改善工作与生活的平衡，这是学术科学家日益关注的问题。通过这些外展活动，他用他的个人经验，鼓励年轻的教师在开发创新的外展活动。另一项活动是在Wilbur Cross High School（一所位于纽黑文的种族和经济多元化的公立高中）为有才华的高年级学生提供大学预科外展服务。技术描述：该项目旨在展示由嵌入III-V族基质中的拉伸应变Ge纳米线组成的新型纳米复合材料。最近的研究表明，Ge纳米膜，纳米线，微盘和微桥的性能可以使用外部应力源来调节，以施加大的双轴或单轴拉伸应变。在这个项目中，表面介导的相分离在分子束外延生长的研究作为一种新的方法来生长外延锗纳米结构嵌入在III-V矩阵与高拉伸应变。具体而言，任务1旨在绘制Ge/III-V纳米复合材料的生长条件，结构和性能之间的联系，包括界面应变耦合的基本理解;任务2侧重于Ge相分离的动力学和由此产生的微观结构上的矩阵组合物和晶格常数的耦合效应。最后，任务3试图了解当纳米线被调制成纳米棒或量子点时结构和性质的变化。设计和生长具有先前无法达到的应变状态的Ge/III-V纳米复合材料的能力可能会导致Ge的一系列前所未有的材料特性，例如间接带隙到直接带隙的转换，甚至成为半金属材料。此外，对外延纳米复合材料的基本理解可以应用于广泛的其他材料系统，如复合氧化物，稀磁半导体和高度失配的合金。