NIRT: Semiconductor Nanowires: Building Blocks for Nanoscale Electronics

这项提案是应“纳米科学与工程”(NSF 00-119)的征集而提交的。该项目致力于半导体纳米线合成和性能的纳米级效应。将开发一种基于模板的通用方法来合成金属/半导体/金属纳米线，利用纳米孔膜作为衬底，使用半导体气-液-固生长和金属电沉积来组装纳米线。这种方法提供了合成单晶半导体结构的能力，该结构夹在单个纳米线中的接触金属段之间，具有可控的直径和长度。在从膜上移除后，将使用场辅助组装方法将悬浮在溶液中的纳米线吸引并对准到衬底上预先图案化的接触垫上。电场被用来极化纳米线，并通过介电泳法诱导排列。现场组装将用于在大面积接触垫上对齐和定位大量纳米线，以进行电学表征。制造研究将集中在两种材料，硅和砷化镓，使研究纳米级效应的间接和直接带隙半导体。将产生尺寸从数百纳米到数十埃的结构，并对其进行表征，以研究长度尺度对纳米线物理性质的影响。在纳米孔膜中气-液-固生长方法的发展将包括对气相传输、反应动力学、成核和纳米柱状几何形状的晶体生长的研究。在单个纳米线中制造金属/半导体结将被用来设计这些结构中的纳米接触，并探测小维度结构中的相平衡、界面反应动力学、费米能级钉扎以及欧姆和肖特基接触特性。快速定位和测量大量单独纳米线的能力将被用来进行详细的电传输测量。对受限几何结构中的能带结构和载流子散射的理论研究将与实验工作相结合，以提供对实验结果的深入了解。一个在半导体晶体生长、金属/半导体接触、纳米线自组装和表征以及纳米结构电子性质理论方面具有专门知识的跨学科团队将开展这项研究。该团队包括来自材料科学与工程、电气工程和物理的教职员工。研究的交织结构和研究人员的密切联系将使研究生的共同建议和个人论文项目的发展成为可能，这些论文项目涵盖纳米级合成、组装、表征和理论方面的一系列主题。该项目还将包括与一名高中物理教师共同开发的教育模块的准备工作，这些模块旨在向普通受众介绍纳米技术的概念。这些模块将被团队成员用于他们目前的K-12教育和外展活动，以及针对科学和工程领域的少数族裔和女性招聘的额外校园计划。%该项目解决具有高度技术相关性的材料科学主题领域的基础研究问题。该计划的一个重要特点是通过在一个具有根本意义和技术意义的领域对学生进行培训，将研究和教育结合起来。该项目旨在通过由前沿研究环境提供的独特教育体验，培养学生强大的技术、沟通和组织/管理技能。本科生将积极参与该项目，并正式强调培养有效的口头和书面沟通技能。该项目由DMR/EM、CTS/CRP和CTS/FPH部门/方案共同支持。*

This proposal was submitted in response to the solicitation "Nanoscale Science and Engineering" (NSF 00-119). The project addresses nanoscale effects on synthesis and properties of semiconductor nanowires. A versatile, template-based approach to the synthesis of metal/semiconductor/metal nanowires will be developed, utilizing nanoporous membranes as substrates for nanowire assembly using semiconductor vapor-liquid-solid growth and metal electrodeposition. This approach provides the ability to synthesize single crystal semiconductor structures sandwiched between contact metal segments in a single nanowire with controlled diameters and lengths. After removal from the membrane, a field assisted assembly method will be used to attract and align the nanowires suspended in solution on to pre-patterned contact pads on a substrate. An electric field is used to polarize the nanowires and induce alignment via dielectrophoresis. Field assembly will be used to align and position large numbers of nanowires on large area contact pads for electrical characterization. Fabrication studies will focus on two materials, Si and GaAs, enabling a study of nanoscale effects in indirect and direct gap semiconductors. Structures with dimensions ranging from hundreds of nanometers to tens of angstroms will be produced and characterized to study the impact of length scale on the physical properties of nanowires. The development of vapor-liquid-solid growth methods in nanoporous membranes will encompass a study of vapor phase transport, reaction kinetics, nucleation and crystal growth in nanoscale cylindrical geometries. The fabrication of metal/semiconductor junctions within individual nanowires will be used to engineer nanocontacts in these structures and probe phase equilibria, interfacial reaction kinetics, Fermi level pinning and ohmic and Schottky contact characteristics in small dimensional structures. The ability to rapidly position and measure large numbers of individual nanowires will be used to carry out detailed measurements of electrical transport. Theoretical studies of band structure and carrier scattering in restricted geometries will be carried out in conjunction with the experimental work to provide insight into the experimental findings. An interdisciplinary team with specific expertise in semiconductor crystal growth, metal/semiconductor contacts, nanowire self-assembly and characterization and the theory of nanostructure electronic properties will carry out the research. The team includes faculty members from Materials Science and Engineering, Electrical Engineering and Physics. The interwoven structure of the research and the close physical proximity of the investigators will enable co-advising of graduate students and the development of individual thesis projects that encompass a range of topics in nanoscale synthesis, assembly, characterization and theory. The project will also include the preparation of educational modules, developed in conjunction with a high school physics instructor, that are designed to introduce concepts in nanotechnology to a general audience. The modules will be used by team members in their current K-12 education and outreach activities and in additional on-campus programs that target minority and female recruitment in science and engineering.%%% The project addresses basic research issues in a topical area of materials science with high technological relevance. An important feature of the program is the integration of research and education through the training of students in a fundamentally and technologically significant area. The project is designed to develop strong technical, communication, and organizational/management skills in students through unique educational experiences made possible by a forefront research environment. There will be active involvement of undergraduates in the program and formal emphasis on developing effective oral and written communication skills. The project is co-supported by the DMR/EM, CTS/CRP, and CTS/FPH Divisions/Programs.***