Scanning Probe Microscopy Studies of Polycrystalline and Nanocrystalline Semiconductors

该项目解决了多晶、半导体材料中的材料问题，强调了界面和晶界对薄膜性能的主要影响。项目目标是：开发一种新的、全面的多晶薄膜表征方法，该方法基于探索薄膜中单个微晶的化学、电子和光学性质，并应用该方法来了解和改进用于电子和光子学应用的多晶CdTe和GaAs，如显示器和高效太阳能电池。该方法利用扫描探针技术，包括低温NSOM、PL和AFM测量多晶膜的表面电位。这些信息将与扫描俄歇能谱、XPS、扫描隧道显微镜和输运测量等其他技术获得的信息相关联。之所以选择CdTe，是因为现有的方法可以制备具有良好少数载流子性质的薄膜，这使得它成为一个潜在的模型系统，可以用来寻找改进多晶材料的一般方法。高质量的砷化镓多晶薄膜一直是一个更大的问题。对砷化镓和相关III-V材料的研究将致力于表征改善少数载流子特性的新方法对电子和光学性能的影响。鉴于III-V材料存在广泛的技术基础，这一系统的成功将具有重要的技术影响。对表面和晶界存在时的NSOM激发进行了数值模拟。随着研究的进行，这些研究的信息将被反馈到薄膜生长过程中，以测试结果，并最终提高薄膜质量。%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。这些研究将提高对限制显示器和太阳能电池效率的因素的基本理解。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。一门新的微电子加工课程将为学生提供材料准备和加工方面的专业知识。CSM学生与威斯康星大学学生的合作将是一个额外的宝贵的学习机会。*

This project addresses materials issues in polycrystalline, semiconductor materials, with emphasis on the dominating influence which interfaces and grain boundaries have on film properties. Project goals are: to develop a new, comprehensive approach to polycrystalline film characterization based on exploring chemical, electronic, and optical properties of individual crystallites within a film, and to apply this approach to understanding and improving polycrystalline CdTe and GaAs for electronics and photonics applications such as displays and high efficiency solar cells. The approach utilizes scanning probe techniques including low temperature NSOM PL and AFM measurements of surface potential on polycrystalline films. This information will be correlated with that from other techniques such as scanning Auger spectroscopy, XPS, STM and transport measurements. CdTe has been chosen because existing approaches allow films with good minority carrier properties to be prepared making it a potential model system to study in terms of finding general methods for improving polycrystalline materials. High quality polycrystalline films of GaAs have been more problematic. Studies of GaAs and related III-V materials will be directed at characterizing the effects on electronic and optical performance of novel approaches for improving minority carrier properties. Success with this system would have important technological implications given the broad technological base which exists for III-V materials. Numerical modeling of NSOM excitation in the presence of surfaces and grain boundaries is included. As the study proceeds, information from these investigations will be fed back into the film growth processes to test results and, ultimately, to improve film quality.%%% The project addresses basic research issues in a topical area of materials science with high technological relevance. These studies will improve fundamental understanding of factors limiting the efficiency of displays and solar cells. 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. A new microelectronic processing course will provide students with expertise in materials preparation and processing. Collaboration of CSM students with students at the University of Wisconsin will be an additional, valuable, learning opportunity.***