Scanning Probe Microscopy Studies of Polycrystalline and Nanocrystalline Semiconductors

本项目研究多晶、半导体材料中的材料问题，重点研究界面和晶界对薄膜性能的主要影响。该项目的目标是：开发一种新的、综合的方法来表征多晶薄膜，该方法基于探索薄膜内单个晶体的化学、电子和光学特性，并应用该方法来理解和改进多晶CdTe和GaAs，用于电子和光子学应用，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对多晶薄膜表面电位的测量。这些信息将与其他技术，如扫描俄歇光谱、XPS、STM和输运测量相关联。之所以选择碲化镉，是因为现有的方法允许制备具有良好少数载流子特性的薄膜，这使得它成为一个潜在的模型系统，可以用来研究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个问题。对砷化镓和相关III-V材料的研究将针对改善少数载流子特性的新方法对电子和光学性能的影响进行表征。鉴于III-V材料的广泛技术基础，这一系统的成功将具有重要的技术影响。包括了在表面和晶界存在下的NSOM激励的数值模拟。随着研究的进行，这些调查的信息将反馈到薄膜生长过程中，以测试结果，并最终提高薄膜质量。该项目涉及材料科学中具有高技术相关性的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培养学生在一个基础和技术上重要的领域的研究和教育的整合。该项目旨在通过独特的教育经历，通过前沿的研究环境，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巧。一门新的微电子加工课程将为学生提供材料制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、有价值的学习机会

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.***