Diffraction Studies of Epitaxy

本文研究了砷化镓衬底表面结构对化合物半导体和金属薄膜分子束外延生长的影响。该研究利用反射高能电子衍射和透射电子显微镜对其结构进行表征。将测定晶体取向错误对生长稳定性和原子扩散的影响。研究结果将使化合物半导体外延生长模型的制定成为可能。根据先前的拨款（DMR-8319821）。科恩教授在这一领域取得了重大进展：(1)提高了对这些材料中反射高能电子衍射过程的理解，例如，确定干涉对衍射振荡角依赖性的影响；(2)测量砷化镓的表面扩散；（iii）确定在单个原子层水平上控制砷化镓蒸发和生长的方法，（iv）测量在应变相关缺陷发生之前砷化镓薄膜可以生长的厚度。这些和其他的进展在七份以上的科学出版物中都有描述。科恩教授被公认为该领域的主要科学家之一。设施和制度环境非常适合学生的研究和培训。他在之前的NSF资助下的研究被他的同行归类为该领域的开创性工作。该项目包括本科生研究经验补充，供两名本科生获得研究实践经验。我们希望这一经历将成为吸引高天赋学生从事研究和教学事业的激励因素，并为该计划的总体目标做出贡献。

This is a study of the effects of the structure of the surface of gallium arsenide substrates upon the molecular beam epitaxial growth of compound semiconductors and thin films of metals. The study utilizes reflection high-energy electron diffraction and transmission electron microscopy to characterize the structures. The effects of misorientation of the crystals on the stability of growth and the diffusion of atoms will be determined. The results of the research will enable the formulation of a model for the epitaxial growth of compound semiconductors. Under the previous grant (DMR-8319821). Professor Cohen made significant advances in the field: (i.) improved understanding of reflection high-energy electron diffraction processes in these materials, e.g., determination of the effects of interference on angular dependence of diffraction oscillations, (ii.) measurement of surface diffusion on gallium arsenide, (iii.) determination of means to control the evaporation and growth of gallium arsenide on the level of individual atomic layers, (iv.) measurement of the thickness that indium gallium arsenide thin films can be grown before the onset of strain-related defects. These and other advances are described in more than seven scientific publications. Professor Cohen is acknowledged as one of the leading scientists in the field. The facilities and the institutional environment are excellent for the performance of the research and training of students. His research under the previous NSF grant has been classified by his peers as the pioneering work in the field. The program includes a Research Experience for Undergraduates Supplement for two undergraduate students to get hands-on experience in research. It is hoped that this experience will serve as a stimulus to attract highly-gifted students into research and teaching careers as well as to contribute to the overall goals of this program.