Atomic-Scale Structure and Surface Kinetics of Semiconductor Heteroepitaxy

本计画探讨以表面活性剂介导制程来成长第四族磊晶材料的几个关键问题。原位研究将集中在硅和锗单晶的（001）表面上的IV-VI族元素的吸附，以探索异质外延的普遍重要性问题。该方法是首先确定相关的单元素吸附物的平衡和亚稳表面相的结构。接下来，将研究假晶层上的吸附，以了解决定特定表面异质相结构的因素，如晶格应变、空间效应和相对化学键强度。表面活性剂的表面过程的动力学的修改，然后将被探索，并利用，以促进亚稳态外延合金结构的生长。异质外延薄膜的结构完整性和晶格应变将被检查作为一个敏感的监测器的研究生长技术的功效。本研究以x-射线驻波、表面x-射线绕射、表面延伸x-射线吸收精细结构光谱为特色，并着重于应变层异质磊晶的初始与第二阶段，以及磊晶成长的动力学。待检查的异质外延生长的具体方面是：（1）由单层（或更少）异质层的沉积产生的表面结构，（2）与生长相关的吸附物（例如，表面活性剂或掺杂剂），（3）在薄应变异质层的表面上发现的结构，和（4）表面活性剂物质的存在改变表面动力学。该项目涉及具有技术相关性的材料科学专题领域的基础研究问题。该项目的一个重要特点是通过在一个基础和技术重要领域培训学生，将研究和教育结合起来。 ***

This project explores several key issues related to growth of group IV epitaxial materials by surfactant mediated processes. In situ studies will center on adsorption of elements from groups IV-VI on the (001) surface of Si and Ge single crystals to explore issues of general importance for heteroepitaxy. The approach is to first determine the structure of equilibrium and metastable surface phases of relevant monoelemental adsorbates. Next, adsorption on pseudomorphic layers will be studied to gain an understanding of factors such as lattice strain, steric effects, and relative chemical bond strength that determine the structure of a particular surface heterophase. The modification of the kinetics of surface processes by surfactants will then be explored, and exploited to facilitate growth of metastable epitaxial alloy structures. The structural perfection and lattice strain of the heteroepitaxial thin films produced will be examined as a sensitive monitor of the efficacy of the investigated growth technique. The study features x-ray standing waves, surface x-ray diffraction, and surface extended x-ray absorption fine structure spectroscopy, and focuses on the initial and secondary phases of strained-layer heteroepitaxy, as well as the kinetics of epitaxial growth. Specific aspects of heteroepitaxial growth to be examined are: (1)surface structure resulting from the deposition of a monolayer (or less) of a heterolayer, (2)surface structure of growth-related adsorbates (e.g., surfactants or dopants) on the surface of the substrate, (3)structure found on the surface of a thin strained heterolayer, and (4)alteration of surface kinetics by the presence of a surfactant species.%%%The project addresses basic research issues in a topical area of materials science having technological relevance. An important feature of the project is the integration of research and education through the training of students in a fundamentally and technologically significant area. ***