Nanoscale Structure of Semiconductor Surfaces, Alloys, and Heterostructures

该项目研究半导体表面和界面的纳米级几何和电子结构。特别关注半导体合金的形成和性质，包括三元材料，如InxGa1-xN和四元材料，如InxGa1-xAs yP1-y。将研究在生长过程中合金成分的并入，以及原子有序、短程聚集和长程合金成分波动(横向成分调制)现象。此外，还将考察离子注入和退火等外部扰动对成分变化的影响。包含晶格常数变化的材料层的异质结构将被用来对材料施加应变。观察这种应变对合金成分和表面形态的影响。这项研究的目的是阐明导致观察到的结构或成分变化的潜在微观机制，目的是设计改进的生长和/或加工技术，通过这些技术可以控制这些机制。用于这些研究的主要技术是扫描隧道显微镜(STM)，它提供关于表面原子排列的纳米级信息。隧道显微镜的光谱研究将用于探测表面的电子态。研究将以平面图模式进行，原位探测薄膜的生长表面，以及横截面模式，其中异质结构被原位解理。该项目解决了材料科学中具有很高潜在技术相关性的主题领域的基础研究问题。这项研究将在基础水平上贡献基本材料科学知识，以促进对电子/光子设备的新理解和能力。在这些调查中要解决各种基本问题。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。***

This project addresses nanoscale geometric and electronic structure of semiconductor surfaces and interfaces. Particular focus is placed on the formation and properties of semiconductor alloys, including both ternary, e.g. In x Ga 1-x N, and quaternary, e.g. In x Ga 1-x As y P 1-y , materials. Incorporation of alloy constituents during growth will be studied, together with the phenomena of atomic ordering, short-range clustering, and long-range alloy compositional fluctuations (lateral composition modulation). The effect of external perturbations such as ion implantation and annealing on the compositional variations will also be examined. Heterostructures, containing layers of material with varying lattice constant, will be used to impose strain on the material. The effect of this strain on the resultant alloy composition and surface morphology will be observed. The intent of the research is to elucidate the underlying microscopic mechanisms responsible for the observed structural or compositional variations, with the aim of designing improved growth and/or processing techniques by which these mechanisms can be controlled. The major technique to be used for these studies is scanning tunneling microscopy (STM), which provides nanoscale information on the atomic arrangement on a surface. Spectroscopic studies with the tunneling microscope will be used to probe electronic states at the surface. Studies will be performed both in a plan-view mode, probing in situ the growth surface of films, as well as in cross-sectional mode in which a heterostructure is cleaved in situ. %%%The project addresses basic research issues in a topical area of materials science having high potential technological relevance. The research will contribute basic materials science knowledge at a fundamental level to new understanding and capabilities in electronic/photonic devices. A variety of fundamental issues are to be addressed in these investigations. 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. ***