Sub-Microsecond RHEED Investigation of Pulsed Laser Deposition Film Growth Dynamics

该项目解决了PLD（脉冲激光沉积）薄膜形成过程中的表面过程。该方法将亚微秒时间分辨反射高能电子衍射（RHEED）分析能力集成到PLD系统中。一个快速增强的CCD成像系统将用于捕获基材的全模式RHEED图像，以允许激光烧蚀羽流的分辨率（10到100 us）。该系统有望提供从目标喷射的烧蚀羽流到达之前、期间和之后的薄膜表面结构变化的详细图像，以及在激光脉冲之间的松弛时间内。研究将主要集中在使用（100）和（111）衬底的硅同外延上。为了研究多组分沉积的细节，硅-锗薄膜的生长也将通过亚微秒时间分辨RHEED进行研究，硅和锗的速度分布将通过光学飞行时间进行测量。观察到的瞬态RHEED模式和测量到的速度分布的相关性将用于深入了解薄膜的形成，包括高能物质的弛豫时间、成核行为和可能形成的短暂亚稳合金结构。该项目涉及材料科学主题领域的基础研究问题，具有潜在的技术相关性。从研究中获得的基本知识和理解有望通过为设计和生产改进的材料和材料组合提供基本的理解和基础，从而有助于提高微电子器件和电路的性能。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；该项目被HBCU的一个机构引用。＊＊＊

This project addresses surface processes during PLD(pulsed laser deposition)film formation. The approach incorporates a sub-microsecond time-resolved reflection high- energy electron diffraction (RHEED) analysis capability into a PLD system. A fast intensified CCD imaging system will be used to capture full- pattern RHEED images of the substrate to permit resolution of the laser ablation plume(10 to 100 us). The system is expected to provide a detailed picture of the changing surface structure of the film before, during and immediately after the arrival of the ablation plume ejected from the target, as well as during the relaxation time between laser pulses. The investigation will concentrate primarily on silicon homoepitaxy using (100) and (111) substrates. In order to examine details of multiple component depositions, silicon-germanium film growth will also be studied by sub-microsecond time-resolved RHEED, and the velocity distributions of both silicon and germanium will be measured by optical time-of-flight. The correlation of observed transient RHEED patterns and measured velocity distributions will be used to gain insight into film formation including the relaxation time of energetic species, nucleation behavior and the possible formation of short-lived metastable alloy structures.%%%The project addresses basic research issues in a topical area of materials science having potential technological relevance. The basic knowledge and understanding gained from the research is expected to contribute to improving the perform-ance of microelectronic devices and circuits by providing a fundamental understanding and a basis for designing and producing improved materials, and materials combinations. 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; the project is cited at an HBCU institution. ***