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

该项目涉及PLD(脉冲激光沉积)薄膜形成过程中的表面处理。该方法将亚微秒时间分辨反射高能电子衍射(RHEED)分析能力融入到PLD系统中。将使用快速增强的电荷耦合器件成像系统来捕捉衬底的全图案RHEED图像，以实现激光烧蚀羽流(10至100微秒)的分辨率。预计该系统将提供从目标喷射出的烧蚀羽流到达之前、期间和紧接之后以及在激光脉冲之间的松弛时间期间薄膜表面结构变化的详细图像。研究将主要集中在使用(100)和(111)衬底的硅同质外延上。为了考察多组分沉积的细节，还将用亚微秒时间分辨RHEED研究硅-锗薄膜的生长，并用光学飞行时间测量硅和锗的速度分布。观察到的瞬时RHEED模式和测量到的速度分布的相关性将被用来深入了解薄膜的形成，包括含能物种的松弛时间、形核行为和可能形成的短暂亚稳合金结构。%该项目解决了材料科学中具有潜在技术相关性的热门领域的基础研究问题。从研究中获得的基本知识和理解将有助于提高微电子器件和电路的性能，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。在这些调查中要解决各种基本问题。该方案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；该项目被HBCU的一所机构引用。***

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. ***