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

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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. ***