ABSTRACT CTS-9312892 CAPPELLI This proposal represents one half of a collaborative research program between Mark Cappelli at Stanford and Iain Boyd at Cornell. The PIs plan to study flowing, low density, chemically reacting plasmas generated by an arc expansion into vacuum for use in material synthesis. The effort will include a combined experimental and numerical investigation. The experimental investigation, which is the subject of this proposal, which will take place at Stanford, will include optical techniques such as laser induced fluorescence to measure number densities, temperatures and plasma velocities. The goal is to develop a mechanistic understanding of boron nitride and silicon carbide syntheses under plasma conditions. The approach to be taken in the experimental study is the injection of carbon, silicon and boron containing reactants into a low-density, supersonic, reactive plasma flow, and the interaction of this flow with a temperature controlled surface to deposit hard ceramic thin films. Laser induced fluorescence and absorption spectroscopy will be used to study the gasdynamic flow and mixing behavior in the plasma. Species fluxes will be monitored by molecular beam mass spectroscopy. Deposited films will be characterized using x-ray photoelectron spectroscopy, scanning electron microscopy and infrared and Raman spectroscopy. The primary objective of the experimental study is to identify plasma flow conditions that favor the synthesis of c:BN or b-SiC over their hexagonal allotropes. Another objective is to provide experimental measurements of: plasma flow properties (e.g.. temperature, velocity), atomic hydrogen concentrations, methyl radical concentrations, and reactive species fluxes.
