REACTION-KINETICS ON DIAMOND - MEASUREMENT OF H-ATOM DESTRUCTION RATES

There is presently a considerable effort to understand the chemistry of diamond film growth by chemical-vapor deposition. The first measurements of reaction kinetics between diamond and a gas-phase species-H atoms-involved in its formation are described. A remarkably simple method to measure H atom concentrations is developed and the method is used to measure gamma(d), the destruction probability of H atoms on diamond at 20 Torr and 1200 K. It is found that gamma(d)=0.12, with an estimated uncertainty of a factor of 2. This value is about half that estimated from gas-phase alkane rate constants and very close to that predicted by molecular-dynamics/Monte Carlo calculations. The agreement to within the estimated uncertainty supports the assumption that gas-phase alkane rate constants are essentially transferable to reactions between a diamond surface and gas-phase species. The H atom measurement technique could be useful for studying growth in other chemical-vapor-deposition systems in which hydrogen is in high concentration.