UNDERSTANDING THE MECHANISM OF CVD DIAMOND

Recent work at GE on the chemical vapor deposition diamond process is discussed. An experimental apparatus is described which allows in situ kinetic studies of the hot filament growth of diamond. This apparatus was used to demonstrate that diamond could be formed on a graphite substrate simultaneously while etching occurred. Substitution of deuterium for hydrogen decreased the deposition rate, suggesting that a C-H bond was involved in the rate-limiting step. The difficulty when using carbon filaments is discussed in terms of equilibrium analysis. Hydrogen, and especially atomic hydrogen, is critical for this process and performs several critical functions, including stabilization of the diamond surface, creation of a volatile source of carbon, formation of vacancies on the growth surface, reduction of the surface free energy, formation of carbon radicals and possibly the etching of graphite material.