HYDROGEN-ATOM RECOMBINATION ON TUNGSTEN AND DIAMOND IN HOT-FILAMENT ASSISTED DEPOSITION OF DIAMOND

A hot-filament chemical vapor deposition reactor in which the substrate is a heated wire was used to analyze the energy transport to the substrate during diamond deposition. In this reactor, radiation and convection contribute negligibly to substrate heating. Atomic hydrogen recombination to molecular hydrogen on the substrate surface accounts for approximately 90% of the energy reaching the substrate. The atomic hydrogen recombination rate and the thermal accommodation coefficient for the energy released by atomic hydrogen recombination were estimated from in situ measurements for tungsten and diamond surfaces. The atomic hydrogen concentration gradient was estimated for simple geometries. The experimental conditions under which atomic hydrogen transport to the substrate is diffusion controlled were found. Addition of methane reduced the atomic hydrogen recombination rate on the substrate. An optimum pressure was found for the transport of atomic hydrogen to the substrate.