MODELING OF THE ROLE OF ATOMIC-HYDROGEN IN HEAT-TRANSFER DURING HOT FILAMENT ASSISTED DEPOSITION OF DIAMOND

The temperature and atomic hydrogen concentration profiles in a hot filament type diamond deposition reactor were determined experimentally and theoretically to demonstrate that the reaction of atomic hydrogen on the substrate surface plays an important role in the heating of the substrate. For a given filament temperature, the substrate temperature in helium was significantly lower than that in either pure hydrogen or 1% methane-hydrogen atmospheres. The presence of small amounts of methane in hydrogen did not have any significant effect in influencing the shape of the atomic hydrogen concentration profile. In the space between the filament and the substrate, the concentration field is established mainly due to the diffusive mixing of the atomic hydrogen with the molecular hydrogen and other species in the gas phase. Homogeneous chemical reactions in the gas phase do not significantly affect the atomic hydrogen concentration distribution in this region.