Gas-phase kinetics during diamond growth: CH4 as-growth species

We have used a one-dimensional kinetic analysis to model the gas-phase chemistry that occurred during the diamond growth experiments of Chauhan, Angus, and Gardner [J. Appl. Phys. 47, 4746 (1976)]. In those experiments the weight of diamond seed crystals heated by lamps in a CH4/H2 environment was monitored by a microbalance. No filament or electric discharge was present. Our analysis shows that diamond growth occurred in this system by direct reaction of CH4 on the diamond surface. C2H2 and CH3, which have been proposed as diamond growth species, played no significant role there, although our results do not address their possible contributions in other systems such as filament- or plasma-assisted diamond growth.