CHEMICAL KINETIC CALCULATIONS OF THE GAS-PHASE IN FILAMENT-ASSISTED CHEMICAL VAPOR-DEPOSITION OF DIAMOND

A chemical kinetic model was developed for the gas mixture in filament-assisted diamond chemical vapor deposition (CVD) systems. CH4/H-2 Mixture was studied as the starting gas mixture. The predictions of gas evolution calculated from this model were used to interpret certain published experimental observations. From the initial analysis, it was concluded that the thermodynamic state of the gas composition determined the effects of transport parameters on diamond growth. In many filament-assisted diamond CVD systems the gas composition was found to be kinetically controlled. The analysis also suggested that CH3 is a major precursor of diamond films. When CH4/H-2/O2 was used as the starting gas mixture, the results indicated that the oxygen additive catalyzed the process to increase the concentrations of CH3 and H, thereby increasing the growth rate and improving the quality of diamond films.