PLASMA DIAMOND DEPOSITION FROM CH4-H2(-O2-AR) IN RELATION TO KINETIC CALCULATIONS

Kinetic calculations in H-2-CH4 have indicated the great influence of the concentration of H atoms on the plasma composition. From the qualitative effects of argon and O2 additions to the reactants, of the sample position in the discharge, of the gas temperature and of the microwave power, on the numbers of H atoms present in the discharge, the experimental results have been correlated with the previous kinetic calculations. These results support the idea that diamond deposition would be favoured by CH(x) (0 less-than-or-equal-to x less-than-or-equal-to 3) radicals (or any other single-C-atom carrier), whereas increasing concentrations of C2 species including pi-bond-containing carriers in the gas phase would correspond to graphitic carbon deposition on the substrate. Thus increasing CH(x) concentrations would enhance the diamond deposition rates, and the quality of the deposits would be strongly related to the relative importance of the CH(x)/H and C2Hy/H ratios.