GAS PHASE KINETICS DURING DIAMOND GROWTH: CH4 AS GROWTH SPECIES

In t roduc t ion There has been considerable interest in the growth of diamond thin films in recent years','. This interest derives from the superlative properties of diamonds: they are very hard, have a high thermal conductivity, are chemically inert, and have an extremely wide optical transmission window. In addition, single crystal diamonds have the potential for being uniquely good semiconductors'. Unfortunately, at present we have little understanding of the chemical processes which are involvedin and which control diamond nucleation and growth. This is because there have been no experiments which have simultaneously characterized both the chemical environment and the kinetics of diamond growth. Recently C2Hz (acetylene)',', c2H4 (ethylene)', CH3 (methyl radical)', and H (atomic h y d r ~ g e n) ~ have been detected during filament-assisted diamond growth experiments. Harris e t al. ' used a simple zero-dimensional chemical kinetics model to show that only CH4 (methane), CzH,, C2H2, and/or CH3 could be contributing significantly to surface growth in those experiments. This result is consistent with semi-empirical quantum mechanical studies of the diamond growth mechanism which sugges