Efficiency of methane and acetylene in forming diamond by microwave plasma assisted chemical vapor deposition

Abstract

Diamond films were grown by microwave plasma assisted chemical vapor deposition using mixtures of 1% 13CH4 and 0.5% 12C2H2 in H2, and stable gaseous products were analyzed by mass spectrometry. The major gaseous products are methane and acetylene, and scrambling of the 13C label can be controlled at relatively high gas flow rates. At the highest flow rate studied a diamond film was grown with 77% 13C incorporation, while the methane in the reactor exhaust gas at this flow rate contained 83% 13C. By comparing gaseous 13C compositions with that of the films, the efficiency of diamond growth from methane (possibly via the methyl radical) is estimated to be about ten times higher than that for acetylene.