Ethynyl (C2H): A major player in the chemical vapor deposition of diamond

Abstract

In situ mass spectrometry of the near-surface composition—with special emphasis on radicals—has been carried out during diamond deposition from a microwave plasma in a CH4∕H2 mixture at 25 and 100mbars. The most abundant species in the former case are C2H2 and CH3, together giving 65% of the hydrocarbon content. At 100mbars, this value drops to 15%, while the C2H content rises to 76%. The factor of ∼8 increase in the C2H ratio is accompanied by a similar increase in the growth rate, indicating a major role of C2H in diamond growth.