The effect of the change in filament characteristics on diamond growth in hot filament chemical vapor deposition

Abstract

The changes in the filament characteristics with deposition conditions and the deposition of diamonds using a hot filament chemical vapor deposition have been studied in order to investigate the relationship between the change in filament characteristics and diamond growth. At low filament temperatures and/or high methane concentrations, the carburization of the filament and the deposition of graphite on the filament takes place, but only carburization of the filament occurs at high filament temperatures and/or low methane concentrations. Under the conditions for graphite deposition on the filament, ball-shaped diamond particles are obtained on the silicon substrate. It is suggested that the deposition of ball-shaped diamond particles is attributed to the etching process of graphite by atomic hydrogen at the filament resulting in severely reduced hydrogen atom concentrations reaching the deposition layer on the substrate. Consequently, it is considered that high quality diamonds can be only obtained under the conditions where no condensed phases are deposited on the filament (i.e., high filament temperature and/or low methane concentration) in hot filament chemical vapor deposition.