Hard amorphous hydrogenated carbon films deposited from an expanding thermal plasma

Diamondlike amorphous hydrogenated carbon is deposited from an expanding thermal argon/acetylene plasma. It is observed that the film quality improves with increasing deposition rate. To obtain the best material quality the admixed acetylene flow has to be of comparable magnitude as the argon ion flow from the plasma source (critical loading). A new method to determine the ion density in an argon/acetylene plasma, by probe measurements, is presented. They reveal that the deposition during critical loading is governed by radicals. It is suggested that acetylene is dissociated once and that the C2H radical is formed dominantly