Diamond deposition and behavior of atomic carbon species in a low-pressureinductively coupled plasma

Diamond was successfully synthesized by using H-2-rich CH4/CO/H-2 and Hi-ri ch CH4/H-2 inductively coupled plasmas at a pressure of 11 Pa. The ratio of particle size to deposition time, as a criterion of the diamond growth rat e, in H-2-rich CH4/CO/H-2 mixture gas plasmas was higher than that in H-2-r ich CH4/H-2 mixture gas plasmas. The deposits in H-2-rich CH4/H-2 and H-2-r ich CH4/CO/H-2 mixture gas plasmas were found to contain nondiamond phases, as confirmed by Roman spectroscopy, in order to investigate the mechanism involved in diamond formation, C-atom densities in the plasmas were measure d by vacuum ultraviolet absorption spectroscopy with a carbon hollow cathod e lamp. In addition, CH, OH and H-atom emission intensities were measured b y optical emission spectroscopy. As a result, it was found that the C-atom densities increased considerably with increasing mixture ratio of CO to CH4 . On the basis of the correlation between the duality of deposits and the C -atom densities, C-atoms were determined to probably contribute to the form ation of nondiamond phases in the deposits.