DIAGNOSTICS OF PLASMA EMISSION-SPECTRA DURING ELECTRON ASSISTED CHEMICAL-VAPOR-DEPOSITION OF DIAMOND FILMS

Diamond films were deposited by hot cathode direct current discharge p lasma chemical vapor deposition from a CH4-H-2 gas mixture. Optical em ission spectroscopy was employed to investigate in situ the plasma emi ssion characterization during diamond synthesis. The dependence of pla sma emission spectra on the input CH4/H-2 ratio and the substrate temp erature was investigated. A significant variation in the emission inte nsity of the CH radical was measured with a change in the CH4 concentr ation. C-2 was detected only at high CH4 concentration. In addition, t he relative emission intensity of the C-2 species was sensitive to a h igh substrate temperature. The correlation between the spectra of some species and the quality of diamond films was studied. These results s uggest that CH and CH+ are all important precursor species in the diam ond deposition reaction, while C-2 is associated with the presence of a nondiamond phase in the films. (C) 1998 American Institute of Physic s.