INFLUENCE OF OXYGEN ON THE DEPOSITION OF DIAMOND COATINGS BY MICROWAVE PLASMA CVD

The effect of oxygen addition in the plasma composition and diamond st ructure has been investigated during diamond film growth by microwave- assisted chemical vapour deposition (MWCVD) from CH4+H-2 gas mixtures. Optical emission spectroscopy (OES) and mass spectrometry have been u sed for detection of chemical species present in the plasma. The resul ts for the gas mixtures with and without O-2 show noticeable changes i n the plasma composition, as detected by the presence of oxygenated sp ecies (mainly CO and OH), produced by the oxygen addition to the disch arge. We have related the diamond content in the films with the CO mol e fraction present in the discharge. The etching of the non-diamond co mpounds seems to be due to OH radicals as well as to atomic oxygen pre sent in the discharge which are able to etch carbon at higher rates.