In situ characterisation of CVD diamond growth under H2S addition by optical emission spectroscopy, mass spectroscopy and laser reflection interferometry

The diamond growth process under the addition of H2S as a precursor for sulfur doping was studied in situ by optical emission spectroscopy (OES) and mass spectroscopy (MS). The changes in gas composition observed were correlated with the growth rate, which was simultaneously measured by laser reflection interferometry (LRI). While MS allows monitoring of the sulfur addition by means of the signal from the original H2S molecule or several reaction products, such as CS, OES only yields a significant signal attributed to S-2 molecules. At high substrate temperatures, H,S in the gas phase causes a reduction in the diamond growth rate. A proportional decrease in the concentration of the relevant hydrocarbon growth species was measured. At the same time, the morphology of the diamond films was only weakly influenced by sulfur, Both observations suggest that the influence of sulfur on diamond growth is restricted to modifications of the gas-phase chemistry. At lower substrate temperatures, the behaviour is changed. with the growth rate slightly increased by H,S addition. (C) 2002 Elsevier Science B.V. All rights reserved.