Non diamond carbon phases in plasma assisted deposition of crystalline diamond film: a Raman study

The micro-Raman technique has proved helpful in the analysis of diamond samples grown on silicon substrates by PA-CVD. With different deposition conditions and substrate preparation, isolated grains or continuous films both containing non-diamond carbon phases as major impurities were obtained. These can be distinguished spectroscopically from pure diamond structures as they show broad features peaked at different frequencies with respect to the diamond Raman line. Non-diamond carbon phases were investigated as a function of deposition parameters and silicon substrate pre-treatment. By deconvolution of the Raman spectra the content of non-diamond carbon phases has been estimated to be 2% for isolated crystals grown on unscratched substrates and as much as 10% for continuous films (small crystallites with extended grain boundaries).