Diamond synthesis on silicon nitride by the hot filament chemical vapor deposition technique

Diamond films have been deposited by hot filament chemical vapor deposition on hot-pressed silicon nitride substrates using a mixture of hydrogen and methane with a CH4/H2 volume ratio fixed to 0.5%. Scratching with diamond paste of the as-received substrates was necessary to obtain high nucleation densities (10(8)-10(9) cm(-2)) in the 750-1000 degrees C deposition temperature range, while, on scratched substrates, the nucleation density decreased at 1050 degrees C, The diamond deposition rate has its maximum at around 850-900 degrees C. The film texture was {111} [100] at the low deposition temperatures, while became {111} {100} [110] at temperatures higher than 750 degrees C. A careful analysis of the Raman spectra allowed us to identify the best deposition conditions for the growth of high quality diamond. Silicon nitride as a substrate for diamond CVD is better than cemented tungsten carbide due to the lower level of residual stress and to the higher phase purity of the coating.