Influence of nucleation density on film quality, growth rate and morphology of thick CVD diamond films

The optimum growth parameters of our 5 kW microwave plasma CVD reactor were obtained using CH4/H-2/O-2 plasma and high quality transparent films can be produced reproducibly. Among the films prepared in this system, the film of best quality has very smooth crystalline facets free of second nucleation and the full width at half maximum (FWHM) of the diamond Raman peak is 2.2 cm(-1), as narrow as that of IIa natural diamond. For this study, diamond films were grown on silicon substrates with low (10(4)-10(5) cm(-2)) and high nucleation densities ( >10(10) cm(-2)), respectively. From the same growth run, a highly <110> textured 300 mum thick white diamond film with a growth rate of 2.4 mum/h was obtained from high nucleation densities (>10(10) cm(-2)), and a white diamond film of 370 mum in thickness with a higher growth rate of 3 mum/h was obtained from low nucleation densities (5 x 10(4)-10(5) cm(-2)) too. The effect of nucleation density on film quality, growth rate, texture and morphology was studied and the mechanism was discussed. Our results suggest that under suitable growth conditions, nucleation density has little effect on film quality and low nucleation density results in higher growth rate than high nucleation density due to less intense grain growth competition. (C) 2003 Elsevier Science B.V. All rights reserved.