Thermodynamics analyses of the effect of CH3 and C2H2 on morphology of CVDdiamond films

CH3 and C2H2 are the dominant growth precursors during chemical vapor depos ition diamond process. The ratio of C2H2 to CH3 concentration will affect t he growth orientation of diamond film. In this paper the dependence of C2H2 and CH3 concentrations on substrate temperature is calculated under 4 kPa pressure according to a non-equilibrium thermodynamic coupling model report ed previously. The concentrations of C2H2 and CH3 increase when the substra te temperature rises. C2H2 concentration rises more highly. The dependence of the ratio of C2H2 to CH3 concentration ([C2H2]/[CH3]) on substrate tempe rature is also calculated. Diamond (111) and (100) facets growth is discuss ed with the ratio of C2H2 to CH3 concentration under various substrate temp eratures and CH4 concentrations. With the increase of substrate temperature or CH4 concentration, the value of [C2H2]/[CH3] will rise. So the growth r ate of diamond (111) facets controlled by C2H2 concentration is higher than that of diamond (100) facets controlled by CH3, and thus (100) facets appe ar. These results are well consistent with many experiments reported by oth er researchers. (C) 2000 Elsevier Science S.A. All rights reserved.