Study of the influence of gas flow on PECVD diamond growth: influence of the separate injection of gases

This study is a follow-up to previously published modeling work examining a bell jar microwave plasma CVD reactor operating at high pressure (Mesbahi et al 2013 J. Phys. D: Appl. Phys . 46 385502). In this paper, we present the influence of gas injection mode on flow structure, on the production and coupled transport of diamond growth key species, and on the resulting diamond growth. Several gas injection configurations have been tested and experimental results in terms of growth rate and thickness uniformity will be compared with numerical simulations. In this study, we found that direct injection of methane closer to the discharge allowed one to significantly increase the diamond growth rate. These results will be discussed using a non-dimensional analysis of the transport phenomena (mass, energy and momentum by convection and diffusion) and production of the CH₃ radical in the reactor. (paper)