Modeling Species and Energy Transport in Moderate Pressure Diamond Deposition H ₂ Plasmas

(Received 9 February 1996, revised 5 June 1996, accepted 26 June 1996)

Abstract
A one-dimensional diffusion model for H ₂ plasma obtained under moderate pressure discharge conditions is presented. The transport equations resulting from this model are solved and enable the estimation of the axial profiles of the plasma species densities and of plasma temperatures on the axis of a diamond deposition microwave plasma reactor. The comparison between the calculated results and experimental measurements shows that the temperatures are well predicted by the model, while some discrepancy was observed for H-atom mole fraction. The analysis of the energy dissipation channels shows that, a low pressure, most of the power lost by the electron is dissipated in activating electron-impact H ₂ dissociation reaction. The model is also used to investigate the effect of the microwave power density on the plasma composition and temperatures. It shows that the increase of the power density leads to a strong and non-linear increase of gas temperature and H-atom mole fraction. This result is also in a good agreement with measurements and is consistent with the high quality of the diamond films obtained at high power density discharge conditions.