EFFECT OF NITROGEN CONCENTRATION ON PLASMA REACTIVITY AND DIAMOND GROWTH IN A H2CH4-N-2 MICROWAVE-DISCHARGE

The effect of nitrogen on the growth of diamond by microwave plasma-as sisted chemical vapour deposition, when added in a H-2-CH4 gas mixture was investigated by micro-Raman spectroscopy and by scanning electron microscopy. A clear improvement in the surface morphology and quality of the diamond films indicates the beneficial effect of adding nitrog en to the gas mixture. The concomitant study of plasma parameters and diamond films properties leads to a better understanding of the effect of nitrogen in the diamond growth process and to the determination of optimal concentrations of nitrogen and methane in the mixture. We rep ort in this paper the effect of varying the concentration of nitrogen introduced in different H-2-CH4 mixtures. The plasma reactivity is stu died by optical emission spectroscopy during diamond film growth, and we focus our experiments on the variation of the emission line of the CH and CN radicals. These species can be considered as key species to explain reactions of the nitrogen in the gaseous phase and its interac tion with the surface of the film in growth.