Influence of the pressure and power on the non-equilibrium plasma chemistry of C2, C2H, C2H2, CH3and CH4affecting the synthesis of nanodiamond thin films from C2H2(1%)/H2/Ar-rich plasmas

We have used a kinetic model to investigate the influence of changing the pressure (0.1–0.8 Torr) and power (100–300 W) on the non-equilibrium plasma chemistry of RF (13.56 MHz) produced C 2 H 2 (1%)/H 2 /Ar plasmas of interest for the synthesis of nanodiamond thin films. We found that the concentrations of the species , C 2 (a 3 Π u ) and C 2 H are not sensitive to variations in the power but they exhibit a significant increase when the pressure decreases at high argon content in the plasma. In addition, the concentrations of C 2 H 2 , CH 4 and CH 3 exhibit a slight (case of C 2 H 2 ) or negligible (case of CH 3 and CH 4 ) power-dependence although they decrease (case of C 2 H 2 and CH 4 ) or remain almost constant (case of CH 3 ) as the pressure decreases. A reasonable agreement is found when comparing the model predictions with available experimental results. These findings provide a basic understanding of the plasma chemistry of hydrocarbon/Ar-rich plasma environments and, at the same time, can be of interest to optimize the processing conditions of nanodiamond films from medium pressure RF hydrocarbon/Ar-rich plasmas.