Plasma deposition of hydrogenated diamond-like carbon films from CH4-Ar mixtures

Hydrogenated diamond-like carbon coatings have been deposited from CH4 radiofrequency plasmas. The effect of the argon addition to the precursor CH4 gas has been investigated. The argon dilution has been found to influence the plasma phase and the structural, optical and mechanical properties of the films. The plasma phase has been monitored and analyzed by optical emission spectroscopy. In particular, it is shown that the prevalence of H*, Ar+*, C2* and H2*, CH* emitting species are observed in Ar-rich and CH4-rich CH4-Ar plasmas, respectively. Furthermore, it is shown that simultaneous sputter-etching and growth processes occur and in Ar-rich CH4-Ar mixtures the sputter-etching process prevails on the growth process. A well-defined transition from sputter-etching to growth process is localized at 15% methane in the feeding mixture.