PLASMA DIAGNOSTICS OF RF DISCHARGES USED FOR THE DEPOSITION OF HYDROGENATED AMORPHOUS-CARBON COATINGS

The deposition process of amorphous hydrogenated carbon has been studied using optical emission spectroscopy and self-bias measurements. For a given rf power, a transition between two distinct discharge regimes is observed when increasing the pressure. This transition is attributed to different mechanisms by which electrons gain energy in the sheaths and the plasma (alpha-gamma-discharge transition). Ionic species are shown to play an important role in the formation of hard carbon layers.