Argon and hydrogen plasma influence on the protective properties of diamond-like carbon films as barrier coating

Diamond like carbon (DLC) films are becoming materials of choice for mechanical and corrosion protection barrier films due to their excellent properties of low-friction and chemical inertness. As DLC functional properties are strictly dependent on process parameters, different DLC coatings have been deposited onto silicon substrates by Plasma Enhanced Chemical Vapour Deposition (PECVD) evaluating the effect of the variation of argon and hydrogen gas flows on the coating resistance properties. It has been observed that the hydrogen variation is the main factor affecting the DLC films resistance in aggressive environments, while DLC samples deposited by varying Ar showed significant delamination phenomena. These differences have been related to the morphological and microstructural characteristics of DLC films taking into account for the specific role of both Ar and H2 in the mechanism of DLC formation. In particular, it has been observed that the resistance against corrosive environment for DLC coatings may be related to the compressive residual stress values in conjunction with surface and structural properties of the film. This can be considered an understanding at the atomic scale providing the key for the optimization of the protective coating performance.