Up scaling of processes for plasma-activated chemical vapour deposition of modified DLC coatings

Diamond-like carbon (DLC) coatings have been extensively investigated for several decades. Their excellent mechanical and tribological properties make them suitable for applications as protective coatings. Among the widespread number of preparation methods, such coatings are most successfully grown by plasma-activated chemical vapour deposition (PACVD). Carbon based hard coatings show physical properties that strongly depend on their microstructure and chemical composition. Thus, the incorporation of new elements in the carbon matrix and the tailoring of its structure are used to obtain coatings with specific properties. However, the up scaling of processes to industrially relevant dimensions is still problematic. The present work deals with the optimization of deposition processes for a-C:H (DLC), a-C:H:Si (SICAN) and a-C:H:Si:O (SICON) coatings using pulsed-DC PACVD in a large scale plasma reactor (1 cubic meter). The characterization procedure consisted in a systematic study of the deposition rate, adhesion, abrasive wear and water contact angle. These features have been discussed in terms of the technological parameters: pressure, concentration of the precursors, input power. The use of additional ionization sources (microwaves) has been considered in order to increase the plasma density and the deposition rate of large area samples.