Tribological properties of copper/carbon films formed by microwave plasma-assisted deposition techniques

Copper/hydrogenated amorphous carbon (a-C:H) composite have been deposited on silicon substrates by sputtering of a copper target associated with microwave plasma-enhanced chemical vapor deposition process of carbon from argon-acetylene gas mixtures of various compositions. The elemental composition, surface morphology, ratio between sp2 and sp3 types of carbon bonds and tribological properties of Cu/a-C:H composite films were investigated as functions of C2H2 concentration varying from 0 to 100% in the gas phase. The carbon content in the films was found to increase from 0 to 78 at.% with increasing C2H2 concentration in the gas phase. For films with relatively high carbon contents, the concentration of sp2-bonded carbon clusters increased and the maximum surface roughness Rmax was reduced to 2–3 nm. The friction coefficient and wear resistance of films were dependent on the composition of films. The wear resistance of films containing 23 to 29 at.% of carbon was higher by a factor of 2 than that of pure copper films. The adhesion and wear resistance of films decreased significantly while the friction coefficient increased with increasing film hardness.