Deformation behavior and interfacial sliding in carbon/copper nanocomposite films deposited by high power DC magnetron sputtering

Amorphous carbon-copper nanocomposite films with a carbon content from 7 to 40at.% have been deposited onto steel, silicon and glass substrates using a high power (>60W/cm²) and high-rate DC magnetron sputtering technique. XRD, Raman spectroscopy and TEM results confirm that the deposited films consist of copper nanograins (size<20nm) incorporated within the matrix of amorphous carbon (a-C). The structure of films varies from fragmented columnar at the highest copper contents (around 90at.% Cu) to disordered at increased carbon concentrations. Nanoindentation tests show a reasonable hardness of films (2-4GPa) with a plasticity approaching that of a pure copper film. The ratio of the plastic work to the total work of the deformation at indentation for copper-rich films (above 90at.% Cu) reaches up to 86%. The study of surface morphology of the deformation zone around indents in such films reveals localized zones of mutual sliding that indicate to a possible contribution of interfacial effects. The results of the structural and nanoindentation study characterize the a-C/Cu nanocomposite films as possible solid lubricants or as a plastic component for complex tribological coatings.