Mechanical and Tribological Properties of a-GeC x Films Deposited by DC-Magnetron Sputtering

Amorphous carbon-germanium films were grown by dc-magnetron sputtering at different argon plasma pressures ranging from 0.17 and 1.4 Pa. The water-cooled sample holder was grounded. The film thickness were typically 0.5 {micro}m. The ratio between germanium and carbon atomic concentration ranges up to 2.8, as measured by Rutherford backscattering spectrometry (RBS). Elastic recoil detection technique was used to measure hydrogen contamination. The film hardness was measured by nanoindentation techniques and the internal stress was determined by the bending of the substrate. The incorporation of Ge reduces both the film hardness and the internal stress. Hardness and internal stress increases when the films are deposited in lower pressures. Atomic Force Microscopy (AFM) was used to measure the surface roughness, which was found to be insensitive to the pressure and to the Ge content. A possible influence of the thickness on the morphology of pure carbon films is discussed. The friction coefficient measured by AFM is independent on the film composition within experimental errors.