Production and characterization of hydrogenated amorphous carbon thin films deposited in methane plasmas diluted by noble gases

The dilution effects of the precursor methane atmosphere by three noble gases (Ar, Ne and He) on the mechanical properties and the microstructure of hydrogenated amorphous carbon films deposited by rf-PECVD were studied. The chemical composition and atomic density of the films were determined by ion beam analysis. The film microstructure was probed by means of Raman spectroscopy. The internal stress was determined through the measurement of the changing of the substrate curvature by a profilometer, while nanoindentation experiments provided the film hardness. The results show that the precursor atmosphere dilution by different noble gases did not induce substantial modifications in the microstructure or in the mechanical properties of the films. On the other hand, the composition, the microstructure and the mechanical properties of the films are strongly dependent on the self-bias voltage. The results confirm the importance of the ion bombardment during film growth on the mechanical properties of the films.