Nano-tribological investigations of carbon overcoats: Correlation with Raman spectra

Nano-indentation and nano-wear tests were performed on carbon overcoats, which were deposited under different conditions on thin film magnetic disks, using the point contact microscope (PCM). Two failure mechanisms of the overcoats during the nano-wear test are described: one is the wear of the carbon overcoat as measured by the wear depth; the other is the damage at the overcoat-substrate interface as indicated by the critical cycle. The hardness of the carbon overcoat correlates well with the wear resistance. Also a certain relation between the Raman spectra and mechanical properties of carbon overcoats is found. However, it is shown that the Raman spectra can not be used as the sole indicator of the wear resistance of carbon overcoats.