Photoluminescence and Raman spectroscopy in hydrogenated carbon films

a-C:H films prepared by DC-magnetron sputtering in an H-2:Ar mixture exhibit strong photoluminescence (PL) peaks superimposed upon the Raman scattering spectrum. PL becomes observable at a hydrogen content of ca. 34%, and increases exponentially thereafter, driven by the progressive saturation of carbon dangling bonds. In this %H range, hardness and elastic modulus decrease and CSS durability reaches an optimum. The Raman G peak position is very sensitive to deposition temperature (shift of 0.1 cm(-1)/C-0) and was found to correlate with the sp(3)/sp(2) bonding ratio as measured by EELS, and therefore can also be used as a predictor of carbon tribological performance.