Analytical characterization of thin carbon films
CHx films on silicon substrates deposited by a Mesh Hollow Cathode Process (MHC) were analyzed by various techniques. The films were produced with varying deposition times, resulting in thicknesses ranging from ~2-20 nm. X-Ray Reflectivity (XRR) was used to determine the film thicknesses and the deposition rate. A good correlation of measured XRR thicknesses with SIMS sputter depths down to the film-substrate transition was found. An AFM-based nanoscratching technique was applied to test the wear resistance of the thin overcoats. The MHC films reveal slightly decreasing scratch resistance for reduced film thicknesses, which can be explained by a higher fraction of soft interface zones for thinner films. This is in accordance with Raman spectroscopic measurements in the visible spectral range which were carried out to examine the carbon bonding properties. Combined analysis of G peak position and D/G peak intensity ratio indicates a more graphitic structure for film thicknesses less than 10 nm.