Characterization of hard diamond-like carbon films formed by Ar gas cluster ion beam-assisted fullerene deposition

The coordination of carbon atoms in diamond-like carbon (DLC) thin films formed by Ar gas cluster ion beam (GCIB) assisted deposition using fullerene as the carbon source was investigated by measuring near-edge X-ray absorption fine structure (NEXAFS) spectra of the carbon K-edge over the excitation energy range 275-320 eV, using synchrotron radiation. With attention to the peak corresponding to the transition of the excitation electron from a carbon Is orbital to a pi* orbital, relative sp(2) contents of various DLC films were estimated. The sp(2) contents of the DLC films formed by the GCIB-assisted deposition were observed to be lower than those of the DLC films formed by other methods. The hardness value measured with a nano-indentation technique was found to be strongly related to the sp(2) content of the DLC film.