The multilayered structure of ultrathin amorphous carbon films synthesized by filtered cathodic vacuum arc deposition

The structure of ultrathin amorphous carbon (a-C) films synthesized by filtered cathodic vacuum arc (FCVA) deposition was investigated by high-resolution transmission electron microscopy, electron energy loss spectroscopy, and x-ray photoelectron spectroscopy. Results of the plasmon excitation energy shift and through-thickness elemental concentration show a multilayereda-C film structure comprising an interface layer consisting of C, Si, and, possibly, SiC, a buffer layer with continuously increasingsp3fraction, a relatively thicker layer (bulk film) of constantsp3content, and an ultrathin surface layer rich insp2hybridization. A detailed study of the C K-edge spectrum indicates that the buffer layer between the interface layer and the bulk film is due to the partial backscattering of C+ions interacting with the heavy atoms of the silicon substrate. The results of this study provide insight into the minimum thickness ofa-C films deposited by FCVA under optimum substrate bias conditions.