Sp³-rich deposition conditions and growth mechanism of tetrahedral amorphous carbon films deposited using filtered arc

Tetrahedral amorphous carbon (ta-C) films with many superior properties approaching those of diamond crystal were prepared using filtered cathodic vacuum arc technology. To ascertain the s p3 -rich deposition condition, the dependence of the film microstructure on the deposition energy was investigated by means of visible Raman spectroscopy, x-ray photoelectron spectroscopy, electron energy loss spectroscopy, x-ray reflectivity, and nanoindentation. The maximum hardness and Young's modulus are achieved at a bias of -80 V, at which the maximum s p3 fraction of about 82% is obtained. Under this condition, the most symmetric Raman line shape, the highest x-ray photoemission C 1s core level position and a π* transition peak with the smallest integral area in the K -edge spectra are simultaneously achieved. The structural properties are found to be strongly correlated with the mass density of the films. At the optimal substrate bias of -80 V, the film mass density reaches its maximum value. The cross section of the films is characterized with a layered distribution in mass density. A surface layer with low density is an intrinsic feature and experimental evidence of the subplantation growth of the films.