Abstract
A compositionally graded film (type-G film) that had Si-rich composition near a substrate of Si or Ti alloy and C-rich composition near the surface and a Si-rich monolithic film (type-S film) were prepared by the ionization deposition method using hexamethyldisiloxane and benzene as raw materials. Diamond-like carbon (DLC) films were deposited successively on to the type-G film, type-S film and the substrate directly. These are denoted in this paper as DLC/G, DLC/S and single-DLC, respectively. There was no difference among their Raman spectra, which suggested that existence of the intermediate layers, type-G and type-S films, did not affect the bonding structure of the DLC film surface. The hardness of DLC/G was 30 GPa, being about as high as that of single-DLC (33 GPa). The type-G film was about 1.4 times harder than the type-S film. X-ray photoelectron spectroscopic analysis revealed that a fairly large amount of SiC and graphite components existed on the surface of the type-G film, which increased the film hardness. In the scratching test, the critical load of DLC/G was 3 or more times grater than that of the single-DLC film, and was 1.2 or more times that of the DLC/S. The scratched mark on DLC/G was clearly different from those of other DLC films. The type-G film was proven to be effective as an intermediate layer in obtaining good adhesion between the DLC film and the substrate.
