Compositionally graded layer produced by low-energy ionization deposition technique

A carbon and silicon based thin layer was produced on a titanium alloy through the supply of accelerated molecular ions, which was called as an ionization deposition technique. Liquid materials of benzene (C6H6) and hexamethyldisiloxane (C6H18Si2O) were individually evaporated under reduced pressure, and mixed in a chamber at a volume ratio changing with time. They were then ionized by an electron impact and accelerated in an electric field of 270 V m−1 toward the alloy substrate. In this process, the ionized molecules were decomposed and fragmented to rearrange their bonding structure. X-ray photoelectron spectroscopic depth analysis revealed that the chemical bonding states of the layer changed from “graphite” to “silicon carbide + graphite” and “silicon carbide + graphite + titanium carbide”, which corresponded to the decrease in C/Si atomic ratio from the surface side towards the substrate. From the results of Raman scattering analysis, both sp2 and sp3 hybrid bonding structures of carbons probably existed in the surface layer, which is similar to a hydrogenated amorphous carbon (a-C:H) structure.