Investigation of TiC-C coatings by X-ray photoelectron spectroscopy

Titanium carbide-based coatings deposited by arc-technology in C₂H₂/Ar atmosphere were studied by X-ray photoelectron spectroscopy. It was found that, in addition to the cubic phase of TiC _x O _y oxycarbide, the films contain carbon in the amorphous, presumably graphite-like state. In carbon C1s spectra, bands at 282.0, 284.4, and 286.0 eV correspond to the TiC _x state, amorphous carbon, and C-C bonds, respectively. The maximum at 283.0 eV was interpreted as the C state in titanium carbide nanoforms, i.e., Ti₁₄C₁₃ clusters or Ti₈C₁₄ carbohedra. The phase ratio was varied by coating deposition conditions, i.e., TiC/a-C deposition by Ti cathode sputtering in C₂H₂/Ar, and composite Ti/C target sputtering in Ar and C₂H₂/Ar. When using the Ti cathode and C₂H₂/Ar gas mixture, the ratio of carbide and amorphous a-C phases was estimated as 1: 1; the surface layer ～15 nm thick was enriched with amorphous carbon. It was assumed that TiC/a-C composite coatings with an additional a-C film on the surface would have an increased stability in reaction media and good biocompatibility.