Property change in multifunctional TiCxOy thin films: Effect of the O/Ti ratio

TiCxOy films with various O/Ti ratios have been deposited by DC magnetron sputtering, using C pieces incrusted in a Ti target erosion area. Composition analysis revealed the existence of three different growth regimes: (i) zone I, corresponding to films with metallic-like appearance, and atomic ratios O/Ti below one; (ii) zone II, with films revealing interference-like colours, and atomic ratios O/Ti higher than 2. Between these two regions, there was a transition zone T, where the atomic ratio O/Ti is between one and two. The films within this zone revealed a brown colour. X-ray diffraction (XRD) structural characterization results showed an evolution from a mixed Ti(C,O) phase at lower O/Ti ratio, to a quasi-amorphous structure within zone T, and poorly crystallized rutile and anatase TiO2 at the highest O/Ti ratios (zone II). These different structural arrangements resulting from different film's compositions had clear effects on electrical resistivity, whose values increased from about 7 × 102 to 2 × 1011 μΩ cm with increase of the O/Ti ratio. Fourier-transform infrared spectroscopy (FTIR) was used to further confirm the different nature of films structure and, thus, to better understand their properties variation. The observed behaviour was found to be in straight correlation with those of XRD.