Spectroscopic analysis of color origins in titanium-based thin films deposited by cathodic arc deposition

The distinctive colors observed in titanium-based (Ti-based) decorative coatings fabricated by cathodic arc deposition originate from the unique electronic, morphological, and chemical properties of these films. Most Tibased film colors arise from their surface band gaps, as measured by electron energy loss spectroscopy, with the exception of the lowest brightness (TLB) and green hues. The green color in titanium dioxide films typically results from interference between light reflected from the film and substrate interfaces. In contrast, the black color in Ti-based coatings stems from the chemical structure, specifically the presence of Ti-C and C=C(sp2) bonds within the film. Moreover, the large band gap of the TLB film surface is attributed to surface oxidation, as detected by soft X-ray spectroscopy. Significantly, the film thickness and surface roughness are characterized by field emission secondary electron microscopy and atomic force microscopy, respectively.