Room-temperature deposition of amorphous titanium dioxide thin film with high refractive index by a filtered cathodic vacuum arc technique

Amorphous titanium dioxide (TiO₂) thin film has been prepared by a filtered cathodic vacuum arc technique at room temperature. It was concluded from the core level of Ti 2p_3/2 (458.3 eV) and O 1s (529.9 eV) and their deviation in binding energy (ΔBE = 71.6 eV) that only one of Ti oxidation states, Ti⁴⁺, existed in the film and the film was of ideal stoichiometry. The film possessed high transmittance, which can reach as high as that of a quartz substrate, especially in the visible range, owing to its optical bandgap of 3.2 eV. The high refractive index (2.56 at 550 nm) and low extinction coefficient (∼10^-4 at 550 nm) suggested that the film had a high packing density and a low scattering-center concentration. These good optical properties implied the film prepared by this technique was a promising candidate for optical application. Besides, the film was found to transform in the structure from amorphous to anatase crystalline when it was annealed at 300°C, as evidenced by Raman and x-ray diffraction.