Characterization of Cr-doped TiO2 thin films prepared by cathodic arc plasma deposition

Cr-doped TiO2 thin films were prepared by co-sputtering of titanium and chromium in a cathodic arc plasma evaporation system. X-ray diffraction (XRD), Auger electron spectroscopy (AES), field emission scanning electron microscopy (FE-SEM), and water contact angle measurement were used to characterize obtained films. As-deposited pure titanium dioxide thin films possessed a mostly anatase structure while Cr-doped TiO2 films was amorphous. After annealing at 450 °C for 3 h, amorphous Cr-doped TiO2 films transformed to a mixed anatase (mostly) and rutile phase. Changes in the morphology and composition of the films were examined by FE-SEM and AES. Crystalline Cr-doped TiO2 films became super-hydrophilic after 20 min of exposure under visible light illumination, indicating that the absorption edge shifted from an ultraviolet region for TiO2 to a visible light range for annealed Cr-doped TiO2 films, which is further confirmed by UV–visible spectra.