Dye degradation studies of Mo-doped TiO₂ thin films developed by reactive sputtering

TiO₂ thin films with various Mo concentrations have been deposited on glass and n-type silicon (100) substrates by this radio-frequency (RF) reactive magnetron sputtering at 400°C substrate temperature. The crystal structure, surface morphology, composition, and elemental oxidation states of the films have been analyzed by using X-ray diffraction, field emission scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy, respectively. Ultraviolet-visible spectroscopy has been used to investigate the degradation, transmittance, and absorption properties of doped and undoped TiO₂ films. The photocatalytic degradation activity of the films was evaluated by using methylene blue under a light intensity of 100 mW cm⁻². The X-ray diffraction patterns show the presence of anatase phase of TiO₂ in the developed films. X-ray photoelectron spectroscopy studies have confirmed that Mo is present only as Mo⁶⁺ ions in all films. The Mo/TiO₂ band gap decreases from ~3.3 to 3.1 eV with increasing Mo dopant concentrations. Dye degradation of ~60% is observed in Mo/TiO₂ samples, which is much higher than that of pure TiO₂.