Abstract: Nanocrystalline TiO₂ thin films doped with different concentrations of Mo were deposited by direct current (DC) reactive magnetron sputtering. The influence of Mo on surfaces, crystal structures, the valence states of elements and the absorption band of Mo doped TiO₂ films were characterized by means of atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Ultraviolet-visible spectroscopy (UV-Vis). To investigate the photoelectric characteristic of ITO (indium tin oxide)/Mo-TiO₂ electrodes, a series of cyclic voltammetry experiments were conducted. The results indicate that an appropriate amount of Mo atoms, observed as Mo⁶⁺ and Mo⁵⁺ by XPS, could inhibit the crystal growth of particles, enhance the surface roughness of the Mo doped TiO₂ thin film, and bring about a remarkable red shift of the absorption spectra. As the concentration of Mo increased, the energy gap declined at first until the amount of doped Mo eventually reached 3.6% (n(Mo)/n(Ti)), when a blue shift of spectra resulted and the energy gap grew wider. The sample doped with 0.9% Mo was irradiated with a Xe lamp and showed the highest photocurrent, which continued to increase with increasing voltage exerted on the anode. An increase in Mo concentration resulted in a decrease in photocurrent. Compared to the pure TiO₂ film, the sample with 3.6% Mo had a much lower photocurrent. Our experiments demonstrate that Mo doping, when the concentration was controlled under a relatively low limit, brought about a significant improvement of the photoelectric properties of the TiO₂ films. The highest photocurrent observed is 2.4 times that of the sample with no Mo doping.

Key words: Photocurrent, Cyclic voltammetry, DC reactive magnetron sputtering, Titanium dioxide thin film, Mo doping