Structure and properties of nitrogen-doped titanium dioxide thin films produced by reactive magnetron sputtering

In modern purification techniques employing semiconductor-mediated photo oxidation of toxic substances, TiO2 materials are the most widely used metal oxides due to their unique blend of properties. However, the band edge of these semiconductors lying in the ultraviolet (UV) region makes them rather inactive under visible light irradiation. Nitrogen-doped titanium dioxide (N-TiO2) is attracting a continuous attention because this doping generates states just above the valence band and consequently narrows the band gap of TiO2. The visible light activity of these materials mainly depends on the location of this impurity state and consequently on the microstructure of the (N-TiO2) materials. The objective of this study is to investigate the correlations between the microstructure of these materials and their electronic and optical properties. The N-TiO2 films have been produced by reactive magnetron sputtering of a titanium target under a mixture of argon, nitrogen and oxygen gases. The microstructure and chemical properties of the films have been investigated by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Ellipsometry and reflection electron energy loss spectroscopy (REELS) have been used to study their electronic and optical properties. The influence of a post-annealing at 550 degrees C on these different properties has been also investigated. Copyright (C) 2010 John Wiley & Sons, Ltd.