Photoinduced hydrophilic and electrochemical properties of nitrogen-doped TiO2 films

A radio frequency sputtering technique was used to fabricate nitrogen-doped titanium dioxide thin films with dopant concentrations of 1.0-2.9 mol %. UV-visible absorption spectra and calculations of the estimated density of states indicated that the changes in the band structure depended on the dopant concentrations. The nitrogen-doped TiO2 films underwent hydrophilic conversion and approximately 1.9 mol % was the optimal dopant concentration for hydrophilic properties when irradiating with visible light. When irradiating with UV light, the hydrophilic properties increased as the dopant concentration decreased, which reflected the changes in the band structure. Photoelectrical and electrochemical analyses of the nitrogen-doped TiO2 suggested that it was an n-type semiconductor, and the carrier concentrations increased as the nitrogen concentration increased. Based on these findings, a mechanism for the visible light response, which involves nitrogen incorporation at some of oxygen sites, is proposed (c) 2005 The Electrochemical Society. All rights reserved.