Photocatalytic Characteristics and Structural Evaluation of TiO2 Thin Films Reactively DC Sputtered with H 2 O

TiO 2 thin films containing Ti-OH bonds have been fabricated using dc reactive sputtering of Ti in a H 2 O ambient. The structures of these films and their photocatalytic characteristics were analyzed. The structures of the TiO 2 thin films were analyzed using Fourier transform infrared spectroscopic analysis, X-ray diffraction, scanning electron microscope inspection, nuclear magnetic resonance, and photoluminescence. To evaluate the photocatalytic characteristics of the TiO 2 films, we used a wet methylene blue method and pure-water contact angle measurement. We found the following: (i) The total quantity of OH groups decreases as the substrate temperature is increased. (ii) OH groups can be either densely or sparsely distributed in the TiO 2 film. (iii) The abundance ratios of the concentrated and sparse OH groups to the total quantity of OH groups change as the substrate temperature is increased. Measurements made with nuclear magnetic resonance and photoluminescence show that the sparse OH groups ([0H] n ) are effective in removing oxygen deficiency and other deficiencies, while the localized, concentrated OH groups ([OH] w ) are ineffective. We concluded that the distribution of OH groups in the TiO 2 thin film is an important factor that must be considered for improvement of photocatalytic characteristics.