Electrochemical preparation of tungsten oxide hydrate films with controlled bandgap energy

Publication date: 1 March 2017
Source:Thin Solid Films, Volume 625
Author(s): Kentaro Nishiyama, Junji Sasano, Seiji Yokoyama, Masanobu Izaki
Tungsten oxide hydrate films of WO3 ∙H2O and WO3 ∙(H2O)0.33 were prepared on conductive glass substrates by anodic deposition in aqueous 0.01–0.5mol/L WO4 ²⁻ solutions. Structural and optical characterizations were carried out by X-ray photoelectron spectroscopy, X-ray diffraction, SEM observation, optical absorption measurements, and photoelectrochemical measurements. The films composed of large WO3 ∙H2O grains with square shapes, which was obtained in the 0.01–0.09mol/L WO4 ²⁻ solutions, possessed a bandgap energy of approximately 2.5eV, and the granular-WO3 ∙(H2O)0.33 films, which was obtained in the 0.05–0.5mol/L WO4 ²⁻ solutions, showed 3.3eV in bandgap energy. The WO3 ∙H2O-WO3 ∙(H2O)0.33 mixtured films prepared in the 0.01–0.09mol/L WO4 ²⁻ solutions showed a photoresponse for visible light at 380–600nm, due to the presence of 2.5eV-bandgap WO3 ∙H2O.