Optical and photoelectrochemical studies on Ag2O/TiO2 double-layer thin films

When two different oxides films stacked together, if the absorption (upper) layer has both its conduction and valence bands more negatively lower than that of the layer underneath, then the photo-excited electrons can be forwarded to the underneath layer to become an effect of energy storage. Recent studies discovered that the double-layers of Cu2O/TiO2 films possess such capacity. In order to investigate this specific phenomenon, we use a DC magnetron reactive sputtering to deposit a double-layer of Ag2O/TiO2 films on glass substrate. The film thicknesses of the double-layer are 300 nm and 200 nm respectively. X-Ray diffraction (XRD), scanning electron microscope (SEM) and UV-VIS-NIR photospectrometer and photoluminance tests were used to study the structure, morphology, optical absorption and band gaps of the stacked films. From XRD and SEM, we can confirm the microstructures of each layer. The UV-VIS-NIR spectrum revealed that the optical absorption of Ag2O/TiO2 fell in between the single film of Ag2O and TiO2. Further, two band gaps were estimated for Ag2O/TiO2 films based on the Beer-Lambert law and Tauc plot. Photoluminance and photoelectrochemical tests indicated that delayed emission by electron-hole recombination and photoelectrical current was effectively support the mechanism of electrons transfer from Ag2O to TiO2 at Ag2O/TiO2 interface in the double-layer films. (C) 2014 Elsevier B.V. All rights reserved.