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.