Influence of substrate temperature on the structural, morphological, and photoelectric properties of Bi2WO6 thin films deposited by magnetron sputtering

The effect of substrate temperature (Ts) increasing from RT (room temperature) to 600 °C on the structural, morphological, optical and photoelectrochemical properties of BixWO6 (1.98≤x≤2.84) thin films deposited by RF magnetron sputtering has been investigated by various techniques including XRD, EDS, SEM, AFM, XPS, UV-vis DRS, PL and EIS. AFM and EDS show that as Ts increases, the Bi/W atomic ratio gradually decreases; the amorphous BixWO6 thin films grown under 300 °C had a very smooth surface with an RRMS value in the range of 0.5-0.8 nm. However, as the substrate temperature increases from 400 to 600 °C, for the crystalline BiWO6 thin films the RRMS value increases to a range of 18.3-30.5 nm and there is a transition of the crystalline orientation from {131} to {200} as confirmed by XRD. The films grown at Ts = 600 °C exhibit some favorable properties such as a Bi/W ratio close to 2:1, lattice expansion relaxation, low Eg and excellent photoelectric reproducibility which is about 3 to 29 times higher than that of other films grown at low Ts (300-500 °C). PL and EIS analysis as well as photoelectrochemical test results demonstrated the enhanced separation efficiency of photogenerated electron-hole pairs and charge transfer for the stoichiometric and well-crystallised BixWO6 thin films, showing their good potential for practical applications such as visible light responsive photocatalyst or photoelectrode.