Structural, Optical, Electrical, and Dielectric Properties of the Spray-Deposited WO3 Thin Films

Studies on effect of the substrate temperature on physicochemical properties of WO3 thin films prepared using spray pyrolysis technique have been presented. Raman spectra of the film shows presence of W-O-W network with stretching and bending vibrations which revealed monoclinic structure of WO3 which is confirmed by XRD studies. XPS studies show that films are sub-stoichiometric and O/W ratio is 2.87, with W present in two valence states W+5 and W+6 with ratio of 0.21. Smallest crystallite size (28 nm) is observed for the film deposited at 425 °C, and on either side crystallite size is larger. Optical studies show band gap energy 2.6 eV and NUV, blue and green photo-emissions from WO3 films. Scanning electron micrographs depict wired network of the WO3, and AFM shows rough nature of the films. The thermo-emf is found to be linearly changing with temperature difference and decreases with increase in the substrate temperature.