Effect of annealing on the physical properties of WO 3 thin films

Abstract

Tungsten trioxide (WO3) thin films were deposited by electron beam evaporation technique at an oxygen partial pressure of 2 × 10−4 mbar and at different substrate temperatures ranging from room temperature (RT) to 450°C. The films were annealed at 400°C about 2 hours and the properties were studied systematically. The x-ray diffraction studies show the diffraction peak of (320) at 2θ = 44.07° which indicate the orthorhombic phase of WO3 and also the other peaks represent the hexagonal phase of WO3. Due to annealing of the films, the monoclinic phase is also observed. The surface morphology of WO3 thin films was investigated by using atomic force microscopy and scanning electron microscopy, which supports the above data. The energy-dispersive x-ray (EDX) compositional analysis confirmed the presence of W and O. The optical properties were studied by UV-VIS spectrophotometer and hence the bandgap values are calculated.