Preparation and characterization of electron beam evaporated WO3 thin films

Thin film of tungsten oxide (WO3) has been extensively studied as an electrochromic material and has numerous applications in electrochromic devices, smart windows, gas sensors and optical windows. In order to explore the possibility of using this in electrochromic devices, a preliminary and thorough study of the optical properties of the host material is an important step. Based on the above criterion, the effect of annealing temperature on the structural, surface morphological and optical properties of WO3 films has been studied in the present work. The host material, WO3 films, has been prepared by the physical vapor deposition method of electron beam evaporation (PVD:EBE) technique under a pressure of 1 × 10−5 mbar. The single phase nature, monoclinic structure and textured nature of the films have been confirmed by the X-ray diffraction analysis. The needle-like crystallites have been observed from surface morphological studies. The evaluated crystallite size is in the nanometer range. The shift in absorption edge towards the higher wavelength region observed from optical studies may be due to the coloration effect on the films.