Refractive index of WO3 thin films grown under various temperatures determined by the Swanepoel method

Abstract

Tungsten oxide films (WO3) deposited on quartz substrates by reactive pulsed laser deposition technique are studied. X-ray diffraction analysis of the crystalline structure of WO3 reveals changes in the diffraction peaks with temperature and deposition time. Scanning electron microscopy shows the presence of compact layers with well-defined nanocrystallites grown along the deposition direction perpendicular to the substrate. The transmission spectra of the films, obtained for normal incidence within the 300–1200 nm spectral range have been analyzed by the method proposed by Swanepoel to calculate the WO3 refractive index. The WO3 layer thickness calculated by the Swanepoel method shows good agreement with the values measured from scanning electron microscopy cross-section. The optical band gap slightly changes with increasing deposition time. In this study, the refractive index of WO3 has been improved and the correlation between the refractive index and the structure of WO3 has been emphasized.