Structural transition and blue emission in textured and highly transparent spray deposited Li doped WO <inf>3</inf> thin films

The effect of Li (0-5 wt%) doping on the properties of WO 3 thin films deposited using an automated homemade spray pyrolysis unit is studied. Change in structural and optical properties is observed on doping with Li. The XRD patterns shows that undoped WO 3 film has an orthorhombic phase while the Li (1-5 wt%) doped WO 3 films have tetragonal phase. The SEM and AFM images confirm relatively smooth surface of Li doped WO 3 films compared to undoped WO 3 film. Transmission spectra reveal that the transparency of the Li-doped films is much greater than that of undoped film. From the transmission data, the direct, indirect bandgap and phonon energies were calculated. Room temperature photoluminescence spectra showed pronounced blue emission on doping with Li. © 2011 Elsevier B.V. All rights reserved.