Sputter deposited crystalline V2O5, WO3 and WO3/V2O5 multi-layers for optical and electrochemical applications

Abstract

Crystalline V2O5, WO3, WO3/V2O5 (bi-layer) and WO3/V2O5/WO3/V2O5 (multi-layer) thin film samples were deposited on fused silica and fluorinated tin oxide coated microscopy glass substrates by reactive dc magnetron sputtering. Structure-property correlation studies were carried out by X-ray diffraction, Raman and X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy, atomic force microscopy, UV–vis spectroscopy and cyclic voltammetry techniques. V2O5 and WO3 layers have orthorhombic and monoclinic crystal structures respectively and their phase formation was confirmed by XPS. Cyclic voltammetry studies were used to determine the electrochemical properties. H+ diffusion coefficient decreases with increase in the voltage scan rate in all samples except for the bi-layer. At each scan rate the highest diffusion coefficient was achieved for multi-layer sample and the values were 7.4 × 10−14 cm2s−1, 2.4 × 10−14 cm2s−1, 1.4 × 10−14 cm2s−1 at scan rates of 10 mVs−1, 100 mVs−1 and 500 mVs−1, respectively. The multi-layer sample has large areal capacitance of 1165 mFcm−2. The study shows that WO3/V2O5/WO3/V2O5 multi-layer sample has significantly enhanced electrochemical properties as compared to the single layer V2O5 and WO3 films.