RF sputtered electrochromic V2O5 films

The properties of vanadium pentoxide (V2O5) films deposited by r.f. reactive sputtering from V2O5 target are investigated. In particular the composition and structure of these films are analysed by Rutherford backscattering spectrometry (RBS), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) together with their electrochromic properties. Information on electrochromic behaviour of these films, like the injected charge and the width of transition from bleached to coloured state when lithium was electrochemically injected, is obtained by voltammetric and spectrophotometric measurements. The dependence of all these properties on the oxygen flow used in the argon-oxygen gas mixture during deposition is analysed. The highest value of injected charge and the greatest differences in transmittance values due to electrochromic transition are shown by samples deposited at low O2 flow. The films appear to be amorphous when the O2 flow is lower than 20% and the stoichiometry is not greatly affected by the O2 flow.