rf reactive sputtered VOx thin films deposited at different oxygen flows

In this work, we investigated the conditions for deposition of vanadium oxide films by r.f. reactive sputtering, by varying the oxygen now (phi) during deposition. The electrochromism presented by these materials upon lithium intercalation was followed. The stoichiometry of the as-deposited films was investigated by Rutherford Backscattering. For high phi, films are mainly V2O5. For the lowest flow investigated, a lower oxide is obtained. Also, RBS indicated an important H content. X-Ray Diffraction (XRD) showed that the films are amorphous. Samples deposited at high phi are transparent/yellow, and show good electrochromic performance, behaving as a cathodic coloring material for insertion charges till -25 mC/cm(2) and wavelengths greater than or equal to 500 nm, but as anodic coloring materials for this insertion level in the lower wavelength range. For higher insertion charges, the reverse behavior was observed. Samples deposited at low O-2 flows did not show any electrochromic behavior.