Characterization of Ni0.92V0.08Ox thin films deposited by the pulse sputter method

Abstract

Based on the use of 8 at.%V-92 at.%Ni alloy target, Ni0.92V0.08Ox thin films are deposited via the pulse sputter method to avoid the ferromagnetic disadvantage when using a pure Ni metallic target. Crystallinity, microstructure and electrochromic (EC) properties are investigated systematically by X-ray diffractometer (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The optical properties of the Ni0.92V0.08Ox films are analyzed by a UV/VIS spectrophotometer (UV–Visible). Electrochromic tests are performed using an electrochemical analyzer. Experimental results indicate that the thickness, chemical composition, microstructure, and electrochromic properties heavily depend on the plasma power and the argon/oxygen ratio. The XPS and XRD analyses reveal that Ni2+, Ni3+, V4+ and V5+ co-exist in the Ni0.92V0.08Ox films and form an ideal stoichiometric compound at plasma power above 250 W, demonstrating that V can stabilize the valence state of Ni2+. Films deposited at 100 W yields the optimal electrochromic properties, with high optical modulation, high coloration efficiency and the lowest color memory effect at wavelengths of 400, 550 and 800 nm.