Electrochemically induced electrochromic properties in nickel thin films deposited by DC magnetron sputtering

Nickel oxide thin films and other electrochromic materials receive particular attention due to the great variety of practical applications in energy conservation and in semitransparent optical devices. In this work, nickel thin films were produced by DC magnetron sputtering on ITO substrates. The nickel–ITO thin films were studied by electrochemical techniques, and electrochromic properties were induced in the films after several different cyclic voltammetry runs. The cyclic potential range was set from 400 to 600 mV and the scan rates were varied from 6.6 to 10 mV/s. The electrochromic phenomena was observed just after 80 cycles as derived from voltammograms and color changes in the nickel oxide films were observed close to 100 cycles. The optical properties of as-deposited films and of the ones tested in the electrochemical cell were determined by optical spectrophotometry in the visible range. The structural properties of the films were studied by X-ray diffractometry, scanning and transmission electron microscopy in conventional and highresolution modes. The electrochemical properties were studied principally by the cyclic voltammetry technique. Noticeable differences in induced electrochromic behavior were observed between the nickel films deposited on two sets of ITO substrates, prepared by DC magnetron sputtering and spray pyrolysis. 2005 Elsevier Ltd. All rights reserved