In this work, Ni oxide and nitrogen (N)-doped Ni oxide electrochromic films were fabricated with radio frequency magnetron sputtering from a ceramic Ni oxide target. Nitrogen gas was used as the precursor for N doping. The N dopant resulted in Ni oxide films with decreased lattice parameters, increased degree of crystallinity and enhanced surface roughness. The electrochromic performance of the resulting films was evaluated in a LiClO4 electrolyte dissolved in propylene carbonate. The charge reversibility and coloration efficiency as well as the coloration and bleaching kinetics for the N-doped Ni oxide films were significantly improved relative to the undoped Ni oxide films. (C) 2012 Elsevier B. V. All rights reserved.