XAS, XRD, AFM and Raman studies of nickel tungstate electrochromic thin films

Systematic studies of nanocrystalline nickel tungstate, NiWO4, thin films were performed by several experimental techniques such as Ni K- and W L-1.3-edges X-ray absorption spectroscopy, X-ray diffraction, Raman spectroscopy, atomic force microscopy and cyclic voltammetry measurements. We found that the NiWO4 thin films exhibit electrochromic properties similar to that of amorphous tungsten trioxide films, but show better structural stability upon multiple colouring/bleaching cycling. It was observed that a nanocrystallinity of the thin films results in strong modifications of the Ni-O and W-O interactions, which affect both local atomic and vibrational structures. (C) 2001 Elsevier Science Ltd. All rights reserved.