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.