ELECTROCHROMISM OF FLUORINATED AND ELECTRON-BOMBARDED TUNGSTEN-OXIDE FILMS

Reactive de magnetron sputtering of W was performed in a plasma of Ar + O-2 with and without CF4 addition and substrate bias. Structural studies by atomic force microscopy, X-ray diffraction, infrared reflectance spectroscopy, and Raman spectroscopy indicated that the electron e bombardment associated with a positive substrate bias led to grain growth and partial crystallization while maintaining a high density of W=O double bonds presumably on internal surfaces. Electrochemical measurements showed that the durability under extended Li+ intercalation/deintercalation was excellent for e-bombarded oxide films and poor for oxyfluoride films. Spectrophotometric studies of the electrochromism yielded that the color/bleach dynamics was slow for the e-bombarded oxide but fast for the oxyfluoride. The range of optical modulation was large. Tandem films, with a thin protective layer of e-bombarded oxide covering a thicker oxyfluoride layer, were able to combine rapid dynamics with good durability. (C) 1995 American Institute of Physics.