ELECTROCHROMISM OF W-OXIDE-BASED THIN-FILMS - RECENT ADVANCES

We summarize some recent work related to electrochromic tungsten-oxide -based thin films. The electronic structure of crystalline cubic (pero vskite) WO3 and HWO3 was calculated from first principles. It was foun d, that hydroxide formation was energetically favoured. Experimental s tudies were made on heavily disordered films prepared by reactive magn etron sputtering in Ar + O-2 with and without CF4 addition and substra te bias. Structural studies, indicated that the electron bombardment a ssociated with a positive substrate bias led to grain growth and parti al crystallization while maintaining a high density of W=O double bond s presumably on grain boundaries. Tandem films, with a thin protective layer of electron bombarded oxide covering a thicker oxyfluoride laye r, were able to combine rapid dynamics of the electrochromism with goo d electrochemical durability. Oblique angle sputtering in Ar + O-2 led to films whose microstructure comprised inclined columns. Pronounced angular selective transmittance was found to coexist with electrochrom ism.