Improvement of electrochromic coloration efficiency by oxygen deficiency in sputtering a-WO/sub x/ films

Experimental results show that the coloration efficiency value and its light modulation capability of oxygen partial pressure at the optimum 6.5*10/sup -3/ torr are improved about tenfold and 234%, respectively, better than that at 2.0*10/sup -3/ torr of amorphous tungsten oxide (a-WO/sub x/) films by oxygen deficient stoichiometries, thus offering good electrochromic performance for opto-switching applications. It is concluded that the optical absorption of a coloured a-WO/sub x/ film can be satisfactorily described by an intervalence charge-transfer transition mechanism between localised W/sup 5+/ and W/sup 6+/ states.