EFFECT OF OXYGEN-CONTENT ON THE ELECTROCHROMIC PROPERTIES OF SPUTTERED TUNGSTEN-OXIDE FILMS WITH LI+ INSERTION

Tungsten oxide films have been deposited at room temperature from meta llic tungsten target onto ITO coated glass substrate with sheet resist ance of 15 Omega/square using reactive rf magnetron sputtering. The fi lms formed in an Ar+2-25% O-2 gas mixture with total pressure of 10 m Torr and sputtering power 300 W. The films were subjected to electroch emical Li+ insertion using in situ lithium triflate (trifluoromethanes ulfonate) anhydrous solution. The electrochromic properties of the rf reactively sputtered tungsten oxide films have been investigated in re lation to the oxygen concentration in the sputtering atmosphere. Trans mittance measurements have been performed in situ during the electroch emical formation of the tungsten bronzes using Bruker IFS-66 Fourier s pectrophotometer with integrating sphere. From the obtained results th e best values of the electrochromic properties can be achieved at oxyg en concentration of 15% with electrochromic parameters as, Delta T-sol = 0.547, Delta (OD)(s) = 0.865 eta(s) = 21.05 cm(2)/C, Q(inj) = 41.09 mC/cm(2) and Q(lef.) = 10.25 mC cm(2) respectively. The films deposit ed with oxygen concentration less than 5% were found in metallic state . (C) 1998 Published by Elsevier Science Ltd. All rights reserved.