Electrochromic properties of bipolar pulsed magnetron sputter deposited tungsten–molybdenum oxide films

There are great interests in electrochromic technology for smart windows and displays over past decades. In this study, the WMoOx thin films were deposited onto indium tin oxide glass and silicon substrates by pulsed magnetron sputter system with W and Mo targets. The films were deposited with fixed W target power while the variant parameter of Mo target power in the range 50, 100, 150 and 200W was investigated. The working pressure was fixed at 1.33Pa with a gas mixture of Ar (30sccm) and O2 (15sccm). The film thickness increased with the Mo target power. Higher plasma power resulted in a crystalline structure which would reduce the electrochromic property of the film. The influence of plasma powers applied to Mo target on the structural, optical and electrochromic properties of the WMoOx thin films has been investigated. WMoOx films grown at Mo target powers less than 100W were found to be amorphous. The films deposited at 150W, which is the optimal fabrication condition, exhibit better electrochromic properties with high optical modulation, high coloration efficiency and less color memory effect at wavelength 400, 550 and 800nm. The improvement resulted from the effect of doping Mo has been tested. The maximum ΔT (%) values are 36.6% at 400nm, 65.6% at 550nm, and 66.6% at 800nm for pure WO3 film. The addition of Mo content in the WMoOx films provides better resistance to the short wavelength light source and can be used in the concerned application.