WO3 Electrochromic Thin Films Doped With Carbon

(WO₃)_100−XC_X thin films (x \(=\) 0−9.3 at%) were cosputtered on indium-tin-oxide glass substrate with W and C targets by reactive dc magnetron sputtering at room temperature. The effects of doped C on the microstructure and optical properties of the (WO₃)_100−XC_X thin film were examined by field emission scanning electron microscopy with energy dispersive X-ray spectroscopy, X-ray diffraction, and a spectrophotometer. It was found that all of the as-deposited films were amorphous. The average transmittances of bleaching and colored WO₃ film in the 400–700 nm range were 75% and 65.9%, respectively. The variation in average transmittance of the bleaching and colored states of (WO₃)_90.7C_9.3 film was 68.3%. The average transmittance of bleaching (WO₃)_100−XC_X thin films did not vary with C doping. However, the average transmittance of colored (WO₃)_100−XC_X film decreased to <48% after C doping. In addition, the optical transmittance contrast of (WO₃)_100−XC_X thin films was found to be suitable for blue laser wavelength recording.