Properties and gasochromic study of WO3 film sensors

Photochromism (PC) and electrochromism (EC) of transition metal oxides have received much attention because of their potential technological applications in gas sensors. The nanocrystalline tungsten trioxide (WO3) films with excellent coloring and bleaching characteristics were developed in this paper. The spectral variations of the optical transmission under illumination were reported for WO3 films of as-deposited and annealed tungsten trioxide prepared by DC sputtering technique. It was found that the film prepared with different O-2 content in the sputtering atmosphere showed the different transmission properties; they reached their highest value with 75% O-2. The crystal structure and the particle size of the samples were determined by X-ray diffractions: the films exhibit better crystallinity with the annealing temperatures higher than 623K and the average nanoparticle size was 45nm. A new method was used to determine the gaschromic for H-2 gas sensors. In this work, the sensitivity of WO3 films was determined by using the optical external stimulus. The experiment results showed that the sensitivity of the annealed WO3 films is more stable than the as-deposited films. Besides, the sensitivity of pure WO3 sensors was dependent on operating temperature and the films response got the greatest at about 348K.