Polycrystalline and amorphous sol-gel derived WO3 thin films and their gas sensing properties

Abstract

Amorphous and polycrystalline tungsten trioxide (WO3) thin films were prepared using the sol-gel process. Tungsten ethoxide was used as precursor material. The WO3 thin films were spun onto the sapphire and silicon substrates at 2500 rpm for 30 s. The X-Ray Diffraction (XRD) results revealed that the films annealed at low temperature 420°C for 1 hr. are. amorphous while annealed at as high as 500°C are polycrystalline. The Scanning Electronic Microscope (SEM) images revealed that the film annealed at 360°C was amorphous and the surface was smooth. The film showed good responses to 100 ppm, 1000 ppm and 1% O2 at an operating temperature of 170°C. At high operating temperatures the films showe..