Gasochromic Properties of Nanostructured Tungsten Oxide Films Prepared by Sputtering Deposition

Abstract
The effects of surface morphology on the gasochromic properties of tungsten trioxide (WO3) films are reported. WO3 films with various crystalline structures and surface morphologies are prepared by reactive rf magnetron sputtering by adjusting the substrate temperature and oxygen concentration in a sputtering gas during deposition. Grain structures on these films were confirmed by atomic force microscopy observation. The gasochromic properties of the WO3 films coated with a palladium catalyst were examined on the basis of a change in optical transmittance with 645-nm-wavelength light in 1% hydrogen in argon gas. WO3 films with a (001) orientation show sufficient gasochromic properties for their application to fiber-optic hydrogen gas sensors. The growth of the nanocrystalline structure in the WO3 films seems to improve gasochromic properties.