Effects of composition and structure on gasochromic coloration of tungsten oxide films investigated with XRD and RBS

Yamamoto, Shunya; Takano, Katsuyoshi; Inoue, Aichi; Yoshikawa, Masahito

Tungsten oxide films coated with Pd catalysts are colored by exposure to hydrogen gas (gasochromic coloration) and it can be used for optical hydrogen sensors. The effects of composition and structure on gasochromic coloration of tungsten oxide films for hydrogen have been investigated. Tungsten oxide films with various O/W atomic ratios from 1.5 to 3.0 are prepared using a reactive rf magnetron sputtering at different oxygen partial pressures. The crystallographic structure and O/W atomic ratio of the films were determined by X-ray diffraction and Rutherford backscattering spectroscopy. The stoichiometric WO film with amorphous structure resulted in superior gasochromic coloration. The superior gasochromic performance was realized in stoichiometric WO films with amorphous structure. It suggests that the gasochromic coloration of tungsten oxide films for hydrogen is strongly influenced by the composition and structure.