抄録
Tungsten tri-oxide (WOa) thin films are prepared by magnetron sputtering and subsequent thermal treatment. Ion irradiations with 4He+ at 350 keV were performed for the films. Gasocbromic coloration of the irradiated films was observed by a measurement of optical transmittance with the exposure of 1 % hydrogen. The extent of coloration level of the irradiated film with the fluence of lxl017 ions/cm2 is 7.5 times lager than that of non-irradiated film. W 4f photoemission spectra for the films were measured by x-ray photoelectron spectroscopy. From the fitting analysis for the spectra, the non-irradiated film has only W6+. In the irradiated film with the fluence of lxl017 ions/cm2, it is estimated that 17% and 4% of the W6+ change into W5+ and W4+, respectively. The irradiation for the films breaks the chemical bonds between tungsten and oxygen, and makes atomic sites of oxygen-deficient tungsten such as W5+ and W4+. The improvement of the gasocbromic coloration for the WO3 films relates to the increment of the W5+ and W4+ sites induced by the irradiation.
