Effect of tungsten valences on gasochromic coloration in tungsten oxide thin films

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

Ion irradiations with He at 350 keV were performed for the tungsten tri-oxide (WO) films. Gasochromic coloration of the irradiated films was observed by a measurement of optical transmittance with the expose of 1 % hydrogen. The extent of coloration level of the irradiated film with the fluence of ions/sm is 7.5 times lager than that of non-irradiated film. W 4 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 W. In the irradiated film with the fluence of ions/sm, it is estimated that 17 % and 4 % of the amount of W change into W and W, respectively. The improvement of the gasochromic coloration of the irradiated WO films relates to the increment of oxygen deficient tungstens induced by the irradiation.