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layersUmenyi, A. V.*; Hommi, Masashi*; Kawashiri, Shinya*; Shinagawa, Teruyoshi*; Miura, Kenta*; Hanaizumi, Osamu*; Yamamoto, Shunya; Inoue, Aichi; Yoshikawa, Masahito
Key Engineering Materials, 459, p.168 - 172, 2011/04
A new type of two-dimensional photonic crystal (2-D PhC) waveguide was designed using finite difference time domain method to operate at a wavelength of 1.55 
m applicable to optical fiber-communication systems. We estimated that a triangular-lattice 2-D PhC structure formed by air holes with a diameter of 465 nm and a period of 664 nm suit our purpose. To form a core of the waveguide, Si ions were implanted into a SiO layer by using a 400-kV ion implanter. The implantation energy was 80 keV and the implantation amount was 1
10
ions/cm
. The electron beam resist was spin-coated on a substrate and the designed pattern was written lithographically in the resist using Electron Beam. Atomic force microscope measurements revealed that the diameter and the period of air holes of the waveguide were 466 and 666 nm. These values were nearly equal to the designed ones. We thus succeeded in fabricating 2-D PhC waveguides in a Si-ion-implanted SiO layer.
Nagata, Shinji*; Fujita, Haruka*; Inoue, Aichi; Yamamoto, Shunya; Tsuchiya, Bun*; Shikama, Tatsuo*
Nuclear Instruments and Methods in Physics Research B, 268(19), p.3151 - 3154, 2010/10
Times Cited Count：3 Percentile：28.78(Instruments & Instrumentation)A tungsten tri-oxide (WO
) film covered with a thin catalyst layer is one of the candidates for hydrogen sensing devices that show a reversible coloration under hydrogen exposure. While the injection of the cations and/or the formation of the oxygen vacancies can be responsible for the coloration of the film, the mechanism of the gasochromic phenomenon is not fully understood. In the present work, the changes of the optical properties in the WO film by ion irradiation were investigated to clarify the relation between the coloration and oxygen vacancies. WO films of 300-500 nm thicknesses were deposited on SiO substrates by magnetron sputtering. Oxygen ions at energies between 200 and 800 keV were irradiated to the WO films. The optical absorption of the film was measured in the wavelengths between 190 and 1000 nm. The results show that the change of optical-absorption coefficient in WO films depends on both electronic and nuclear stopping powers.
Nagata, Shinji*; Katsui, Hirokazu*; Tsuchiya, Bun*; Inoue, Aichi; Yamamoto, Shunya; To, Kentaro; Shikama, Tatsuo*
Journal of Nuclear Materials, 386-388, p.1045 - 1048, 2009/04
Times Cited Count：14 Percentile：66.87(Materials Science, Multidisciplinary)no abstracts in English
Inoue, Aichi; Yamamoto, Shunya; Nagata, Shinji*; Yoshikawa, Masahito; Shikama, Tatsuo*
Nuclear Instruments and Methods in Physics Research B, 267(8-9), p.1480 - 1483, 2009/03
Times Cited Count：12 Percentile：62.2(Instruments & Instrumentation)We quantitatively studied the relation between hydrogen retention and optical properties induced by hydrogen ion implantation in tungsten trioxide (WO) films. Films of WO (300 nm) covered with tungsten metal layers (200 nm) were prepared on transparent SiO substrates by a reactive sputtering in Ar and O mixture. When H
ions were implanted into the samples at an acceleration voltage of 10 kV, the concentration of hydrogen retaining in the WO films increased up to 0.4 H/W in proportion to the fluence of H ions. The optical absorption coefficient at 750 nm of samples increased linearly by 3 m
with increasing the concentration of hydrogen implanted up to 0.1 H/W. And then, increased and saturated at 4 m with the increase of hydrogen concentration higher than 0.1 H/W. It was found that the hydrogen retention up to 0.1 H/W in tungsten trioxide layers can be monitored by measuring the optical absorbance.
Nagata, Shinji*; Sasase, Masato*; Takahiro, Katsumi*; Tsuchiya, Bun*; Inoue, Aichi; Yamamoto, Shunya; Shikama, Tatsuo*
Nuclear Instruments and Methods in Physics Research B, 267(8-9), p.1514 - 1517, 2009/03
Times Cited Count：9 Percentile：53.42(Instruments & Instrumentation)In this study, effects of the ion implantation on the phase transformation and nano-crystalline formation were examined in Zr-based metallic glasses. Samples were 2 mm thick plates and thin films of Zr
Al
Ni
Cu
prepared by casting in a copper mold and by using RF magnetron sputtering, respectively. Ions of Mg, P, Au and Bi with 100-500 keV were implanted in the samples up to 2 10
ions/cm at room temperature. Nano-crystalline structure was found in implanted samples by TEM observation, while the long-range order in the structure was not found for the X-ray diffraction patterns. The electron diffraction patterns indicated the formation of fcc-ZrCu in the P, Au, and Bi implanted region. Changes of the binding energy of the core level electron and valence band structure suggested the formation of Au-Zr or Au-Cu alloys in the Au ion implanted region.
Inoue, Aichi; Yamamoto, Shunya; Nagata, Shinji*; Yoshikawa, Masahito; Shikama, Tatsuo*
Transactions of the Materials Research Society of Japan, 33(4), p.1127 - 1130, 2008/12
We investigated effects of catalyst on gasochromic properties in tungsten oxide films. Amorphous WO films coated with Pd and Pt catalysts were prepared on SiO substrates by employing reactive RF magnetron sputtering. The field emission scanning electron microscope (FE-SEM) showed that particles with a dozes nm diameter of Pd and with a few nm of Pt grew on the surface at beginning of deposition. The continuous catalytic layers were observed with increasing the amounts of more than 2 nm for Pd and 0.2 nm for Pt catalysts, respectively. When the continuous layers formed on WO surface, the excellent gasochromic properties were obtained. The results indicated that Pt catalysts were suitable for high sensitive hydrogen sensors consisting of gasochromic WO films.
Inoue, Aichi; Yamamoto, Shunya; Nagata, Shinji*; Yoshikawa, Masahito; Shikama, Tatsuo*
Nuclear Instruments and Methods in Physics Research B, 266(15), p.3381 - 3386, 2008/08
Times Cited Count：5 Percentile：38.63(Instruments & Instrumentation)The effects of composition and structure on hydrogen incorporation property in tungsten oxide films were investigated. The tungsten oxide was deposited on carbon and SiO substrates to form films by varying the temperature from 30 to 600 
C using a reactive sputtering in argon and oxygen mixture. We obtained amorphous structure in the films deposited below 400 C and (0 1 0) oriented monoclinic WO in the films deposited beyond 400 C. Hydrogen concentration in the films increased from 0.1 to 0.7 H/W with changing the composition from WO
to WO. The hydrogen concentration in WO films decreased to 0.4 H/W with increasing the substrate temperature during deposition. The Raman spectra of the WO films revealed that decreasing of W
=O terminals was related to that of the hydrogen concentration. It was considered in detail that the incorporated hydrogen in tungsten oxide films was bonded at the end of W=O terminals.
films prepared by pulsed laser depositionYamamoto, Shunya; Inoue, Aichi; Yoshikawa, Masahito
Nuclear Instruments and Methods in Physics Research B, 266(5), p.802 - 806, 2008/03
Times Cited Count：30 Percentile：86.25(Instruments & Instrumentation)We investigated the structural and gasochromic properties of epitaxial tungsten trioxide (WO) thin films on the 
-AlO r-plane substrates, prepared by ArF excimer pulsed laser deposition under the controlled oxygen atmosphere. The deposited films were characterized by Rutherford backscattering spectroscopy (RBS)/channeling, X-ray diffraction and Raman spectroscopy. RBS and XRD results demonstrated that monoclinic WO(001) films were successfully grown on the -AlO substrates. The crystal quality was improved by increasing both the oxygen pressure and the substrate temperature. Gasochromic coloration in the WO films by exposure to diluted hydrogen gas was found to correlate with the crystal quality of the films. The gasochromic coloration was suppressed by the epitaxial growth of the films.
Inoue, Aichi; Yamamoto, Shunya; Nagata, Shinji*; Yoshikawa, Masahito; Shikama, Tatsuo*
Nuclear Instruments and Methods in Physics Research B, 266(2), p.301 - 307, 2008/01
Times Cited Count：14 Percentile：66.6(Instruments & Instrumentation)Changes in the composition and crystalline structure of gasochromic tungsten oxide films resulting from the incorporation of hydrogen were investigated. An uniaxial oriented films in the (0 1 0) plane of monoclinic WO were obtained by reactive RF magnetron sputtering at 600 C. The elastic recoil detection analysis for the films on glassy carbon revealed that the hydrogen impurity was uniformly distributed up to a concentration of 0.24 H/W. The Pd-coated films on SiO turned to blue when they were exposed to a mixture of Ar and 5% H gases. When the sample became colored, the hydrogen concentration in the film increased to 0.47 H/W and the crystalline structure of the film changed from monoclinic to tetragonal. These results indicated that the gasochromic coloration of the tungsten oxide films was accompanied by formation of hydrogen compounds called tungsten bronze (H
WO).
Nagata, Shinji*; Inoue, Aichi; Yamamoto, Shunya; Tsuchiya, Bun*; Takano, Katsuyoshi; To, Kentaro*; Shikama, Tatsuo*
Journal of Alloys and Compounds, 446-447, p.558 - 561, 2007/10
Times Cited Count：20 Percentile：69.78(Chemistry, Physical)The effect of the composition of non-stoichiometric WO films on the gasochromic coloration are investigated. The films are prepared by a reactive RF magnetron sputtering with varying oxygen partial pressure. To determine the quantitative composition of deposited films, Rutherford backscattering spectroscopy (RBS) and Elastic recoil detection (ERD) are employed. Gasochromic coloration of the films coated with Pd catalyst is examined by optical transmission in hydrogen gas. O/W atomic ratio of the films increases from 0.25 to 3.0 with increasing the oxygen partial pressure in the sputtering gas. H/W ratio increases up to 0.7 with increasing the O/W ration. As regards gasochromic coloration, the film with O/W atomic ratio of 3.0 shows superior coloration performance comparing with that of less than 3.0. Therefore, it is assumed that the good gasochromic coloration of tungsten oxide films is realized by near-stoichiometric WO. In addition, gasochromic coloration state, increasing of hydrogen concentration in WO films is observed. It indicates that gasochromic coloration of WO is relate to formation of HWO structure.
Takano, Katsuyoshi; Inoue, Aichi; Yamamoto, Shunya; Sugimoto, Masaki; Yoshikawa, Masahito; Nagata, Shinji*
Japanese Journal of Applied Physics, Part 1, 46(9B), p.6315 - 6318, 2007/09
Times Cited Count：11 Percentile：39.15(Physics, Applied)The amorphous, polycrystalline, and oriented films of the tungsten oxide were fabricated by sputtering deposition. It is found that each film has different roughness in the surface. The films with rough surface show fast coloration in 1% hydrogen. There is possibility that the gasochromic properties are improved effectively by the control of the surface morphology, and the films with large grains on the surface have better gasochromic coloration.
Takano, Katsuyoshi; Inoue, Aichi; Yamamoto, Shunya; Sugimoto, Masaki; Sugiyama, Akira; Yoshikawa, Masahito
Transactions of the Materials Research Society of Japan, 32(3), p.673 - 676, 2007/09
The deposition of tungsten oxide on the sheet of polyethylene terephthalate or polyvinylindene chloride was performed by sputtering method. It was found that the color of the sheets changes within few minuets to expose 0.1 vol.% diluted hydrogen, so as to be able to confirm the change by viewing. The sheets can be produced with low cost, and are useful as convenient sheet-type hydrogen sensors for the utilization of hydrogen in fuel cell as a clean energy source.
Nagata, Shinji*; Yamamoto, Shunya; Inoue, Aichi*; Tsuchiya, Bun*; To, Kentaro*; Shikama, Tatsuo*
Journal of Nuclear Materials, 367-370(2), p.1009 - 1013, 2007/08
Times Cited Count：32 Percentile：88.3(Materials Science, Multidisciplinary)no abstracts in English
Inoue, Aichi; Nagata, Shinji*; To, Kentaro*; Tsuchiya, Bun*; Yamamoto, Shunya; Shikama, Tatsuo*
Journal of Nuclear Materials, 367-370(2), p.1112 - 1116, 2007/08
Times Cited Count：5 Percentile：37.16(Materials Science, Multidisciplinary)The ion-induced luminescence behavior has been investigated for Cr-doped alumina (ruby, -AlO: 0.5 wt% Cr) under MeV region H and He ion irradiation. The initial yield of the R-line luminescence (693 nm) increased proportionally to the projected range of the incident H ions, indicating that the ion- induced luminescence efficiency for an H ion was constant with independence of the electronic energy loss. However, the He induced luminescence yield was not directly related to either the projected range or the incident energy, corresponding that the efficiency decreased with increasing the electronic energy loss. The reduction of R-line yields by the ion irradiation was adequately explained by decreasing R-line luminescence centers.
Yamamoto, Shunya; Takano, Katsuyoshi; Inoue, Aichi; Yoshikawa, Masahito
Nuclear Instruments and Methods in Physics Research B, 262(1-2), p.29 - 32, 2007/08
Times Cited Count：21 Percentile：79.51(Instruments & Instrumentation)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.
Nagata, Shinji*; Higashi, Seijiro*; Tsuchiya, Bun*; To, Kentaro*; Shikama, Tatsuo*; Takahiro, Katsumi*; Ozaki, Koichi*; Kawatsura, Kiyoshi*; Yamamoto, Shunya; Inoue, Aichi
Nuclear Instruments and Methods in Physics Research B, 257(1-2), p.420 - 423, 2007/04
Times Cited Count：16 Percentile：71.98(Instruments & Instrumentation)Structural modification and primary precipitates in the ZrAlNiCu alloy films (50-100 m thickness) caused by radiation with 300-500 keV H, Ag, Cu and Au ions has been studied. The results of XRD indicated that a metastable primary phase was formed in the alloy by the heat treatment after ion irradiation, but no difference was observed just after the ion irradiation at room temperature. Furthermore, higher incident Au ion fluence effectively suppressed thermal precipitation of the ZrNi type crystalline phase in the alloy. The deposited energy dependence of the precipitation behavior indicated an increase of the nucleation sites by the implanted metal atoms, simultaneously with a decrease of the growth rate by higher energy deposition density.
Takano, Katsuyoshi; Inoue, Aichi; Yamamoto, Shunya; Miyashita, Atsumi; Yoshikawa, Masahito
Transactions of the Materials Research Society of Japan, 32(1), p.159 - 162, 2007/03
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.
filmsInoue, Aichi; Yamamoto, Shunya; Nagata, Shinji*; Takano, Katsuyoshi; Yoshikawa, Masahito; Shikama, Tatsuo*
Transactions of the Materials Research Society of Japan, 32(1), p.107 - 110, 2007/03
We investigated the gasochromic coloration of amorphous tungsten oxide films having compositions between WO and WO
. The films were deposited on SiO or glassy carbon substrates by the reactive radio frequency (r. f.) magnetron sputtering with varying oxygen partial pressure. The oxygen and hydrogen concentration of the tungsten oxide films were determined using the Rutherford Backscattering Spectrometry (RBS) and the Elastic Recoil Detection Analysis (ERDA), respectively. The optical transmission was examined for the films coated with palladium catalysis during the exposure of diluted hydrogen gas. Superior gasochromic properties were obtained for the films consisting of tungsten trioxide WO. For the films with lower oxygen concentration than WO, the optical transmission hardly changed during the hydrogen exposure. A large concentration of hydrogen about 0.7 per a tungsten atom was found in the WO films. The hydrogen retention drastically decreased with a decrease of the oxygen concentration.
Yamamoto, Shunya; Takano, Katsuyoshi; Inoue, Aichi; Yoshikawa, Masahito
Transactions of the Materials Research Society of Japan, 32(1), p.171 - 174, 2007/03
The gasochromic materials have considerable promise as the optical gas sensors. Palladium oxide is known to exhibit optical absorbance changes due to the reduction reaction with hydrogen gas. However, the gasochromic performance of palladium oxide films is strongly influenced by preparation conditions, such as a heat-treatment temperature. We investigate the correlation between of oxidation temperature of Pd films and the gasochromic performance for hydrogen. Palladium oxide films are prepared by thermal oxidation of the Pd films at temperature ranging from 300 to 900C in air. The gasochromic performance of palladium oxide films coated with Pd catalyst was examined by optical transmission in 1% hydrogen with argon gas. The palladium oxide film, thermally oxidized at 600C in air, shows the good gasochromic performance. The results should lead to an optimization of preparation conditions to provide the gasochromic films used for the optical hydrogen sensors.
Takano, Katsuyoshi; Inoue, Aichi; Yamamoto, Shunya; Yoshikawa, Masahito
JAEA-Review 2006-042, JAEA Takasaki Annual Report 2005, P. 160, 2007/02
Gasochromic properties for hydrogen gas on tungsten oxide thin films have been investigated for an optical hydrogen gas sensors. The gasochromic properties are considered to relate to oxygen vacancies or defects in the tungsten oxide. In this study, it is tried to make oxygen vacancies or defects in the tungsten oxide thin films by ion beam irradiation, to investigate the relation between the amount of fluency and the gasochromic properties. The coloration for 1 % hydrogen was measured by time resolved optical spectroscopy with 630 nm light. The coloration is enhanced with the increasing the fluence, over 
ions/cm.
