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species at SiO/Si interfaces in Si dry oxidation; Comparison between p-Si(001) and n-Si(001) surfacesTsuda, Yasutaka; Yoshigoe, Akitaka; Ogawa, Shuichi*; Sakamoto, Tetsuya*; Yamamoto, Yoshiki*; Yamamoto, Yukio*; Takakuwa, Yuji*
Journal of Chemical Physics, 157(23), p.234705_1 - 234705_21, 2022/12
Times Cited Count：0 Percentile：0.01(Chemistry, Physical)Kimata, Tetsuya*; Kakitani, Kenta*; Yamamoto, Shunya*; Shimoyama, Iwao; Matsumura, Daiju; Iwase, Akihiro*; Mao, W.*; Kobayashi, Tomohiro*; Yamaki, Tetsuya*; Terai, Takayuki*
Physical Review Materials (Internet), 6(3), p.035801_1 - 035801_7, 2022/03
Times Cited Count：4 Percentile：66.71(Materials Science, Multidisciplinary)
Pt
Ga
Matsumoto, Yuji*; Haga, Yoshinori; Yamamoto, Etsuji; Takeuchi, Tetsuya*; Miyake, Atsushi*; Tokunaga, Masashi*
Journal of the Physical Society of Japan, 90(7), p.074707_1 - 074707_6, 2021/07
Times Cited Count：0 Percentile：0(Physics, Multidisciplinary)Sakai, Kenji; Oku, Takayuki; Okudaira, Takuya; Kai, Tetsuya; Harada, Masahide; Hiroi, Kosuke; Hayashida, Hirotoshi*; Kakurai, Kazuhisa*; Shimizu, Hirohiko*; Hirota, Katsuya*; et al.
JPS Conference Proceedings (Internet), 33, p.011116_1 - 011116_6, 2021/03
In neutron fundamental physics, study of correlation term 
of a neutron spin 
and a target nuclear spin 
is important because term interferes to parity non-conserving (PNC) and time reversal non-conserving terms. For this study, a xenon (Xe) is an interesting nucleus because it has been observed an enhancement of PNC effect around neutron resonance peaks, and polarizes up to 
by using a spin exchange optical pumping (SEOP) method. We would plan to develop a polarized Xe gas target with a compact in-situ SEOP system, and to study term by utilizing epithermal neutron beams supplied from a high intense pulsed spallation neutron source. As the first step, we attempted to measure neutron polarizing ability caused by term at a 9.6 eV s-wave resonance peak of 
Xe at BL10 in MLF, by detecting change 
of ratio between neutron transmissions with the polarized and unpolarized Xe target. After demonstrating that our apparatus could detect small change (
) of neutron transmissions caused by Doppler broadening effect, a signified value of has been obtained as preliminary results. For analyzing the obtained in detail, we are improving our nuclear magnetic resonance and electron paramagnetic resonance systems for evaluating Xe polarization independently of neutron beams.
irradiationOkazaki, Hiroyuki*; Kakitani, Kenta*; Kimata, Tetsuya*; Idesaki, Akira*; Koshikawa, Hiroshi*; Matsumura, Daiju; Yamamoto, Shunya*; Yamaki, Tetsuya*
Journal of Chemical Physics, 152(12), p.124708_1 - 124708_5, 2020/03
Times Cited Count：2 Percentile：13.07(Chemistry, Physical)
and Nb-doped SrTiO surfaces irradiated with swift heavy ionsKitamura, Akane; Ishikawa, Norito; Kondo, Keietsu; Yamamoto, Shunya*; Yamaki, Tetsuya*
Nuclear Instruments and Methods in Physics Research B, 460, p.175 - 179, 2019/12
Times Cited Count：3 Percentile：34.96(Instruments & Instrumentation)Irradiation at grazing incidence formed chains of multiple hillocks on the surface of strontium titanate (SrTiO) and titanium oxide (TiO). They were observed with an atomic force microscope (AFM), however, the AFM measurement gives resolution errors in a nanometer order due to the curvature of the probe tip. To prevent these errors, a field emission scanning electron microscope (FE-SEM) would be a better option for observation. In this study, we performed SEM observations for the chains of the multiple hillocks. Single crystals of SrTiO and TiO were irradiated with 200 MeV 
Xe
in the tandem accelerator at JAEA-Tokai. It was revealed that a lot of isolated hillocks were formed in a line on these surface. The diameter and the interval of those hillocks are discussed in comparison to AFM observation.
irradiated with swift heavy ionsKitamura, Akane; Ishikawa, Norito; Kondo, Keietsu; Fujimura, Yuki; Yamamoto, Shunya*; Yamaki, Tetsuya*
Transactions of the Materials Research Society of Japan, 44(3), p.85 - 88, 2019/06
Swift heavy ions can create nanosized hillocks on the surfaces of various ceramics. When these materials are irradiated with swift heavy ions at normal incidence, each ion impact results in the formation of a single hillock on the surfaces. In contrast, irradiation at grazing incidence forms chains of multiple hillocks on the surface, for example, for strontium titanate (SrTiO). So far, chains of multiple hillocks have been investigated using atomic force microscopy (AFM). It should be noted that AFM measurements involve systematic errors of several nanometers due to the finite size of the probe tip. Consequently, it is possible that the image of one hillock may merge with that of a neighboring hillock even if the two hillocks are well separated. In contrast to AFM, field-emission scanning electron microscopy (FE-SEM) is a useful technique for obtaining higher-resolution images. In this study, we observed multiple nanohillocks on the surfaces of SrTiO using FE-SEM. Crystals of SrTiO(100) and 0.05 wt% Nb-doped SrTiO(100) were irradiated with 350 MeV Xe ions, respectively, at grazing incidence, where the angle between the sample surface and the beam was less than 2
. On the SrTiO surface, a chain of periodic nanohillocks is created along the ion path. In contrast, black lines accompanied by hillocks are observed on the Nb-doped SrTiO surface.
Kakitani, Kenta*; Kimata, Tetsuya*; Yamaki, Tetsuya*; Yamamoto, Shunya*; Matsumura, Daiju; Taguchi, Tomitsugu*; Terai, Takayuki*
Radiation Physics and Chemistry, 153, p.152 - 155, 2018/12
Times Cited Count：2 Percentile：22.17(Chemistry, Physical)Kimata, Tetsuya*; Kato, Sho*; Yamaki, Tetsuya; Yamamoto, Shunya; Kobayashi, Tomohiro*; Terai, Takayuki*
Surface & Coatings Technology, 306(Part A), p.123 - 126, 2016/11
Times Cited Count：11 Percentile：48.31(Materials Science, Coatings & Films)Platinum (Pt) nanoparticle catalysts with oxygen reduction reaction (ORR) activity are required for practical applications of polymer electrolyte fuel cells. We prepared Pt nanoparticles on an Ar
-irradiated glassy carbon (GC) surface by a radio-frequency magnetron sputtering method to investigate the influence of the ion-induced lattice defects in GC on the ORR activity of the deposited Pt nanoparticles. Interestingly, the Pt nanoparticles on the irradiated surface exhibited ca. 2.5 times higher specific activity than those on the non-irradiated one. X-ray photoelectron spectroscopy suggested the interfacial Pt-C interaction occurring between the irradiated GC and Pt nanoparticles, which should be a reason for improvement of the ORR activity.
pre-concentration of Sr from large volume of freshwater sample using Powdex resinTomita, Jumpei; Yamamoto, Masayoshi*; Nozaki, Teo; Tanimura, Yoshihiko*; Oishi, Tetsuya
Journal of Environmental Radioactivity, 146, p.88 - 93, 2015/08
Times Cited Count：11 Percentile：36.46(Environmental Sciences)Zn
and UCoZnHirose, Yusuke*; Takeuchi, Tetsuya*; Honda, Fuminori*; Yoshiuchi, Shingo*; Hagiwara, Masayuki*; Yamamoto, Etsuji; Haga, Yoshinori; Settai, Rikio*; Onuki, Yoshichika
Journal of the Physical Society of Japan, 84(7), p.074704_1 - 074704_10, 2015/07
Times Cited Count：6 Percentile：46.01(Physics, Multidisciplinary)Horiguchi, Hironori*; Sato, Tatsuhiko; Kumada, Hiroaki*; Yamamoto, Tetsuya*; Sakae, Takeji*
Journal of Radiation Research, 56(2), p.382 - 390, 2015/03
Times Cited Count：21 Percentile：69.05(Biology)For evaluating the irradiation effect in tumors and surrounding normal tissues in BNCT, it is of great importance to estimate the relative biological effectiveness (RBE) for each dose component in the same framework. We have therefore established a new method for estimating the RBE of all BNCT dose components on the basis of the microdosimetric kinetic model. This method employs the probability densities of lineal energy, y, in a subcellular structure as the index for expressing RBE, which can be calculated using the microdosimetric function implemented in the particle transport simulation code PHITS. The accuracy of this method was tested by comparing the calculated RBE values with corresponding measured data in a water phantom irradiated with an epithermal neutron beam. The calculation technique developed in this study will be useful for biological dose estimation in the treatment planning of BNCT.
and EuAlNakamura, Ai*; Hiranaka, Yuichi*; Hedo, Masato*; Nakama, Takao*; Miura, Yasunao*; Tsutsumi, Hiroki*; Mori, Akinobu*; Ishida, Kazuhiro*; Mitamura, Katsuya*; Hirose, Yusuke*; et al.
JPS Conference Proceedings (Internet), 3, p.011012_1 - 011012_6, 2014/06
Zn (T: Co, Ir)Hirose, Yusuke*; Takeuchi, Tetsuya*; Yoshiuchi, Shingo*; Yamamoto, Etsuji; Haga, Yoshinori; Settai, Rikio*; Onuki, Yoshichika
JPS Conference Proceedings (Internet), 3, p.011056_1 - 011056_6, 2014/06
Yoshimura, Kimio; Koshikawa, Hiroshi; Yamaki, Tetsuya; Shishitani, Hideyuki*; Yamamoto, Kazuya*; Yamaguchi, Susumu*; Tanaka, Hirohisa*; Maekawa, Yasunari
Journal of the Electrochemical Society, 161(9), p.F889 - F893, 2014/06
Times Cited Count：20 Percentile：60.9(Electrochemistry)Graft-type anion-conducting electrolyte membranes (AEMs) with imidazolium cations on graft polymers were synthesized through radiation-induced graft polymerization of 
-vinylimidazole (NVIm) on poly(ethylene-co-tetrafluoroethylene) (ETFE) films, followed by -propylation and ion-exchange reactions. The -propylation proceeded quantitatively, whereas the ion-exchange reactions in 1 M KOH at 60C were accompanied by partial 
-elimination of the imidazolium cations(AEM2), which exhibited an ion-exchange capacity (IEC) of 0.85 mmol g
and ionic conductivity of 10 mS cm. AEM2 showed alkaline stability at 60C but it gradually degraded at 80C for ca. 150 h. The copolymer-type AEM (AEM3) with an IEC of 1.20 mmol g was prepared through the copolymerization of NVIm with styrene on ETFE films, followed by the same -propylation and ion-exchange reactions. AEM3 was shown higher alkaline durability in 1 M KOH at 80C. As a result, it exhibited higher conductivity (
10 mS cm) for 250 h. Therefore, alkylimidazolium cations in copolymer grafts are a promising anion conducting group for alkaline-durable AEMs. A maximum power density of 75 mW cm
is obtained for AEM3 in a direct hydrazine hydrate fuel cell.
Hasegawa, Noboru; Ochi, Yoshihiro; Kawachi, Tetsuya; Nishikino, Masaharu; Ishino, Masahiko; Imazono, Takashi; Kaihori, Takeshi; Morita, Toshimasa; Sasaki, Akira; Terakawa, Kota*; et al.
X-Ray Lasers 2012; Springer Proceedings in Physics, Vol.147, p.117 - 120, 2014/00
Times Cited Count：0 Percentile：0We have developed the femto-second laser pump and soft X-ray laser probe system in order to observe the dynamical processes of the femto-second laser ablation. By using this system, we succeed to obtain the temporal evolution of the soft X-ray reflectivity from the laser induced Pt surface. The results lead that the rate of decrease in the reflectivity of the probe beam has a non-linear relation with the pump laser fluence.
Kato, Sho; Yamaki, Tetsuya; Yamamoto, Shunya; Hakoda, Teruyuki; Kawaguchi, Kazuhiro; Kobayashi, Tomohiro*; Suzuki, Akihiro*; Terai, Takayuki*
Nuclear Instruments and Methods in Physics Research B, 314, p.149 - 152, 2013/11
Times Cited Count：2 Percentile：19.93(Instruments & Instrumentation)We implanted 100 keV W in unpolished GC substrates at nominal fluences up to 
ions/cm
. The implanted samples were electrochemically anodized in a NaOH aqueous solution to etch the surface layer. The analyses were performed by X-ray photoelectron spectroscopy (XPS), Rutherford backscattering spectrometry (RBS), and transmission electron microscopy (TEM). XPS W 4f spectra indicated the formation of carbides as reported previously. The electrochemical etching clearly increased the W concentration on the surface. According to the RBS results, half of the implanted W atoms were retained in the substrate, while the rest should escape to the etching solution. The cross-sectional TEM image revealed a uniform distribution of WC particles with a diameter of less than 10 nm just near the surface region.
Nakamura, Ai*; Hiranaka, Yuichi*; Hedo, Masato*; Nakama, Takao*; Miura, Yasunao*; Tsutsumi, Hiroki*; Mori, Akinobu*; Ishida, Kazuhiro*; Mitamura, Katsuya*; Hirose, Yusuke*; et al.
Journal of the Physical Society of Japan, 82(10), p.104703_1 - 104703_10, 2013/10
Times Cited Count：32 Percentile：81.08(Physics, Multidisciplinary)Nishikino, Masaharu; Hasegawa, Noboru; Ishino, Masahiko; Yamagiwa, Mitsuru; Kawachi, Tetsuya; Minami, Yasuo*; Terakawa, Kota*; Takei, Ryota*; Baba, Motoyoshi*; Suemoto, Toru; et al.
JAEA-Conf 2013-001, p.16 - 19, 2013/09
The dynamics of the femtosecond laser ablation is still not clear at the early stage. Several studies on the time-resolved imaging of femtosecond laser ablation process have been performed on various materials. In this study, we have demonstrated a pump and probe imaging of the metal surface morphology during the femtosecond laser ablation by using the laser-driven plasma induced soft X-ray laser (SXRL) as a probe beam. The pumping laser used for ablation was a Ti:Sapphire laser system based on chirped pulse amplification. The pump beam had a Gaussian profile and the focal spot size on the metal surface was about 70 micron at FWHM. The dependence for the pump laser fluence of the ablation surface expansion and the surface condition (roughness and density gradient) were observed from the soft X-ray interferogram and reflective image, respectively.
Onuki, Yoshichika; Settai, Rikio*; Sugiyama, Kiyohiro*; Takeuchi, Tetsuya*; Honda, Fuminori*; Haga, Yoshinori; Yamamoto, Etsuji; Matsuda, Tatsuma; Tateiwa, Naoyuki; Aoki, Dai*; et al.
Journal of the Korean Physical Society, 63(3), p.409 - 415, 2013/08
Times Cited Count：2 Percentile：20.37(Physics, Multidisciplinary)