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molecule adsorption on polar and 
-plane surfaces of GaNSumiya, Masatomo*; Sumita, Masato*; Asai, Yuya*; Tamura, Ryo*; Uedono, Akira*; Yoshigoe, Akitaka
Journal of Physical Chemistry C, 124(46), p.25282 - 25290, 2020/11
Times Cited Count：12 Percentile：48.76(Chemistry, Physical)The initial oxidation of different GaN surfaces [the polar Ga-face (+c) and N-face (-c) and the nonpolar (10
0) ()plane] under O molecular beam irradiation was studied by real-time synchrotron radiation X-ray photoelectron spectroscopy and DFT molecular dynamics calculation. The results predict that triplet O either dissociates or chemisorbs at the bridge position on the +c-surface, while on N-terminated -c-surface the O
2 molecule only undergoes dissociative chemisorption. On the -GaN surface, although the dissociation of O is dominant, the bond length and angle were found to fluctuate from those of O molecules adsorbed on the polar surfaces. The computational model including both the surface spin and polarity of GaN is useful for understanding the interface between GaN and oxide layers in metal-oxide electronic.
Ito, Kenji*; Oka, Toshitaka*; Kobayashi, Yoshinori*; Shirai, Yasuharu*; Wada, Kenichiro*; Matsumoto, Masataka*; Fujinami, Masanori*; Hirade, Tetsuya; Honda, Yoshihide*; Hosomi, Hiroyuki*; et al.
Materials Science Forum, 607, p.248 - 250, 2009/00
So far no standard procedure for the positron annihilation lifetime (PAL) technique has been established. A lack of the standards has led to difficulty in ensuring the equivalency and reliability of data from different laboratories. As a first, we conducted an interlaboratory comparison of PAL measurements for metal, polymer and silica glass with agreed procedures for data recording and analysis. The PAL data recorded at different laboratories were analyzed with a single lifetime component for the metal sample and with three components for the others, respectively. Based on the results of the reported positron and ortho-positronium lifetimes, the possible sources of the uncertainties in the PAL measurements are discussed. To reduce the effect of scattered 
rays, a lead shield was placed between the detectors. The uncertainty was significantly decreased, signifying that placing lead shields between the detectors effectively reduced the false signals due to the scattered rays.
Ito, Kenji*; Oka, Toshitaka*; Kobayashi, Yoshinori*; Shirai, Yasuharu*; Wada, Kenichiro*; Matsumoto, Masataka*; Fujinami, Masanori*; Hirade, Tetsuya; Honda, Yoshihide*; Hosomi, Hiroyuki*; et al.
Journal of Applied Physics, 104(2), p.026102_1 - 026102_3, 2008/07
Times Cited Count：50 Percentile：83.92(Physics, Applied)Interlaboratory comparison of positron annihilation lifetime measurements using synthetic fused silica and polycarbonate was conducted with the participation of 12 laboratories. By regulating procedures for the measurement and data analysis the uncertainties of the positron lifetimes obtained at different laboratories were significantly reduced in comparison with those reported in the past.
Oshima, Takeshi; Uedono, Akira*; Eryu, Osamu*; Lee, K. K.; Abe, Koji*; Ito, Hisayoshi; Nakashima, Kenshiro*
Materials Science Forum, 433-436, p.633 - 636, 2003/08
no abstracts in English
Abe, Hiroshi; Uchida, Hirohisa*; Azuma, Yorito*; Uedono, Akira*; Chen, Z. Q.*; Ito, Hisayoshi
Nuclear Instruments and Methods in Physics Research B, 206(1-4), p.224 - 227, 2003/05
Times Cited Count：21 Percentile：77.96(Instruments & Instrumentation)Palladium(Pd) is used for the purification of H gas and as a catalyst for the dissociation of H molecules. Therefore, much work has been made until now. Since low energy ion irradiation, i.e., ion implantation is quite useful for surface modification of materials, the hydrogen absorption properties of Pd is expected to be improved by ion irradiation. In this work, we aimed at investigating the effect of ion irradiation on the hydrogen absorption rate of Pd. Ion irradiation was made with H
, He and Ar in an acceleration energy rage from 30 to 350keV up to a dose of 1 x 10
/cm
. As a result, ion irradiated Pd sample was found to induce a higher absorption rate than that of the unirradiated one. The initial hydrogen results suggest that defects introduced in Pd by ion irradiation facilitate tha rate of nucleation and growth of hydride.
Oshima, Takeshi; Uedono, Akira*; Abe, Hiroshi; Chen, Z. Q.*; Ito, Hisayoshi; Yoshikawa, Masahito; Abe, Koji*; Eryu, Osamu*; Nakashima, Kenshiro*
Physica B; Condensed Matter, 308-310, p.652 - 655, 2001/12
Times Cited Count：6 Percentile：36.77(Physics, Condensed Matter)Co-implantation of Al(2E18/cm3) and C(1E18/cm3) into 6H-SiC and subsequent thermal annealing up to 1650 C werer carried out. Vacancy-type defects in the implanted layer were studied by monoenergetic positron beams. The mean size of vacancy-type defects in as-implanted samples is found to be close to the size of divacancy. Although vacancy clsters near a surface region were created by 1000 C-annealing, clustering is suppressed in a deep region.The mean size of vacancys decrease by annealing above 1000 C, and major vacancy defects annealed out after annealing at 1400 C. No significant difference in defect annealing between only Al- and co-implanted samles was observed.This result suggests that electrical activation of Al is enhanced by the site competition mechanism.
Abe, Hiroshi; Uedono, Akira*; Uchida, Hirohisa*; Komatsu, A.*; Okada, Sohei; Ito, Hisayoshi
Materials Science Forum, 363-365, p.156 - 158, 2001/05
no abstracts in English
-implanted 6H-SiC studied by monoenergetic positron beamsUedono, Akira*; Tanigawa, Shoichiro*; Oshima, Takeshi; Ito, Hisayoshi; Yoshikawa, Masahito; Nashiyama, Isamu; Frank, T.*; Pensl, G.*; Suzuki, Ryoichi*; Odaira, Toshiyuki*; et al.
Journal of Applied Physics, 87(9), p.4119 - 4125, 2000/05
Times Cited Count：12 Percentile：48.98(Physics, Applied)no abstracts in English
Oshima, Takeshi; Uedono, Akira*; Ito, Hisayoshi; Yoshikawa, Masahito; Kojima, Kazutoshi; Okada, Sohei; Nashiyama, Isamu; Abe, Koji*; Tanigawa, Shoichiro*; Frank, T.*; et al.
Materials Science Forum, 338-342, p.857 - 860, 2000/00
no abstracts in English
Oshima, Takeshi; Ito, Hisayoshi; Uedono, Akira*; Suzuki, Ryoichi*; Ishida, Yuki*; Takahashi, Tetsuo*; Yoshikawa, Masahito; Kojima, Kazutoshi; Odaira, Toshiyuki*; Nashiyama, Isamu; et al.
Denshi Gijutsu Sogo Kenkyujo Iho, 62(10-11), p.469 - 476, 1999/00
no abstracts in English
-implanted 6H-SiC studied by monoenergetic positron beamsUedono, Akira*; Tanigawa, Shoichiro*; Oshima, Takeshi; Ito, Hisayoshi; Aoki, Yasushi; Yoshikawa, Masahito; Nashiyama, Isamu
Journal of Applied Physics, 86(10), p.5392 - 5398, 1999/00
Times Cited Count：10 Percentile：45.75(Physics, Applied)no abstracts in English
Uedono, Akira*; ; Morishita, Norio; Ito, Hisayoshi; Tanigawa, Shoichiro*; Fujii, Satoshi*;
Journal of Physics; Condensed Matter, 11(25), p.4925 - 4934, 1999/00
Times Cited Count：12 Percentile：56.55(Physics, Condensed Matter)no abstracts in English
Uedono, Akira*; Fujii, Satoshi*; Morishita, Norio; Ito, Hisayoshi; Tanigawa, Shoichiro*;
Journal of Physics; Condensed Matter, 11(20), p.4109 - 4122, 1999/00
Times Cited Count：9 Percentile：48.31(Physics, Condensed Matter)no abstracts in English
Suzuki, Ryoichi*; ; Uedono, Akira*; Y.K.Cho*; Yoshida, Sadafumi*; Ishida, Yuki*; Oshima, Takeshi; Ito, Hisayoshi; ; Mikado, Tomohisa*; et al.
Japanese Journal of Applied Physics, Part 1, 37(8), p.4636 - 4643, 1998/08
Times Cited Count：28 Percentile：74.20(Physics, Applied)no abstracts in English
-implanted 6H-SiC using monoenergetic positron beamsUedono, Akira*; Oshima, Takeshi; Ito, Hisayoshi; Suzuki, Ryoichi*; ; Tanigawa, Shoichiro*; Aoki, Yasushi; Yoshikawa, Masahito; Nashiyama, Isamu; Mikado, Tomohisa*
Japanese Journal of Applied Physics, Part 1, 37(5A), p.2422 - 2429, 1998/05
Times Cited Count：13 Percentile：53.31(Physics, Applied)no abstracts in English
Oshima, Takeshi; Uedono, Akira*; Abe, Koji*; Ito, Hisayoshi; Aoki, Yasushi; Yoshikawa, Masahito; Tanigawa, Shoichiro*; Nashiyama, Isamu
Applied Physics A, 67(4), p.407 - 412, 1998/00
Times Cited Count：28 Percentile：73.33(Materials Science, Multidisciplinary)no abstracts in English
Oshima, Takeshi; Uedono, Akira*; Ito, Hisayoshi; Abe, Koji*; Suzuki, Ryoichi*; ; Aoki, Yasushi; Tanigawa, Shoichiro*; Yoshikawa, Masahito; Mikado, Tomohisa*; et al.
Mater. Sci. Forum, 264-268, p.745 - 748, 1998/00
no abstracts in English
Ito, Hisayoshi; Oshima, Takeshi; Aoki, Yasushi; Abe, Koji*; Yoshikawa, Masahito; Nashiyama, Isamu; Okumura, Hajime*; Yoshida, Sadafumi*; Uedono, Akira*; Tanigawa, Shoichiro*
Journal of Applied Physics, 82(11), p.5339 - 5347, 1997/12
Times Cited Count：13 Percentile：57.30(Physics, Applied)no abstracts in English
Uedono, Akira*; Ito, Hisayoshi; Oshima, Takeshi; Suzuki, Ryoichi*; ; Tanigawa, Shoichiro*; Aoki, Yasushi; Yoshikawa, Masahito; Nashiyama, Isamu; Mikado, Tomohisa*; et al.
Japanese Journal of Applied Physics, Part 1, 36(11), p.6650 - 6660, 1997/11
Times Cited Count：16 Percentile：63.06(Physics, Applied)no abstracts in English
Ito, Hisayoshi; Uedono, Akira*; Oshima, Takeshi; Aoki, Yasushi; Yoshikawa, Masahito; Nashiyama, Isamu; Tanigawa, Shoichiro*; Okumura, Hajime*; Yoshida, Sadafumi*
Applied Physics A, 65(3), p.315 - 323, 1997/00
Times Cited Count：16 Percentile：63.06(Materials Science, Multidisciplinary)no abstracts in English
