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scattering length from 
photoproduction on the proton near the reaction thresholdIshikawa, Takatsugu*; Fujimura, Hisako*; Fukasawa, Hiroshi*; Hashimoto, Ryo*; He, Q.*; Honda, Yuki*; Hosaka, Atsushi; Iwata, Takahiro*; Kaida, Shun*; Kasagi, Jirota*; et al.
Physical Review C, 101(5), p.052201_1 - 052201_6, 2020/05
Times Cited Count：4 Percentile：39.70(Physics, Nuclear)
Mn
Si/Ge(111) heteroepitaxial interfacesNoguchi, Masaya*; Hirata, Tomoaki*; Kawakubo, Yuki*; Narumi, Kazumasa; Sakai, Seiji; Maeda, Yoshihito
Physica Status Solidi (C), 10(12), p.1732 - 1734, 2013/12
Times Cited Count：0 Percentile：0.00(Nanoscience & Nanotechnology)
(Mn
Fe)Si(111) epitaxially grown on Ge(111)Kawakubo, Yuki*; Noguchi, Masaya*; Hirata, Tomoaki*; Narumi, Kazumasa; Sakai, Seiji; Yamada, Shinya*; Hamaya, Kohei*; Miyao, Masanobu*; Maeda, Yoshihito
Physica Status Solidi (C), 10(12), p.1828 - 1831, 2013/12
Times Cited Count：0 Percentile：0.00(Nanoscience & Nanotechnology)
ionsNarumi, Kazumasa; Naramoto, Hiroshi*; Yamada, Keisuke; Chiba, Atsuya; Saito, Yuichi; Maeda, Yoshihito
JAEA-Review 2012-046, JAEA Takasaki Annual Report 2011, P. 166, 2013/01
no abstracts in English
-FeSi nanocrystals embedded in SiMaeda, Yoshihito; Nishimura, Kentaro*; Nakajima, Takahito*; Matsukura, Bui*; Narumi, Kazumasa; Sakai, Seiji
Physica Status Solidi (C), 9(10-11), p.1888 - 1891, 2012/10
Times Cited Count：3 Percentile：82.04(Materials Science, Multidisciplinary)We have systematically investigated photoluminescence (PL) properties of -phase nanocrystals which are formed by a phase transition from metastable 
-FeSi with a Fluorite structure to -FeSi, and succeeded in enhancement of the PL intensity in the optimum conditions of double annealing process. For the PL enhancement, the time of postannealing at 800
C is dominated by the time of the preannealing at 400 or 500C which is related to amount of the -phase. After discussing some possible factors, we speculate that the PL enhancement observed in this study may be attributed mainly to improvement of the interface condition between the nanocrystal and Si, because the crystallographic epitaxial relationship among the phases, Si(111)//(111)//(202)/(220) can be maintained during precipitation of the nanocrystal on Si(111).
-FeSi nanocrystalsMaeda, Yoshihito; Nishimura, Kentaro*; Nakajima, Takahito*; Matsukura, Bui*; Narumi, Kazumasa; Sakai, Seiji
Physica Status Solidi (C), 9(10-11), p.1884 - 1887, 2012/10
Times Cited Count：4 Percentile：87.53(Materials Science, Multidisciplinary)We report enhancement of intrinsic photoluminescence (PL) from -FeSi nanocrystals by doping carbon. In the appropriate dose of C
ion implantation into the average nanocrystal size of 14 nm, the PL intensity was enhanced by 260% and increase of the exciton binding energy of 1.8 meV in comparison with that of the non-doped nanocrystal. Furthermore, we found that there was a clear correlation between the PL enhancement and increase of the exciton binding energy. This important result suggests that carbon atoms doped in the silicide lattice may play as an isoelectronic trap and probably form bound excitons with stable states as predicted theoretically. We found a new mechanism of the PL enhancement for -FeSi nanocrystals.
ionsNarumi, Kazumasa; Naramoto, Hiroshi*; Yamada, Keisuke; Saito, Yuichi; Chiba, Atsuya; Takahashi, Yasuyuki*; Maeda, Yoshihito
JAEA-Review 2011-043, JAEA Takasaki Annual Report 2010, P. 155, 2012/01
no abstracts in English
Maeda, Yoshihito; Narumi, Kazumasa; Sakai, Seiji; Terai, Yoshikazu*; Hamaya, Kohei*; Sado, Taizo*; Miyao, Masanobu*
Thin Solid Films, 519(24), p.8461 - 8467, 2011/10
Times Cited Count：8 Percentile：34.92(Materials Science, Multidisciplinary)-Co filmsSakai, Seiji; Mitani, Seiji*; Sugai, Isamu; Takanashi, Koki; Matsumoto, Yoshihiro; Entani, Shiro; Naramoto, Hiroshi*; Avramov, P.; Maeda, Yoshihito
Physical Review B, 83(17), p.174422_1 - 174422_6, 2011/05
Times Cited Count：8 Percentile：34.92(Materials Science, Multidisciplinary)Entani, Shiro; Sakai, Seiji; Matsumoto, Yoshihiro; Naramoto, Hiroshi*; Hao, T.; Maeda, Yoshihito
Japanese Journal of Applied Physics, 50(4), p.04DN03_1 - 04DN03_5, 2011/04
Times Cited Count：4 Percentile：18.54(Physics, Applied)-FeSiMaeda, Yoshihito; Ichikawa, Takayuki*; Jonishi, Takafumi*; Narumi, Kazumasa
Physics Procedia, 11, p.83 - 86, 2011/00
Times Cited Count：0 Percentile：0.00(Optics)Entani, Shiro; Sakai, Seiji; Matsumoto, Yoshihiro; Naramoto, Hiroshi*; Hao, T.; Maeda, Yoshihito
Journal of Physical Chemistry C, 114(47), p.20042 - 20048, 2010/11
Times Cited Count：38 Percentile：70.43(Chemistry, Physical)-Co granular thin filmsSugai, Isamu*; Sakai, Seiji; Matsumoto, Yoshihiro; Naramoto, Hiroshi*; Mitani, Seiji*; Takanashi, Koki; Maeda, Yoshihito
Journal of Applied Physics, 108(6), p.063920_1 - 063920_7, 2010/09
Times Cited Count：8 Percentile：33.69(Physics, Applied)Hao, T.; Ono, Masao; Okayasu, Satoru; Sakai, Seiji; Narumi, Kazumasa; Hiraiwa, Yusuke*; Naramoto, Hiroshi*; Maeda, Yoshihito
Nuclear Instruments and Methods in Physics Research B, 268(11-12), p.1867 - 1870, 2010/06
Times Cited Count：6 Percentile：43.17(Instruments & Instrumentation) ionsTakahashi, Yasuyuki; Narumi, Kazumasa; Chiba, Atsuya; Saito, Yuichi; Yamada, Keisuke; Ishikawa, Norito; Sugai, Hiroyuki; Maeda, Yoshihito
EPL; A Letters Journal Exploring the Frontiers of Physics, 88(6), p.63001_1 - 63001_6, 2009/12
Times Cited Count：7 Percentile：44.97(Physics, Multidisciplinary)C and C
ions with 62.5-250 keV/u were incident on self-supporting amorphous carbon foils of 1.4-150 
g/cm
(70-7500 
). The secondary electrons emitted in the forward direction from a carbon foil were detected by a microchannel-plate detector placed at the exit side of the target. The vicinage effect on the secondary-electron yield was evaluated with the ratio of the secondary-electron yield R = /2, where and are the yields induced by the C and C ion with the same velocity, respectively. For the first time the disappearance of the vicinage effect on the secondary-electron yield from amorphous carbon foils bombarded with 62.5 keV/u C ions was observed for thick foils of 61-150 g/cm. The internuclear distance between the fragment ions at the exit of the target was evaluated by calculating trajectories of the fragment ions considering the Coulomb explosion. For a 62.5 keV/u C ion, we have determined the threshold internuclear distance where the vicinage effect disappears exits between 6 and 23 . It is expected that the vicinage effect on the energy loss (production process) in this velocity region disappears at the internuclear distance of a few . This result means that the transport or transmission process is important for the appearance of the vicinage effect. Moreover, the threshold internuclear distance depends on the velocity of the ion and increases as the velocity increases. The average charge of the ion increases with increase of the velocity of the ion. These mean that there is a possibility that a charge state plays an important role in the origin of the vicinage effect. In order to account for the experimental results, we discussed two models taking account of two kinds of potentials induced in response to the charge of the fragment ion in the transport process.
-Co films with giant tunnel magnetoresistanceMatsumoto, Yoshihiro; Sakai, Seiji; Takagi, Yasumasa*; Nakagawa, Takeshi*; Yokoyama, Toshihiko*; Shimada, Toshihiro*; Mitani, Seiji*; Naramoto, Hiroshi*; Maeda, Yoshihito
Chemical Physics Letters, 470(4-6), p.244 - 248, 2009/03
Times Cited Count：17 Percentile：50.22(Chemistry, Physical)Electronic and spin states of the codeposited C-Co films with large tunnel magnetoresistance (TMR) effect were investigated with the X-ray absorption and magnetic circular dichroism (MCD) spectroscopies. It is revealed that a C-Co compound generated in the C-Co films shows the clear MCD signal attributed to the spin-polarized Co 3d states hybridized with C 
orbitals. The magnetic response of these Co 3d-derived states agrees well with temperature dependence of the observed MR ratios of the granular C-Co films. This suggests the incorporation of the spin-polarized Co 3d-derived states of the C-Co compound into the observed TMR effect.
(C)
(x=3-8, n=1,2) somplex nanoclustersAvramov, P.*; Sakai, Seiji; Naramoto, Hiroshi*; Narumi, Kazumasa; Matsumoto, Yoshihiro; Maeda, Yoshihito
Journal of Physical Chemistry C, 112(36), p.13932 - 13936, 2008/08
Times Cited Count：6 Percentile：22.71(Chemistry, Physical)Atomic structure and spin states of a set of Co and Co(C) (x=3-8, n=1,2) clusters are studied using a sophisticated ab initio GGA calculations. It is shown that high-spin low-symmetry structure of free-standing Co clusters is determined by Jahn-Teller distortions. Formation of 
2, 2' or 1 coordination bonds between Co fragment and C molecules through carbon hexagons results in stable complex nanoclusters with nonmonotonic change of average spin momentum upon the number of cobalt atoms in the Co cores. The theoretical results are compared with corresponding experimental data.
Matsumoto, Yoshihiro; Sakai, Seiji; Naramoto, Hiroshi*; Hirao, Norie*; Baba, Yuji; Shimada, Toshihiro*; Sugai, Isamu; Takanashi, Koki; Maeda, Yoshihito
Materials Research Society Symposium Proceedings, Vol.1081 (Internet), 6 Pages, 2008/03
Recently, we have found the appearance of substantial MR ratio (80%) in a C/Co hybrid material. Such the MR ratio cannot be explained enough only by tunnel conduction through Co grains. Therefore, to obtain information about electronic structures of C/Co hybrid material is necessary. Absorption spectra of CCo are different from that of pristine C. In particular, peak intensity corresponding to 
(LUMO) 
C 1s excitation of CCo is clearly attenuated. In addition, C 1s photoelectron peak of CCo slightly shifted to lower binding energy compared to that of pristine C. These results indicate that 3d electron of Co transfers to orbital of C and new electronic states are formed in the C-Co compound. In fact, XPS spectra of valence excitation region also demonstrate the formation of hybrid orbital near the Fermi level due to the coupling of C and Co.
Sakai, Seiji; Sugai, Isamu; Mitani, Seiji*; Takanashi, Koki; Matsumoto, Yoshihiro; Naramoto, Hiroshi*; Avramov, P.; Okayasu, Satoru; Maeda, Yoshihito
Applied Physics Letters, 91(24), p.242104_1 - 242104_3, 2007/12
Times Cited Count：30 Percentile：71.18(Physics, Applied)
Si/Ge hybrid structures and its degradationMaeda, Yoshihito; Jonishi, Takafumi*; Narumi, Kazumasa; Ando, Yuichiro*; Ueda, Koji*; Kumano, Mamoru*; Sado, Taizo*; Miyao, Masanobu*
Applied Physics Letters, 91(17), p.171910_1 - 171910_3, 2007/10
Times Cited Count：31 Percentile：72.10(Physics, Applied)The axial orientation of molecular-beam-epitaxy (MBE)-grown FeSi(111)/Ge(111) hybrid structures was investigated by Rutherford backscattering spectroscopy. We confirmed that during MBE above 300C, the interdiffusion of Fe and Ge atoms results in a composition change and the epitaxial growth of FeGe in FeSi. Low-temperature (
200 C) MBE can realize fully ordered DO-FeSi with highly axial orientation [minimum yield (
)=2.2%]. Postannealing above 400 C results in a composition change and the degradation of axial orientation in the off-stoichiometric FeSi. The significance of stoichiometry with regard to thermal stability and the interfacial quality of FeSi(111)/Ge(111) hybrid structures was also discussed.
