Electronic structure of Li@C; Photoelectron spectroscopy of the Li@C[PF] salt and STM of the single Li@C molecules on Cu(111)

Yamada, Yoichi*; Kuklin, A. V.*; Sato, Sho*; Esaka, Fumitaka; Sumi, Naoya*; Zhang, C.*; Sasaki, Masahiro*; Kwon, E.*; Kasama, Yasuhiko*; Avramov, P. V.*; et al.

Carbon, 133, p.23 - 30, 2018/07

https://doi.org/10.1016/j.carbon.2018.02.106

We report first STM observation of the Li ion endohedral C, which is of a new class of endohedral fullerenes, prepared by means of evaporation of high-purity Li@C[PF] salt in ultra-high vacuum. Prior to the STM measurements, the electronic structure of Li@C in the Li@C[PF] salt was also precisely determined. In the salt, it is shown that Li and PF have nearly single positive and negative charge, respectively, and the C cage is nearly neutral, suggesting that Li@C in the salt retains its original electronic state.

X-ray photoelectron and X-ray absorption spectroscopic study on -FeSi thin films fabricated by ion beam sputter deposition

Esaka, Fumitaka; Yamamoto, Hiroyuki; Matsubayashi, Nobuyuki*; Yamada, Yoichi*; Sasase, Masato*; Yamaguchi, Kenji; Shamoto, Shinichi; Magara, Masaaki; Kimura, Takaumi

Applied Surface Science, 256(10), p.3155 - 3159, 2010/03

https://doi.org/10.1016/j.apsusc.2009.11.090

A combination of X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) using synchrotron radiation is applied to clarify surface chemical states of -FeSi films fabricated by an ion-beam sputtering deposition method. The differences in the chemical states of the films fabricated at substrate temperatures of 873, 973 and 1173 K are investigated.

Formation of isotopically enriched silicon film from fluorosilane produced by isotopically selective infrared multiphoton dissociation

Oba, Hironori; Suzuki, Hiroshi*; Esaka, Fumitaka; Taguchi, Tomitsugu; Yamada, Yoichi; Yamamoto, Hiroyuki; Sasase, Masato*; Yokoyama, Atsushi

Journal of the Vacuum Society of Japan, 52(6), p.292 - 295, 2009/07

no abstracts in English

Progress of the research and development on the geological disposal technology of HLW with aid of the industry/university collaboration system and fixed term researcher system

Yamada, Fumitaka; Sonobe, Hitoshi; Igarashi, Hiroshi

JAEA-Review 2007-061, 67 Pages, 2008/02

JAEA-Review-2007-061.pdf:8.39MB

In JAEA, various systems associated with the collaboration with industries and universities are enacted. These systems have been operated considering the needs of JAEA's program, industry and academia, resultantly contributed, for example, to basic research and the project development. Activities under these systems contain personal exchanges, the publication of the accomplishments and utilization of those, in R&D concerning geological disposal technology of HLW. These activities have progressed in PNC and JNC, through JAEA. The accomplishments from these systems have contributed to the advancement of the national program on the geological disposal of HLW. In this report, the progress of the R&D under these systems was investigated from the beginning of their operation. The contribution to the R&D on geological disposal technology of HLW was also studied. On the basis of these studies, the future utilization of the systems of the collaboration was also discussed.

Local neutron transmutation doping using isotopically enriched silicon film

Yamada, Yoichi; Yamamoto, Hiroyuki; Oba, Hironori; Sasase, Masato*; Esaka, Fumitaka; Yamaguchi, Kenji; Udono, Haruhiko*; Shamoto, Shinichi; Yokoyama, Atsushi; Hojo, Kiichi

Journal of Physics and Chemistry of Solids, 68(11), p.2204 - 2208, 2007/11

https://doi.org/10.1016/j.jpcs.2007.08.056

Si in natural Si has been widely used for a doping source, since Si can be transmuted into P by thermal neutron (Neutron Transmutation Doping, NTD). NTD of nanostructure fabricated from Si-enriched materials can serve as a controlled local doping method with tunable dopant concentration, which cannot be realized by conventional doping methods such as ion implantation. In the present study, Si-enriched thin film has been fabricated in order to demonstrate the local NTD. The Si-enriched film with thickness of 100 nm was deposited on the Si(100) substrate by plasma enhanced chemical vapor deposition using Si-enriched SiF as the source gases. The film contains 7.1 % of Si, which is twice higher than that of natural Si. Possible contaminant, fluorine, is lower than 0.6 at.% determined from X-ray photoelectron spectra. Nanostructure of films and changes of electronic properties by the neutron irradiation will also be discussed.

Vacuum-permeability test for estimation of loosened area at Kitanobe NATM drift

Yamada, Fumitaka*; Kita, Haruyuki*; Nakata, Masao*

PNC TJ7176 98-002, 135 Pages, 1998/03

PNC-TJ7176-98-002.pdf:4.33MB

None

Fabrication and estimation of Si-enriched thin films for local neutron transmutation doping

Yamada, Yoichi; Yamamoto, Hiroyuki; Oba, Hironori; Sasase, Masato*; Esaka, Fumitaka; Yamaguchi, Kenji; Udono, Haruhiko*; Shamoto, Shinichi; Yokoyama, Atsushi; Hojo, Kiichi

no journal, , 

Fabrication and estimation of Si-enriched thin films for local neutron transmutation doping has been attempted.

Homoepitaxy of -FeSi thin films on various oriented substrates by MBE

Ouchi, Shinji*; Wakaya, Ippei*; Udono, Haruhiko*; Yamada, Yoichi; Yamamoto, Hiroyuki; Esaka, Fumitaka

no journal, , 

Homoepitaxial formation of -FeSi thin films on various oriented substrates has been discussed.

Non-destructive analysis of Ge/Si interface; High energy X-ray photoelectron spectroscopy using synchrotron radiation

Yamamoto, Hiroyuki; Esaka, Fumitaka; Yamada, Yoichi; Sasase, Masato*

no journal, , 

Analyzing depth of XPS can be varied with the energy tunable excitation source, such as the synchrotron-radiation (SR), since the escape depth of the photoelectrons depends on their kinetic energy. In the present study, Ge thin films (2,4 nm) on two different Si substrates (hydrogen terminated, native oxide) has been analyzed to obtain depth profile of the thin film and buried interface of Ge/Si under the film with two different Si substrates. The XPS spectra clearly show the difference obtained from the varied analyzing depth. These results suggest that the SR-XPS can be applicable for non-destructive depth profile analysis of surface and buried interface.

Surface analysis on single-crystalline -FeSi

Mao, W.; Wakaya, Ippei*; Yamada, Yoichi; Esaka, Fumitaka; Yamamoto, Hiroyuki; Shamoto, Shinichi; Yamaguchi, Kenji; Udono, Haruhiko*

no journal, , 

Thin films of semiconducting -FeSi keep attracting considerable attentions for their promising applicability to the Si-based optoelectronics devices. Recently, large single-crystalline -FeSi has successfully been synthesized, providing a substrate for a well-defined homoepitaxy film. As a first step toward good homoepitaxy of -FeSi, we prepare and characterize low-index surfaces of -FeSi single crystal. Both LEED and STM reveal the absence of the long-ranged surface reconstruction for each face, which is favorable for the homoepitaxy on this substrate. On the other hand, STM suggests a presence of a significant amount of surface defects for each face, which should be improved in the next step. In addition to structural analysis, the stoichiometry of clean surfaces will be discussed on the basis of XPS and SIMS measurements.