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Journal Articles

Electronic structure of Li$$^{+}$$@C$$_{60}$$; Photoelectron spectroscopy of the Li$$^{+}$$@C$$_{60}$$[PF$$_{6}$$$$^{-}$$] salt and STM of the single Li$$^{+}$$@C$$_{60}$$ 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

 Times Cited Count:13 Percentile:55.55(Chemistry, Physical)

We report first STM observation of the Li$$^{+}$$ ion endohedral C$$_{60}$$, which is of a new class of endohedral fullerenes, prepared by means of evaporation of high-purity Li$$^{+}$$@C$$_{60}$$[PF$$_{6}$$$$^{-}$$] salt in ultra-high vacuum. Prior to the STM measurements, the electronic structure of Li$$^{+}$$@C$$_{60}$$ in the Li$$^{+}$$@C$$_{60}$$[PF$$_{6}$$$$^{-}$$] salt was also precisely determined. In the salt, it is shown that Li and PF$$_{6}$$ have nearly single positive and negative charge, respectively, and the C$$_{60}$$ cage is nearly neutral, suggesting that Li$$^{+}$$@C$$_{60}$$ in the salt retains its original electronic state.

Journal Articles

Surface analysis of single-crystalline $$beta$$-FeSi$$_2$$

Yamada, Yoichi*; Mao, W.*; Asaoka, Hidehito; Yamamoto, Hiroyuki; Esaka, Fumitaka; Udono, Haruhiko*; Tsuru, Tomohito

Physics Procedia, 11, p.67 - 70, 2011/02

 Times Cited Count:3 Percentile:82.27

Clean surfaces of the single crystalline $$beta$$-FeSi$$_2$$ have been prepared and investigated. From XPS (X-ray Photoelectron Spectroscopy) measurements of the surface oxide, it is found that the surface Si is mainly oxidized while Fe isn't. After removing the surface oxide, clean surface can be obtained showing reasonable structure in LEED (Low-Energy Electron Diffraction) and STM (Scanning Tunneling Microscope). No drastic surface reconstruction is found reflecting strong Fe-Si bond. DFT (Density Functional Theory) calculation suggests the spin polarized surface DOS (Density Of State) when Fe comes at the surface.

Journal Articles

X-ray photoelectron and X-ray absorption spectroscopic study on $$beta$$-FeSi$$_{2}$$ 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

 Times Cited Count:16 Percentile:56.97(Chemistry, Physical)

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 $$beta$$-FeSi$$_{2}$$ 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.

Journal Articles

Characterization of ablation plasma from h-BN by excimer laser irradiation

Oba, Hironori; Saeki, Morihisa; Esaka, Fumitaka; Yamada, Yoichi; Yamamoto, Hiroyuki; Yokoyama, Atsushi

Journal of the Vacuum Society of Japan, 52(6), p.369 - 371, 2009/07

no abstracts in English

Journal Articles

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

JAEA Reports

Study on a collapse mechanism of a junction between greatly deeper shaft and horizontal drifts (Contract research)

Kurosaki, Yukio*; Yamachi, Hiroshi*; Katsunuma, Yoshio*; Nakata, Masao*; Kuwahara, Hideki*; Yamada, Fumitaka*; Matsushita, Kiyoshi*; Sato, Toshinori*

JAEA-Research 2008-048, 274 Pages, 2008/03

JAEA-Research-2008-048.pdf:10.93MB

A junction space between a super deep shaft and horizontal drifts forms a 3-dimensional geo-structure, which would take a complicated mechanical behavior during a junction excavation. However, a quantitative design method for a deep junction has not yet established. In order to examine a collapse mechanism of super deep shaft junction, we have conducted literature surveys and interview studies concerned with a collapses. Considering the results of investigations with reviews of intellectuals, the collapse mechanism depends on both a construction procedure of shaft junction and a geological condition. On the other hand, where a deep junction intersects faults and/or fractures with a large angle, a collapse called taka-nuke may occur and a numerical studies that can simulate a practical rock mass behavior around a shaft junction should be carry out. We demonstrate finite difference method is most adequate for these simulations with intellectual review.

JAEA Reports

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.

Journal Articles

Non-destructive depth profile analysis for surface and buried interface of Ge thin film on Si substrate by high-energy synchrotron radiation X-ray photoelectron spectroscopy

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

Journal of Physics; Conference Series, 100, p.012044_1 - 012044_4, 2008/00

 Times Cited Count:6 Percentile:88.24

Non-destructive depth profile analysis with better depth resolution is required for the characterization of nano-materials. X-ray photoelectron spectroscopy (XPS) is the typically non-destructive analysis, however, XPS with fixed excitation energy source cannot provide depth profile without additional technique. On the other hand, 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.

Journal Articles

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

 Times Cited Count:6 Percentile:31.38(Chemistry, Multidisciplinary)

$$^{30}$$Si in natural Si has been widely used for a doping source, since $$^{30}$$Si can be transmuted into $$^{31}$$P by thermal neutron (Neutron Transmutation Doping, NTD). NTD of nanostructure fabricated from $$^{30}$$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, $$^{30}$$Si-enriched thin film has been fabricated in order to demonstrate the local NTD. The $$^{30}$$Si-enriched film with thickness of 100 nm was deposited on the Si(100) substrate by plasma enhanced chemical vapor deposition using $$^{30}$$Si-enriched SiF$$_{4}$$ as the source gases. The film contains 7.1 % of $$^{30}$$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.

Journal Articles

Hydrogen production and morphological change of chrysotile asbestos in the radiolysis of aqueous solutions

Aoyagi, Noboru; Nagaishi, Ryuji; Esaka, Fumitaka; Yamada, Reiji

Chemistry Letters, 36(7), p.890 - 891, 2007/07

 Times Cited Count:0 Percentile:0(Chemistry, Multidisciplinary)

A high yield of H$$_{2}$$ gas was unprecedentedly produced due to the radiolysis of water containing asbestos while the morphology of them turned fibrous bundles into non-fibrous particles in 0.40 M H$$_{2}$$SO$$_{4}$$ solution over 2.0 MGy dose of irradiation. In conclusion, irradiation against asbestos in solutions can promote the hydrogen gas production and cause the morphological change of chrysotile without providing heat or chemicals.

JAEA Reports

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

Oral presentation

Study on excavation response at the connection part of deep shaft and gallery

Yamada, Fumitaka*; Yamachi, Hiroshi*; Sato, Toshinori; Funatsu, Takahiro*; Shimizu, Norikazu*

no journal, , 

no abstracts in English

Oral presentation

Study on numerical analysis for stability mechanism of rock mass around the shaft excavated by short-step shaft-sinking method

Yamachi, Hiroshi*; Yamada, Fumitaka*; Sato, Toshinori; Funatsu, Takahiro*; Shimizu, Norikazu*

no journal, , 

no abstracts in English

Oral presentation

Fabrication of $$^{30}$$Si-enriched thin film 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, , 

$$^{30}$$Si in natural Si has been widely used for a doping source, since $$^{30}$$Si can be transmuted into $$^{31}$$P by thermal neutron (Neutron Transmutation Doping, NTD). NTD of nanostructure fabricated from $$^{30}$$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, $$^{30}$$Si-enriched thin film has been fabricated in order to demonstrate the local NTD. The $$^{30}$$Si-enriched film with thickness of 100 nm was deposited on the Si(100) substrate by plasma enhanced chemical vapor deposition using $$^{30}$$Si-enriched SiF$$_{4}$$ as the source gases. The film contains 7.1 % of $$^{30}$$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.

Oral presentation

Promoted reaction of hydrogen gas generation and deformed morphology of chrysotile in aqueous solutions under irradiation

Aoyagi, Noboru; Nagaishi, Ryuji; Esaka, Fumitaka; Yamada, Reiji

no journal, , 

Interfacial reaction on chrysotile in acidic aqueous solutions which ispromoted by irradiation of $$^{60}$$Co $$gamma$$-ray or electron beam was studied by analyzing the production of hydrogen gas and morphological alteration of fibril structure. The amount of generated hydrogen gas was proportional to the dose of irradiation and larger than the other particles such as alumina or silica known as a reactive surface donor for radicals. An expedited reaction in which chrysotile fibrous structure fell apart and come into particles was found more in SEM-EDX measurementwith increasing the concentrations of sulfuric acid as 0.2M, 0.4M, 0.8M and 2.0M.

Oral presentation

$$^{30}$$Si-enriched thin film 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, , 

$$^{30}$$Si in natural Si has been widely used for a doping source, since $$^{30}$$Si can be transmuted into $$^{31}$$P by thermal neutron (Neutron Transmutation Doping, NTD). In the present study, $$^{30}$$Si-enriched thin film has been fabricated in order to demonstrate the local NTD. The $$^{30}$$Si-enriched film with thickness of 100 nm was deposited on the Si(100) substrate by plasma enhanced chemical vapor deposition using $$^{30}$$Si-enriched SiF$$_{4}$$ as the source gases. Nanostructure of films and changes of electronic properties by the neutron irradiation will be discussed.

Oral presentation

$$^{30}$$Si-enriched thin film 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, , 

$$^{30}$$Si in natural Si has been widely used for a doping source, since $$^{30}$$Si can be transmuted into $$^{31}$$P by thermal neutron (Neutron Transmutation Doping, NTD). In the present study, $$^{30}$$Si-enriched thin film has been fabricated in order to demonstrate the local NTD. The $$^{30}$$Si-enriched film with thickness of 100 nm was deposited on the Si(100) substrate by plasma enhanced chemical vapor deposition using $$^{30}$$Si-enriched SiF$$_{4}$$ as the source gases. Nanostructure of films and changes of electronic properties by the neutron irradiation will be discussed.

Oral presentation

Structure of the a-SiC film prepared by reactive Pulsed Laser Deposition (PLD)

Saeki, Morihisa; Oba, Hironori; Yamada, Yoichi; Yamamoto, Hiroyuki; Esaka, Fumitaka; Yokoyama, Atsushi

no journal, , 

no abstracts in English

Oral presentation

Fabrication and estimation of $$^{30}$$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 $$^{30}$$Si-enriched thin films for local neutron transmutation doping has been attempted.

Oral presentation

Promoted reaction of hydrogen gas generation and deformed morphology of chrysotile in aqueous solutions under irradiation

Aoyagi, Noboru; Nagaishi, Ryuji; Esaka, Fumitaka; Yamada, Reiji

no journal, , 

Interfacial reaction on chrysotile in acidic aqueous solutions which is promoted by irradiation of $$^{60}$$Co $$gamma$$-ray or electron beam was studied by analyzing the production of hydrogen gas and morphological alteration offibril structure. The amount of generated hydrogen gas was proportional to the dose of irradiation and larger than the other particles such as alumina or silica known as a reactive surface donor for radicals. An expedited reaction in which chrysotile fibrous structure fell apart and come into particles was found more in SEM-EDX measurement with increasing the concentrations of sulfuric acid as 0.2M, 0.4M, 0.8M and 2.0M.

33 (Records 1-20 displayed on this page)