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Journal Articles

Analysis of bonding structure of ultrathin films of oligothiophene molecules grown on passivated silicon surfaces

Toyoshima, Hiroaki*; Hiraga, Kenta*; Ono, Shinya*; Tanaka, Masatoshi*; Ozawa, Kenichi*; Mase, Kazuhiko*; Hirao, Norie; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Baba, Yuji

Photon Factory Activity Report 2011, Part B, P. 102, 2012/00

The knowledge of the interaction between organic molecules and semiconductor surfaces plays an important role in adapting organic semiconductors into the semiconductor technology. In the present study, the process of $$alpha$$-sexithiophene ($$alpha$$-6T) thin layer formation on passivated silicon (Si) surfaces has been investigated in-situ by means of PES, angle-depended NEXAFS (near-edge X-ray absorption fine-structure), SDRS, and RDS. For water-adsorbed Si(001), it was found that the majority of $$alpha$$-6T molecules are standing on the substrate. Above 3 nm, most of molecules are standing and constitute well ordered islands or films. For ethylene adsorbed Si(001) on the contrary, some of $$alpha$$-6T molecules are flat-lying, resulting in less prominent orientation. Thus, the orientation of molecules depends on the method of passivation, which opens the possibility of controlling the molecular orientation by the surface modification.

Journal Articles

Performance of the H$$_{p}$$(10) and H$$_{p}$$(0.07) measurable electronic pocket dosimeter for $$gamma$$- and $$beta$$-rays

Takahashi, Masa; Sekiguchi, Masato; Miyauchi, Hideaki; Tachibana, Haruo; Yoshizawa, Michio; Kato, Toru*; Yamaguchi, Akihito*

Journal of Nuclear Science and Technology, 45(Suppl.5), p.225 - 228, 2008/06

 Times Cited Count:5 Percentile:36.71(Nuclear Science & Technology)

Journal Articles

Statistics of individual doses of JAERI for the past 48 Years

Sekiguchi, Masato; Takahashi, Masa; Miyauchi, Hideaki; Tachibana, Haruo; Komuro, Yuji*; Nemoto, Kiyoko*; Okawa, Ikuko*; Yoshizawa, Michio

Proceedings of 2nd Asian and Oceanic Congress Radiological Protection (AOCRP-2) (CD-ROM), p.114 - 117, 2006/10

In the Japan Atomic Energy Research Institute (JAERI), which was merged with the Japan Nuclear Cycle Development Institute into the Japan Atomic Energy Agency in 2005, individual monitoring and dose record keeping for radiation workers have been conducted since 1957. This report outlines the statistics of the number of radiation workers and individual doses, such as annual collective doses, annual average doses, the maximum doses and dose distributions, over the past 48 years from 1957 to 2005. Individual doses were increased due to the augment of trouble and maintenance of new experimental facilities in 1960's. The collective doses and annual average doses in 1960's exceeded 1,200 man-mSv and 0.4mSv, respectively, in some years. Then, consecutive dose reduction efforts made the collective dose significantly decrease to less than 400 man-mSv ($$sim$$1/3 of the highest) and the average dose to $$sim$$0.04 mSv ($$sim$$1/10 of the highest). The collective doses in recent years keep almost constant even though radiation works increase in some high-contaminated hot laboratories for the decontamination and maintenance of experimental equipments. It was found from the analysis of cumulative distributions that there was a specific work-group exposed to significantly high dose compared with other workers.

JAEA Reports

Statistics of individual doses of JAERI for the past 48 years

Shiraishi, Akemi; Sekiguchi, Masato; Tachibana, Haruo; Yoshizawa, Michio; Komuro, Yuji*; Nemoto, Kiyoko*; Okawa, Ikuko*

JAEA-Data/Code 2006-014, 36 Pages, 2006/06

JAEA-Data-Code-2006-014.pdf:2.46MB

In Japan Atomic Energy Research Institute (JAERI), individual monitoring and dose data recording for radiation workers have been conducted since 1957, the next year of which JAERI was established. This report compiles the statistics of individual doses, such as average doses, collective doses, the number of radiation workers and dose distributions, over the past 48 years from 1957 to 2005, when JAERI merged with Japan Nuclear Cycle Development Institute into Japan Atomic Energy Agency. Transition of the statistics showed the history of radiation works in JAERI and many efforts for dose reduction based on the ALARA principle recommended by ICRP. In addition, it was found from the analysis of cumulative distributions that, in recent years, there was a specific work-group exposed to significantly high dose compared with other workers.

Journal Articles

Lung counting for $$^{241}$$Am in the lung

Kinase, Sakae; Oi, Yoshihiro; Sekiguchi, Masato

Radioisotopes, 52(8), p.378 - 382, 2003/08

no abstracts in English

Oral presentation

Statistics of individual doses of JEARI for the past 48 years

Shiraishi, Akemi; Sekiguchi, Masato; Tachibana, Haruo; Yoshizawa, Michio; Komuro, Yuji*; Nemoto, Kiyoko*; Okawa, Ikuko*

no journal, , 

no abstracts in English

Oral presentation

Applicability of electronic pocket dosimeter in $$gamma$$-beta mixed fields

Takahashi, Masa; Sekiguchi, Masato; Tachibana, Haruo; Hoshi, Shintaro; Yoshizawa, Michio; Kato, Toru*; Yamaguchi, Akihito*

no journal, , 

no abstracts in English

Oral presentation

Operation of computerized radiation work passport system

Miyauchi, Hideaki; Sekiguchi, Masato; Takahashi, Masa; Yasuda, Takayuki; Tachibana, Haruo; Yoshizawa, Michio

no journal, , 

no abstracts in English

Oral presentation

The Structure of $$alpha$$-sexithiophene ultra-thin films on passivated Si(001) surfaces

Hiraga, Kenta*; Toyoshima, Hiroaki*; Ono, Shinya*; Hirao, Norie; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Baba, Yuji; Mukai, Kozo*; Yoshinobu, Jun*; Tanaka, Masatoshi*

no journal, , 

It is important to control orientation structure and electric property at the interface between organic semiconductor molecule and surfaces of semiconductor substrates in order for the development of commercial base organic transistors and solar cells. In the present work, we have investigated the surface reflection spectroscopy (RDS, SRDS), S-1s angle resolved near-edge X-ray absorption fine-structure (NEXAFS), and UPS for $$alpha$$-sexithiophene ($$alpha$$-6T) ultra-thin films with a variety of thickness from 0.25 to 1.0 nm. The results of RDS and SDRS, and NEXAFS gave the information on orientation structure of the $$alpha$$-6T molecules. In contrast, UPS gave the uniformity of the thin films. We report on how orientation structures and condensed structures are changed depending on the method of passivation and the film thickness.

Oral presentation

Structure of $$alpha$$-sexithiophene thin films grown on semiconductor surface studied by near-edge X-ray absorption fine structure

Hiraga, Kenta*; Toyoshima, Hiroaki*; Nakajima, Junki*; Tanaka, Hiroya*; Ono, Shinya*; Tanaka, Masatoshi*; Sekiguchi, Tetsuhiro; Hirao, Norie; Shimoyama, Iwao; Baba, Yuji

no journal, , 

It is important to investigate structure of organic thin films grown on semiconductor surfaces for fabrication of the organic semiconductors.

Oral presentation

Analysis of oligothiophene thin films grown on semiconductor surfaces

Kodama, Hiraku*; Hiraga, Kenta*; Ono, Shinya*; Sekiguchi, Tetsuhiro; Baba, Yuji; Tanaka, Masatoshi*

no journal, , 

The electronic property of organic semiconductor depends strongly on the interfacial structure between organic molecule and the substrate. We have investigated the structure of a-sexithiophene ($$alpha$$-6T) molecule thin films grown on semiconductor surfaces including SiO$$_{2}$$, GaSe, and WSe$$_{2}$$, using NEXAFS spectroscopy. Using polarized X-ray, orientation structure of a-6T molecules can be precisely determined. It was found that the orientation structure depend on the substrates. $$alpha$$-6T on GaSe is oriented with long molecular axis being flat-lying parallel to the surface. On the hand, $$alpha$$-6T on SiO$$_{2}$$ is up-right standing. The tendency of orientation direction change was interpreted in terms of the interfacial interaction between $$alpha$$-6T molecule and the substrates.

Oral presentation

Analysis of the structure of $$alpha$$-sexithiophene thin films grown on layered materials

Kodama, Hiraku*; Hiraga, Kenta*; Ono, Shinya*; Sekiguchi, Tetsuhiro; Baba, Yuji; Tanaka, Masatoshi*

no journal, , 

Orientation of organic semiconductor has been important issue because of its strong anisotropy of the electronic property. We have investigated the orientation effect of $$alpha$$-sexithiphene (6T) molecule deposited on WSe$$_{2}$$ or GaSe substrate, which is layered semiconductor material. Thickness was controlled by regulating deposition rate and time. Orientation angle was analyzed by angle-resolved NEXAFS spectroscopy. The results show that molecular orientation angle depend not only on the substrate but also the thickness. Tilt angle is thought to be determined by the energy stability due to the commensurate at the interface as well as the molecule-substrate interaction.

Oral presentation

Evaluating stability of the solution of the problem to determine the size distributions of particles using Mie scattering theory

Sekiguchi, Kentaro; Jinno, Satoshi*; Tanaka, Hirotaka*; Ichinose, Kosuke*; Kanasaki, Masato*; Sakaki, Hironao; Kondo, Kiminori; Matsui, Ryutaro; Kishimoto, Yasuaki; Fukuda, Yuji

no journal, , 

The size of clusters, produced in an expansion of supercooled, high pressure molecular hydrogen gas into vacuum, has been evaluated by measuring the angular distribution of scattered light. The data are analyzed based on the Mie scattering theory. Here obtaining the size distribution of clusters reduces to solving the inverse problem. Since the scattering coefficient is a matrix, it is necessary to determine the inverse matrix. However, if you solve this equation straightforward, the size distribution often oscillates to the negative values and becomes the discrete distribution by external factors such as noise included in the measurement results. Therefore, we have built an algorithm to determine the size distribution in combination with a non-negative least square method and a Phillips-Twomey method to obtain a smooth solution.

Oral presentation

Studies on the size distribution of submicron size hydrogen clusters using the Mie theory

Tanaka, Hirotaka; Jinno, Satoshi*; Kanasaki, Masato*; Sekiguchi, Kentaro; Ichinose, Kosuke*; Sakaki, Hironao; Kondo, Kiminori; Matsui, Ryutaro; Kishimoto, Yasuaki; Fukuda, Yuji

no journal, , 

The size of clusters, produced in an expansion of supercooled, high pressure molecular hydrogen gas into vacuum, has been evaluated by measuring the angular distribution of scattered light. The data are analyzed based on the Mie scattering theory. Here obtaining the size distribution of clusters reduces to solving the inverse problem. Since the scattering coefficient is a matrix, it is necessary to determine the inverse matrix. However, if you solve this equation straightforward, the size distribution often oscillates to the negative values and becomes the discrete distribution by external factors such as noise included in the measurement results. Here, the validity of the method is confirmed by performing a calibration study using the standard micro-particles.

Oral presentation

Development of a high energy particle generation method using intense lasers

Fukuda, Yuji; Kanasaki, Masato*; Sekiguchi, Kentaro; Sugiyama, Akira; Kondo, Kiminori

no journal, , 

In the characterization of ion beams using CR-39, information on ion energies, incident angles, and ion species can be extracted from the geometrical structure of the etch pits. In this study, the spatial distribution of accelerated ions has been measured by using 5$$times$$5 cm$$^2$$ wide CR-39 detectors. In addition, by measuring the etch pit open mouth radius and the gray scale, the energy distributions of accelerated ions were also evaluated.

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