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Journal Articles

Application of radiation technology for resolving serious issues related to the nuclear accident in Fukushima

Ito, Hisayoshi

Hoshasen To Sangyo, (138), p.2 - 3, 2015/06

no abstracts in English

Journal Articles

Present status and prospects of R&D of radiation-resistant semiconductor devices at JAEA

Ito, Hisayoshi

Proceedings of SPIE, Vol.8725 (CD-ROM), 7 Pages, 2013/05

 Times Cited Count:0 Percentile:100

Research and development of radiation resistant semiconductor devices have been performed at Japan Atomic Energy Agency (JAEA) for their application to electronic system used in harsh environments like space, accelerator and nuclear facilities. Such devices are also indispensable for robots and equipment necessary for decommissioning of the damaged reactors at Fukushima Daiichi Nuclear Power Plants. For this purpose, we have fabricated transistors based on a wide band-gap semiconductor SiC and examined their radiation degradation. As a result, SiC-based transistors exhibited no significant degradation up to 1MGy, indicating their excellent radiation resistance. Recent our R&Ds of radiation resistant devices based on SiC are summarized and reviewed.

Journal Articles

R&D of removal technology of radioactive contaminants from the environment by using polymer absorbents

Ito, Hisayoshi; Seko, Noriaki; Kuroki, Ryota; Yaita, Tsuyoshi; Naganawa, Hirochika; Nakayama, Shinichi

Hoshasen Kagaku (Internet), (93), p.31 - 36, 2012/03

For removing radioactive contaminants from the environment due to the nuclear plant accident, we have synthesized highly efficient cesium absorbents by introducing molybdophosphoric acid groups into polyethylene matrix with radiation grafting. Cesium absorbents based on protein or crown ether materials have been newly developed. We have also established immobilization-collection technology of cesium-adsorbed surface soil by using a mixture of polyion and bentonitic clay material. The effectiveness of these materials has been demonstrated through the field examination in Fukushima.

Journal Articles

Removal of radioactive cesium from surface soils solidified using polyion complex; Rapid communication for decontamination test at Iitate-mura in Fukushima Prefecture

Naganawa, Hirochika; Kumazawa, Noriyuki*; Saito, Hiroshi*; Yanase, Nobuyuki; Mitamura, Hisayoshi; Nagano, Tetsushi; Kashima, Kaoru*; Fukuda, Tatsuya*; Yoshida, Zenko; Tanaka, Shunichi*

Nippon Genshiryoku Gakkai Wabun Rombunshi, 10(4), p.227 - 234, 2011/12

no abstracts in English

Journal Articles

Charge generated in 6H-SiC n$$^{+}$$p diodes by MeV range heavy ions

Oshima, Takeshi; Iwamoto, Naoya; Onoda, Shinobu; Wagner, G.*; Ito, Hisayoshi; Kawano, Katsuyasu*

Surface & Coatings Technology, 206(5), p.864 - 868, 2011/11

 Times Cited Count:4 Percentile:77.21(Materials Science, Coatings & Films)

Charge induced in n$$^{+}$$p Silicon Carbide (6H-SiC) diodes by heavy ions, oxygen (O), silicon (Si), nickel (Ni), and gold (Au) using a Transient Ion Beam Induced Current (TIBIC) measurement system. The slight increase in collected charge shows in a low bias region, and then, the values are saturated in a high bias region. This indicates that in the low bias region, since the length of the depletion layer is shorter than the ion range, carriers induced in deeper than the depletion layer diffuse and annihilate before they reach the depletion layer. Since the length of the depletion layer increases with increasing bias voltage, the charge collected by diodes increases with increasing bias voltage. In the case of the high bias, the length of the depletion layer is longer than the ion range. As a result, all carriers are induced in the depletion layer, and they can be collected by the electric field. Thus, This indicates that the value of collected charge does not depend on bias voltage. From the point of view of charge collection efficiency (CCE), the collected charge decrease with increasing atomic number. From the calculation, it is found that dense electron-hole pairs were generated in SiC by irradiation of ions with heavy mass. The decrease in the CCE due to ion irradiation with heavy mass can be interpreted in terms of the annihilation of e-h pairs in plasma due to the Auger recombination.

Journal Articles

Current transient effect in N-channel 6H-SiC MOSFET induced by heavy ion irradiation

Lee, K. K.*; Laird, J. S.*; Oshima, Takeshi; Onoda, Shinobu; Hirao, Toshio; Ito, Hisayoshi

Materials Science Forum, 645-648, p.1013 - 1016, 2010/04

no abstracts in English

Journal Articles

Deep defects in 3C-SiC generated by H$$^{+}$$- and He$$^{+}$$-implantation or by irradiation with high-energy electrons

Weidner, M.*; Trapaidze, L.*; Pensl, G.*; Reshanov, S. A.*; Sch$"o$ner, A.*; Ito, Hisayoshi; Oshima, Takeshi; Kimoto, Tsunenobu*

Materials Science Forum, 645-648, p.439 - 442, 2010/00

Intrinsic defects in 3C-SiC generated by implantation of H$$^{+}$$ and He$$^{+}$$ ions or by irradiation of high energy electrons were investigated using DLTS (Deep Level Transient Spectroscopy). The defect parameters and the thermal stability of the observed defects are determined. The dominant DLTS peak was named W6-center and its capture-cross-section was directly measured by variation of the filling pulse length. The charge state of the W6-center is obtained from double-correlated DLTS investigations according to the Poole-Frenkel effect.

Journal Articles

The Role of a radial ion-track distribution in semiconductors studied by numerical simulations

Onoda, Shinobu; Hirao, Toshio; Oshima, Takeshi; Ito, Hisayoshi

Radiation Physics and Chemistry, 78(12), p.1116 - 1119, 2009/12

 Times Cited Count:5 Percentile:58.88(Chemistry, Physical)

The effects of radial ion track distribution on the unexpected noise (transient current) in semiconductors by a high energy heavy ion strike have been studied. The measured transient currents were compared with the numerically observed one, which was calculated with the wide variety of ion track radii. In the case of low energy (several MeVs) ion, the calculated transient currents were independent of the radial track distribution. However, in the case of high energy (several hundreds of MeVs) ion, the transient currents strongly depend on the radial track distribution. This difference is interpreted in terms of the carrier concentration at the core of track, resulting in the extremely different carrier mobility. When the radius of ion track used in numerical simulator was shorter than, or equivalent to, the penumbra radius, the reasonable agreement was found between experimental and calculated transient currents.

Journal Articles

Characterization of light element impurities in ultrathin silicon-on-insulator layers by luminescence activation using electron irradiation

Nakagawa, Satoko*; Tajima, Michio*; Hirose, Kazuyuki*; Oshima, Takeshi; Ito, Hisayoshi

Japanese Journal of Applied Physics, 48(3), p.031201_1 - 031201_4, 2009/03

 Times Cited Count:3 Percentile:83.55(Physics, Applied)

Light element impurities in ultrathin top Silicon layers of silicon-on-insulator (SOI) wafers were investigated by a luminescence activation method using electron irradiation. Photoluminescence (PL) measurement using ultraviolet (UV) light excitation was carried out of various commercial SOI wafers irradiated with electrons. The C-line related to a complex of interstitial carbon and oxygen impurities and the G-line related to a complex of interstitial and substitutional carbon impurities in the top Si layer with a thickness down to 62 nm were observed after electron irradiation. There were differences in the impurity concentration depending on the wafer fabrication methods and also that there were variations in these concentrations in the respective wafers. The present method is a verypromising tool to evaluate the light element impurities in top Si layers.

Journal Articles

Effects of fabrication process on the electrical characteristics of n-channel MOSFETs irradiated with gamma-rays

Hishiki, Shigeomi; Iwamoto, Naoya; Oshima, Takeshi; Ito, Hisayoshi; Kojima, Kazutoshi*; Kawano, Katsuyasu*

Materials Science Forum, 600-603, p.707 - 710, 2009/00

The n-channel 6H-SiC MOSFETs were fabricated using different process. The carbon-coated MOSFETs showed higher radiation resistance than non-coated ones. The generation of interface traps for carbon-coated MOSFETs was smaller than that for non-coated MOSFETs. This origin can be interptered in terms of the surface degradation by thermal annealing process after ion implantation.

Journal Articles

Photo-EPR study of vacancy-type defects in irradiated ${it n}$-type 4${it H}$-SiC

Umeda, Takahide*; Morishita, Norio; Oshima, Takeshi; Ito, Hisayoshi; Isoya, Junichi*

Materials Science Forum, 600-603, p.409 - 412, 2009/00

We have performed photo-electron paramagnetic resonance (photo-EPR) analyses on four types of fundamental vacancy-related defects in 3MeV electron-irradiated 4${it H}$-SiC, i.e., carbon vacancies $$V$$$$_{rm C}$$$$^{-}$$), silicon vacancies ($$T$$$$_{V2a}$$-type $$V$$$$_{rm Si}$$$$^{-}$$), divacancies $$V$$$$_{rm Si}$$$$V$$$$_{rm C}$$$$^{0/-}$$), and carbon antisite-vacancy pairs (C$$_{rm Si}$$$$V$$$$_{rm C}$$$$^{-}$$). The photo-induced transitions from their -2 to -1 charged states or from their -1 charged to neutral states were detected in the photon energy range between 0.80 and 1.20 eV. Based on these transitions, we have discussed positions of their defect levels with respect to the conduction band edge.

Journal Articles

Reduction of interface traps and enhancement of channel mobility in n-channel 6H-SiC MOSFETs by irradiation with $$gamma$$-rays

Hishiki, Shigeomi; Reshanov, S. A.*; Oshima, Takeshi; Ito, Hisayoshi; Pensl, G.*

Materials Science Forum, 600-603, p.703 - 706, 2009/00

 Times Cited Count:1 Percentile:47.28

N-channel 6H-SiC MOSFETs has been investigated radiation effect. The MOSFETs were irradiated by $$gamma$$-rays up to 3.16 MGy(SiO$$_{2}$$) at room temperature. The electrical characteristic was estimated by Hall effect measurement and current vs. voltage measurement. The $$gamma$$-rays irradiated MOSFETs were observed that channel mobility increased due to decrease interface traps.

Journal Articles

Defects introduced by electron-irradiation at low temperatures in SiC

Son, N. T.*; Isoya, Junichi*; Morishita, Norio; Oshima, Takeshi; Ito, Hisayoshi; Gali, A.*; Janz$'e$n, E.*

Materials Science Forum, 615-617, p.377 - 380, 2009/00

Defects introduced by electron irradiation at $$sim$$ 80-100 K in 3C-, 4H- and 6H-Silicon Carbide (SiC) were investigated by Electron Paramagnetic Resonance (EPR). A number of EPR spectra, labelled LE1-10, were detected. Combining EPR and theoretical calculations (supercell calculation), the LE1 center in 3C-SiC with C$$_{2v}$$ symmetry and an electron spin S=3/2 could be determined to be the (V$$_{Si}$$-Si$$_{i}$$)$$^{3+}$$ Frenkel pair between the silicon vacancy and a second neighbor Si$$_{i}$$ interstitial along the $$<$$ 100 $$>$$ direction.

Journal Articles

Quantum beams open up the future, 2

Namba, Hideki; Tanaka, Atsushi; Ito, Hisayoshi

Nippon Genshiryoku Gakkai-Shi, 50(12), p.785 - 789, 2008/12

The outline of the quantum beam applied research, which attracts world-wide attention in recent years as a key technology for innovation, was introduced in the previous review article. The researches using charged particles and radio-isotopes (RIs), namely with $$gamma$$ rays, electron beams and ion beams, have the longest history in the application of quantum beam technology, and the results were used in wide range of activities in the fields of industry, agriculture and health care, as well as academic field. In this paper, the applications using charged particles and RIs in the fields of biotechnology, medical application, environment and energy will be introduced.

Journal Articles

Contribution of radiation application technology to our daily life; Industrial applications

Ito, Hisayoshi

FBNews,  (374), p.1 - 6, 2008/02

The contribution of radiation application technology to our daily life is summarized. Especially industrial applications of radiation like ion-beams, electron-beams, and $$gamma$$-rays are described and some examples of such applications are introduced.

Journal Articles

Application to semiconductor device fabrication and evaluation

Ito, Hisayoshi

Hoshasen No Sekai 2008, p.77 - 82, 2008/00

Radiation application techniques like ion implantation, electron-beam lithography, neutron transmutation doping, etc., are recognized as key technology for fabricating sophisticated semiconductor devices. Ion beams, electron beams, neutron beams and $$gamma$$-rays are also used for evaluating the durability and reliability of highly integrated semiconductor devices. In this document, the outlines of radiation applications in the fabrication and evaluation of semiconductor devices are described.

Journal Articles

Magnetic resonance studies of defects in electron-irradiated ZnO substrates

Son, N. T.*; Ivanov, I. G.*; Kuznetsov, A. Yu.*; Svensson, B. G.*; Zhao, Q. X.*; Willander, M.*; Morishita, Norio; Oshima, Takeshi; Ito, Hisayoshi; Isoya, Junichi*; et al.

Physica B; Condensed Matter, 401-402, p.507 - 510, 2007/12

 Times Cited Count:3 Percentile:80.16(Physics, Condensed Matter)

Defects in electron-irradiated (3, 6 MeV) ZnO substrates were investigated using optical detection of magnetic response (ODMR). The shallow donor and the Zn vacancy were detected. In addition, several ODMR centers with S=$$frac{1}{2}$$ were also observed. Among these, LU3 and LU4 shows a behavior as recombination centers. After annealing at 400$$^{circ}$$C, both LU3 and LU4 still remain in ZnO substrates.

Journal Articles

Recombination centers in as-grown and electron-irradiated ZnO substrates

Son, N. T.*; Ivanov, G.*; Kuznetsov, A.*; Svensson, B. G.*; Zhao, Q. X.*; Willander, M.*; Morishita, Norio; Oshima, Takeshi; Ito, Hisayoshi; Isoya, Junichi*; et al.

Journal of Applied Physics, 102(9), p.093504_1 - 093504_5, 2007/11

 Times Cited Count:16 Percentile:42.77(Physics, Applied)

Optical detection of magnetic resonance (ODMR) was performed to investigate defects in ZnO irradiated with 3 MeV electrons at room temperature. As a result, the Zn vacancy and some other centers were detected by ODMR. The Zn vacancy and two other centers whish are labeled as LU3 and LU4, were also commonly observed in different types of as-grown ZnO. Therefore, it can be concluded that the both LU3 and LU4 might be related to intrinsic defects, and they act as dominating recombination centers in irradiated and as-grown ZnO.

Journal Articles

Energetically deep defect centers in vapor-phase grown zinc oxide

Frank, T.*; Pensl, G.*; Tana-Zaera, R.*; Z$'u$$~n$iga-P$'e$rez, J.*; Mart$'i$nez-Tom$'a$s, C.*; Mu$~n$oz-Sanjos$'e$, V.*; Oshima, Takeshi; Ito, Hisayoshi; Hofmann, D.*; Pfisterer, D.*; et al.

Applied Physics A, 88(1), p.141 - 145, 2007/07

 Times Cited Count:46 Percentile:14.72(Materials Science, Multidisciplinary)

Deep Level Transient Spectroscopy (DLTS) measurements were carried out to investigate defects in vapor-phase grown ZnO crystals. The generation of defect center labeled E4 subsequent to annealing in different ambients was monitored. By conducting electron irradiations with energies, where either both the Zn- and O-sublattice are damaged or according to only the Zn-lattice, a chemical assignment to the defect centers E4 and E3 could be accomplished. DLTS investigations of ZnO samples under illumination give an evidence that E4 is a negative-U center.

Journal Articles

Heavy-ion induced current through an oxide layer

Takahashi, Yoshihiro*; Oki, Takahiro*; Nagasawa, Takaharu*; Nakajima, Yasuhito*; Kawanabe, Ryu*; Onishi, Kazunori*; Hirao, Toshio; Onoda, Shinobu; Mishima, Kenta; Kawano, Katsuyasu*; et al.

Nuclear Instruments and Methods in Physics Research B, 260(1), p.309 - 313, 2007/07

 Times Cited Count:4 Percentile:61.67(Instruments & Instrumentation)

no abstracts in English

326 (Records 1-20 displayed on this page)