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Journal Articles

Numerical interpretation of hydrogen thermal desorption spectra for iron with hydrogen-enhanced strain-induced vacancies

Ebihara, Kenichi; Sugiyama, Yuri*; Matsumoto, Ryosuke*; Takai, Kenichi*; Suzudo, Tomoaki

Metallurgical and Materials Transactions A, 52(1), p.257 - 269, 2021/01

 Times Cited Count:0 Percentile:100(Materials Science, Multidisciplinary)

We simulated the thermal desorption spectra of a small-size iron specimen to which was applied during charging with hydrogen atoms using a model incorporating the behavior of vacancies and vacancy clusters. The model considered up to vacancy clusters $$V_9$$, which is composed of nine vacancies and employed the parameters based on atomistic calculations, including the H trapping energy of vacancies and vacancy clusters that we estimated using the molecular static calculation. As a result, we revealed that the model could, on the whole, reproduced the experimental spectra except two characteristic differences, and also the dependence of the spectra on the aging temperature. By examining the cause of the differences, the possibilities that the diffusion of clusters of $$V_2$$ and $$V_3$$ is slower than the model and that vacancy clusters are generated by applying strain and H charging concurrently were indicated.

Journal Articles

Irradiation induced reactivity in Monju zero power operation

Takano, Kazuya; Maruyama, Shuhei; Hazama, Taira; Usami, Shin

Proceedings of Reactor Physics Paving the Way Towards More Efficient Systems (PHYSOR 2018) (USB Flash Drive), p.1725 - 1735, 2018/04

Irradiation dependence of the core excess reactivity was investigated for the Monju system startup tests at zero-power carried out in 2010. The excess reactivity basically decreases with the $$beta$$ decay of $$^{241}$$Pu in zero-power operation. However, the excess reactivity little changed in the two month period of the startup tests, which suggests a positive reactivity insertion during the period. The investigated irradiation dependence shows that the positive reactivity increases with reactor operation and mostly saturates by the fission-dose attained during the Monju zero-power operation in a month ($$sim$$10$$^{17}$$ fissions/cm$$^{3}$$). The saturated positive reactivity is equivalent to approximately 47% of the initially accumulated self-irradiation damage recovery assuming the defects were recovered by the fission-fragment irradiation in the reactor operation.

Journal Articles

Identification of divacancies in 4H-SiC

Son, N. T.*; Umeda, Takahide*; Isoya, Junichi*; Gali, A.*; Bockstedte, M.*; Magnusson, B.*; Ellison, A.*; Morishita, Norio; Oshima, Takeshi; Ito, Hisayoshi; et al.

Physica B; Condensed Matter, 376-377, p.334 - 337, 2006/04

 Times Cited Count:3 Percentile:80.94(Physics, Condensed Matter)

no abstracts in English

Journal Articles

Interaction of nitrogen with vacancy defects in N$$^{+}$$-implanted ZnO studied using a slow positron beam

Chen, Z. Q.; Maekawa, Masaki; Kawasuso, Atsuo; Suzuki, Ryoichi*; Odaira, Toshiyuki*

Applied Physics Letters, 87(9), p.091910_1 - 091910_3, 2005/08

 Times Cited Count:28 Percentile:29.06(Physics, Applied)

Zinc oxide crystals were implanted with N$$^+$$, O$$^+$$, and co-implanted with O$$^+$$/N$$^+$$ ions. Positron annihilation measurements show the introduction of vacancy clusters upon implantation. In the N$$^+$$-implanted sample, these vacancy clusters are only partially annealed at 800$$^{circ}$$C as compared to their full recovery in the O$$^+$$-implanted sample, suggesting a strong interaction between nitrogen and vacancy clusters. At 1000-1100$$^{circ}$$C, nitrogen also forms stable complexes with thermally generated vacancies. To remove all the detectable vacancy defects, a high temperature annealing at 1250$$^{circ}$$C is needed. Furthermore, Hall measurements of this sample show n-type conductivity though nitrogen is expected as acceptors. On the contrary, in the O$$^+$$/N$$^+$$ co-implanted sample, most vacancy clusters disappear at 800$$^{circ}$$C. Probably oxygen scavenges nitrogen to form N-O complexes and hence enhance the annealing of vacancy clusters. A highly compensated semi-insulating layer is formed in the co-implanted sample.

Journal Articles

Microvoid formation in hydrogen-implanted ZnO probed by a slow positron beam

Chen, Z. Q.; Kawasuso, Atsuo; Xu, Y.; Naramoto, Hiroshi*; Yuan, X. L.*; Sekiguchi, Takashi*; Suzuki, Ryoichi*; Odaira, Toshiyuki*

Physical Review B, 71(11), p.115213_1 - 115213_8, 2005/03

 Times Cited Count:100 Percentile:5.84(Materials Science, Multidisciplinary)

ZnO crystals were implanted with 20-80 keV hydrogen ions up to a total dose of 4.4$$times$$10$$^{15}$$ cm$$^{-2}$$. Positron annihilation measurements show introduction of zinc vacancies, which are filled with hydrogen atoms. After isochronal annealing at 200-500 $$^{circ}$$C, the vacancies agglomerate into hydrogen bubbles. Further annealing at 600-700 $$^{circ}$$C causes release of hydrogen out of the bubbles, leaving large amount of microvoids. These microvoids are annealed out at high temperature of 1000 $$^{circ}$$C. Cathodoluminescence measurements reveal that hydrogen ions also passivate deep level emission centers before their release from the sample, and lead to the improvement of the UV emission.

Journal Articles

Production and recovery of defects in phosphorus-implanted ZnO

Chen, Z. Q.; Kawasuso, Atsuo; Xu, Y.; Naramoto, Hiroshi; Yuan, X. L.*; Sekiguchi, Takashi*; Suzuki, Ryoichi*; Odaira, Toshiyuki*

Journal of Applied Physics, 97(1), p.013528_1 - 013528_6, 2005/01

 Times Cited Count:132 Percentile:3.68(Physics, Applied)

Phosphorus ions were implanted into ZnO crystals with energies of 50-380 keV to a dose of 10$$^{13}$$-10$$^{15}$$ cm$$^{-2}$$. Positron annihilation measurements show the introduction of vacancy clusters after implantation. These vacancy clusters evolve to microvoids after annealing at a temperature of 600$$^{circ}$$C, and disappear gradually up to 1100$$^{circ}$$C. Raman scattering measurements show the production of oxygen vacancies (V$$_{O}$$). They are annealed up to 700$$^{circ}$$C accompanying the agglomeration of vacancy clusters. The light emissions of ZnO are suppressed due to the competing nonradiative recombination centers introduced by implantation. Recovery of the light emission occurs above 600$$^{circ}$$C. The vacancy-type defects detected by positrons might be part of the nonradiative recombination centers. Hall measurement shows n-type conductivity for the P$$^+$$-implanted ZnO layer, which suggests that phosphorus is an amphoteric dopant.

Journal Articles

Hydrogen bubble formation in H-implanted ZnO studied using a slow positron beam

Chen, Z. Q.; Maekawa, Masaki; Kawasuso, Atsuo; Yamamoto, Shunya; Yuan, X. L.*; Sekiguchi, Takashi*; Suzuki, Ryoichi*; Odaira, Toshiyuki*

JAERI-Review 2004-025, TIARA Annual Report 2003, p.193 - 195, 2004/11

20-80 keV hydrogen ions were implanted into ZnO single crystals up to a total dose of 4.4$$times$$10$$^{15}$$ cm$$^{-2}$$. Positron annihilation measurements using a slow positron beam revealed introduction of vacancies after implantation, which are filled with hydrogen impurities. After annealing, these hydrogen filled vacancies grow into large hydrogen bubbles. At annealing temperature of 500-700$$^{circ}$$C, these hydrogen impurities are released from the bubbles, and remain open microvoids. These microvoids are finally annealed out at about 1100$$^{circ}$$C. The effects of hydrogen implantation on the light luminescence in ZnO will also be discussed.

Journal Articles

N$$^+$$ ion-implantation-induced defects in ZnO studied with a slow positron beam

Chen, Z. Q.; Sekiguchi, Takashi*; Yuan, X. L.*; Maekawa, Masaki; Kawasuso, Atsuo

Journal of Physics; Condensed Matter, 16(2), p.S293 - S299, 2004/01

 Times Cited Count:24 Percentile:27.57(Physics, Condensed Matter)

Undoped ZnO single crystals were implanted with multiple energy N$$^+$$ ions ranging from 50 to 380 keV with dose from 10$$^{12}$$/cm$$^2$$ to 10$$^{14}$$/cm$$^2$$. Positron annihilation measurements show that vacancy defects are introduced in the implanted layers. The concentration of the vacancy defects increases with increasing ion dose. Annealing behavior of the defects can be divided into four stages, which correspond to the formation and recovery of large vacancy clusters, formation and disappearance of vacancy-impurity complexes, respectively. All the implantation induced defects are removed by annealing at 1200$$^{circ}$$C. Cathodoluminescence measurements show that the ion implantation induced defects act as nonradiative recombination centers to suppress the ultraviolet emission. After annealing, these defects disappear gradually and the ultraviolet emission reappears, which coincides with positron annihilation measurement. The Hall measurements reveal that after N$$^+$$-implantation, the ZnO layer still shows n-type conductivity.

Journal Articles

Evolution of voids in Al$$^+$$-implanted ZnO probed by a slow positron beam

Chen, Z. Q.; Maekawa, Masaki; Yamamoto, Shunya; Kawasuso, Atsuo; Yuan, X. L.*; Sekiguchi, Takashi*; Suzuki, Ryoichi*; Odaira, Toshiyuki*

Physical Review B, 69(3), p.035210_1 - 035210_10, 2004/01

 Times Cited Count:89 Percentile:5.95(Materials Science, Multidisciplinary)

Introduction and annealing behavior of defects in Al$$^+$$-implanted ZnO have been studied using energy variable slow positron beam. Vacancy clusters are produced after Al$$^+$$-implantation. With increasing ion dose above 10$$^{14}$$ Al$$^+$$/cm$$^2$$ the implanted layer is amorphized. Heat treatment up to 600 $$^{circ}$$C enhances the creation of large voids that allow the positronium formation. The large voids disappear accompanying the recrystallization process by the further heat treatment above 600 $$^{circ}$$C. Afterwards, implanted Al impurities are completely activated to contribute the n-type conduction. The ZnO crystal quality is also improved after recrystallization.

Journal Articles

Ion-implantation induced defects in ZnO studied by s slow positron beam

Chen, Z. Q.; Maekawa, Masaki; Sekiguchi, Takashi*; Suzuki, Ryoichi*; Kawasuso, Atsuo

Materials Science Forum, 445-446, p.57 - 59, 2004/00

no abstracts in English

Journal Articles

Study of ion beam induced defects in ZnO by using slow positron beam

Chen, Z. Q.; Maekawa, Masaki; Yamamoto, Shunya; Sekiguchi, Takashi*; Kawasuso, Atsuo

JAERI-Review 2003-033, TIARA Annual Report 2002, p.209 - 211, 2003/11

Undoped ZnO crystals were implanted with Al$$^+$$, N$$^+$$ and Al$$^+$$/N$$^+$$ respectively. The implantation induced defects and their recovery were studied using a variable energy slow positron beam. Vacancy clusters are introduced in all the implanted samples. The annealing of the defects in Al$$^+$$-implanted sample shows two stages, which might be due to the agglomeration of vacancy clusters and their recovery, respectively. Large voids are also observed when the Al$$^+$$ dose is higher than 10$$^{14}$$ cm$$^{-2}$$, which suggest amorphization of ZnO. However, for both the N$$^+$$-implanted and the Al$$^+$$/N$$^+$$ co-implanted sample, the annealing behavior of the defects shows four stages. The last two stages might be related with the formation and recovery of nitrogen related defect complexes. Hall measurements show a strong n-type conductive layer after Al$$^+$$ implantation and annealing, suggesting that all the Al$$^+$$ ions are activated. However, for the N$$^{+}$$-implanted and Al$$^+$$/N$$^+$$ co-implanted ZnO, the implanted layer still shows n-type conductivity. The possible reason is discussed.

Journal Articles

Change in pinning properties of Bi$$_{2}$$Sr$$_{2}$$CaCu$$_{2}$$O$$_{8+x}$$ single crystals by neutron irradiation followed by thermal annealing

Nakano, M.*; Ogikubo, Koji*; Terai, Takayuki*; Yamaguchi, Kenji; Yamawaki, Michio*

Physica C, 357-360(Part.1), p.277 - 279, 2001/09

no abstracts in English

Journal Articles

Molecular dynamics analysis of laser shock phenomena due to Gaussian beam irradiation

Fukumoto, Ichiro; Omura, Etsuji*

Seimitsu Kogakkai-Shi, 67(6), p.916 - 921, 2001/06

no abstracts in English

JAEA Reports

Study on defect state and tritium behavior in neutron-irradiated Li-Al alloy

Sugai, Hiroyuki

JAERI-Research 99-041, 164 Pages, 1999/07

JAERI-Research-99-041.pdf:6.7MB

no abstracts in English

Journal Articles

Defect accumulation behavior in iron irradiated with energetic ions and electrons at $$sim$$80K

Chimi, Yasuhiro; Iwase, Akihiro; Ishikawa, Norito

Journal of Nuclear Materials, 271-272, p.236 - 240, 1999/00

 Times Cited Count:8 Percentile:44.52(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Monte Carlo simulation of point defects in BCC iron

Itakura, Mitsuhiro*; Kaburaki, Hideo; *

Nuclear Instruments and Methods in Physics Research B, 153(1-4), p.122 - 125, 1999/00

 Times Cited Count:2 Percentile:71.75(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Electrical conductivity of uranium-neptunium mixed oxides

Yamashita, Toshiyuki; *; Tsuji, Toshihide*; Kato, Tetsuya*; *; Iwashita, Mitsushige*

Journal of Alloys and Compounds, 271-273, p.400 - 403, 1998/00

 Times Cited Count:3 Percentile:65.17(Chemistry, Physical)

no abstracts in English

Journal Articles

Electronic excitation effects on defect production and radiation annealing in Fe irradiated at$$sim$$80K with energetic particles

Chimi, Yasuhiro; Iwase, Akihiro; Ishikawa, Norito

Mat. Res. Soc. Symp. Proc., 504, p.221 - 226, 1998/00

no abstracts in English

Journal Articles

Characterization of defects in electron irradiated 6H-SiC by positron lifetime and electron spin resonance

Kawasuso, Atsuo; Ito, Hisayoshi; Okada, Sohei; D.Cha*

Mater. Sci. Forum, 264-268, p.611 - 614, 1998/00

no abstracts in English

JAEA Reports

PNC Technical Review No.104

PNC-TN1340 97-004, 170 Pages, 1997/12

PNC-TN1340-97-004.pdf:26.83MB

no abstracts in English

45 (Records 1-20 displayed on this page)