Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Ishikawa, Norito; Taguchi, Tomitsugu*; Ogawa, Hiroaki
Quantum Beam Science (Internet), 4(4), p.43_1 - 43_14, 2020/12
Amorphizable ceramics were irradiated with 200 MeV Au ions, and the as-irradiated samples were observed by transmission electron microscopy (TEM). The ion track diameter and hillock diameter are similar for all the amorphizable ceramics. For SrTiO
and niobium-doped STO, 200 MeV Au ion irradiation and TEM observation were also performed. The ion track diameters in these materials are found to be markedly smaller than the hillock diameters. The ion tracks in these materials exhibit inhomogeneity, which is similar to that reported for non-amorphizable ceramics. On the other hand, the hillocks appear to be amorphous, and the amorphous feature is in contrast to the crystalline feature of hillocks observed in non-amorphizable ceramics. No marked difference is recognized between the nanostructures in STO and those in Nb-STO.
Amekura, Hiroshi*; Li, R.*; Okubo, Nariaki; Ishikawa, Norito; Chen, F.*
Quantum Beam Science (Internet), 4(4), p.39_1 - 39_11, 2020/12
Evolution of depth profiles of the refractive index in YAl
O
(YAG) crystals were studied under 200 MeV Xe ion irradiation. The index changes were observed at three different depth regions; (i) a plateau near the surface between 0 and 3 
m in depth, which can be ascribed to the electronic stopping Se, (ii) a broad peak at 6 m in depth, and (iii) a sharp dip at 13 m in depth, which is attributed to the nuclear stopping Sn peak.
Tsuchida, Hidetsugu*; Kai, Takeshi; Kitajima, Kensei*; Matsuya, Yusuke; Majima, Takuya*; Saito, Manabu*
European Physical Journal D, 74(10), p.212_1 - 212_7, 2020/10
Times Cited Count：0 Percentile：100(Optics)Fundamental study of interaction between biomolecules and heavy ions in water is very important to predict an initial stage of radiation biological effects. A heavy ion irradiation experiment into droplet target assumed as a biological system in a vacuum was performed to measure production yields of cations and anions for glycine, which was ejected from the droplet target to the vacuum. However, the production mechanisms have been unknown. The PHITS code adapting ion track structure mode was used to analyze the production mechanisms from the dose evaluation at the surface between the vacuum and the water. It is found that induction yields of ionization and excitation, and dissociative electron attachment involved in the secondary electrons were correlated with the production yields of cations and anions of the glycine. The results provide us newly scientific insights to predict an initial stage of radiation biological effects.
by using Poisson distribution functionYamamoto, Yuki*; Ishikawa, Norito; Hori, Fuminobu*; Iwase, Akihiro*
Quantum Beam Science (Internet), 4(3), p.26_1 - 26_13, 2020/09
The lattice constant and the magnetic state of CeO are modified by the irradiation with 200 MeV Xe ions. Under the assumption that these modifications are induced in the narrow one-dimensional region (the ion track) along the ion beam path, the dependence of the lattice constant and the saturation magnetization of CeO on the Xe ion fluence can be analyzed by using the Poisson distribution function. The analysis reveals that the lattice constant inside the ion track, which is larger than outside the ion track is not affected by the overlapping of the ion track. The present result implies that the Poisson distribution function is useful for describing the effect of ion track overlapping on the ion irradiation induced ferromagnetic state in CeO.
Okayasu, Satoru; Harii, Kazuya*; Kobata, Masaaki; Yoshii, Kenji; Fukuda, Tatsuo; Ishida, Masahiko*; Ieda, Junichi; Saito, Eiji
Journal of Applied Physics, 128(8), p.083902_1 - 083902_7, 2020/08
Okuno, Yasuki*; Ishikawa, Norito; Akiyoshi, Masafumi*; Ando, Hirokazu*; Harumoto, Masaki*; Imaizumi, Mitsuru*
Japanese Journal of Applied Physics, 59(7), p.074001_1 - 074001_7, 2020/07
Times Cited Count：0 Percentile：100(Physics, Applied)Performance degradation prediction for space solar cells under irradiation with low-energy electrons is greatly affected by displacement threshold energy (Ed) when a displacement damage dose (DDD) model is used. According to recent studies, the Ed of P atoms is much lower than the conventional Ed value in InP-type solar cells irradiated with low-energy electrons. This indicates that the value of Ed typically used in DDD model leads to significant error in performance degradation prediction. In this study, degradation of AlInGaP solar cells is observed after irradiation with 60 keV electrons. The results suggest that the Ed of P atoms in AlInGaP solar cells is much smaller than the conventionally used Ed value. By using the DDD model with the Ed value obtained in this study, we demonstrated that the performance degradation predicted by the DDD model agrees well with the experimental results.
and amorphizable YAlO (YAG) crystalsAmekura, Hiroshi*; Li, R.*; Okubo, Nariaki; Ishikawa, Norito; Chen, F.*
Nuclear Instruments and Methods in Physics Research B, 474, p.78 - 82, 2020/07
Times Cited Count：3 Percentile：39.48(Instruments & Instrumentation)Yttrium-aluminum-garnet (YAG) and calcium fluoride (CaF) were irradiated with 200 MeV Xe ions. YAG crystal was transformed to an amorphous phase, whereas CaF shows the non-amorphizable nature. In spite of amorphization, YAG maintained its transparency, whereas CaF markedly loses it transparency showing a broad absorption band centered at 550 nm.
and 200 MeV Xe ion irradiationLi, R.*; Narumi, Kazumasa*; Chiba, Atsuya*; Hirano, Yu*; Tsuya, Daiju*; Yamamoto, Shunya*; Saito, Yuichi*; Okubo, Nariaki; Ishikawa, Norito; Pang, C.*; et al.
Nanotechnology, 31(26), p.265606_1 - 265606_9, 2020/06
Times Cited Count：1 Percentile：100(Nanoscience & Nanotechnology)We report the elongation of embedded Au nanoparticles (NPs) in three different matrices under irradiations of 4 MeV C ions and 200 MeV Xe ions. Large elongation of Au NPs was observed for crystalline indium tin oxide (ITO) under both 4 MeV C and 200 MeV Xe irradiation. The ITO layer preserved the crystallinity even after large elongation was induced. This is the first report of the elongation of metal NPs in a crystalline matrix.
irradiationOkazaki, Hiroyuki*; Kakitani, Kenta*; Kimata, Tetsuya*; Idesaki, Akira*; Koshikawa, Hiroshi*; Matsumura, Daiju; Yamamoto, Shunya*; Yamaki, Tetsuya*
Journal of Chemical Physics, 152(12), p.124708_1 - 124708_5, 2020/03
Times Cited Count：0 Percentile：100(Chemistry, Physical)Sueyoshi, Tetsuro*; Kotaki, Tetsuya*; Furuki, Yuichi*; Fujiyoshi, Takanori*; Semboshi, Satoshi*; Ozaki, Toshinori*; Sakane, Hitoshi*; Kudo, Masaki*; Yasuda, Kazuhiro*; Ishikawa, Norito
Japanese Journal of Applied Physics, 59(2), p.023001_1 - 023001_7, 2020/02
Times Cited Count：1 Percentile：52.74(Physics, Applied)We show that Xe ion irradiation with 80 MeV to GdBaCuOy-coated conductors creates different morphologies of columnar defects (CDs) depending on the irradiation angles relative to the c-axis: continuous CDs with a larger diameter are formed for oblique irradiation at 
= 45
, whereas the same ion beam at a different angle ( = 0) induces the formation of discontinuous CDs. The direction-dependent morphologies of CDs significantly affect the angular behavior of the critical current density 
.
FeOIshikawa, Norito; Taguchi, Tomitsugu*; Kitamura, Akane; Szenes, G.*; Toimil-Molares, M. E.*; Trautmann, C.*
Journal of Applied Physics, 127(5), p.055902_1 - 055902_7, 2020/02
Times Cited Count：3 Percentile：19.61(Physics, Applied)Hillock formation is one of the important aspects of radiation-induced modification of solid material. To our knowledge this is first result showing that the hillock formation in ceramics is affected by the velocity effect. The present result include Se-dependences of hillock dimensions based on precise measurement using TEM (transmission electron microscopy). The paper should be published to make researchers aware that hillock size is actually comparable to ion-track size in wide Se range. In addition, the results include important insight about the hillock formation mechanism of ceramics irradiated with swift heavy ions.
; A Molecular dynamics studySasajima, Yasushi*; Ajima, Naoki*; Kaminaga, Ryuichi*; Ishikawa, Norito; Iwase, Akihiro*
Nuclear Instruments and Methods in Physics Research B, 440, p.118 - 125, 2019/02
In the present paper, we have extensively analyzed the atomic structures generated by supplying a thermal spike to the single crystal CeO. Our analysis results were compared with the atomic structures obtained by the microscope experiments. Our simulation reproduced the distribution of the numbers of oxygen atoms obtained from the analysis of microscope images. We found that the number of vacancies was increased abruptly immediately after the thermal spike, and the number subsequently dropped through a relaxation process within 3 ps.
Kakitani, Kenta*; Kimata, Tetsuya*; Yamaki, Tetsuya*; Yamamoto, Shunya*; Matsumura, Daiju; Taguchi, Tomitsugu*; Terai, Takayuki*
Radiation Physics and Chemistry, 153, p.152 - 155, 2018/12
Times Cited Count：1 Percentile：79.08(Chemistry, Physical)Li, R.*; Pang, C.*; Amekura, Hiroshi*; Ren, F.*; H
bner, R.*; Zhou, S.*; Ishikawa, Norito; Okubo, Nariaki; Chen, F.*
Nanotechnology, 29(42), p.424001_1 - 424001_8, 2018/10
Times Cited Count：4 Percentile：61.64(Nanoscience & Nanotechnology)We report on the fabrication of reshaped Ag nanoparticles (NPs) embedded in a Nd:YAG crystal by combining Ag ion implantation and swift heavy Xe ion irradiation. The localized surface plasmon resonance (LSPR) effect is proved to be efficiently modulated according to the phenomenon of polarization-dependent absorption. The LSPR peak located at 448 nm shows red shift and blue shift at 0 degree and 90 degree polarization, respectively, which is in good agreement with calculation by discrete dipole approximation. Based on the near-field intensity distribution, the interaction between reshaped NPs shows a non-ignorable effect on the optical absorption. Furthermore, the polarization-dependence of the photoluminescence (PL) intensity is analyzed, which is positively related to the modulated LSPR absorption. It demonstrates the potential of the enhancement of PL intensity by embedded plasmonic Ag NPs.
is not a prerequisite for the core/shell ion tracks or ion shapingAmekura, Hiroshi*; Kluth, P.*; Mota-Santiago, P.*; Sahlberg, I.*; Jantunen, V.*; Leino, A. A.*; Vazquez, H.*; Nordlund, K.*; Djurabekova, F.*; Okubo, Nariaki; et al.
Physical Review Materials (Internet), 2(9), p.096001_1 - 096001_10, 2018/09
Times Cited Count：6 Percentile：55.54(Materials Science, Multidisciplinary)When a swift heavy ion (SHI) penetrates amorphous SiO, a core/shell (C/S) ion track is formed due to vaporization, where the ion track consists of a lower-density core and a higher-density shell. Here we reexamine this hypothesis. The MD simulations indicate that the vaporization is not induced under 50-MeV Si irradiation (
= 3 keV/nm), but the C/S tracks and the ion shaping of nanoparticles are nevertheless induced. Thus, the vaporization is not a prerequisite for the C/S tracks and the ion shaping.
O
induced by swift heavy ionsYoshioka, Satoru*; Tsuruta, Konosuke*; Yamamoto, Tomokazu*; Yasuda, Kazuhiro*; Matsumura, Sho*; Ishikawa, Norito; Kobayashi, Eiichi*
Physical Chemistry Chemical Physics, 20(7), p.4962 - 4969, 2018/02
Times Cited Count：3 Percentile：83(Chemistry, Physical)Cationic disorder in the MgAlO spinel induced by swift heavy ions was investigated using the X-ray absorption near edge structure. With changes in the irradiation fluences of 200 MeV Xe ions, the Mg K-edge and Al K-edge spectra were synchronously changed. The calculated spectra based on density function theory indicate that the change in the experimental spectra was due to cationic disorder between Mg in tetrahedral sites and Al in octahedral sites. These results suggest a high inversion degree to an extent that the completely random configuration is achieved in MgAlO induced by the high density electronic excitation under swift heavy ion irradiation.
Ishikawa, Norito; Taguchi, Tomitsugu*; Okubo, Nariaki
Nanotechnology, 28(44), p.445708_1 - 445708_11, 2017/11
Times Cited Count：11 Percentile：34.8(Nanoscience & Nanotechnology)TEM method is applied to YFeO (YIG) and three fluorides (CaF, SrF and BaF) for observing hillocks. For YIG which is one of the amorphizable materials, hillocks are found to have amorphous feature which is consistent with amorphous feature of ion-tracks. For the fluorides, it is found that the hillocks do not exhibit amorphous feature, and they are composed of nano-crystallites. It is found for the first time that for YIG the hillock diameter is comparable to the ion-track diameter, whereas for the fluorides it is always larger than the ion-track diameter. The results indicate that recrystallization after transient melting plays an important role for formation of hillocks and ion-tracks in fluorides.
Nb and NiTa intermetallic compoundsKojima, Hiroshi*; Kaneno, Yasuyuki*; Ochi, Masaaki*; Semboshi, Satoshi*; Hori, Fuminobu*; Saito, Yuichi*; Ishikawa, Norito; Okamoto, Yoshihiro; Iwase, Akihiro*
Materials Transactions, 58(5), p.739 - 748, 2017/05
Times Cited Count：4 Percentile：72.06(Materials Science, Multidisciplinary)Bulk samples of NiNb and NiTa intermetallic compounds were irradiated with 16 MeV Au, 4.5 MeV Ni, 4.5 MeV Al, 200 MeV Xe and 1.0 MeV He ions, and the change in near-surface lattice structure was investigated by means of the grazing incidence X-ray diffraction (GIXD)and EXAFS. The NiNb and NiTa lattice structures transform from the ordered structures (orthorhombic and monoclinic structures for NiNb and NiTa, respectively) to the amorphous state by the Au, Ni, Al and Xe ion irradiations. Irrespective of such heavy ion species or energies, the lattice structure transformation to the amorphous state almost correlate with the density of energy deposited through elastic collisions.
Sueyoshi, Tetsuro*; Kotaki, Tetsuya*; Uraguchi, Yusei*; Suenaga, Momotaro*; Makihara, Takahiro*; Fujiyoshi, Takanori*; Ishikawa, Norito
Physica C, 530, p.72 - 75, 2016/11
Times Cited Count：5 Percentile：65.32(Physics, Applied)In order to clarify the influence of size and spatial distribution of three-dimensional pinning centers (3D-PCs) on hybrid flux pinning, columnar defects (CDs) were installed by using 200 MeV Xe ions along the 
-axis direction into quasi-multilayered films consisting of YBaCuOy layers and pseudo layers of BaSnO. The positive effect of the BaSnO doping on the hybrid flux pinning stands out for the critical current density around 
in high magnetic field and/or inclined magnetic field off the -axis, whereas there is little difference in the at among the same growth temperature samples for low magnetic field. In the case of the in-plane distributed BaSnO nano-dots, the Jc around 
is remarkably enhanced, whereas there is a detrimental effect on the Jc around . These imply that the tuning of 3D-PCs is one of the keys to improve the at all magnetic field orientations for the hybrid flux pinning.
Sueyoshi, Tetsuro*; Nishimura, Takahiro*; Fujiyoshi, Takanori*; Mitsugi, Fumiaki*; Ikegami, Tomoaki*; Ishikawa, Norito
Superconductor Science and Technology, 29(10), p.105006_1 - 105006_7, 2016/10
Times Cited Count：6 Percentile：60.05(Physics, Applied)A systematic investigation of flux pinning by widely direction-dispersed columnar defects (CDs) in YBaCuOy thin films was carried out by using heavy-ion irradiation: a parallel configuration of CDs aligned along the -axis, and two trimodal splay configurations composed of crossing CDs; relative to the -axis, where the splay plane defined by the three irradiation angles is perpendicular (trimodal-A) or parallel (trimodal-B) to the transport current direction. The trimodal configurations show high pinning efficiency over a wide range of magnetic field orientations compared to the parallel one at low magnetic field. In particular, trimodal-B shows the higher critical current density of the two trimodal configurations.
