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 YAlO (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.
Yamamoto, 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.
Yoshioka, Satoru*; Tsuruta, Konosuke*; Yamamoto, Tomokazu*; Yasuda, Kazuhiro*; Matsumura, Sho*; Sugiyama, Takeharu*; Oba, Yojiro; Ishikawa, Norito; Kobayashi, Eiichi*; Okudaira, Koji*
Journal of the American Ceramic Society, 103(8), p.4654 - 4663, 2020/08
X-ray absorption near edge structure (XANES) and small-angle X-ray scattering (SAXS) reveal the damaged structures in MgAlO spinel induced by swift heavy ions. SAXS indicates the formation of ion tracks with cylindrical shape with a diameter of 5 nm. XANES indicates the cationic disordering between tetrahedral and octahedral sites by the irradiation. Quantitative analysis of XANES also reveals that cations preferably occupy the octahedral sites at high fluence.
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
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.
Amekura, Hiroshi*; Li, R.*; Okubo, Nariaki; Ishikawa, Norito; Chen, F.*
Nuclear Instruments and Methods in Physics Research B, 474, p.78 - 82, 2020/07
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.
Li, 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
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.
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
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 .
Ishikawa, 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
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.
Ogawa, Tatsuhiko; Ishikawa, Norito; Kai, Takeshi
Nuclear Instruments and Methods in Physics Research B, 461, p.272 - 275, 2019/12
Heavy ion irradiation, which deposits energy locally in materials, is widely used to study new material modification and radiation-induced damage. So far, radial distribution of energy deposition by heavy ions were well studied. By contrast, depth profile of energy deposition was usually assumed to be uniform but the energy deposition near the incident surface is likely suppressed because the delta-rays are pushed by the incident heavy ions. In this study, spatial distribution of energy deposition in the materials exposed to heavy ions is calculated by using a track structure simulation code RITRACKS. The result showed that energy deposition is suppressed in the first 2 nm of water and that beyond 2 nm is uniform. This result can be applied to the materials other than water by scaling with electron density. It is indicated that reactor fuel pins damaged by fission products and the materials modified by heavy ions receive less energy deposition and less radiation effect in the first 2 nm.
Kitamura, Akane; Ishikawa, Norito; Kondo, Keietsu; Yamamoto, Shunya*; Yamaki, Tetsuya*
Nuclear Instruments and Methods in Physics Research B, 460, p.175 - 179, 2019/12
Irradiation at grazing incidence formed chains of multiple hillocks on the surface of strontium titanate (SrTiO) and titanium oxide (TiO). They were observed with an atomic force microscope (AFM), however, the AFM measurement gives resolution errors in a nanometer order due to the curvature of the probe tip. To prevent these errors, a field emission scanning electron microscope (FE-SEM) would be a better option for observation. In this study, we performed SEM observations for the chains of the multiple hillocks. Single crystals of SrTiO and TiO were irradiated with 200 MeV Xe in the tandem accelerator at JAEA-Tokai. It was revealed that a lot of isolated hillocks were formed in a line on these surface. The diameter and the interval of those hillocks are discussed in comparison to AFM observation.
Kitamura, Akane; Ishikawa, Norito; Kondo, Keietsu; Fujimura, Yuki; Yamamoto, Shunya*; Yamaki, Tetsuya*
Transactions of the Materials Research Society of Japan, 44(3), p.85 - 88, 2019/06
Swift heavy ions can create nanosized hillocks on the surfaces of various ceramics. When these materials are irradiated with swift heavy ions at normal incidence, each ion impact results in the formation of a single hillock on the surfaces. In contrast, irradiation at grazing incidence forms chains of multiple hillocks on the surface, for example, for strontium titanate (SrTiO). So far, chains of multiple hillocks have been investigated using atomic force microscopy (AFM). It should be noted that AFM measurements involve systematic errors of several nanometers due to the finite size of the probe tip. Consequently, it is possible that the image of one hillock may merge with that of a neighboring hillock even if the two hillocks are well separated. In contrast to AFM, field-emission scanning electron microscopy (FE-SEM) is a useful technique for obtaining higher-resolution images. In this study, we observed multiple nanohillocks on the surfaces of SrTiO using FE-SEM. Crystals of SrTiO(100) and 0.05 wt% Nb-doped SrTiO(100) were irradiated with 350 MeV Xe ions, respectively, at grazing incidence, where the angle between the sample surface and the beam was less than 2. On the SrTiO surface, a chain of periodic nanohillocks is created along the ion path. In contrast, black lines accompanied by hillocks are observed on the Nb-doped SrTiO surface.
Sasajima, 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.
Li, R.*; Pang, C.*; Amekura, Hiroshi*; Ren, F.*; Hbner, R.*; Zhou, S.*; Ishikawa, Norito; Okubo, Nariaki; Chen, F.*
Nanotechnology, 29(42), p.424001_1 - 424001_8, 2018/10
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.
Amekura, 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
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.
Yoshioka, Satoru*; Tsuruta, Konosuke*; Yamamoto, Tomokazu*; Yasuda, Kazuhiro*; Matsumura, Sho*; Ishikawa, Norito; Kobayashi, Eiichi*
Physical Chemistry Chemical Physics, 20(7), p.4962 - 4969, 2018/02
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.
Kondo, Masatoshi*; Okubo, Nariaki; Irisawa, Eriko; Komatsu, Atsushi; Ishikawa, Norito; Tanaka, Teruya*
Energy Procedia, 131, p.386 - 394, 2017/12
The chemical behaviors of lead (Pb) based coolants in the air ingress accident of fast reactors were investigated by means of the thermodynamic considerations and the static oxidation experiments for Pb alloys at various chemical compositions. The results of the static oxidation tests for lead-bismuth (Pb-Bi) alloys indicated that Pb was depleted from the alloy due to the preferential formation of PbO in air at 773K. Pb-Bi oxide and BiO were formed after the enrichment of Bi in the alloys due to the Pb depletion. The oxidation rates of the alloys were much larger than that of the steels, and became larger with higher Pb concentration in the alloys. The compatibility of Pb-Bi alloys with stainless steel was worse when the Pb concentration in the alloys became low, since the dissolution type corrosion was promoted by the Bi composition in the alloy. The Pb-Li alloys were oxidized as they formed LiPbO and LiCO. Then, Li was depleted from the alloy.
Pospisil, J.; Haga, Yoshinori; Nakajima, Kunihisa; Ishikawa, Norito; Csaov, I.*; Tateiwa, Naoyuki; Yamamoto, Etsuji; Yamamura, Tomoo*
Solid State Communications, 268, p.12 - 14, 2017/12
Ishikawa, Norito; Taguchi, Tomitsugu*; Okubo, Nariaki
Nanotechnology, 28(44), p.445708_1 - 445708_11, 2017/11
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.