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Ishikawa, Norito; Fukuda, Shoma; Nakajima, Toru; Ogawa, Hiroaki; Fujimura, Yuki; Taguchi, Tomitsugu*
Materials, 17(3), p.547_1 - 547_21, 2024/02
Times Cited Count：0 Percentile：0.04(Chemistry, Physical)Natural monoclinic zirconia (baddeleyite) was irradiated with 340-MeV Au ions, and the irradiation-induced nanostructures (i.e., ion tracks and nanohillocks) were observed using transmission electron microscopy. The diameter of the nanohillocks is approximately 10 nm, which is similar to the maximum molten region size calculated using the analytical thermal spike model. Ion tracks are imaged as strained regions that maintain their crystalline structure. The cross-sections of most of the ion tracks are imaged as parallelopiped or rectangular contrasts as large as 10 nm. These results strongly indicate that the molten region is recrystallized anisotropically, reflecting the lattice structure. Furthermore, low-density track cores are formed in the center of the ion tracks. The formation of low-density track cores can be attributed to the ejection of molten matter toward the surface.
irradiated with swift heavy ions at grazing incidenceIshikawa, Norito; Fujimura, Yuki; Kondo, Keietsu; Szabo, G. L.*; Wilhelm, R. A.*; Ogawa, Hiroaki; Taguchi, Tomitsugu*
Nanotechnology, 33(23), p.235303_1 - 235303_10, 2022/06
Times Cited Count：4 Percentile：48.5(Nanoscience & Nanotechnology)A single crystal of SrTiO doped with niobium (Nb-STO) was irradiated with 200 MeV Au ions at grazing incidence. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) are used to study the relation between irradiation-induced change of surface topography and corresponding material property changes. As expected, multiple hillocks as high as 5-6 nm are imaged by AFM observation. It is also found that the region in between the adjacent hillocks is slightly elevated rather than depressed. Line-like contrasts along the ion paths are found in both AFM phase images and SEM images, indicating the formation of continuous ion tracks in addition to multiple hillocks. Cross-sectional transmission electron microscopy (TEM) observation shows that the ion tracks in the near-surface region are found to be relatively large, whereas buried ion tracks in the deeper region are relatively small. The results suggest that recrystallization plays an important role in the formation of small ion tracks in the deep region, whereas formation of large ion tracks in the near-surface region is likely due to the absence of recrystallization.
Motokawa, Ryuhei; Kaneko, Koji; Oba, Yojiro; Nagai, Takayuki; Okamoto, Yoshihiro; Kobayashi, Taishi*; Kumada, Takayuki; Heller, W. T.*
Journal of Non-Crystalline Solids, 578, p.121352_1 - 121352_7, 2022/02
Times Cited Count：3 Percentile：22.84(Materials Science, Ceramics)Fe
O
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
Times Cited Count：7 Percentile：44.34(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.
Yamane, Yuta*; Ieda, Junichi
Magune, 13(5), p.235 - 241, 2018/10
Yamaki, Tetsuya*; Kitamura, Akane; Sawada, Shinichi*; Koshikawa, Hiroshi*
Nihon Kaisui Gakkai-Shi, 72(2), p.62 - 74, 2018/04
This review paper is devoted to two topics, i.e., fluoropolymer-based porous and ion-exchange membranes, both of which include the creation of nanostructure-controlled functional membranes with high-energy ion beams. Latent tracks of the MeV-GeV heavy ions in a polymer foil can sometimes be chemically etched out to form a membrane with micro- and nano-sized through-pores, the so-called ion-track membrane. Our focus is on ion-track membranes of poly (vinylidene fluoride) (PVDF) and cation- and anion-exchange membranes (CEMs and AEMs, respectively).
Amekura, Hiroshi*; Kono, Kenichiro*; Okubo, Nariaki; Ishikawa, Norito
Physica Status Solidi (B), 252(1), p.165 - 169, 2015/01
Times Cited Count：10 Percentile：42.11(Physics, Condensed Matter)Zinc nanoparticles (NPs) of 10 nm in diameter were irradiated with 200 MeV Xe
ions with various fluences. The shape elongation of the NPs and the mean inter-particle (IP) distance were evaluated by small angle X-ray scattering (SAXS) in the transmission configuration using synchrotron X-ray of 18 keV. The azimuth angle dependence of SAXS signal, which was isotropic for unirradiated state, changed to anisotropic. It indicated that the NPs collectively deformed from spheres to spheroids.
optical spectroscopy of ablation plume for preparations of nanostructured TiO
thin films by pulsed laser depositionKitazawa, Shinichi
Japanese Journal of Applied Physics, Part 1, 43(9A), p.6335 - 6341, 2004/09
Times Cited Count：17 Percentile：54.99(Physics, Applied)Nanostructured TiO thin films on 
-AlO (0001) substrates prepared by pulsed laser deposition (PLD) were analyzed and evaluated in terms of the buffer O gas pressure (0 - 80 Pa) dependencies by optical spectroscopy and surface morphology. Optical emission spectra of the ablation plume from Ti and TiO targets were measured in-situ. The contribution from TiO molecules was observed by narrow-band photometry. The surface morphology was observed by an atomic force microscope (AFM), revealing the pressure dependence of nanostructures. The crystallographic structures of prepared TiO thin films were observed by X-ray diffraction (XRD). The optically observed band-gaps of the prepared thin films show that the crystallographic structures are mixed crystals of rutile and anatase. Evaporated Ti particles combine with buffer O gas thereby producing TiO molecules, which affect the formation of nanostructures on TiO thin films.
-FeSi thin film formation processesYamamoto, Hiroyuki; Yamaguchi, Kenji; Hojo, Kiichi
Thin Solid Films, 461(1), p.99 - 105, 2004/08
Times Cited Count：10 Percentile：46.84(Materials Science, Multidisciplinary)no abstracts in English
Yamamoto, Hiroyuki; Saito, Takeru
Nuclear Instruments and Methods in Physics Research B, 206(1-4), p.42 - 46, 2003/05
Times Cited Count：14 Percentile：66.94(Instruments & Instrumentation)no abstracts in English
Koizumi, Hitoshi*; Taguchi, Mitsumasa; Kobayashi, Yasuhiko; Ichikawa, Tsuneki*
Nuclear Instruments and Methods in Physics Research B, 179(4), p.530 - 535, 2001/09
Times Cited Count：7 Percentile：48.68(Instruments & Instrumentation)no abstracts in English
Yamamoto, Hiroyuki; Saito, Takeru; Asaoka, Hidehito
Applied Surface Science, 178(1-4), p.127 - 133, 2001/07
Times Cited Count：5 Percentile：32.77(Chemistry, Physical)no abstracts in English
Yamamoto, Hiroyuki
Hoshasen Kagaku, 2001(71), p.17 - 21, 2001/03
no abstracts in English
Yamamoto, Hiroyuki; Baba, Yuji
Journal of the Korean Vacuum Society, 9(S2), p.84 - 88, 2000/11
no abstracts in English
/Si layer by high-energy XPSYamamoto, Hiroyuki; Baba, Yuji
Journal of Surface Analysis, 7(1), p.122 - 127, 2000/03
no abstracts in English
Yamaki, Tetsuya
no journal, ,
My talk is devoted to the following two topics, both of which include the creation of fluoropolymer-based nanostructures with swift heavy ions mainly from the cyclotron of the Takasaki Ion Accelerators for Advanced Radiation Application. (1) We have prepared the ion-track membranes of poly(vinylidene fluoride) (PVDF), a type of fluoropolymer, by etching out latent tracks of MeV-GeV heavy ions in an alkaline solution. (2) The electrolyte membranes for fuel cell applications have been prepared by the direct grafting of a styrene monomer into the ion tracks in a fluoropolymer substrate, poly(ethylene-co-tetrafluoroethylene) (ETFE) film.
Yamaki, Tetsuya; Nuryanthi, N.*; Kitamura, Akane; Koshikawa, Hiroshi; Yoshimura, Kimio; Sawada, Shinichi; Asano, Masaharu; Maekawa, Yasunari; Suzuki, Akihiro*; Terai, Takayuki*
no journal, ,
Heavy ions at kinetic energies typically from several hundreds of MeV to a few GeV passing through a polymer substrate induce a continuous trail of excitations and ionizations called latent tracks. We used a direct ion-track grafting method for preparation of anion exchange membranes for fuel cells. The functional anion exchange groups were introduced inside the latent tracks, thereby achieving OH
-conductive channels through the thickness. These straight channels increased conductivities, while the isolated cylindrical structure of tracks restricted the water uptake.
Yamaki, Tetsuya; Nuryanthi, N.*; Koshikawa, Hiroshi; Asano, Masaharu*; Sawada, Shinichi; Kitamura, Akane; Maekawa, Yasunari; Kay-Obbe, V.*; Severin, D.*; Seidl, T.*; et al.
no journal, ,
Practically, polyvinylidene fluoride (PVDF) has been said to be the only fluoropolymer in which ion tracks can be developed by chemical etching. We thus investigated the possibility of varying the beam parameters and applying the effect of a pre-etching treatment for PVDF ion-track membranes with the goal of achieving enhanced track etching for effective control of the pore size and shape. Our activities also cover all types of fluoropolymers including PVDF. Compared to PVDF, poly(ethylene-
-tetrafluoroethylene) and a series of perfluoropolymers are known to be very stable in highly-concentrated acid or alkaline solutions or at higher temperatures. Although this property might make their ion-track etching very challenging, the ongoing research is expected to allow one to accumulate know-how on methods of chemical etching, which can be generalized for the chemical structures. These will give feedback to a guiding principle for effective ion-track etching in fluoropolymers.
Ishikawa, Norito; Okubo, Nariaki; Taguchi, Tomitsugu
no journal, ,
In this study, CeO was irradiated with 200 MeV Au ions at oblique incidence. Observation of as-irradiated samples by transmission electron microscope (TEM) shows that hillocks are created not only at the wide surfaces, but also at the side faces of the thin samples. Since the hillocks created at the side faces can be imaged by TEM, their shape and crystallographic features can be revealed. From the images of hillocks created at the side faces, many of the hillocks are found to be spherical. We present an experimental evidence that hillocks created for CeO irradiated with swift heavy ions have a crystal structure whose lattice spacing and orientation coincide with those of the matrix. The present method1) of observing hillocks can be a complementary technique to AFM(Atomic Force Microscopy.
Ishikawa, Norito
no journal, ,
Radiation damage due to irradiation with swift heavy ions (SHI) with the energy above 1 MeV/u has many different features compared to that due to irradiation with electrons and neutrons. One of the well-known phenomena related to SHI irradiation is formation of ion tracks. An ion track is a cylindrical region where the material near ion-path is locally modified in nanometric scale. Ion tracks are of great interest in a wide variety of research fields including nuclear materials science, physics of ion-solid interaction, nanotechnology, archaeology and so on. Mechanism of ion track formation in inorganic materials has always been one of the central and intriguing subjects in the SHI research community. It is still challenging to untangle the related problems. In this plenary talk, I would like to concentrate on the vital part of the recent advancement so that the audience can understand the logical pathway of the latest research works.
