九州大学 研究者情報
論文一覧
斉藤 光(さいとう ひかる) データ更新日:2023.11.22

准教授 /  先導物質化学研究所 融合材料部門


原著論文
1. Sreejith P Nandan, Nadiia Gumerova, Jasmin S Schubert, Hikaru Saito, Annette Rompel, Alexey Cherevan, Dominik Eder, Immobilization of a [CoᴵᴵᴵCoᴵᴵ (H₂O) W₁₁O₃₉] ⁷⁻ Polyoxoanion for the Photocatalytic Oxygen Evolution Reaction, ACS Materials Au, 2, 4, 505-515, 2, 4, 505-515, 2022.07.
2. Shiro Ihara, Hikaru Saito, Mizumo Yoshinaga, Lavakumar Avala, Mitsuhiro Murayama, Deep learning-based noise filtering toward millisecond order imaging by using scanning transmission electron microscopy, Scientific reports, 12, 1, 13462, 12, 1, 13462, 2022.08.
3. Dongyi Qin, Kazumasa Iida, Zimeng Guo, Chao Wang, Hikaru Saito, Satoshi Hata, Michio Naito, Akiyasu Yamamoto, K-doped Ba122 epitaxial thin film on MgO substrate by buffer engineering, Superconductor Science and Technology, 35, 9, 09LT01, 35, 9, 09LT01, 2022.08.
4. Shiro Ihara, Mizumo Yoshinaga, Hiroya Miyazaki, Kota Wada, Satoshi Hata, Hikaru Saito, Mitsuhiro Murayama, In situ electron tomography for the thermally activated solid reaction of anaerobic nanoparticles, Nanoscale, 15, 10133-10140, 15, 10133-10140, 2023.06.
5. Jesada Punyafu, Sukyoung Hwang, Shiro Ihara, Hikaru Saito, Nobuhiro Tsuji, Mitsuhiro Murayama, Microstructural factors dictating the initial plastic deformation behavior of an ultrafine-grained Fe–22Mn-0.6 C TWIP steel, Materials Science and Engineering: A, 862, 144506, 862, 144506, 2023.01.
6. Takaaki Noguchi, Toru Matsumoto, Akira Miyake, Yohei Igami, Mitsutaka Haruta, Hikaru Saito, Satoshi Hata, Yusuke Seto, Masaaki Miyahara, Naotaka Tomioka, Hope A Ishii, John P Bradley, Kenta K Ohtaki, Elena Dobrică, Hugues Leroux, Corentin Le Guillou, Damien Jacob, Francisco de la Peña, Sylvain Laforet, Maya Marinova, Falko Langenhorst, Dennis Harries, Pierre Beck, Thi HV Phan, Rolando Rebois, Neyda M Abreu, Jennifer Gray, Thomas Zega, Pierre-M Zanetta, Michelle S Thompson, Rhonda Stroud, Kate Burgess, Brittany A Cymes, John C Bridges, Leon Hicks, Martin R Lee, Luke Daly, Phil A Bland, Michael E Zolensky, David R Frank, James Martinez, Akira Tsuchiyama, Masahiro Yasutake, Junya Matsuno, Shota Okumura, Itaru Mitsukawa, Kentaro Uesugi, Masayuki Uesugi, Akihisa Takeuchi, Mingqi Sun, Satomi Enju, Aki Takigawa, Tatsuhiro Michikami, Tomoki Nakamura, Megumi Matsumoto, Yusuke Nakauchi, Masanao Abe, Masahiko Arakawa, Atsushi Fujii, Masahiko Hayakawa, Naru Hirata, Naoyuki Hirata, Rie Honda, Chikatoshi Honda, Satoshi Hosoda, Yu-ichi Iijima, Hitoshi Ikeda, Masateru Ishiguro, Yoshiaki Ishihara, Takahiro Iwata, Kousuke Kawahara, Shota Kikuchi, Kohei Kitazato, Koji Matsumoto, Moe Matsuoka, Yuya Mimasu, Akira Miura, Tomokatsu Morota, Satoru Nakazawa, Noriyuki Namiki, Hirotomo Noda, Rina Noguchi, Naoko Ogawa, Kazunori Ogawa, Tatsuaki Okada, Chisato Okamoto, Go Ono, Masanobu Ozaki, Takanao Saiki, Naoya Sakatani, Hirotaka Sawada, Hiroki Senshu, Yuri Shimaki, Kei Shirai, Seiji Sugita, Yuto Takei, Hiroshi Takeuchi, Satoshi Tanaka, Eri Tatsumi, Fuyuto Terui, Ryudo Tsukizaki, Koji Wada, Manabu Yamada, Tetsuya Yamada, Yukio Yamamoto, Hajime Yano, Yasuhiro Yokota, Keisuke Yoshihara, Makoto Yoshikawa, Kent Yoshikawa, Ryohta Fukai, Shizuho Furuya, Kentaro Hatakeda, Tasuku Hayashi, Yuya Hitomi, Kazuya Kumagai, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Hiromichi Soejima, Ayako I Suzuki, Tomohiro Usui, Toru Yada, Daiki Yamamoto, Kasumi Yogata, Miwa Yoshitake, Harold C Connolly Jr, Dante S Lauretta, Hisayoshi Yurimoto, Kazuhide Nagashima, Noriyuki Kawasaki, Naoya Sakamoto, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Shogo Tachibana, Sei-ichiro Watanabe, Yuichi Tsuda, A dehydrated space-weathered skin cloaking the hydrated interior of Ryugu, Nature Astronomy, 7, 2, 170-181, 7, 2, 170-181, 2023.02.
7. Takeshi Ono, Sae Mitamura, Takuro Hosomi, Hikaru Saito, Midori Ikeuchi, Jiangyang Liu, Kazuki Nagashima, Tsunaki Takahashi, Wataru Tanaka, Masaki Kanai, Takeshi Yanagida, Interfacial Molecular Compatibility for Programming Organic–Metal Oxide Superlattices, ACS Applied Materials & Interfaces, 15, 22, 27099-27109, 15, 22, 27099-27109, 2023.03.
8. Satoshi Hata, Daiki Fukuda, Hikaru Saito, Yusuke Shimada, Zimeng Guo, Akiyoshi Matsumoto, Hideharu Nakashima, Hitoshi Kitaguchi, Microstructure and Its Heat Treatment Process of Thin Films Fabricated by Alternate Sputtering of (Bi, Pb) 2 Sr 2 CaCu 2 O x and Pb–Ca–Cu–O Targets on SrTiO 3 Substrates, IEEE Transactions on Applied Superconductivity, 33, 5, 1-5, 33, 5, 1-5, 2023.03.
9. Norio Baba, Satoshi Hata, Hikaru Saito, Kenji Kaneko, Three-dimensional electron tomography and recent expansion of its applications in materials science, Microscopy, 72, 2, 111-134, 72, 2, 111-134, 2023.04.
10. Elena Dobrică, Hope A Ishii, John P Bradley, Kenta Ohtaki, Adrian J Brearley, Takaaki Noguchi, Toru Matsumoto, Akira Miyake, Yohei Igami, Mitsutaka Haruta, Hikaru Saito, Satoshi Hata, Yusuke Seto, Masaaki Miyahara, Naotaka Tomioka, Hugues Leroux, Corentin Le Guillou, Damien Jacob, Francisco de la Peña, Sylvain Laforet, Maya Marinova, Falko Langenhorst, Dennis Harries, Pierre Beck, Thi HV Phan, Rolando Rebois, Neyda M Abreu, Jennifer Gray, Thomas Zega, Pierre-M Zanetta, Michelle S Thompson, Rhonda Stroud, Kate Burgess, Brittany A Cymes, John C Bridges, Leon Hicks, Martin R Lee, Luke Daly, Phil A Bland, Michael E Zolensky, David R Frank, James Martinez, Akira Tsuchiyama, Masahiro Yasutake, Junya Matsuno, Shota Okumura, Itaru Mitsukawa, Kentaro Uesugi, Masayuki Uesugi, Akihisa Takeuchi, Mingqi Sun, Satomi Enju, Aki Takigawa, Tatsuhiro Michikami, Tomoki Nakamura, Megumi Matsumoto, Yusuke Nakauchi, Hisayoshi Yurimoto, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Shogo Tachibana, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Sei-ichiro Watanabe, Yuichi Tsuda, Nonequilibrium spherulitic magnetite in the Ryugu samples, Geochimica et Cosmochimica Acta, 346, 65-75, 345, 65-75, 2023.04.
11. Avala Lavakumar, Shuhei Yoshida, Jesada Punyafu, Shiro Ihara, Yan Chong, Hikaru Saito, Nobuhiro Tsuji, Mitsuhiro Murayama, Yield and flow properties of ultra-fine, fine, and coarse grain microstructures of FeCoNi equiatomic alloy at ambient and cryogenic temperatures, Scripta Materialia, 230, 115392, 2023.06.
12. Dung Thi Vu, Nikolaos Matthaiakakis, Hikaru Saito, Takumi Sannomiya, Exciton-dielectric mode coupling in MoS2 nanoflakes visualized by cathodoluminescence, Nanophotonics, 11, 9, 2129-2137, 2022.01, [URL].
13. Jiangyang Liu, Kazuki Nagashima, Takuro Hosomi, Wenjin Lei, Guozhu Zhang, Tsunaki Takahashi, Xixi Zhao, Yosuke Hanai, Atsuo Nakao, Masaya Nakatani, Wataru Tanaka, Hikaru Saito, Masaki Kanai, Taisuke Shimada, Takao Yasui, Yoshinobu Baba, Takeshi Yanagida, Water-Selective Nanostructured Dehumidifiers for Molecular Sensing Spaces, ACS sensors, 7, 2, 534-544, 2022.01, [URL].
14. Samar Batool, Sreejith P Nandan, Stephen Nagaraju Myakala, Ashwene Rajagopal, Jasmin S Schubert, Pablo Ayala, Shaghayegh Naghdi, Hikaru Saito, Johannes Bernardi, Carsten Streb, Alexey Cherevan, Dominik Eder, Surface Anchoring and Active Sites of [Mo3S13]2– Clusters as Co-Catalysts for Photocatalytic Hydrogen Evolution, ACS Catalysis, 12, 11, 6641-6650, 2022.05, [URL].
15. Atsushi Inoishi, Hiroki Sato, Yixin Chen, Hikaru Saito, Ryo Sakamoto, Hikari Sakaebe, Shigeto Okada, High capacity all-solid-state lithium battery enabled by in situ formation of an ionic conduction path by lithiation of MgH 2, RSC advances, 12, 17, 10749-10754, 2022.04, [URL].
16. Wojciech Klich, Miki Inada, Hongy Gao, Hikaru Saito, Michitaka Ohtaki, Microwave synthesis of ZnO microcrystals with novel asymmetric morphology, Advanced Powder Technology, 32, 11, 4356-4363, 2021.11, [URL].
17. Yifang Zhao, Suguru Koike, Rikuto Nakama, Shiro Ihara, Masatoshi Mitsuhara, Mitsuhiro Murayama, Satoshi Hata, Hikaru Saito, Five-second STEM dislocation tomography for 300 nm thick specimen assisted by deep-learning-based noise filtering, Scientific reports, 11, 1, 1-12, 2021.10, [URL].
18. Kazumasa Iida, Dongyi Qin, Chiara Tarantini, Takafumi Hatano, Chao Wang, Zimeng Guo, Hongye Gao, Hikaru Saito, Satoshi Hata, Michio Naito, Akiyasu Yamamoto, Approaching the ultimate superconducting properties of (Ba, K) Fe2As2 by naturally formed low-angle grain boundary networks, NPG Asia Materials, 13, 1, 1-9, 2021.10, [URL].
19. Hikaru Saito, Daichi Yoshimoto, Yuto Moritake, Taeko Matsukata, Naoki Yamamoto, Takumi Sannomiya, Valley-polarized plasmonic edge mode visualized in the near-infrared spectral range, Nano Letters, 21, 15, 6556-6562, 2021.07, [URL].
20. Yuta Shimizu, Koichiro Suekuni, Hikaru Saito, Pierric Lemoine, Emmanuel Guilmeau, Bernard Raveau, Raju Chetty, Michihiro Ohta, Toshiro Takabatake, Michitaka Ohtaki, Synergistic Effect of Chemical Substitution and Insertion on the Thermoelectric Performance of Cu26V2Ge6S32 Colusite, Inorganic chemistry, 60, 15, 11364-11373, 2021.07, [URL].
21. Takashi Hagiwara, Koichiro Suekuni, Pierric Lemoine, Andrew R Supka, Raju Chetty, Emmanuel Guilmeau, Bernard Raveau, Marco Fornari, Michihiro Ohta, Rabih Al Rahal Al Orabi, Hikaru Saito, Katsuaki Hashikuni, Michitaka Ohtaki, Key Role of d0 and d10 Cations for the Design of Semiconducting Colusites: Large Thermoelectric ZT in Cu26Ti2Sb6S32 Compounds, Chemistry of Materials, 10.1021/acs.chemmater.1c00872, 33, 9, 3449-3456, 2021.04.
22. Kazumasa Iida, Jens Hänisch, Keisuke Kondo, Mingyu Chen, Takafumi Hatano, Chao Wang, Hikaru Saito, Satoshi Hata, Hiroshi Ikuta, High J(c) and low anisotropy of hydrogen doped NdFeAsO superconducting thin film, SCIENTIFIC REPORTS, 10.1038/s41598-021-85216-3, 11, 1, 2021.03.
23. Dongyi Qin, Kazumasa Iida, Takafumi Hatano, Hikaru Saito, Yiming Ma, Chao Wang, Satoshi Hata, Michio Naito, Akiyasu Yamamoto, Realization of epitaxial thin films of the superconductor K-doped BaFe2As2, PHYSICAL REVIEW MATERIALS, 10.1103/PhysRevMaterials.5.014801, 5, 1, 2021.01.
24. Jiangyang Liu, Kazuki Nagashima, Yuki Nagamatsu, Takuro Hosomi, Hikaru Saito, Chen Wang, Wataru Mizukami, Guozhu Zhang, Benjarong Samransuksamer, Tsunaki Takahashi, Masaki Kanai, Takao Yasui, Yoshinobu Baba, Takeshi Yanagida, The impact of surface Cu 2+ of ZnO/(Cu 1− x Zn x) O heterostructured nanowires on the adsorption and chemical transformation of carbonyl compounds, Chemical Science, 12, 14, 5073-5081, 2021.02.
25. S Hata, T Honda, H Saito, M Mitsuhara, TC Petersen, M Murayama, Electron tomography: An imaging method for materials deformation dynamics, Current Opinion in Solid State and Materials Science, 24, 4, 100850, 2020.08.
26. Satoshi Hata, Hiromitsu Furukawa, Takashi Gondo, Daisuke Hirakami, Noritaka Horii, Ken-Ichi Ikeda, Katsumi Kawamoto, Kosuke Kimura, Syo Matsumura, Masatoshi Mitsuhara, Hiroya Miyazaki, Shinsuke Miyazaki, Mitsu Mitsuhiro Murayama, Hideharu Nakashima, Hikaru Saito, Masashi Sakamoto, Shigeto Yamasaki, Electron tomography imaging methods with diffraction contrast for materials research, Microscopy, 69, 3, 141-155, 2020.06.
27. Takuya Tanimoto, Koichiro Suekuni, Taiki Tanishita, Hidetomo Usui, Terumasa Tadano, Taiga Kamei, Hikaru Saito, Hirotaka Nishiate, Chul Ho Lee, Kazuhiko Kuroki, Michitaka Ohtaki, Enargite Cu3PS4
A Cu–S-Based Thermoelectric Material with a Wurtzite-Derivative Structure, Advanced Functional Materials, 10.1002/adfm.202000973, 30, 22, 2020.05, [URL], Compound semiconductors derived from ZnS (zincblende and wurtzite) with tetrahedral framework structures have functions for various applications. Examples of such materials include Cu–S-based materials with zincblende-derivative structures, which have attracted attention as thermoelectric (TE) materials over the past decade. This study illuminates superior TE performance in polycrystalline samples of enargite Cu3P1− xGexS4 with a wurtzite-derivative structure. The substitution of Ge for P dopes holes into the top of the valence band composed of Cu-3d and S-3p, whereby its multiband characteristic leads to a high TE power factor. Furthermore, a reduction in the grain size to 50–300 nm can effectively decrease phonon mean free paths, leading to low thermal conductivity. These features result in a dimensionless TE figure of merit ZT of 0.5 at 673 K for the x = 0.2 sample. Environmentally benign and low-cost characteristics of the constituent elements of Cu3PS4, as well as its high-performance thermoelectricity, make it a promising candidate for large-scale TE applications. Furthermore, this finding extends the development field of Cu–S-based TE materials to those with wurtzite-derivative structures..
28. Hikaru Saito, Hugo Lourenço-Martins, Noémie Bonnet, Xiaoyan Li, Tracy C. Lovejoy, Niklas Dellby, Odile Stéphan, Mathieu Kociak, Luiz Henrique Galvão Tizei, Emergence of point defect states in a plasmonic crystal, Physical Review B, 10.1103/PhysRevB.100.245402, 100, 24, 2019.12, [URL], Plasmonic crystals are well known to have band structure including a band gap, enabling the control of surface plasmon propagation and confinement. The band dispersion relation of bulk crystals has been generally measured by momentum-resolved spectroscopy using far field optical techniques while the defects introduced in the crystals have separately been investigated by near field imaging techniques so far. Particularly, defect related energy levels introduced in the plasmonic band gap have not been observed experimentally. In order to investigate such a localized mode, we performed electron energy-loss spectroscopy (EELS) on a point defect introduced in a plasmonic crystal made up of flat cylinders protruding out of a metal film and arranged on a triangular lattice. The energy level of the defect mode was observed to lie within the full band-gap energy range. This was confirmed by a momentum-resolved EELS measurement of the band gap performed on the same plasmonic crystal. Furthermore, we experimentally and theoretically investigated the emergence of the defect states by starting with a corral of flat cylinders protrusions and adding sequentially additional shells of those in order to eventually form a plasmonic band-gap crystal encompassing a single point defect. It is demonstrated that a defectlike state already forms with a crystal made up of only two shells..
29. Koichiro Suekuni, Yuta Shimizu, Eiji Nishibori, Hidetaka Kasai, Hikaru Saito, Daichi Yoshimoto, Katsuaki Hashikuni, Yohan Bouyrie, Raju Chetty, Michihiro Ohta, Emmanuel Guilmeau, Toshiro Takabatake, Kosuke Watanabe, Michitaka Ohtaki, Atomic-scale phonon scatterers in thermoelectric colusites with a tetrahedral framework structure, Journal of Materials Chemistry A, 10.1039/c8ta08248k, 7, 1, 228-235, 2019.01, [URL], Copper-based chalcogenides with tetrahedral framework structures have been attracting increasing attention as environmentally friendly thermoelectric materials. A representative group of such thermoelectric chalcogenides is the Cu 26 A 2 M 6 S 32 (A = V, Nb, Ta; M = Ge, Sn) family of colusites, which exhibit low electrical resistivity, a large Seebeck coefficient, and low thermal conductivity; these properties are necessary for efficient thermal-to-electronic energy conversion. Here, we show the impact of crystal structure on the lattice thermal conductivity of colusite with A = Nb, M = Sn. The crystal structure can be modified by controlling the cationic compositions and the deficiency in the sulfur content as Cu 26-x Nb 2 Sn 6+x S 32-δ . The Cu/Sn ratio is found to be the key parameter for exsolution into distinct phases with ordered and disordered arrangements of cations. For the ordered-structure phase, sulfur sublimation induces atomic-scale defects/disordered states including interstitial defects, anti-site defects, and site splitting, which function as strong phonon scatterers, and the lowest lattice thermal conductivity of ∼0.5 W K -1 m -1 is achieved for the modified ordered structure. This finding provides a simple approach to modifying the crystal structure of thermoelectric chalcogenides via the loss of anions to reduce their lattice thermal conductivity..
30. Hikaru Saito, Daichi Yoshimoto, Hugo Lourenco-Martins, Naoki Yamamoto, Takumi Sannomiya, Hybridization of Gap Modes and Lattice Modes in a Plasmonic Resonator Array with a Metal-Insulator-Metal Structure, ACS Photonics, 10.1021/acsphotonics.9b00977, 2019.01, [URL], Plasmonic resonator arrays have attracted a great interest as a platform to enhance light-matter interaction and have been examined for their applicability to various types of optical devices, such as sensors, light emitter, and photocatalyst, to name a few. In a plasmonic resonator array, localized and propagating plasmon modes can hybridize, which is known to result in an anticrossing of the plasmon bands in the dispersion curves. However, it was so far unclear how the modal symmetry affects such a hybridization, especially when it occurs at a specific reciprocal lattice point with a high degree of symmetry, for example, the Î" point. In this work, we used momentum-resolved cathodoluminescence-scanning transmission electron microscopy to comprehensively characterize the modal hybridization at the Î" point. Our study reveals theoretically and experimentally the existence of mode symmetry selection rules that specify hybrid pairs of the lattice mode and localized mode..
31. Itto Sugimoto, Seung Hwan C. Park, Satoshi Hirano, Hikaru Saito, Satoshi Hata, Microscopic observation of precipitation behavior at friction stirring zone of super duplex stainless steel, Materials Transactions, 10.2320/matertrans.M2019069, 60, 9, 2003-2007, 2019.01, [URL], To investigate the precipitation behavior of super duplex stainless steel in its weld by friction stir welding (FSW) at a low welding speed, we carried out microstructural observation and analysis. An intermetallic compound phase, ·, was observed in the heat affected zone (HAZ). The · phase precipitated at the interfaces between ¤-Fe (ferrite) and £ -Fe (austenite) grains 12 mm away from the stir zone (SZ)/HAZ boundary. On the other hand, the Cr2N was observed together with the belt-like £ -Fe grain aggregates in the vicinity of the advancing side (AS) of the SZ. The other intermetallic phase,», was also observed at a triple junction of £ -Fe grains. This demonstrates that the precipitation of the Cr2N and» phases correlates with the transformation of ¤-Fe to £A-Fe (secondary austenite)..
32. 波多 聰, 宮崎 裕也, 斉藤 光, 村山 光宏, 佐藤 和久, 工藤 博幸, 古河 弘光, 川本 克巳, 堀井 則孝, 加茂 勝己, 宮崎 伸介, 權堂 貴志, TEM内その場変形トモグラフィー観察システムの開発, Kenbikyo, 10.11410/kenbikyo.54.1_44, 54, 1, 44-48, 2019, [URL], We have developed a unique methodology and a new hardware/software-integrated system for in-situ straining and electron tomography (ET) experiments. The central software of the system controls a straining-and-tomography specimen holder, imaging devices and the specimen stage of a transmission electron microscope (TEM) in an integrated manner. Using the system, one can perform in-situ time-resolved three-dimensional (3D) studies that explore in real-time and at sub-microscopic levels the internal behavior of materials subjected to external stresses. 3D visualization of a Pb–Sn solder alloy thin foil's deformation dynamics by iterative step-wise stress loading and tilt-series data sets acquisition is introduced as an application of the system..
33. Daichi Yoshimoto, Hikaru Saito, Satoshi Hata, Yoshifumi Fujiyoshi, Hiroki Kurata, Characterization of Nonradiative Bloch Modes in a Plasmonic Triangular Lattice by Electron Energy-Loss Spectroscopy, ACS Photonics, 10.1021/acsphotonics.8b00936, 5, 11, 4476-4483, 2018.11, [URL], Electron beam spectroscopy has recently attracted much attention in the modal analysis of nanophotonic and plasmonic systems. In principle, electron energy-loss spectroscopy (EELS) provides information about the electromagnetic local density of states of all sorts of electromagnetic modes as well as nonradiative modes. However, there have not been many examples related to the EELS analyses for electromagnetic Bloch modes. Herein, EELS measurements are performed for the characterization of nonradiative band-edge modes facing the first bandgap in a plasmonic crystal with a triangular lattice, which is well-known for its full bandgap formation. The obtained spectrum images clearly determine the characteristics of the lower and upper band-edge modes, compared with an analytical model based on group theory and a numerical simulation by the finite-difference time-domain method. The EELS spectra also reveal differences in the plasmonic density of states between the lower and upper band-edges, which provides information about the band deformation near the bandgap..
34. 波多 聰, 斉藤 光, 村山 光宏, 佐藤 和久, 工藤 博幸, マテリアル系電子線トモグラフィーの実際と動向, まてりあ : 日本金属学会会報, 10.2320/materia.57.589, 57, 12, 589-594, 2018, [URL].
35. Kana L. Hasezaki, Hikaru Saito, Takumi Sannomiya, Hiroya Miyazaki, Takashi Gondo, Shinsuke Miyazaki, Satoshi Hata, Three-dimensional visualization of dislocations in a ferromagnetic material by magnetic-field-free electron tomography, Ultramicroscopy, 10.1016/j.ultramic.2017.07.016, 182, 249-257, 2017.11, [URL], In conventional transmission electron microscopy, specimens to be observed are placed in between the objective lens pole piece and therefore exposed to a strong magnetic field about 2 T. For a ferromagnetic specimen, magnetization of the specimen causes isotropic and anisotropic defocusing, deflection of the electron beam as well as deformation of the specimen, which all become more severe when the specimen tilted. Therefore electron tomography on a ferromagnetic crystalline specimen is highly challenging because tilt-series data sets must be acquired without changing the excitation condition of a specific diffraction spot. In this study, a scanning transmission electron microscopy (STEM) tomography method without magnetizing a ferromagnetic specimen has been developed for three-dimensional (3D) visualization of dislocations in α-Fe, which is a typical ferromagnetic material. Magnetic-field-free environment down to 0.38 ± 0.07 mT at the specimen position is realized by demagnetizing the objective lens pole piece of a commercial STEM instrument. By using a spherical aberration corrector with the magnetic-field-free environment, an “aberration corrected Low-Mag STEM mode” with no objective lens field reaches a convergence semi angle ∼1 mrad and a spatial resolution ∼5 nm, and shows an adequate performance of imaging dislocations under a two-beam excitation condition for a low-index diffracted beam. The illumination condition for the aberration corrected Low-Mag STEM mode gives no overlap between the direct beam disk (spot) and neighboring diffraction disks. An electron channeling contrast imaging technique, in which an annular detector was located at a doughnut area between the direct beam and the neighboring diffracted beams, was effectively employed with the aberration corrected Low-Mag STEM mode to keep image intensity high enough even at large specimen-tilt angles. The resultant tomographic observation visualized 3D dislocation arrangements and active slip planes in a deformed α-Fe specimen..
36. Hikaru Saito, Naoki Yamamoto, Takumi Sannomiya, Waveguide Bandgap in Crystalline Bandgap Slows Down Surface Plasmon Polariton, ACS Photonics, 10.1021/acsphotonics.6b00943, 4, 6, 1361-1370, 2017.06, [URL], Next generation on-chip optical devices require light manipulation in time and space, that is, control of group velocity of light in subwavelength dimensions. A waveguide in plasmonic crystal fulfills such requirements offering nanoscale light confinement in the dispersion-tunable plasmonic crystal matrix. However, there has been no direct access to the local dispersion of the waveguide mode itself, and the group velocity of light could not be evaluated. Herein, for the first time, we experimentally clarify the dispersion of the waveguide modes by use of angle-resolved cathodoluminescence scanning transmission electron microscopy. Their group velocity can be extremely slowed down by the existence of a bandgap formed in the waveguide in the energy range of the plasmonic crystal bandgap..
37. Takumi Sannomiya, Hikaru Saito, Juliane Junesch, Naoki Yamamoto, Coupling of plasmonic nanopore pairs
Facing dipoles attract each other, Light: Science and Applications, 10.1038/lsa.2016.146, 5, 9, 2016.09, [URL], Control of the optical properties of nano-plasmonic structures is essential for next-generation optical circuits and high-throughput biosensing platforms. Realization of such nano-optical devices requires optical couplings of various nanostructured elements and field confinement at the nanoscale. In particular, symmetric coupling modes, also referred to as dark modes, have recently received considerable attention because these modes can confine light energy to small spaces. Although the coupling behavior of plasmonic nanoparticles has been relatively well studied, couplings of inverse structures, that is, holes and pores, remain partially unexplored. Even for the most fundamental coupling system of two dipolar holes, comparison of the symmetric and anti-symmetric coupling modes has not been performed. Here we present, for the first time, a systematic study of the symmetric and anti-symmetric coupling of nanopore pairs using cathodoluminescence by scanning transmission electron microscopy and electromagnetic simulation. The symmetric coupling mode, approximated as a pair of facing dipoles, is observed at a lower energy than that of the anti-symmetric coupling mode, indicating that the facing dipoles attract each other. The anti-symmetric coupling mode splits into the inner- and outer-edge localized modes as the coupling distance decreases. These coupling behaviors cannot be fully explained as inverses of coupled disks. Symmetric and anti-symmetric coupling modes are also observed in a short-range ordered pore array, where one pore supports multiple local resonance modes, depending on the distance to the neighboring pore. Accessibility to the observed symmetric modes by far field is also discussed, which is important for nanophotonic device applications..
38. Chanmin Lee, Yukwon Jeon, Satoshi Hata, Joo Il Park, Ryutaro Akiyoshi, Hikaru Saito, Yasutake Teraoka, Yong Gun Shul, Hisahiro Einaga, Three-dimensional arrangements of perovskite-type oxide nano-fiber webs for effective soot oxidation, Applied Catalysis B: Environmental, 10.1016/j.apcatb.2016.03.001, 191, 157-164, 2016.08, [URL], Perovskite-type oxides have been widely applied in heterogeneous catalytic reactions, such as soot oxidation. However, a poor contact point between the catalyst and solid reactant (soot) often limits the catalytic performance. Here, we report La
1 - x
Sr
x
Co
0.2
Fe
0.8
O
3 - δ
perovskite oxide catalysts with a unique three-dimensional (3D) fiber web structure that increases the high-contact area by trapping soot in the unique pore structure for effective catalytic activity. This feature was carefully analyzed using scanning transmission electron microscopy (STEM) tomography to investigate the location of the soot on the web. The structure of the web, with a thickness of approximately 55 μm, indicated that the soot particles were caught by the 3D pores between the fibers. The relationship between the Sr amount and activate oxygen was also characterized by means of XPS. The results show that the Sr amount of 0.4 produced the highest amount of active oxygen species (O
-
) that are essential for soot oxidation reaction. The developed catalyst exhibited a good catalytic performance due to the optimized perovskite chemical structure and the greatly increased number of the contact points owing to the 3D inter-fiber spaces. Hence, our proposed approach is reasonable for application to real soot combustion processes and can also be easily extended to numerous other catalytic processes to enhance the catalytic activity..
39. Jesbains Kaur, Noriyuki Kuwano, Khairur Rijal Jamaludin, Masatoshi Mitsuhara, Hikaru Saito, Satoshi Hata, Shuhei Suzuki, Hideto Miyake, Kazumasa Hiramatsu, Hiroyuki Fukuyama, Electron microscopy analysis of microstructure of postannealed aluminum nitride template, Applied Physics Express, 10.7567/APEX.9.065502, 9, 6, 2016.06, [URL], The microstructure of an AlN template after high-temperature annealing was investigated by transmission electron microscopy (TEM). The AlN template was prepared by depositing an AlN layer of about 200nm thickness on a sapphire (0001) substrate by metal-organic vapor phase epitaxy. The AlN template was annealed under (N2 + CO) atmosphere at 1500-1650 °C. TEM characterization was conducted to investigate the microstructural evolution, revealing that the postannealed AlN has a two-layer structure, the upper and lower layers of which exhibit Al and N polarities, respectively. It has been confirmed that postannealing is an effective treatment for controlling the microstructure..
40. Hisahiro Einaga, Yusaku Nasu, Manabu Oda, Hikaru Saito, Catalytic performances of perovskite oxides for CO oxidation under microwave irradiation, Chemical Engineering Journal, 10.1016/j.cej.2015.07.051, 283, 97-104, 2016.01, [URL], Microwave-assisted heterogeneous catalytic oxidation of CO over ABO3 type perovskite oxides (A: La; B: Mn, Fe, Co) was carried out and the factors controlling the catalytic properties were investigated. The heating behavior of perovskite oxides depended on the physical state of catalyst particles and catalyst compositions. Catalytic activity of the perovskite oxide decreased in the order of LaCoO3>LaMnO3>LaFeO3 under conventional heating, although LaMnO3 exhibited similar activity to LaCoO3 under microwave heating. The partial substitution of A site cation La by Sr enhanced the heating and catalytic properties under microwave heating conditions. Catalytic properties of the perovskite oxides under microwave heating were compared with those under conventional external heating..
41. Hikaru Saito, Shohei Mizuma, Naoki Yamamoto, Confinement of Surface Plasmon Polaritons by Heterostructures of Plasmonic Crystals, Nano Letters, 10.1021/acs.nanolett.5b02623, 15, 10, 6789-6793, 2015.10, [URL], Square lattice plasmonic crystals (SQ-PlCs) composed of silver pillars generate large bandgaps for surface plasmon polaritons (SPPs). SPP confinement is demonstrated using one- and two-dimensional heterostructures of SQ-PlCs comprised of cylindrical pillars with different diameters in a common square lattice. Two kinds of localized modes are observed to appear in the heterostructures by photon map imaging using cathodoluminescence (CL) technique combined with a scanning transmission electron microscopy (STEM). Angle-resolved CL spectroscopy reveals contrasting characteristics of the two localized modes in their emission distributions, indicating that they originate from the band-edge A and E modes of the matrix SQ-PlC..
42. Hikaru Saito, Naoki Yamamoto, Control of Light Emission by a Plasmonic Crystal Cavity, Nano Letters, 10.1021/acs.nanolett.5b01719, 15, 9, 5764-5769, 2015.09, [URL], Surface plasmon-polaritons (SPPs) localized inside a plasmonic crystal (PlC) cavity are probed by STEM-CL technique to characterize the influence of the surface shape parameters on the cavity modes. The results elucidate the formation mechanism of the cavity mode in terms of the symmetry and quality factor, which provide a clear design guide for the PlC cavity to control the coupling between SPPs and photons in plasmonic devices and future integrated circuits..
43. H. Saito, H. Kurata, Formation of a hybrid plasmonic waveguide mode probed by dispersion measurement, Journal of Applied Physics, 10.1063/1.4916800, 117, 13, 2015.04, [URL], Hybrid waveguides, i.e., dielectric waveguides combined with plasmonic waveguides, have great potential for concomitantly exhibiting subwavelength confinement and long range propagation, enabling a highly integrated photonic circuit. We report the characterization of hybrid waveguide modes excited in Si/SiO2/Al films, by dispersion measurement using angle-resolved electron energy-loss spectroscopy. This experiment directly verifies the formation of the hybrid waveguide mode with a strongly localized electromagnetic field in a 6-nm-thick SiO2 layer. The results clearly describe the characteristic behavior of the hybrid waveguide mode, which depends on the effective index of the constituent dielectric waveguide and the surface plasmon-polariton modes..
44. Hikaru Saito, Naoki Yamamoto, Size dependence of bandgaps in a two-dimensional plasmonic crystal with a hexagonal lattice, Optics Express, 10.1364/OE.23.002524, 23, 3, 2524-2540, 2015.02, [URL], The optical properties of surface plasmon polaritons (SPPs) are investigated at the Γ point in a two-dimensional plasmonic crystal with a hexagonal lattice (Hex-PlC). The cathodoluminescence (CL) technique combined with a scanning transmission electron microscope (STEM) are used to produce spectral images of the SPP standing waves at the Γ point and identify the four types of band-edge modes predicted by group theory. The systematic measurement of the band-edge energies employed here is used to determine the characteristic dependence of each band-edge mode on the structure parameters, which provides some criteria for the design of plasmonic devices with Hex-PlCs..
45. Hisahiro Einaga, Ryo Shiranita, Hikaru Saito, Satoshi Hata, Codeposition of colloidal platinum particles and iron chloride precursor on TiO2 for efficient catalytic oxidation of CO to CO2, Chemistry Letters, 10.1246/cl.150903, 44, 12, 1786-1788, 2015, [URL], Codeposition of metal chlorides with Pt colloidal nanoparticles on TiO2 followed by oxidation at 400 °C and reduction at 200 °C improved the activity for Pt-catalyzed CO oxidation with stoichiometric amount of O2. The highest activity was obtained when FeCl3 was used as the additive with the Fe/Pt ratio of 0.2. XAFS, X-EDS, FTIR, and catalytic studies revealed that the deposition of Fe species on the reduced Pt sites gave active sites, which exhibited CO oxidation with high efficiency..
46. Naoki Yamamoto, Hikaru Saito, Size dependence of band structures in a two-dimensional plasmonic crystal with a square lattice, Optics Express, 10.1364/OE.22.029761, 22, 24, 29761-29777, 2014.12, [URL], A scanning transmission electron microscope (STEM) -cathodoluminescence (CL) technique is used to investigate the size dependence of the band structures in two-dimensional plasmonic crystals with a square lattice (SQ-PlCs) composed of cylindrical pillars and holes. The experimentally determined and calculated dependences of the band edge energies of the three SPP modes at the γ point on the diameter of the cylindrical structure agree well. The photon maps reveal the field strength distributions of the standing SPP waves of the three eigenmodes. Additionally, a mechanism is proposed to explain the dependence of the contrast on the detected light polarization..
47. Hikaru Saito, Naoki Yamamoto, Cathodoluminescence of 2D plasmonic crystals with hexagonal lattice, JSAP-OSA Joint Symposia, JSAP 2014
JSAP-OSA Joint Symposia, JSAP 2014
, 2014.09.
48. Hikaru Saito, Hiroki Kurata, Direct measurement of dispersion relation for surface plasmon-polaritons on silver nanoantennas, Microscopy, 10.1093/jmicro/dft048, 63, 2, 155-159, 2014.01, [URL], We investigated the degree to which the dispersion relation of surface plasmon-polaritons excited on silver nanoantennas depends on length. To accomplish this, dispersion measurements for individual silver nanoantennas with lengths from 220 nm to 2.5 μm were performed using angle-resolved electron energy-loss spectroscopy (AREELS) and spatially resolved EELS (SREELS). AREELS enabled measurements of the dispersion relation extending into the high-energy region of 2.6 eV for a 2.5-μm-long silver nanoantenna, without the need to excite Fabry–Perot-type resonances. Our experiments showed that the dispersion relation of silver nanoantennas that have the same diameter is independent of their individual lengths..
49. Hikaru Saito, Kyoko Namura, Motofumi Suzuki, Hiroki Kurata, Dispersion relations for coupled surface plasmon-polariton modes excited in multilayer structures, Microscopy, 10.1093/jmicro/dft047, 63, 1, 85-93, 2014.01, [URL], The coupled surface plasmon-polariton (SPP) modes excited in an Al/SiO2/ Al multilayer structure were analyzed using angle-resolved electron energy-loss spectroscopy (AREELS) with a relativistic electron probe. The dispersion relations for the coupled SPP modes were then directly observed and compared with predicted relations obtained via calculations. Good agreement was noted between the experimental and calculated results. In the multilayer structures, the dispersion relation for the coupled SPP modes was found to be sensitive to the thickness of each film, which could be interpreted qualitatively by the electron energy-loss probability calculated for thin aluminum (Al) films and narrow Al gaps using Kröger’s formula. It was demonstrated that significant differences in the excitation probability for SPPs could be observed depending on the coupling modes..
50. H. Saito, C. H. Chen, H. Kurata, Optical guided modes coupled with Čerenkov radiation excited in Si slab using angular-resolved electron energy-loss spectrum, Journal of Applied Physics, 10.1063/1.4796140, 113, 11, 2013.03, [URL], Retardation effects in the valence electron energy-loss spectrum (EELS) of a Si slab are analyzed by angular-resolved EELS. The dispersion curves of the valence spectra excited in a slab are directly observed from a specimen area with several different thicknesses and are interpreted by performing a calculation of the dispersion relation using Krögers formula. The dispersion curves observed below about 3 eV are attributed to guided modes coupled with Čerenkov radiation (ČR). The coupling between guided modes and ČR is found to be dependent on the sample thickness (t). For the sample with t > 150 nm, the intensity of the guided modes increased linearly with thickness, revealing the coupling with ČR. For t 150 nm, however, the intensity of the guided modes rapidly decreased due to a diminished coupling with ČR, resulting from the thickness-dependent dispersion curves of the guided modes..
51. Amporn Wiengmoon, John T.H. Pearce, Torranin Chairuangsri, Seiji Isoda, Hikaru Saito, Hiroki Kurata, HRTEM and HAADF-STEM of precipitates at peak ageing of cast A319 aluminium alloy, Micron, 10.1016/j.micron.2012.10.009, 45, 32-36, 2013.02, [URL], High-resolution transmission electron microscopy (HRTEM) and high-angle annular-dark-field scanning transmission electron microscopy (HAADF-STEM) were applied to investigate the precipitates formed during age hardening at 170 ± 5 °C for up to 48. h of cast A319 aluminium alloy (Al-4.93. wt%Si-3.47. wt%Cu). The precipitates at the peak-aged condition have been identified as mainly θ" together with a smaller amount of θ'. It is proposed that the θ" is responsible for hardening at peak ageing at 170 °C of the cast A319 aluminium alloy..
52. Wan Hsien Lin, Hikaru Saito, Takashi Nemoto, Hiroki Kurata, Mitch M.C. Chou, Seiji Isoda, Jih Jen Wu, Photoassisted scanning tunneling microscopy investigation on the ZnO(0001)-Zn surface treated by alkaline solution, Journal of Physical Chemistry C, 10.1021/jp302045j, 116, 19, 10664-10671, 2012.05, [URL], In this study, the surface geometric structures of epitaxial (0001) ZnO films treated by NaOH solution are investigated using photoassisted scanning tunneling microscopy (STM). By illuminating ultraviolet (UV) light on the epitaxial (0001) ZnO film, the tunneling current can be significantly enhanced to construct the well-defined STM images. Polarity identification of the epitaxial (0001) ZnO film by convergent-beam electron diffraction indicates that the epitaxial (0001) ZnO film exhibits the Zn-polar surface. Two types of topographic features, i.e., hexagonal pyramid and flat plane, are observed in the AFM images of the as-grown epitaxial (0001) ZnO film. UV-assisted STM images reveal the anisotropic etching behaviors of the epitaxial (0001) ZnO films in NaOH solution. The faceted and symmetrically layered hexagonal-pyramid feature gets asymmetrical and rounded with increasing etching time. On the other hand, few small hexagonal pits on the as-grown flat ZnO(0001)-Zn surface are developed to asymmetrically hexagonal cavities with flat terraces and steps after NaOH treatments. In addition, triangular reconstruction of the NaOH-treated ZnO(0001)-Zn surface and evidently layer-stacking feature on a faceted ZnO surface with a step height resolved in the atomic scale are also demonstrated in ambience using the photoassisted STM..

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