Nature Portfolio Acta Medica Okayama 2045-2322 15 1 2025 Local-structure insight into the improved superconducting properties of Pb-substituted La(O, F)BiS2: a photoelectron holography study 8366 EN Yajun Li Graduate School of Natural Science and Technology, Okayama University Yusuke Hashimoto Nara Institute of Science and Technology (NAIST) Noriyuki Kataoka Graduate School of Natural Science and Technology, Okayama University Zexu Sun Nara Institute of Science and Technology (NAIST) Sota Kawamura Nara Institute of Science and Technology (NAIST) Hiroto Tomita Nara Institute of Science and Technology (NAIST) Taro Setoguchi Graduate School of Natural Science and Technology, Okayama University Soichiro Takeuchi Nara Institute of Science and Technology (NAIST) Shunjo Koga Nara Institute of Science and Technology (NAIST) Kohei Yamagami Japan Synchrotron Radiation Research Institute (JASRI) Yoshinori Kotani Japan Synchrotron Radiation Research Institute (JASRI) Satoshi Demura Department of Physics, College of Science and Technology(CST), Nihon University Kanako Noguchi Tokyo University of Science Hideaki Sakata Tokyo University of Science Tomohiro Matsushita Nara Institute of Science and Technology (NAIST) Takanori Wakita Graduate School of Natural Science and Technology, Okayama University Yuji Muraoka Graduate School of Natural Science and Technology, Okayama University Takayoshi Yokoya Graduate School of Natural Science and Technology, Okayama University Pb-substituted La(O, F)BiS2 (Pb-LaOFBiS2) exhibits improved superconducting properties and a resistivity anomaly around 100 K that is attributed to a structural transition. We have performed temperature(T)-dependent photoelectron holography (PEH) to study dopant incorporation sites and the local structure change across the anomaly. The PEH study of Pb-LaOFBiS2 provided evidence for the dominant incorporation sites of Pb and F: Pb atoms are incorporated into the Bi sites and F atoms are incorporated into the O site. No remarkable difference in the local structures around Pb and Bi atoms was observed. Across the temperature of the resistivity anomaly (T*), photoelectron holograms of Bi 4f changed. Comparisons of holograms with those of non-substituted LaOFBiS2 sample, as well as simulated holograms, suggested that (1), above T*, the tetragonal structure of Pb-LaOFBiS2 is different from the tetragonal structure of LaOFBiS2 and (2), below T*, the tetragonal structure still remains in Pb-LaOFBiS2. We discuss a possible origin of the difference in the structure above T* and the implication of the result below T*, which are necessary ingredients to understand the physical properties of Pb-LaOFBiS2. No potential conflict of interest relevant to this article was reported.

IOP Publishing Acta Medica Okayama 0021-4922 62 12 2023 Photoelectron holographic evidence for the incorporation site of Se and suppressed atomic displacement of the conducting layer of La(O,F)BiSSe 125001 EN YaJun Li Engineering Research Center of Integrated Circuit Packaging and Testing, Ministry of Education, Tianshui Normal University ZeXu Sun Nara Institute of Science and Technology (NAIST) Noriyuki Kataoka Graduate School of Natural Science and Technology, Okayama University Taro Setoguchi Graduate School of Natural Science and Technology, Okayama University Yusuke Hashimoto Nara Institute of Science and Technology (NAIST) Soichiro Takeuchi Nara Institute of Science and Technology (NAIST) Shunjo Koga Nara Institute of Science and Technology (NAIST) Kazuhisa Hoshi Department of Physics, Tokyo Metropolitan University Yoshikazu Mizuguchi Department of Physics, Tokyo Metropolitan University Tomohiro Matsushita Nara Institute of Science and Technology (NAIST) Takanori Wakita Graduate School of Natural Science and Technology, Okayama University Yuji Muraoka Graduate School of Natural Science and Technology, Okayama University Takayoshi Yokoya Graduate School of Natural Science and Technology, Okayama University La(O,F)BiS2-xSex is a layered material that is considered to be a candidate exotic superconductor as well as a promising thermoelectrical material. We performed soft X-ray photoelectron holography to study the Se incorporation site and the local atomic arrangement of the conducting layer. A comparison of the experimental holograms with the simulated holograms indicates that Se atoms preferentially occupy the S sites in the conducting Bi–S plane of La(O,F)BiS2. A comparison between the state-of-the-art holographic reconstructions of La(O,F)BiSSe and La(O,F)BiS2 suggests that Se substitution suppresses the displacement of S atoms in La(O,F)BiS2. These results provide photoelectron holographic evidence for the Se incorporation site and the Se-induced suppression of in-plane disorder. No potential conflict of interest relevant to this article was reported.

IOP Publishing Acta Medica Okayama 0953-8984 33 3 2020 Soft x-ray irradiation induced metallization of layered TiNCl 035501 EN Noriyuki Kataoka Graduate School of Natural Science and Technology, Okayama University Masashi Tanaka Graduate School of Engineering, Kyushu Institute of Technology Wataru Hosoda Graduate School of Natural Science and Technology, Okayama University Takumi Taniguchi Graduate School of Natural Science and Technology, Okayama University Shin-ichi Fujimori Materials Sciences Research Center, Japan Atomic Energy Agency Takanori Wakita Graduate School of Natural Science and Technology, Okayama University Yuji Muraoka Graduate School of Natural Science and Technology, Okayama University Takayoshi Yokoya Graduate School of Natural Science and Technology, Okayama University We have performed soft x-ray spectroscopy in order to study the photoirradiation time dependence of the valence band structure and chemical states of layered transition metal nitride chloride TiNCl. Under the soft x-ray irradiation, the intensities of the states near the Fermi level (EF) and the Ti3+ component increased, while the Cl 2p intensity decreased. Ti 2p–3d resonance photoemission spectroscopy confirmed a distinctive Fermi edge with Ti 3d character. These results indicate the photo-induced metallization originates from deintercalation due to Cl desorption, and thus provide a new carrier doping method that controls the conducting properties of TiNCl. No potential conflict of interest relevant to this article was reported.

Elsevier Acta Medica Okayama 0040-6090 698 2020 Strain effects on spinodal decomposition in TiO2-VO(2)films on TiO2(100) substrates 137854 EN Yuji Muraoka Research Institute for Interdisciplinary Science (RIIS), Okayama University Fumiya Yoshii Graduate School of Natural Science and Technology, Okayama University Takahiro Fukuda Graduate School of Natural Science and Technology, Okayama University Yuji Manabe Graduate School of Natural Science and Technology, Okayama University Mikiko Yasuno Graduate School of Natural Science and Technology, Okayama University Yoshito Takemoto Graduate School of Natural Science and Technology, Okayama University Kensei Terashima Research Institute for Interdisciplinary Science, Okayama University Takanori Wakita Research Institute for Interdisciplinary Science (RIIS), Okayama University Takayoshi Yokoya We investigate the influence of lattice strain in the c-axis direction on spinodal decomposition in rutile TiO2-VO2 films on TiO2(100) substrates. The [100]-oriented Ti0.4V0.6O2 (TVO) solid-solution films are fabricated on rutile TiO2(100) substrates using a pulsed laser deposition with a KrF excimer laser, and are annealed inside the spinodal region. X-ray diffraction and scanning transmission electron microscopy are employed for characterization. Consequently, the in-plane tensile strain in the c-axis direction promotes the Ti-V interdiffusion in TVO/TiO2(100) under thermal annealing. In contrast, relaxation of the tensile strain results in the occurrence of spinodal decomposition along the c-axis direction in the film. These results indicate that the relaxation of the tensile strain in the c-axis direction is critically important for enabling spinodal decomposition in TVO/TiO2(100). Our work helps deepen the understanding of spinodal decomposition in the TVO film and provides information on achieving novel nanostructures via spinodal decomposition in TVO/TiO2(100). No potential conflict of interest relevant to this article was reported.

American Chemical Society Acta Medica Okayama 15306984 19 9 2019 Asymmetric Phosphorus Incorporation in Homoepitaxial P-Doped (111) Diamond Revealed by Photoelectron Holography 5915 5919 EN T. Yokoya Research Institute for Interdisciplinary Science (RIIS), Okayama University K. Terashima Research Institute for Interdisciplinary Science (RIIS), Okayama University A. Takeda Graduate School of Science and Technology, Okayama University T. Fukura Graduate School of Science and Technology, Okayama University H. Fujiwara Graduate School of Science and Technology, Okayama University T. Muro Japan Synchrotron Radiation Research Institute (JASRI)/SPring-8 T. Kinoshita Japan Synchrotron Radiation Research Institute (JASRI)/SPring-8 H. Kato Energy Technology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST) S. Yamasaki Energy Technology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST) T. Oguchi Institute of Scientific and Industrial Research, Osaka University T. Wakita Research Institute for Interdisciplinary Science (RIIS), Okayama University Y. Muraoka Research Institute for Interdisciplinary Science (RIIS), Okayama University T. Matsushita Japan Synchrotron Radiation Research Institute (JASRI)/SPring-8 Diamond has two crystallographically inequivalent sites in the unit cell. In doped diamond, dopant occupation in the two sites is expected to be equal. Nevertheless, preferential dopant occupation during growth under nonequilibrium conditions is of fundamental importance, for example, to enhance the properties of nitrogen-vacancy (N-V) centers; therefore, this is a promising candidate for a qubit. However, the lack of suitable experimental techniques has made it difficult to study the crystal- and chemical-site-resolved local structures of dopants. Here, we confirm the identity of two chemical sites with asymmetric dopant incorporation in the diamond structure, via the photoelectron holography (PEH) of heavily phosphorus (P)-doped diamond prepared by chemical vapor deposition. One is substitutionally incorporated P with preferential site occupations and the other can be attributed to a PV split vacancy complex with preferential orientation. The present study shows that PEH is a valuable technique to study the local structures around dopants with a resolution of crystallographically inequivalent but energetically equivalent sites/orientations. Such information provides strategies to improve the properties of dopant related-complexes in which alignment is crucial for sensing of magnetic field or quantum spin register using N-V centers in diamond. No potential conflict of interest relevant to this article was reported.

American Physical Society Acta Medica Okayama 2469-9950 95 8 2017 Ce 4f electronic states of CeO1-xFxBiS2 studied by soft x-ray photoemission spectroscopy 085109 EN Takanori Wakita Research Laboratory for Surface Science and the Graduate School of Natural Science and Technology, Okayama University Kensei Terashima Research Laboratory for Surface Science and the Graduate School of Natural Science and Technology, Okayama University Takahiro Hamada Research Laboratory for Surface Science and the Graduate School of Natural Science and Technology, Okayama University Hirokazu Fujiwara Research Laboratory for Surface Science and the Graduate School of Natural Science and Technology, Okayama University Makoto Minohara Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK) Masaki Kobayashi Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK) Koji Horiba Hiroshi Kumigashira Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK) Galif Kutluk Synchrotron Radiation Center, Hiroshima University Masanori Nagao Center for Crystal Science and Technology, University of Yamanashi Satoshi Watauchi Center for Crystal Science and Technology, University of Yamanashi Isao Tanaka Center for Crystal Science and Technology, University of Yamanashi Satoshi Demura National Institute for Materials Science Hiroyuki Okazaki National Institute for Materials Science Yoshihiko Takano National Institute for Materials Science Yoshikazu Mizuguchi Department of Electrical and Electronic Engineering, Tokyo Metropolitan University Osuke Miura Department of Electrical and Electronic Engineering, Tokyo Metropolitan University Kozo Okada Department of Physics and the Graduate school of Natural Science and Technology, Okayama University Yuji Muraoka Research Laboratory for Surface Science and the Graduate School of Natural Science and Technology, Okayama University Takayoshi Yokoya Research Laboratory for Surface Science and the Graduate School of Natural Science and Technology, Okayama University We use soft x-ray photoemission spectroscopy (SXPES) to investigate Ce 4f electronic states of a new BiS2 layered superconductor CeO1-xFxBiS2, for polycrystalline and single-crystal samples. The Ce 3d spectrum of the single crystal of nominal composition x = 0.7 has no f(0) component and the spectral shape closely resembles the ones observed for Ce trivalent insulating compounds, strongly implying that the CeO layer is still in an insulating state even after the F doping. The Ce 3d-4f resonant SXPES for both polycrystalline and single-crystal samples shows that the prominent peak is located around 1 eV below the Fermi level (E-F) with negligible spectral intensity at EF. The F-concentration dependence of the valence band spectra for single crystals shows the increases of the degeneracy in energy levels and of the interaction between Ce 4f and S 3p states. These results give insight into the nature of the CeO1-xFx layer and the microscopic coexistence of magnetism and superconductivity in CeO1-xFxBiS2. No potential conflict of interest relevant to this article was reported.

The American Physical Society Acta Medica Okayama 1098-0121 90 22 2014 Proximity to Fermi-surface topological change in superconducting LaO0.54F0.46BiS2 EN Kensei Terashima Junki Sonoyama Takanori Wakita Masanori Sunagawa Kanta Ono Hiroshi Kumigashira Takayuki Muro Masanori Nagao Satoshi Watauchi Isao Tanaka Hiroyuki Okazaki Yoshihiko Takano Osuke Miura Yoshikazu Mizuguchi Hidetomo Usui Katsuhiro Suzuki Kazuhiko Kuroki Yuji Muraoka Takayoshi Yokoya The electronic structure of nearly optimally doped novel superconductor LaO1�|xFxBiS2(x = 0.46) was investigated using angle-resolved photoemission spectroscopy (ARPES). We clearly observed band dispersions from 2 to 6 eV binding energy and near the Fermi level (EF), which are well reproduced by first-principles calculations when the spin-orbit coupling is taken into account. The ARPES intensity map near EF shows a squarelike distribution around the (Z) point in addition to electronlike Fermi-surface (FS) sheets around the X(R) point, indicating that FS of LaO0.54F0.46BiS2 is in close proximity to the theoretically predicted topological change. No potential conflict of interest relevant to this article was reported.