Faculty Profiles - YOKOYA Takayoshi

Papers - YOKOYA Takayoshi

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Soft x-ray irradiation induced metallization of layered TiNCl Reviewed

Noriyuki Kataoka, Masashi Tanaka, Wataru Hosoda, Takumi Taniguchi, Shin-ichi Fujimori, Takanori Wakita, Yuji Muraoka, Takayoshi Yokoya

Journal of Physics: Condensed Matter 33 ( 3 ) 035501 - 035501 2021.1

Authorship：Last author,　Corresponding author Publishing type：Research paper (scientific journal) Publisher：IOP Publishing

Abstract

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 (E_F) 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.

DOI： 10.1088/1361-648x/abbbc3

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Other Link： https://iopscience.iop.org/article/10.1088/1361-648X/abbbc3/pdf

Momentum Dependent Band Renormalization and Surface Aging Effect on a Zone Center Electron Pocket in NaSn2As2 Revealed by Angle-Resolved Photoemission Spectroscopy Reviewed

Yuka Akabane, Taiki Shimaiwa, Yosuke Goto, Yoshikazu Mizuguchi, Takayoshi Yokoya, Masashi Arita, Shiv Kumar, Eike F. Schwier, Kenya Shimada, Naurang L. Saini, Takashi Mizokawa

Journal of the Physical Society of Japan 89 ( 11 ) 114707 - 114707 2020.11

The local structure of self-doped BiS2-based layered systems as a function of temperature Reviewed

G. M. Pugliese, E. Paris, F. G. Capone, F. Stramaglia, T. Wakita, K. Terashima, T. Yokoya, T. Mizokawa, Y. Mizuguchi, N. L. Saini

Physical Chemistry Chemical Physics 22 ( 39 ) 22217 - 22225 2020.10

Formation of Q-carbon by adjusting sp3 content in diamond-like carbon films and laser energy density of pulsed laser annealing Reviewed

Hiroki Yoshinaka, Seiko Inubushi, Takanori Wakita, Takayoshi Yokoya, Yuji Muraoka

Carbon 167 504 - 511 2020.10

Theory for High‐Angular‐Resolution Photoelectron Holograms Considering the Inelastic Mean Free Path and the Formation Mechanism of Quasi‐Kikuchi Band Reviewed

Tomohiro Matsushita, Takayuki Muro, Takayoshi Yokoya, Kensei Terashima, Yukako Kato, Hirosuke Matsui, Naoyuki Maejima, Yusuke Hashimoto, Fumihiko Matsui

physica status solidi (b) 2000117 - 2000117 2020.7

Skewed electronic band structure induced by electric polarization in ferroelectric BaTiO<inf>3</inf> Reviewed

Norihiro Oshime, Jun Kano, Eiji Ikenaga, Shintaro Yasui, Yosuke Hamasaki, Sou Yasuhara, Satoshi Hinokuma, Naoshi Ikeda, Pierre Eymeric Janolin, Jean Michel Kiat, Mitsuru Itoh, Takayoshi Yokoya, Tatsuo Fujii, Akira Yasui, Hitoshi Osawa

Scientific Reports 10 ( 1 ) 2020.7

Publishing type：Research paper (scientific journal)

© 2020, The Author(s). Skewed band structures have been empirically described in ferroelectric materials to explain the functioning of recently developed ferroelectric tunneling junction (FTJs). Nonvolatile ferroelectric random access memory (FeRAM) and the artificial neural network device based on the FTJ system are rapidly developing. However, because the actual ferroelectric band structure has not been elucidated, precise designing of devices has to be advanced through appropriate heuristics. Here, we perform angle-resolved hard X-ray photoemission spectroscopy of ferroelectric BaTiO3 thin films for the direct observation of ferroelectric band skewing structure as the depth profiles of atomic orbitals. The depth-resolved electronic band structure consists of three depth regions: a potential slope along the electric polarization in the core, the surface and interface exhibiting slight changes. We also demonstrate that the direction of the energy shift is controlled by the polarization reversal. In the ferroelectric skewed band structure, we found that the difference in energy shifts of the atomic orbitals is correlated with the atomic configuration of the soft phonon mode reflecting the Born effective charges. These findings lead to a better understanding of the origin of electric polarization.

DOI： 10.1038/s41598-020-67651-w

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High-pressure x-ray absorption and diffraction study of the self-doped superconductor EuFBiS2 Reviewed

E. Paris, B. Joseph, C. Marini, K. Terashima, T. Wakita, T. Yokoya, Y. Mizuguchi, T. Mizokawa, N. L. Saini

Physical Review B 101 ( 21 ) 2020.6

Change in the electronic structure of the bismuth chalcogenide superconductor CsBi4−x Pb x Te6 by dissociation of the bismuth dimers Reviewed

Hiroyuki Okazaki, Kensei Terashima, David Billington, Keiji Iwata, Takanori Wakita, Masashi Tanaka, Yoshihiko Takano, Yuji Muraoka, Takayoshi Yokoya

Journal of Physics: Condensed Matter 32 ( 14 ) 145501 - 145501 2020.4

Change in the work function of VO2 thin film across the metal-insulator transition in VO2/TiO2:Nb(001) heterostructures Reviewed

Yuji Muraoka, Yuki Suga, Hayato Nakahara, Takayoshi Yokoya

JPS Conf. Proc. 30 011071 - 011071 2020.3

Language：English Publishing type：Research paper (international conference proceedings) Publisher：IOP Publishing

DOI： 10.1088/1361-648x/abbbc3

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Other Link： https://iopscience.iop.org/article/10.1088/1361-648X/abbbc3/pdf

Strain effects on spinodal decomposition in TiO2-VO2 films on TiO2(100) substrates Reviewed

Yuji Muraoka, Fumiya Yoshii, Takahiro Fukuda, Yuji Manabe, Mikiko Yasuno, Yoshito Takemoto, Kensei Terashima, Takanori Wakita, Takayoshi Yokoya

Thin Solid Films 698 137854 2020.2

Data-driven exploration for pressure-induced superconductors using diamond anvil cell with boron-doped diamond electrodes and undoped diamond insulating layer Reviewed

Ryo Matsumoto, Zhufeng Hou, Shintaro Adachi, Masanori Nagao, Sayaka Yamamoto, Peng Song, Noriyuki Kataoka, Pedro Baptista de Castro, Kensei Terashima, Hiroyuki Takeya, Hiromi Tanaka, Takayoshi Yokoya, Tetsuo Irifune, Kiyoyuki Terakura, Yoshihiko Takano

HIGH PRESSURE RESEARCH 40 ( 1 ) 22 - 34 2020.1

Temperature dependent local atomic displacements in NaSn2As2 system Reviewed

Pugliese G. M, Stramaglia F, Goto Y, Terashima K, Simonelli L, Fujiwara H, Puri A, Marini C, Hacisalihoglu M. Y, d'Acapito F, Yokoya T, Mizokawa T, Mizuguchi Y, Saini N. L

JOURNAL OF PHYSICS-CONDENSED MATTER 31 ( 42 ) 2019.10

mu-PES Studies on TiNCl and Quasi-two-dimensional Superconductor Na-intercalated TiNCl Reviewed

Kataoka Noriyuki, Terashima Kensei, Tanaka Masashi, Hosoda Wataru, Taniguchi Takumi, Wakita Takanori, Muraoka Yuji, Yokoya Takayoshi

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 88 ( 10 ) 104709 - 104709 2019.10

Pressure-induced superconductivity in B i2-x S bx T e3-y S ey Reviewed

Tong He, Xiaofan Yang, Tomoya Taguchi, Teppei Ueno, Kaya Kobayashi, Jun Akimitsu, Hitoshi Yamaoka, Hirofumi Ishii, Yen Fa Liao, Hiromi Ota, Hidenori Goto, Ritsuko Eguchi, Kensei Terashima, Takayoshi Yokoya, Harald O. Jeschke, Xianxin Wu, Yoshihiro Kubozono

Physical Review B 100 ( 9 ) 2019.9

Publishing type：Research paper (scientific journal)

© 2019 American Physical Society. We systematically investigated the pressure dependence of electrical transport and the crystal structure of topological insulator, Bi2-xSbxTe3-ySey, which showed no superconductivity down to 2.0 K at ambient pressure. The Bi2-xSbxTe3-ySey crystal showed two structural phase transitions under pressure, from rhombohedral structure (space group No. 166, R3m, termed phase I) to monoclinic structure (space group No. 12, C2/m, termed phase II), and from phase II to another monoclinic structure (space group No. 12, C2/m, termed phase III). Superconductivity appeared when applying pressure; actually the superconductivity of all Bi2-xSbxTe3-ySey samples emerged in phase I. The superconducting transition temperature, Tc, increased against pressure in a pressure range of 0-15 GPa for all Bi2-xSbxTe3-ySey samples, and the maximum Tc was 5.45 K, recorded at 13.5 GPa in Bi2-xSbxTe3-ySey at x=0 and y=1.0. The magnetic field (H) dependence of the R-T plot for Bi2-xSbxTe3-ySey was measured to characterize the superconducting pairing mechanism of pressure-induced superconducting phase.

DOI： 10.1103/PhysRevB.100.094525

Web of Science

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Asymmetric Phosphorus Incorporation in Homoepitaxial P-Doped (111) Diamond Revealed by Photoelectron Holography Reviewed

T. Yokoya, K. Terashima, A. Takeda, T. Fukura, H. Fujiwara, T. Muro, T. Kinoshita, H. Kato, S. Yamasaki, T. Oguchi, T. Wakita, Y. Muraoka, T. Matsushita

Nano Letters 19 ( 9 ) 5915 - 5919 2019.9

Selective Reduction Mechanism of Graphene Oxide Driven by the Photon Mode versus the Thermal Mode Reviewed

Masaki Hada, Kiyoshi Miyata, Satoshi Ohmura, Yusuke Arashida, Kohei Ichiyanagi, Ikufumi Katayama, Takayuki Suzuki, Wang Chen, Shota Mizote, Takayoshi Sawa, Takayoshi Yokoya, Toshio Seki, Jiro Matsuo, Tomoharu Tokunaga, Chihiro Itoh, Kenji Tsuruta, Ryo Fukaya, Shunsuke Nozawa, Shin-ichi Adachi, Jun Takeda, Ken Onda, Shin-ya Koshihara, Yasuhiko Hayashi, Yuta Nishina

ACS NANO 13 ( 9 ) 10103 - 10112 2019.9

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

A two-dimensional nanocarbon, graphene, has attracted substantial interest due to its excellent properties. The reduction of graphene oxide (GO) has been investigated for the mass production of graphene used in practical applications. Different reduction processes produce different properties in graphene, affecting the performance of the final materials or devices. Therefore, an understanding of the mechanisms of GO reduction is important for controlling the properties of functional two-dimensional systems. Here, we determined the average structure of reduced GO prepared via heating and photoexcitation and clearly distinguished their reduction mechanisms using Graphene oxide ultrafast time-resolved electron diffraction, time-resolved infrared vibrational spectroscopy, and time-dependent density functional theory calculations. The oxygen atoms of epoxy groups are selectively removed from the basal plane of GO by photoexcitation (photon mode), in stark contrast to the behavior observed for the thermal reduction of hydroxyl and epoxy groups (thermal mode). The difference originates from the selective excitation of epoxy bonds via an electronic transition due to their antibonding character. This work will enable the preparation of the optimum GO for the intended applications and expands the application scope of two-dimensional systems.

DOI： 10.1021/acsnano.9b03060

Web of Science

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The local structure of the Ca0.9Pr0.1Fe2As2 superconductor as a function of temperature Reviewed

Paris E, Wakita T, Simonelli L, Marini C, Olszewski W, Terashima K, Stramaglia F, Pugliese G. M, Mizokawa T, Loka S, Kudo K, Nohara M, Yokoya T, Saini N. L

SUPERCONDUCTOR SCIENCE & TECHNOLOGY 32 ( 9 ) 2019.9

Inhomogeneous charge distribution in a self-doped EuFBiS2 superconductor Reviewed

Sugimoto T, Paris E, Terashima K, Barinov A, Giampietri A, Wakita T, Yokoya T, Kajitani J, Higashinaka R, Matsuda T, Aoki Y, Mizokawa T, Saini N

PHYSICAL REVIEW B 100 ( 6 ) 2019.8

Three-dimensional dopant imaging in semiconductor crystals using photoelectron holography with chemical state identification

Tomohiro Matsushita, Takayuki Muro, Kazuo Tsutsui, Takayoshi Yokoya

19th International Workshop on Junction Technology, IWJT 2019 2019.6

Language：English Publishing type：Research paper (international conference proceedings) Publisher：Institute of Electrical and Electronics Engineers Inc.

Doping is an important technology for modern science. For example, to create a semiconductor device, a circuit is formed by controlling carriers by doping. It is important to search for appropriate conditions since the carrier emission from dopant differs depending on the doping conditions. The atomic arrangement around the dopant differs depending on the conditions. Therefore, it has been desired to observe the atomic arrangement around the dopant, but it has been difficult with conventional measurement methods. The atomic resolution holography such as photoelectron holography, X-ray fluorescence holography, neutron holography, which are methods that can measure the three-dimensional (3D) atomic arrangement of the dopant. Among them, photoelectron holography can measure the atomic structure of each dopant depending on the chemical state. We have built photoelectron holography apparatuses at BL25SU in SPring-8. We also developed a software platform 3D-AIR-IMAGE for data processing, simulation of photoelectron holograms, and 3D atomic image reconstruction.

DOI： 10.23919/IWJT.2019.8802898

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Recent Photoemission Studies on BiCh(2)-Based Compounds Invited Reviewed

Terashimas Kensei, Wakita Takanori, Yokoya Takayoshi

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 88 ( 4 ) 2019.4

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Papers - YOKOYA Takayoshi