Faculty Profiles - MUTO, Shunsuke

Papers - MUTO, Shunsuke

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Structural and chemical modifications of oxides and OH generation by space weathering: Electron microscopic/spectroscopic study of hydrogen-ion-irradiated Al2O3

Igami Yohei, Muto Shunsuke, Takigawa Aki, Ohtsuka Masahiro, Miyake Akira, Suzuki Kohtaku, Yasuda Keisuke, Tsuchiyama Akira

GEOCHIMICA ET COSMOCHIMICA ACTA Vol. 315 page： 61 - 72 2021.12

Dynamics of Rh nanoparticle surface structure during NO reduction revealed by operando transmission electron microscopy

Tanaka Hiromochi, Orita Koji, Maede Atsushi, Ishikawa Hiroyuki, Miura Masahide, Arai Shigeo, Higuchi Tetsuo, Ohta Shigemasa, Muto Shunsuke

APPLIED CATALYSIS A-GENERAL Vol. 626 2021.9

2D-HARECXS analysis of dopant and oxygen vacancy sites in Al-doped yttrium titanate Reviewed

M. Ohtsuka, K. Oda, M. Tanaka, S. Kitaoka, S. Muto

Journal of the American Ceramic Society Vol. 104 ( 7 ) page： 3760 - 3769 2021.7

Quantitative Atomic-Site Analysis of Functional Dopants/Point Defects in Crystalline Materials by Electron-Channeling-Enhanced Microanalysis Reviewed

M. Ohtsuka, S. Muto

JoVE Journal ( 171 ) 2021.5

Twinned/untwinned catalytic gold nanoparticles identified by applying a convolutional neural network to their Hough transformed Z-contrast images (vol 67, pg 321, 2018) Reviewed

Yamamoto Yuta, Hattori Mizuki, Ohyama Junya, Satsuma Atsushi, Tanaka Nobuo, Muto Shunsuke

MICROSCOPY Vol. 68 ( 2 ) page： 194 - 194 2019.4

Control of surface potential and hydroxyapatite formation on TiO2 scales containing nitrogen-related defects Reviewed

Masami Hashimoto, Takafumi Ogawa, Satoshi Kitaoka, Shunsuke Muto, Maiko Furuya, Hiroyasu Kanetaka, Masayuki Abe, Hayato Yamashita

Acta Materialia Vol. 155 page： 379 - 385 2018.8

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Acta Materialia Inc

The hydroxyapatite (HAp) formation ability and related surface potentials of rutile-type TiO2 scales formed on Ti are controlled by varying the Ti heat treatment conditions in a N2 atmosphere containing a trace amount of O2. The zeta potentials of the samples heated at 873 and 973 K for 1 h are large negative and positive values, respectively, where HAp formation on the surface is enhanced in both cases. Upon longer heat treatment at those temperatures, the HAp forming ability diminishes and the zeta potential becomes more neutral. Kelvin probe force microscopy indicates that, under dry conditions, the surface charges on the TiO2 scales formed at 873 and 973 K in 1 h are positive and negative, respectively, opposite to the signs of the zeta potentials measured under wet conditions. Scanning transmission electron microscopy, electron energy loss spectroscopy, and calculations of defect formation energies reveal that nitrogen atoms incorporated into TiO2 during scale formation produce the charged defects (NO)O −1 and (N2)O +2 for the scales formed in 1 h at 873 and 973 K, respectively. In the case of longer treatments, nitrogen-related defects presumably transform into more stable states, such as N2 gas, in voids, resulting in a neutral surface. The present findings lead to physical models of surface charge distributions that elucidate the relationship between nitrogen-related defects, charged surfaces, and HAp formation mechanisms.

DOI： 10.1016/j.actamat.2018.05.072

Web of Science

Scopus

EPR Study of Porous Si:C and SiO2:C Layers

Dariya Savchenko, Andrii Vasin, Shunsuke Muto, Ekaterina Kalabukhova, Alexei Nazarov

Physica Status Solidi (B) Basic Research Vol. 255 ( 6 ) 2018.6

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Wiley-VCH Verlag

Initial porous silicon (por-Si), carbonized porous silicon (por-Si:C), and carbon-incorporated porous silicon oxide (por-SiO2:C) layers are studied by electron paramagnetic resonance (EPR) at T = 10–13 K. Scanning transmission electron microscopy and electron energy loss (EEL) spectroscopy show that por-Si:C and por-SiO2:C layers have a highly disordered structure with mixing sp2 and sp3 CC bonds. In the por-SiO2:C layers, the peak of the oxygen bonded to carbon in the form of hydroxyl groups is found in the EEL spectrum of the C K-edge region. Low-intensity signals of Lorentzian lineshape are detected in the EPR spectrum of por-Si, por-Si:C, por-SiO2:C layers. One of them is attributed to the Pb0 defect at the Si/SiO2 interface of nanocrystalline grain and the second to the silicon dangling bonds (SiDB) localized in nanocrystalline Si. The carbonization of por-Si layers and subsequent oxidation of por-Si:C gives rise to the appearance of additional EPR signals of high intensity at g = 2.0035(3) in por-Si:C and at g = 2.0030(3) in por-SiO2:C, which are assigned to carbon-related defects (CRD) and carbon clusters, correspondingly. It was found that predominant defect types in por-Si:C and por-SiO2:C layers are CRD and carbon clusters, respectively, while the spin concentration of Pb0 interface defects and SiDB is low.

DOI： 10.1002/pssb.201700559

Web of Science

Scopus

Interfacial fracture strength evaluation of Cu/SiN micro-components: applicability of the linear fracture mechanics criterion under a hydrogen environment Reviewed

Yoshimasa Takahashi, Itaru Ashida, Shigeo Arai, Kimitaka Higuchi, Yuta Yamamoto, Shunsuke Muto

International Journal of Fracture Vol. 210 ( 1-2 ) page： 223 - 231 2018.3

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Springer Netherlands

The strength against fracture initiation from an interface free-edge of bonded copper (Cu) and silicon nitride (SiN) micro-components is studied. Quantitative fracture tests are conducted either in a vacuum environment or in a gaseous hydrogen (H2) environment. By using two kinds of specimens, Types I and II, having the same free-edge geometry (135∘/135∘) but different outer shape, the validity of the linear fracture mechanics criterion is critically evaluated. For specimens tested in vacuum, fracture initiation strength represented by the elastic stress intensity factor of the near-edge normal stress component is found to be the same irrespective of the specimen type, indicating that the fracture mechanics criterion holds. For specimens tested in H2 gas, the strength of both types is reduced and, interestingly, Type II strength shows greater reduction than Type I. In other words, the fracture mechanics criterion does not hold in H2 gas. Such a difference may be attributable to the difference of local plasticity in each specimen type.

DOI： 10.1007/s10704-018-0269-8

Web of Science

Scopus

Unmixing hyperspectral data by using signal subspace sampling

Jakob Spiegelberg, Shunsuke Muto, Masahiro Ohtsuka, Kristiaan Pelckmans, Jan Rusz

ULTRAMICROSCOPY Vol. 182 page： 205 - 211 2017.11

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

This paper demonstrates how Signal Subspace Sampling (SSS) is an effective pre-processing step for Non-negative Matrix Factorization (NMF) or Vertex Component Analysis (VCA). The approach allows to uniquely extract non-negative source signals which are orthogonal in at least one observation channel, respectively. It is thus well suited for processing hyperspectral images from X-ray microscopy, or other emission spectroscopies, into its non-negative source components. The key idea is to resample the given data so as to satisfy better the necessity and sufficiency conditions for the subsequent NMF or VCA. Results obtained both on an artificial simulation study as well as based on experimental data from electronmicroscopy are reported. (C) 2017 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ultramic.2017.07.009

Web of Science

High-precision quantitative atomic-site-analysis of functional dopants in crystalline materials by electron-channelling-enhanced microanalysis

Shunsuke Muto, Masahiro Ohtsuka

PROGRESS IN CRYSTAL GROWTH AND CHARACTERIZATION OF MATERIALS Vol. 63 ( 2 ) page： 40 - 61 2017.6

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：PERGAMON-ELSEVIER SCIENCE LTD

Knowledge of the location and concentration of impurity atoms doped into a synthesized material is of great interest to investigate the effect of doping. This would usually be investigated using X-ray or neutron diffraction methods in combination with Rietveld analysis. However, this technique requires a large-scale facility such as a synchrotron radiation source and nuclear reactor, and can sometimes fail to produce the desired results, depending on the constituent elements and the crystallographic conditions that are being analysed. Thus, it would be preferable to use an element-selective spectroscopy technique that is applicable to any combination of elements. We have established a quantitative method to deduce the occupation sites and their occupancies, as well as the site-dependent chemical states of the doped elements, using a combination of transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) spectroscopy, and electron energy-loss spectroscopy (EELS). The method is based on electron channelling phenomena where the symmetries of the Bloch waves excited in a crystal are dependent on the diffraction condition or incident beam direction with respect to the crystal axes. By rocking the incident electron beam with a fixed pivot point on the sample surface, a set of EDX/EELS spectra are obtained as a function of the beam direction. This is followed by a statistical treatment to extract the atom-site-dependent spectra, thereby quantitatively enabling the estimation of the site occupancies and chemical states of the dopants. This is an extension of the 'ALCHEMI' (Atom Location by Channelling Enhanced Microanalysis) method or 'HARECXS/HARECES' (High Angular Resolution Channelled X-ray/Electron Spectroscopy), and we further extended the method to be applicable to cases where the crystal of interest contains multiple inequivalent atomic sites for a particular element, applying the precise spectral predictions based on electron elastic/inelastic dynamical scattering theory. After introduction of conceptual aspects of the method, we describe the extension of the method together with the development of the theoretical calculation method. We then demonstrate several useful applications of the method, including luminescent, ferrite, and battery materials. We discuss the advantages and drawbacks of the present method, compared with those of the recently developed atomic column-by-column analysis using aberration-corrected scanning TEM and high-efficiency X-ray detectors. (C) 2017 Elsevier Ltd. All rights reserved

DOI： 10.1016/j.pcrysgrow.2017.02.001

Web of Science

Localization of magnetic circular dichroic spectra in transmission electron microscopy experiments with atomic plane resolution

Jan Rusz, Jakob Spiegelberg, Shunsuke Muto, Thomas Thersleff, Masahiro Ohtsuka, Klaus Leifer, Peter M. Oppeneer

PHYSICAL REVIEW B Vol. 95 ( 17 ) 2017.5

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：AMER PHYSICAL SOC

Inelastic electron scattering is a consequence of mostly Coulomb interaction between electrons in the sample and electron beam and, as such, it is a nonlocal event. In atomic resolution experiments, it thus opens the following question: How far is the origin of the inelastic scattering signal that is observed when the electron beam is passing nearby an atomic column or plane? We analyze computationally the delocalization of the magnetic signal in electron magnetic circular dichroism (EMCD) experiments in the so-called three-beam orientation, allowing one to image individual atomic planes. We compare the classical EMCD setup using the double-difference procedure (DD-EMCD) to a recently introduced atomic plane resolution EMCD (APR-EMCD) geometry, assuming the same probe size. We observe a strong localization of the EMCD signal to the closest atomic plane, confirming the potential of EMCD to study an evolution of magnetic properties near surfaces or interfaces with atomic plane resolution. The localization of the EMCD signal is remarkably higher than the localization of the nonmagnetic component of the inelastic scattering cross section. We also analyze double-channeling effects and find them particularly strong for the DD-EMCD method, while for APR-EMCD they appear to be minor. The DD-EMCD signal, on the other hand, appears to be more robust with respect to sample thickness than that of the APR-EMCD.

DOI： 10.1103/PhysRevB.95.174412

Web of Science

Towards sub-nanometer real-space observation of spin and orbital magnetism at the Fe/MgO interface

Thomas Thersleff, Shunsuke Muto, Miroslaw Werwinski, Jakob Spiegelberg, Yaroslav Kvashnin, Bjorgvin Hjorvarsson, Olle Eriksson, Jan Rusz, Klaus Leifer

SCIENTIFIC REPORTS Vol. 7 2017.3

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：NATURE PUBLISHING GROUP

While the performance of magnetic tunnel junctions based on metal/oxide interfaces is determined by hybridization, charge transfer, and magnetic properties at the interface, there are currently only limited experimental techniques with sufficient spatial resolution to directly observe these effects simultaneously in real-space. In this letter, we demonstrate an experimental method based on Electron Magnetic Circular Dichroism (EMCD) that will allow researchers to simultaneously map magnetic transitions and valency in real-space over interfacial cross-sections with sub-nanometer spatial resolution. We apply this method to an Fe/MgO bilayer system, observing a significant enhancement in the orbital to spin moment ratio that is strongly localized to the interfacial region. Through the use of first-principles calculations, multivariate statistical analysis, and Electron Energy-Loss Spectroscopy (EELS), we explore the extent to which this enhancement can be attributed to emergent magnetism due to structural confinement at the interface. We conclude that this method has the potential to directly visualize spin and orbital moments at buried interfaces in magnetic systems with unprecedented spatial resolution.

DOI： 10.1038/srep44802

Web of Science

Microscopic origin of ultra-low friction coefficient between the wear track formed on carbon nitride coating and transfer layer on sliding ball in friction tests under dry N-2

Hiroshi Inoue, Shunsuke Muto, Shigeo Arai, Hiroaki Wasada, Noritsugu Umehara

SURFACE & COATINGS TECHNOLOGY Vol. 313 page： 31 - 39 2017.3

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE SA

Carbon nitride (CN) coatings have been found to exhibit an ultra-low friction coefficient (less than 0.01) after repeated sliding against a silicon nitride (Si3N4) ball in a dry nitrogen gas (N-2) atmosphere. However, the mechanism for this has not yet been fully elucidated with respect to analyzing changes in the space structure of CNN. In the present study, we examined the microscopic structural changes in the near-surface structural transition layers of the wear track in the CN, coating and the transfer layer of the Si3N4 ball, using scanning transmission electron microscopy and electron energy-loss spectroscopy. We investigated the nitrogen concentration, density, and curvature of fragmented graphitic planes in the structural transition layers of both the CN,, coating and the transfer layer of the Si3N4 ball by analyzing the plasmon peak and carbon K-edge. In addition, we theoretically examined the chemical bonding states of nitrogen doping in various model clusters using an ab initio molecular orbital method to clarify the role of nitrogen in the ultra -low friction behavior. The mechanism behind the ultra low friction behavior is explained by nano-graphitization of the fragmented carbon structure with optimal nitrogen concentration passivating the contacting counter surfaces of the coating and ball formed during sliding. (C) 2017 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.surfcoat.2017.01.048

Web of Science

Detection of local chemical states of lithium and their spatial mapping by scanning transmission electron microscopy, electron energy-loss spectroscopy and hyperspectral image analysis Reviewed

Shunsuke Muto, Kazuyoshi Tatsumi

MICROSCOPY Vol. 66 ( 1 ) page： 39 - 49 2017.2

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：OXFORD UNIV PRESS

Advancements in the field of renewable energy resources have led to a growing demand for the analysis of light elements at the nanometer scale. Detection of lithium is one of the key issues to be resolved for providing guiding principles for the synthesis of cathode active materials, and degradation analysis after repeated use of those materials. We have reviewed the different techniques currently used for the characterization of light elements such as high-resolution transmission electron microscopy, scanning transmission electron microscopy ( STEM) and electron energy-loss spectroscopy (EELS). In the present study, we have introduced a methodology to detect lithium in solid materials, particularly for cathode active materials used in lithium-ion battery. The chemical states of lithium were isolated and analyzed from the overlapping multiple spectral profiles, using a suite of STEM, EELS and hyperspectral image analysis. The method was successfully applied in the chemical state analyses of hetero-phases near the surface and grain boundary regions of the active material particles formed by chemical reactions between the electrolyte and the active materials.

DOI： 10.1093/jmicro/dfw038

Web of Science

Stain-free mapping of polymer-blend morphologies via application of high-voltage STEM-EELS hyperspectral imaging to low-loss spectra Reviewed International journal

Umemoto Hiroki, Arai Shigeo, Otobe Hirohide, Muto Shunsuke

POLYMER JOURNAL Vol. 55 ( 9 ) page： 997 - 1006 2023.9

Cathode Properties of xLiF-LiCrO2 Composites (x=0-1.5) Prepared by Dry Ball-Milling Method for Lithium Ion Batteries Reviewed International journal

Kitajou Ayuko, Hiroi Satoshi, Ohara Koji, Ikeda Kazutaka, Nanami Takuma, Muto Shunsuke

JOURNAL OF PHYSICAL CHEMISTRY C Vol. 127 ( 6 ) page： 2866 - 2874 2023.2

Cathode properties of xLiF-LiCrO2 composites (x = 0-1.5) prepared by dry ball-milling method for lithium ion batteries Reviewed

A. Kitajou, S. Hiroi, K. Ohara, K. Ikeda, T. Nanami, S. Muto

J. Phys. Chem. C Vol. 127 page： 2866 - 2874 2023

Formation mechanism of dislocation network of cell structure in cyclically deformed near-[1¯11] copper single crystals Reviewed International coauthorship

B. Wang, Y. Umeda, T. Miyazawa, M. Ohtsuka, S. Muto, S. Arai, T. Fujii

Materials Science and Engineering: A Vol. 879 page： 145287 2023

Anode Properties of NaTi2(PO4)3 Prepared by Adding Excess Na2CO3 for Aqueous Sodium-Ion Batteries Reviewed

Ayuko Kitajou*Ayuko Kitajou Graduate School of Sciences and Technology for Innovation, Yamaguchi University, 2-16-1 Tokiwadai, Ube 755-8611, Yamaguchi, Japan *Email: kitajou@yamaguchi-u.ac.jp More by Ayuko Kitajou Orcidhttps://orcid.org/0000-0002-7639-2990 , Maho Yamashita, Wataru Kobayashi, Masaki Okada, Takuma Nanami, and Shunsuke Muto

ACS Applied Energy Materials Vol. 5 ( 8 ) page： 9587 - 9594 2022.8

先端材料開発に向けた，AI先端計測技術の多角的視点からの考察(第1回) Reviewed

岡本和也, 杉山昌章, 武藤俊介, 青柳里果, 冨谷茂隆

日本金属学会会報「まてりあ」 Vol. 61 ( 8 ) page： 470 - 478 2022

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Papers - MUTO, Shunsuke