Faculty Profiles - TANIGUCHI Hiroki

Papers - TANIGUCHI Hiroki

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26pEN-6 Mechanism of Ferroelectricity in Perovskite-type Oxides from a Viewpoint of Chemical Bonds and Prospect for New Ferroelectric Materials Open Access

Taniguchi Hiroki

Meeting Abstracts of the Physical Society of Japan Vol. 68.1.4 ( 0 ) page： 1022 2013

Fractal dynamics in a single crystal of a relaxor ferroelectric Reviewed

Akitoshi Koreeda, Hiroki Taniguchi, Seishiro Saikan, Mitsuru Itoh

Physical Review Letters Vol. 109 ( 19 ) page： 197601 2012.11

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

We report the high-resolution and broadband light-scattering spectroscopy of a single crystal of a prototypical relaxor ferroelectric, Pb(Mg 1/3Nb 2/3)O 3. A self-similar broad central peak, whose intensity is expressed as I(ω)∞ωα has been observed, indicating the presence of a fractal in the crystal. A strong correspondence exists between the temperature dependence of the exponent α and that of the reported behaviors of polar nanoregions. The estimated fractal dimension (d f≈2.6) at low temperatures clearly indicates a percolation transition of the polar nanoregions at around 240 K. © 2012 American Physical Society.

DOI： 10.1103/PhysRevLett.109.197601

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PubMed

Ferroelectric material studies using state-of-the-art first-principles calculations and experiments Reviewed

MORIWAKE Hiroki, TANIGUCHI Hiroki, HASHIMOTO Tamotsu

Oyo Buturi Vol. 81 ( 9 ) page： 760 - 764 2012.9

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japan Society of Applied Physics

Ferroelectric material studies, e.g., those involving ferroelectric phase transition, structure and finite-temperature properties, using state-of-the-art first-principles calculations and experiments are described.

DOI： 10.11470/oubutsu.81.9_760

CiNii Research

Growth of Cu <inf>2</inf>ZnSnSe <inf>4</inf> single crystals from Sn solutions Reviewed

Akira Nagaoka, Kenji Yoshino, Hiroki Taniguchi, Tomoyasu Taniyama, Hideto Miyake

Journal of Crystal Growth Vol. 354 ( 1 ) page： 147 - 151 2012.9

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

We investigated the pseudobinary phase diagram of the Cu 2ZnSnSe 4 (CZTSe)-Sn system in order to obtain the knowledge useful for the growth of high-quality CZTSe single crystals using a solution-based method. For Sn solutions saturated with less than ∼60 mol% CZTSe, the solutes are separated into two phases, whereas for Sn solutions with more than 60 mol% CZTSe, the solutes are of single phase. The CZTSe single crystals were obtained from a 80 mol% CZTSe solution (liquid temperature 850 °C) at 900 °C. The powder X-ray diffraction pattern of the CZTSe single crystal shows preferred orientations of (112), (220) and (312) planes, confirming the Kesterite structure of CZTSe. The Raman spectrum shows three peaks at 170, 193 and 231 cm -1, which correspond to CZTSe peaks. The composition of the CZTSe single crystal along the growth direction is found to be slightly Cu-poor, Zn-rich and Se-rich. Therefore, we obtained good-quality homogeneous CZTSe single crystal grown by Sn solutions. © 2012 Elsevier B.V.

DOI： 10.1016/j.jcrysgro.2012.05.030

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Ionic liquid-mediated epitaxy of high-quality C <inf>60</inf> crystallites in a vacuum Reviewed

Yoko Takeyama, Shingo Maruyama, Hiroki Taniguchi, Mitsuru Itoh, Keiji Ueno, Yuji Matsumoto

CrystEngComm Vol. 14 ( 15 ) page： 4939 - 4945 2012.8

Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

Ionic liquid-mediated vacuum deposition was demonstrated as a novel growth technique for high-quality C 60 crystallites. In this process the ionic liquid worked as a solvent, i.e. the gas phase C 60 precursors were continuously fed into the ionic liquid on a substrate in a vacuum chamber, from which the nucleation and the subsequent growth of C 60 crystallites proceeded. The impact of varying the substrate on the growth behaviour was intensively examined in terms of not only the lattice-mismatch between C 60 and the substrates, but also the wetting behavior of the ionic liquid on the substrates. This led to a significant improvement of the C 60 crystallinity and epitaxial growth was successfully found on certain substrates. In particular, molecularly smooth and thick C 60 hexagonal-shaped crystallites epitaxially grew on a MoS 2 substrate, the average size of which reached as large as 10 μm. © 2012 The Royal Society of Chemistry.

DOI： 10.1039/c2ce25163a

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Origin of the dielectric response in Ba <inf>0.767</inf>Ca <inf>0.233</inf>TiO <inf>3</inf> Reviewed

Takao Shimizu, Desheng Fu, Hiroki Taniguchi, Tomoyasu Taniyama, Mitsuru Itoh

Applied Physics Letters Vol. 100 ( 10 ) 2012.3

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER INST PHYSICS

We perform a Raman scattering study to elucidate the mechanism of temperature independent dielectric response of Ba 0.767Ca 0.233TiO 3 (BCTO-0.233) from a viewpoint of phonon dynamics. BCTO-0.233 remains tetragonal below T c down to 3.5 K. Over-damped soft phonon observed in a pure BaTiO 3 is found to become underdamped in BCTO-0.233, suggesting that local dipoles induced by Ca 2 off-centering suppress the hopping of Ti ions to reduce damping of the soft-mode. The temperature dependence of the soft-mode frequency agrees qualitatively with the dielectric permittivity through Lyddane-Sachs-Teller relationship, indicating that the dielectric response of BCTO-0.233 is governed by the soft-mode. © 2012 American Institute of Physics.

DOI： 10.1063/1.3693524

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Preparation of Cu <inf>2</inf>ZnSnS <inf>4</inf> single crystals from Sn solutions Reviewed

Akira Nagaoka, Kenji Yoshino, Hiroki Taniguchi, Tomoyasu Taniyama, Hideto Miyake

Journal of Crystal Growth Vol. 341 ( 1 ) page： 38 - 41 2012.2

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER

We investigated the phase diagrams of the Cu 2ZnSnS 4 (CZTS)Sn pseudobinary system in order to obtain knowledge useful for the growth of high-quality CZTS single crystals using a solution-based method. For Sn solutions saturated with less than ∼60 mol% CZTS, the solutes are separated into two phases (CZTS phaseSnS x phaseliquid phase). On the other hand, for solutions with more than 60 mol% CZTS, the solutes are single phase (CZTS phaseliquid phase). The CZTS single crystals were obtained from a 70 mol% CZTS solution (liquid temperature 850 °C) at 900 °C. The powder X-ray diffraction (XRD) pattern of the CZTS single crystal shows preferred orientations of (112), (220) and (312) planes, confirming the Kesterite structure of CZTS. The Raman spectrum shows three peaks at 287, 338, 371 cm -1, which corresponded to CZTS peaks. The composition of the CZTS single crystal along the growth direction is found to be slightly Cu-poor, Zn-rich and S-rich. Therefore, it is assumed that the Cu vacancy is the dominant p-type conduction mechanism. © 2011 Elsevier B.V.

DOI： 10.1016/j.jcrysgro.2011.12.046

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Effect of Ca-substitution on CdTiO <inf>3</inf> studied by raman scattering and first principles calculations Reviewed

Hiroki Taniguchi, Hwee Ping Soon, Hiroki Moriwake, Yue Jin Shan, Mitsuru Itoh

Ferroelectrics Vol. 426 ( 1 ) page： 268 - 273 2012.1

Language：English Publishing type：Research paper (scientific journal) Publisher：TAYLOR & FRANCIS LTD

An effect of Ca-substitution on ferroelectricity of CdTiO 3, whose paraelectric structure involves rotated oxygen octahedra, is studied by Raman scattering and first-principle calculations from a viewpoint of a relation between covalency and instability of lattice vibrations. Raman scattering experiments reveal that the Ca-substitution suppresses softening of a soft mode and reduces the phase transition temperature. An origin of the soft mode is elucidated by first principles calculations to be an asymmetric stretching of O-Cd-O bonds. The mechanism of Ca-induced suppression of the soft mode softening is clarified as follows: off-centering of Cd, which stems from freezing of the O-Cd-O asymmetric stretching vibration, is suppressed by the Ca-substitution through weakening of the covalency between Cd and O. The present results indicate that the covalency of ions plays a key role even in the perovskite-type oxides with pre-existing octahedral rotations. © Taylor & Francis Group, LLC.

DOI： 10.1080/00150193.2012.672035

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Origin of Ferroelectricity in Perovskite-Type Ferroelectric Oxides

TANIGUCHI Hiroki, MORIWAKE Hiroki, SHAN Yue Jin, ITOH Mitsuru

Nihon Kessho Gakkaishi Vol. 54 ( 5 ) page： 276 - 281 2012

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Crystallographic Society of Japan

An Origin of ferroelectricity in Perovskite-type oxides is discussed from a viewpoint of relation between lattice dynamics and chemical bonding state, through comprehensive study of a Ca-substitution effect on the ferroelectricity in CdTiO3. The result indicates covalency of constituent elements plays an important role on the ferroelectricity in the perovskite-type oxides.

DOI： 10.5940/jcrsj.54.276

CiNii Research

Growth of KH<inf>2</inf>PO<inf>4</inf> single crystal with an artificial isotope gradient Reviewed

K. Osada, H. Taniguchi, T. Taniyama, M. Itoh

Ferroelectrics Vol. 440 ( 1 ) page： 25 - 30 2012

Language：English Publishing type：Research paper (international conference proceedings) Publisher：TAYLOR & FRANCIS LTD

KH2PO4 (KDP) single crystals internally including an artificial isotope gradient are grown by a controlled solution-recrystallization method. The deuteron exchange rate of KDP single crystal is spatially tailored through crystal growth in a KD2PO4 (DKDP) saturated solution, where the deuteron concentration decreases with time. The position dependence of the deuteron concentration was precisely determined with confocal micro-Raman scanning giving a change in the Raman spectrum as a proof. The result indicates that the deuteron concentration continuously varies from 77 % to 7 % within 100 microns. Copyright © Taylor & Francis Group, LLC.

DOI： 10.1080/00150193.2012.743786

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Other Link： http://orcid.org/0000-0003-3683-5416

Photolumunescence in single crystalline MgTiO3 thin film

Hamasaki Yousuke, Shimizu Takao, Taniguchi Hiroki, Taniyama Tomoyasu, Itoh Mitsuru

Preprints of Annual Meeting of The Ceramic Society of Japan Preprints of Fall Meeting of The Ceramic Society of Japan Vol. 2012 ( 0 ) page： 192 - 192 2012

Publishing type：Research paper (scientific journal) Publisher：The Ceramic Society of Japan

Photoluminescence properties of MgTiO3 thin film deposited by the pulsed laser deposition technique were investigated. Contrary to the spectrum for bulk MgTiO3, broad spectra around 605 nm was found to grow with the decrease of the target-substrate distance. The origin of the broad spectrum is discussed based on the defect chemistry of MgTiO3.

DOI： 10.14853/pcersj.2012S.0.192.0

CiNii Research

25aPS-10 Quantitative Raman spectroscopy utilizing a broadband waveplate Open Access

Fujii Y., Noju M., Shimizu T., Taniguchi H., Itoh M., Nishio I.

Meeting Abstracts of the Physical Society of Japan Vol. 67.1.4 ( 0 ) page： 997 2012

25aPS-9 Quantitative polarized Raman spectroscopic study on Bi_2WO_6 Open Access

Noju M., Fujii Y., Shimizu T., Taniguchi H., Fu D., Itoh M., Nishio I.

Meeting Abstracts of the Physical Society of Japan Vol. 67.1.4 ( 0 ) page： 997 2012

Growth of Cu<inf>2</inf>ZnSnS<inf>4</inf> single crystal by traveling heater method Reviewed

Akira Nagaoka, Kenji Yoshino, Hiroki Taniguchi, Tomoyasu Taniyama, Hideto Miyake

Japanese Journal of Applied Physics Vol. 50 ( 12 ) 2011.12

Language：English Publishing type：Research paper (scientific journal) Publisher：IOP PUBLISHING LTD

A Cu2ZnSnS4 (CZTS) single crystal was grown at 900 °C, which is less than its melting point (962 °C) using a traveling heater method, which is one of the solution growth methods. No twins and no secondary phases could be distinguished from the Laue and X-ray diffraction patterns, respectively. © 2011 The Japan Society of Applied Physics.

DOI： 10.1143/JJAP.50.128001

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Mechanism for suppression of ferroelectricity in Cd<inf>1-x</inf>Ca <inf>x</inf>TiO<inf>3</inf> Reviewed

Hiroki Taniguchi, Hwee Ping Soon, Takao Shimizu, Hiroki Moriwake, Yue Jin Shan, Mitsuru Itoh

Physical Review B - Condensed Matter and Materials Physics Vol. 84 ( 17 ) 2011.11

Language：English Publishing type：Research paper (scientific journal)

A mechanism for cation-substitution-induced suppression of ferroelectricity in a perovskite-type ferroelectric oxide, CdTiO3, has been elucidated in terms of the relationship between the covalency and the lattice dynamics. Raman scattering experiments and first-principles calculations clarified that a change in the covalency of Cd sites due to Ca substitution selectively decreases the frequencies of the modes associated with octahedral rotations whose axes are perpendicular to the spontaneous polarization direction. The resulting destabilization of zigzag octahedral chains synchronizes the hardening of the ferroelectric soft mode, which suppresses the ferroelectricity. This result enhances our understanding of the relationship between local chemical bonds and macroscopic ferroelectricity. © 2011 American Physical Society.

DOI： 10.1103/PhysRevB.84.174106

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Mechanism for suppression of ferroelectricity in Cd1-xCaxTiO3 Reviewed

Hiroki Taniguchi, Hwee Ping Soon, Takao Shimizu, Hiroki Moriwake, Yue Jin Shan, Mitsuru Itoh

PHYSICAL REVIEW B Vol. 84 ( 17 ) 2011.11

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

DOI： 10.1103/PhysRevB.84.174106

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High-throughput CW-IR laser deposition and laser microscope imaging of binary ionic liquids in vacuum Reviewed Open Access

Shingo Maruyama, Hiroki Taniguchi, Yoko Takeyama, Mitsuru Itoh, Yuji Matsumoto

Science and Technology of Advanced Materials Vol. 12 ( 5 ) page： 054204 2011.10

Language：English Publishing type：Research paper (scientific journal) Publisher：TAYLOR & FRANCIS LTD

A combinatorial library of binary mixtures of ionic liquids with various mixing ratios was fabricated on a single sapphire substrate using the composition-spread technique combined with a continuous-wave infrared (CW-IR) laser deposition method; the mixtures were condensed in the form of micro-scale droplets. The mixing ratio within the droplets was examined by Raman spectroscopy. The contact angle of the droplets was found to systematically vary with the mixing ratio. Their thermal behavior was characterized with an ultrahigh-vacuum laser microscope, revealing the dependence of the evaporation rate on the mixing ratio. © 2011 National Institute for Materials Science.

DOI： 10.1088/1468-6996/12/5/054204

Enhancement of Quantum Ferroelectricity in SrTi^<18>O_3 Thin Film

Fujii Yasuhiro, Maeda Yuki, Katayama Masao, TANIGUCHI Hiroki, TAKASHIMA Hiroshi, ITOH Mitsuru, MATSUMOTO Yuji

Applied physics express Vol. 4 ( 9 ) page： "091501 - 1"-"091501-3" 2011.9

Erratum: Spontaneous polarization estimation from the soft mode in strain-free epitaxial polar axis-oriented Pb(Zr,Ti)O<inf>3</inf> thick films with tetragonal symmetry (Applied Physics Letters (2011) 98 (141914)) Reviewed Open Access

Yoshitaka Ehara, Satoru Utsugi, Mitsumasa Nakajima, Tomoaki Yamada, Takashi Iijima, Hiroki Taniguchi, Mitsuru Itoh, Hiroshi Funakubo

Applied Physics Letters Vol. 99 ( 12 ) 2011.9

First-principles calculations of lattice dynamics in CdTiO<inf>3</inf> and CaTiO<inf>3</inf>: Phase stability and ferroelectricity Reviewed

Hiroki Moriwake, Akihide Kuwabara, Craig A.J. Fisher, Hiroki Taniguchi, Mitsuru Itoh, Isao Tanaka

Physical Review B - Condensed Matter and Materials Physics Vol. 84 ( 10 ) page： 104114 2011.9

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

First-principles calculations of various phases of CdTiO3 carried out with the aim of obtaining insights into the mechanism of the ferroelectric phase transition and the structure of the low-temperature ferroelectric phase are reported. The results indicate that the preferred symmetry of the low-temperature phase is Pna21, rather than P2 1ma, corresponding to a small relative shift of the Ti and O ions in the paraelectric Pnma phase with the polarization axis parallel to the long axis. Calculated phonon dispersion curves show a distinct soft mode at the Γ point of the Pnma phase, which vanishes in the Pna21 phase, confirming that the transition to the ferroelectric phase is of the soft-mode displacive type. Calculations of perovskite CaTiO3, which also has an orthorhombic Pnma structure at room temperature but, unlike CdTiO3, does not exhibit a ferroelectric phase transition down to 4.2 K, were also carried out to help characterize the factors controlling ferroelectric phase transitions in perovskite titanates. © 2011 American Physical Society.

DOI： 10.1103/PhysRevB.84.104114

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Papers - TANIGUCHI Hiroki