研究者詳細 - 長田　実

論文 - 長田　実

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Gigantic plasmon resonance effects on magneto-optical activity of molecularly thin ferromagnets near gold surfaces 査読有り

Minoru Osada, Natália Hajduková-Šmídová, Kosho Akatsuka, Satoshi Yoguchi, Takayoshi Sasaki

Journal of Materials Chemistry C 1 巻 ( 14 ) 頁： 2520 - 2524 2013年4月

記述言語：英語掲載種別：研究論文（学術雑誌）

We report on a new magneto-plasmonic material consisting of 1 nm thick ferromagnetic nanosheets and Au nanoparticles. The magneto-optical (MO) Kerr spectra of Ti0.8Co0.2O2 nanosheets near Au surfaces showed a gigantic MO response (∼106 deg cm-1) in the visible wavelength region (380-600 nm), not present in Ti 0.8Co0.2O2 nanosheets on a bare glass substrate. The observed peaks correspond to intrinsic d-d* electronic transitions in Ti0.8Co0.2O2 and are consistent with the near-field enhancement of the MO response resulting from the spectral overlap of the surface-plasmon-resonance (SPR) in the Au surface with the electronic transitions in Ti0.8Co0.2O2. Similar SPR effects were also achieved in ferromagnetic nanosheet/Au with different compositions and with different separation distances (&lt
5 nm). This demonstration of SPR-enhanced magneto-optics in the ferromagnetic/plasmonic nanosystem may enable designing of nanoarchitectures for miniaturized high-performance MO devices and for remote sensing and imaging of magnetic fields. © The Royal Society of Chemistry 2013.

DOI： 10.1039/c3tc00952a

Synthesis of Highly Strained Mesostructured SrTiO3/BaTiO3 Composite Films with Robust Ferroelectricity 査読有り

Norihiro Suzuki, Mohamed B. Zakaria, Nagy L. Torad, Kevin C-W Wu, Yoshihiro Nemoto, Masataka Imura, Minoru Osada, Yusuke Yamauchi

CHEMISTRY-A EUROPEAN JOURNAL 19 巻 ( 14 ) 頁： 4446 - 4450 2013年4月

Fabrication of Ruthenium Metal Nanosheets via Topotactic Metallization of Exfoliated Ruthenate Nanosheets 査読有り

Katsutoshi Fukuda, Jun Sato, Takahiro Saida, Wataru Sugimoto, Yasuo Ebina, Tatsuo Shibata, Minoru Osada, Takayoshi Sasaki

INORGANIC CHEMISTRY 52 巻 ( 5 ) 頁： 2280 - 2282 2013年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

The metallization behavior of molecularly thin RuO2 nanosheets obtained from complete delamination of layered ruthenates was studied. Interestingly, the RuO2 nanosheets in a monolayer state topotactically transformed into a single layer of Ru atoms, i.e., ruthenium metal nanosheets, which can be regarded as a new family of nanosized metals.

DOI： 10.1021/ic302720d

Low-frequency Raman scattering in binary silicate glass: Boson peak frequency and its general expression 査読有り

Kensaku Nakamura, Yoshihiro Takahashi, Minoru Osada, Takumi Fujiwara

Journal of the Ceramic Society of Japan 121 巻 ( 1420 ) 頁： 1012 - 1014 2013年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Ceramic Society of Japan

Low-frequency Raman measurement was performed in alkali and alkaline-earth silicate glasses to elucidate the effect of introduction of network modifiers on boson peak nature. Our study illustrated that introduction of small/medium ions tended to increase in the boson peak frequency (ωBP), whereas the introduction of large ions tended to decrease the frequency. Although ωBP has been suggested to be proportional to the shear modulus, no linear relationship was obtained in these binary systems. Instead, we experimentally demonstrated that mean atomic volume can explain variations in ωBP regardless of the trend of boson peaks. © 2013 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.121.1012

Room temperature multiferroic heterostructure: Nd: BiFeO3/YMnO3 査読有り

Hongyang Zhao, Hideo Kimura, Zhenxiang Cheng, Xiaolin Wang, Qiwen Yao, Minoru Osada, Baowen Li

Journal of Crystal Growth 365 巻頁： 19 - 23 2013年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Elsevier B.V.

In order to search candidate multiferroics, a heterostructure of Nd:BiFeO3/YMnO3 (BFO/YMO) was designed. It was fabricated using a pulsed laser deposition (PLD) method on (111) Nb: SrTiO3 substrate through layer-by-layer growth. The particularly interesting phases for Nd:BiFeO3 (P4mm) and YMnO3 (hexagonal and orthorhombic) were observed. This film has a high ferromagnetic Curie temperature at 420 K. The ferroelectric domain switching was observed and it exhibited large electromechanical coupling with maximum d33∼73 pm/V at 10 V. © 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jcrysgro.2012.12.023

Structural relaxation and quasi-elastic light scattering in glass: Approach by ferroelectric and ion-conducting phases 査読有り

Yoshihiro Takahashi, Kensaku Nakamura, Minoru Osada, Takumi Fujiwara

SCIENTIFIC REPORTS 2 巻 2012年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：NATURE PUBLISHING GROUP

Inelastic light scattering has been utilized for examining the structure of glass and its relaxation. However, the quasi-elastic-light-scattering (QLS) phenomenon has not been addressed in much detail. In this study, we observed pronounced QLS-intensity variations in two temperature domains-supercooled liquid (SCL) state (alpha-relaxation regime) and below the glass-transition temperature (beta-relaxation regime)-in niobium-oxide (Nb2O5)-rich glass. These variations may be interpreted on the basis of the concept of ferroelectric and ion-conducting phases. It was suggested that the observed QLS originates as a result of the polarization fluctuation of NbO6 units, which is due to the dynamics of the nanometric phase separation in the SCL phase (alpha-regime), and the fluctuation due to the migration/hopping of conductible ions that are localized in the vicinity of the NbO6 units (beta-regime).

DOI： 10.1038/srep00714

The formation of graphene-titania hybrid films and their resistance change under ultraviolet irradiation 査読有り

Pengzhan Sun, Renzhi Ma, Minoru Osada, Takayoshi Sasaki, Jinquan Wei, Kunlin Wang, Dehai Wu, Yao Cheng, Hongwei Zhu

CARBON 50 巻 ( 12 ) 頁： 4518 - 4523 2012年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD

We report the fabrication of hybrid films of graphene and monolayer titania using a simple electrostatic self-assembly method. Ultraviolet (UV) responses of the hybrid films based on the graphene-titania structure were investigated. We observed that the resistance of the graphene-titania hybrid increased exponentially with UV irradiation time and decreased exponentially when UV was turned off. Time constants of the order of hundreds of seconds were identified and found to be sensitive to the gas environment of graphene. The UV response as well as the time constant is tunable by varying the number of titania layers. Our results confirmed that UV irradiation played a significant role in the resistance modulation of graphene as well as graphene-titania hybrid films. (C) 2012 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.carbon.2012.05.035

Interfacial phenomena in solid-state lithium battery with sulfide solid electrolyte 査読有り

Kazunori Takada, Narumi Ohta, Lianqi Zhang, Xiaoxiong Xu, Bui Thi Hang, Tsuyoshi Ohnishi, Minoru Osada, Takayoshi Sasaki

SOLID STATE IONICS 225 巻頁： 594 - 597 2012年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

The effects of surface coating on electrode properties of LiMn2O4 in a sulfide solid electrolyte were investigated. The surface coating with LiNbO3 reduced the electrode resistance by two orders of magnitude. Changes in the electrode properties were very similar to those observed for the corresponding LiCoO2 electrodes, which strongly suggest that the space-charge layer formed at the high-voltage cathode/sulfide electrolyte interface is rate-determining and must be controlled to improve the rate capability. (c) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ssi.2012.01.009

Nano-Materials Design for High-TC Ferromagnets of Ti1-xCoxO2 Nanosheets 査読有り

Minoru Osada, Takayoshi Sasaki, Kanta Ono

INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY 9 巻 ( 5 ) 頁： 936 - 941 2012年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：WILEY-BLACKWELL

We present materials design of high-TC ferromagnetic nanomaterials based on first-principles calculations. Two-dimensional (2D) titania nanosheet, a recently discovered room-temperature (RT) ferromagnetic nanomaterial, is an important target for 2D ferromagnets. In Ti1-xCoxO2 nanosheets with Co2+ oxidation state, the ferromagnetic states are highly stabilized up to x=0.5 with a modest doping dependence of magnetic moment (1 mu B/Co). Moreover, we find that tailoring properties could be achieved by tuning Co oxidation states, and the optimally doped Ti1-xCoxO2 nanosheets (Co3+; x=0.125, 0.25) are found to be an excellent RT half-metallic ferromagnet with a large magnetic moment (similar to 4 mu B/Co). 2D nanosheet is therefore expected to provide a very useful platform for nanoscale spinelectronics devices.

DOI： 10.1111/j.1744-7402.2012.02783.x

Percolative BaTiO3/Carbon-Nanotube Composite Films Employing Aerosol Deposition 査読有り

Yoon-Hyun Kim, Minoru Osada, Hong-Ki Kim, Song-Min Nam

JAPANESE JOURNAL OF APPLIED PHYSICS 51 巻 ( 9 ) 2012年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IOP PUBLISHING LTD

Percolative BaTiO3/multiwalled carbon nanotube (MWNT) composite thick films were developed using an aerosol deposition (AD) process at room temperature. Well-dispersed mixed powders with various volume ratios were utilized as the starting powders for AD, and dense BaTiO3/MWNT composite thick films were successfully fabricated with the starting mixed powders with 0.01 vol% MWNTs. The existence of MWNTs in the composite films was confirmed using Raman spectroscopy. The composite films show a high relative dielectric constant (657 at 1 kHz), which is approximately 7 times larger than that (91 at 1 kHz) of the BaTiO3 films. In addition, the strong frequency dispersion of the dielectric constant in the low-frequency range was confirmed for the composite films. The dielectric properties of the composite films were investigated using the dielectric mechanism used in percolative composites. (C) 2012 The Japan Society of Applied Physics

DOI： 10.1143/JJAP.51.09LC07

SE(R)RS excitation profile of free-base 5,10,15,20-tetrakis(1-methyl-4-pyridyl) porphyrin on immobilized gold nanoparticles 査読有り

Natalia Hajdukova-Smidova, Marek Prochazka, Minoru Osada

VIBRATIONAL SPECTROSCOPY 62 巻頁： 115 - 120 2012年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

Surface-enhanced (resonance) Raman scattering - SE(R)RS - excitation profile (dependence of SE(R)RS intensity on excitation wavelength) is a key point for optimizing of electromagnetic enhancement of particular SE(R)RS system. In this paper, we measured SE(R)RS excitation profile of free-base 5,10,15,20-tetrakis(1-methyl-4-pyridyl) porphyrin (TMPyP) on immobilized Au nanoparticles using confocal Raman microspectrometer with six excitation wavelengths (457.9, 488.0, 514.5, 530.9, 568.2 and 647.1 nm). Au colloidal nanoparticles were immobilized to a glass slide via a self-assembled monolayer of 3-aminopropyltrimethoxysilane. SE(R)RS excitation profile is correlated with the corresponding surface plasmon extinction (SPE) spectrum of immobilized Au nanoparticles although the maximum of SE(R)RS intensity is slightly shifted from maximum of SPE. In our case of resonant molecule, SE(R)RS enhancement is coupled with molecular resonance enhancement and SE(R)RS excitation profile for particular vibrational mode depends on its TMPyP molecular resonance contribution. SE(R)RS excitation profile shows that maximal SE(R)RS intensity is obtained for 568.2 nm excitation that provides limit of detection (LOD) of TMPyP 2 x 10(-8) M in soaking solution. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.vibspec.2012.04.007

RbBiNb2O7: A New Lead-Free High-T-c Ferroelectric 査読有り

Bao-Wen Li, Minoru Osada, Tadashi C. Ozawa, Takayoshi Sasaki

CHEMISTRY OF MATERIALS 24 巻 ( 16 ) 頁： 3111 - 3113 2012年8月

酸化物ナノシートを用いた機能性セラミックスコーティング

長田実, 佐々木高義, 佐々木高義, 佐々木高義

スマートプロセス学会誌 = Journal of smart processing 1 巻 ( 4 ) 頁： 150 - 154 2012年7月

NANOCRYSTALLIZATION AND OPTICAL PROPERTY OF WILLEMITE-TYPE SEMICONDUCTIVE Zn2GeO4 IN GLASS 査読有り

Yoshihiro Takahashi, Masataka Ando, Rie Ihara, Takumi Fujiwara, Minoru Osada

FUNCTIONAL MATERIALS LETTERS 5 巻 ( 2 ) 2012年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：WORLD SCIENTIFIC PUBL CO PTE LTD

A wide band-gap semiconductive oxide Zn2GeO4 has recently attracted considerable interest because it is a multifunctional material; excellent photoluminescent (PL) and photocatalytic property, high-capacity anode for lithium batteries, and so on. Recently, present authors' group have fabricated transparent Zn2GeO4-nanocrystallized glass from a lithium zincogermanate glass. This article briefly describes a series of our studies on the nanocrystallized glass. Particularly, the phase-formation dynamics in supercooled-liquid phase and PL property of nanocrystallized glasses are presented.

DOI： 10.1142/S1793604712600089

Effect of annealing at maximum nucleation temperature on boson peak in lithium-disilicate glass 査読有り

Kensaku Nakamura, Yoshihiro Takahashi, Minoru Osada, Rie Ihara, Takumi Fujiwara

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 120 巻 ( 1402 ) 頁： 256 - 258 2012年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

Low-frequency Raman scattering and TEM observations were conducted in 1Li(2)O-2SiO(2) glass subjected to annealing at maximum homogeneous nucleation temperature (similar to 460 degrees C) to elucidate the annealing effect on Boson-peak behavior and its relation to the structural evolution in nanoscale. It is suggested that the 1Li(2)O-2SiO(2) glass possesses a successive medium-range ordering through phase separation, and the Boson-peak frequency was largely affected by the ordering/phase-separation. (C) 2012 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.120.256

Photochromogenic Nanosheet Crystallites of Tungstate with a 2D Bronze Structure 査読有り

Katsutoshi Fukuda, Kosho Akatsuka, Yasuo Ebina, Minoru Osada, Wataru Sugimoto, Mutsumi Kimura, Takayoshi Sasaki

INORGANIC CHEMISTRY 51 巻 ( 3 ) 頁： 1540 - 1543 2012年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

Layered rubidium tungstate, Rb4W11O35, with a two-dimensional (2D) bronze-type tunnel structure was successfully delaminated into colloidal nanosheets via a soft-chemical process involving acid exchange and subsequent intercalation of tetrabutylammonium ions. Characterizations by transmission electron microscopy and atomic force microscopy confirmed the formation of unilamellar 2D nanosheet crystallites with a unique thickness of similar to 3 nm and an average lateral size of 400 nm. The obtained nanosheets exhibited reversible color change upon UV-light excitation via an optical band gap of 3.5 eV. The ultimate 2D aspect ratio favorable for an adsorption of charge-compensating cations to trapped electrons working as a color center is presumably responsible for highly efficient photochromic behavior. Its coloration mainly consists of a broad band at a wavelength of 1800 nm and longer, which is much different from that of the common tungstate nanomaterials. Thus, the chromogenic nanosheet obtained in this study features the intense UV absorption and optically switchable visible-to-IR absorption, which may be useful for window applications such as cutoff filters and heat-absorbing films.

DOI： 10.1021/ic201834y

Soft-phonon mode observation in Li2Ge4O9 phase above room temperature 査読有り

Yoshihiro Takahashi, Jun Kunitomo, Kensaku Nakamura, Minoru Osada, Takumi Fujiwara

APPLIED PHYSICS LETTERS 100 巻 ( 9 ) 2012年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER INST PHYSICS

Li2Ge4O9 is known to be a ferroelectric phase with Curie temperature at T-c similar to -93 degrees C. In this study, we found both the lowest-frequency phonon and heat-capacity anomalies around 100 degrees C in the Li2Ge4O9 phase, demonstrating their presence in the structural phase-transition. The phase transition is probably triggered by regularization of distorted GeO6 octahedra in the paraelectric phase, resulting in another phase consisting of the regular octahedral GeO6 unit, which was supported by in situ measurement of emission of E-2 -> (4)A(2) transition in the Mn4+-doped phase. It is deduced that the phase transition is more dynamic than ferroelectric phase-transition originating in ordering of the Li ions. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3688603]

DOI： 10.1063/1.3688603

Two-Dimensional Dielectric Nanosheets: Novel Nanoelectronics From Nanocrystal Building Blocks 査読有り

Minoru Osada, Takayoshi Sasaki

ADVANCED MATERIALS 24 巻 ( 2 ) 頁： 210 - 228 2012年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：WILEY-V C H VERLAG GMBH

Two-dimensional (2D) nanosheets, which possess atomic or molecular thickness and infinite planar lengths, are regarded as the thinnest functional nanomaterials. The recent development of methods for manipulating graphene (carbon nanosheet) has provided new possibilities and applications for 2D systems; many amazing functionalities such as high electron mobility and quantum Hall effects have been discovered. However, graphene is a conductor, and electronic technology also requires insulators, which are essential for many devices such as memories, capacitors, and gate dielectrics. Along with graphene, inorganic nanosheets have thus increasingly attracted fundamental research interest because they have the potential to be used as dielectric alternatives in next-generation nanoelectronics. Here, we review the progress made in the properties of dielectric nanosheets, highlighting emerging functionalities in electronic applications. We also present a perspective on the advantages offered by this class of materials for future nanoelectronics.

DOI： 10.1002/adma.201103241

A- and B-Site Modified Perovskite Nanosheets and Their Integrations into High-k Dielectric Thin Films 査読有り

Minoru Osada, Takayoshi Sasaki

INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY 9 巻 ( 1 ) 頁： 29 - 36 2012年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：WILEY-BLACKWELL

We investigated dielectric properties of perovskite nanosheets with different compositions (Ca2-xSrxNb3-yTayO10) to study the influence of A- and B-site modifications on dielectric properties. LangmuirBlodgett deposition was employed to fabricate multilayer nanofilms of perovskite nanosheets. In these nanosheets, the A-site modification by Sr2+ ions causes the increase in epsilon(r) value, whereas the B-site modification with Ta5+ ions improves leakage current characteristics and reduces permittivity value. The optimized property (epsilon(r) = 240) is obtained for Sr2Nb3O10 nanosheet. We also discuss high-kappa properties of Ca2-xSrxNb3-yTayO10 nanosheets by detailed investigations on first-principles calculations and interfacial structures.

DOI： 10.1111/j.1744-7402.2011.02713.x

Two-dimensional dielectric nanosheets: novel nanoelectronics from building blocks 招待有り査読有り

M. Osada, T. Sasaki

Adv. Mater. 24 巻頁： 210-228 2012年

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