研究者詳細 - 長田　実

論文 - 長田　実

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Impact of perovskite layer stacking on dielectric responses in KCa2Nan-3NbnO3n+1 (n=3-6) Dion-Jacobson homologous series 査読有り

Bao-Wen Li, Minoru Osada, Yasuo Ebina, Tadashi C. Ozawa, Renzhi Ma, Takayoshi Sasaki

APPLIED PHYSICS LETTERS 96 巻 ( 18 ) 2010年5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

The dielectric properties of KCa(2)Na(n-3)NbnO(3n+1) (n=3-6) Dion-Jacobson homologous series have been investigated. The dielectric constants (epsilon) increase with the number of octahedral units (n), and the n=6 compound (KCa2Na3Nb6O19) exhibits a stable dielectric response with epsilon = similar to 500 between 1 kHz and 1 MHz. This n-dependent behavior is similar to those observed in other layered perovskites such as Ruddlesden-Popper and Aurivillius phases. Raman scattering studies reveal that increase in n in KCa2Nan-3NbnO3n+1 leads to higher polarizability of the lattice and softening of the lowest-frequency phonon mode, which is responsible for the observed enhancement in epsilon with n. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3402761]

DOI： 10.1063/1.3402761

酸化物ナノシートの誘電材料および磁気材料への応用 Open Access

長田実, 佐々木高義

表面技術 = The journal of the Surface Finishing Society of Japan 61 巻 ( 1 ) 頁： 18 - 22 2010年1月

Engineered interfaces of artificial perovskite oxide superlattices via nanosheet deposition process 査読有り

B. W. Li, M. Osada, T. C. Ozawa, Y. Ebina, K. Akatsuka, R. Ma, H. Funakubo, T. Sasaki

ACS Nano 4 巻頁： 6673-6680 2010年

Robust high-k response in molecularly thin perovskite nanosheets 査読有り

M. Osada, Y. Ebina, H. Funakubo, K. Ono, K. Takada, T. Sasaki

ACS Nano 4 巻頁： 5225-5232 2010年

A-Site-Modified Perovskite Nanosheets and Their Integration into High-kappa Dielectric Thin Films with a Clean Interface 査読有り

Bao-Wen Li, Minoru Osada, Tadashi C. Ozawa, Kosho Akatsuka, Yasuo Ebina, Renzi Ma, Kanta Ono, Hiroshi Funakubo, Takayoshi Sasaki

JAPANESE JOURNAL OF APPLIED PHYSICS 49 巻 ( 9 ) 2010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：JAPAN SOC APPLIED PHYSICS

We investigated dielectric properties of La1-xEuxNb2O7 perovskite nanosheets in order to study the effect of A-site modification on dielectric properties. Langmuir-Blodgett deposition was employed to fabricate multilayer nanofilms of perovskite nanosheets. In these nanosheets, A-site modification with Eu3+ ions improves the leakage current characteristics and, at the same time, reduces permittivity. The slight modification with Eu3+ ions in La0.95Nb2O7 nanosheets causes a 50% reduction in epsilon(r) value. We also discuss the high-kappa properties of La0.95Nb2O7 nanosheets by performing detailed investigations based on first-principles calculations and interfacial structures. (C) 2010 The Japan Society of Applied Physics

DOI： 10.1143/JJAP.49.09MA01

Well-Controlled Crystal Growth of Zinc Oxide Films on Plastics at Room Temperature Using 2D Nanosheet Seed Layer 査読有り

Tatsuo Shibata, Tsuyoshi Ohnishi, Isao Sakaguchi, Minoru Osada, Kazunori Takada, Toshihiro Kogure, Takayoshi Sasaki

JOURNAL OF PHYSICAL CHEMISTRY C 113 巻 ( 44 ) 頁： 19096 - 19101 2009年11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

ZnO crystal films having a nearly perfect (001) orientation were successfully grown at room temperature on plastic and glass substrates by modifying their surface with Cs(4)W(11)O(36) nanosheets through a solution-based process. To clarify the effect of the monolayer film of Cs(4)W(11)O(36) nanosheets, the films were characterized by X-ray diffraction (XRD), 2D X-ray diffraction (2D-XRD), and high-resolution transmission electron microscopy (HRTEM). The results showed that the introduction of a typical 2D crystal surface with 2D-hexagonal structure (a = 0.727 nm) of Cs(4)W(11)O(36) nanosheet promotes high-quality crystal growth of (001) oriented ZnO film (a = 0 325 nm). Highly crystalline texture directly formed on top of the substrates has been, to the best of our knowledge, realized for the first time, and it dramatically improves the film property, especially at the small film thickness region of <50 nm. The resistivity of the ZnO films significantly decreased when the films were fabricated on glass or plastic substrates with the nanosheet seed layer

DOI： 10.1021/jp9074288

Orientation controlled deposition of Pb(Zr,Ti)O-3 films using a micron-size patterned SrRuO3 buffer layer 査読有り

Ken Nishida, Takashi Yamamoto, Minoru Osada, Osami Sakata, Shigeru Kimura, Keisuke Saito, Masamichi Nishide, Takashi Katoda, Shintaro Yokoyama, Hiroshi Funakubo

JOURNAL OF MATERIALS SCIENCE 44 巻 ( 19 ) 頁： 5339 - 5344 2009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：SPRINGER

Orientation controlled, micron-sized dot-patterned PZT films were grown by metal organic chemical vapor phase deposition (MOCVD), and their crystal structure was evaluated. A micron-size dot-patterned SrRuO3 (SRO) buffer layer was initially prepared by MOCVD through a metal mask on the (111) Pt/Ti/SiO2/Si substrate. Then, a PZT film was deposited over the entire substrate. Micron-beam X-ray diffraction and Raman spectroscopy indicated that (111)-orientated PZT was prepared on the SRO covered area, while the (100)/(001)-orientated one was directly grown on Pt-covered substrates. The PZT film grown on SRO was thinner than that on the Pt-covered substrate. The estimated ferroelectric property on the center of the dot pattern was larger than that at the circumference by Raman spectroscopy because the strain is accelerated at the center of the dot.

DOI： 10.1007/s10853-009-3683-5

Synthesis of Mn-Substituted Titania Nanosheets and Ferromagnetic Thin Films with Controlled Doping 査読有り

Xiaoping Dong, Minoru Osada, Hidekazu Ueda, Yasuo Ebina, Yoshinori Kotani, Kanta Ono, Shigenori Ueda, Keisuke Kobayashi, Kazunori Takada, Takayoshi Sasaki

CHEMISTRY OF MATERIALS 21 巻 ( 19 ) 頁： 4366 - 4373 2009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：AMER CHEMICAL SOC

We report the synthesis of Mn-substituted titania nanosheets and the preparation of room-temperature ferromagnetic thin films via layer-by-layer assembly of these nanosheets. Ti(5.2-2x)/6Mnx/2O2 (x = 0.0-0.4) nanosheets were synthesized by delaminating layered titanates [K0.8Ti(5.2-2x)/3Li(0.8-x)/3-MnxO(4)], in which the Mn content was systematically controlled by Li+ doping. We found that Mn content in the host layers was preserved upon exfoliation, and controlled Mn doping was achieved in exfoliated Ti(5.2-2x)/6Mnx/2O2 (x = 0.0-0.4) nanosheets, where Li+ tons were completely extracted by acid-exchange reaction in the exfoliation process. The multilayer films of Ti(5.2-2x)/6Mnx/2O2 (x = 0.0-0.4) nanosheets exhibit a clear magnetic hysteresis loop at room-temperature in similar to what observed in ferromagnetic Ti1-xCoxO2 nanosheets. Electronic absorption, magnetic circular dichroism, and hard X-ray photoelectron spectroscopy were used to identify Mn-derived states, and analyze the properties of these states related to ferromagnetism. The first-principles calculation of Ti(5.2-2x)/6Mnx/2O2 was also employed to characterize the doping effect on electronic structures.

DOI： 10.1021/cm900210m

Solution-Based Fabrication of Perovskite Nanosheet Films and Their Dielectric Properties 査読有り

Bao-Wen Li, Minoru Osada, Tadashi C. Ozawa, Renzhi Ma, Kosho Akatsuka, Yasuo Ebina, Hiroshi Funakubo, Shigenori Ueda, Keisuke Kobayashi, Takayoshi Sasaki

JAPANESE JOURNAL OF APPLIED PHYSICS 48 巻 ( 9 ) 2009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：JAPAN SOCIETY APPLIED PHYSICS

We report a solution-based approach for fabricating perovskite nanofilms using a La(0.95)Nb(2)O(7) perovskite nanosheet, a two-dimensional nanomaterial prepared by delaminating layered perovskite KLa(0.95)Nb(2)O(7) into single-molecule-thick sheets. A layer-by-layer approach using Langmuir-Blodgett deposition was effective for fabricating uniform and highly dense nanofilms of perovskite nanosheets on an atomically flat SrRuO(3) substrate. Structural analysis using X-ray diffraction, transmission electron microscopy, and hard X-ray photoelectron spectroscopy revealed that these films are composed of a well-ordered lamellar structure without an interfacial dead layer. The nanofilms showed stable dielectric response with epsilon(r) similar or equal to 45 for thickness even down to 6 nm. (C) 2009 The Japan Society of Applied Physics

DOI： 10.1143/JJAP.48.09KA15

Raman Spectroscopy Evaluation of Oxygen Vacancy Migration by Electrical Field in Multilayer Ceramic Capacitors 査読有り

Ken Nishida, Hiroshi Kishi, Minoru Osada, Hiroshi Funakubo, Masamichi Nishide, Hironari Takeuchi, Takashi Katoda, Takashi Yamamoto

JAPANESE JOURNAL OF APPLIED PHYSICS 48 巻 ( 9 ) 2009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：JAPAN SOCIETY APPLIED PHYSICS

Raman spectroscopy is used to evaluate migration behavior of oxygen vacancies in BaTiO(3)-based multilayer ceramic capacitors with Ni internal electrodes (Ni-MLCCs) before and after a highly accelerated life test (HALT). The B(1) phonon mode of BaTiO(3) that is associated with oxygen vibration was hardened and broadened near the Ni electrodes before HALT. However, the hardening and broadening of the B, mode were observed near the cathodes after HALT. It is considered that the oxygen vacancies were localized near the Ni electrodes before HALT and they electromigrated toward the cathode because they have the positive charges. These results show that oxygen vacancies migrated and accumulated near the cathode under a dc bias and caused insulation resistance degradation in MLCCs. In addition, Raman spectroscopy is a powerful tool for investigation of structural defect distribution including oxygen vacancies with a relatively high spatial resolution. (C) 2009 The Japan Society of Applied Physics

DOI： 10.1143/JJAP.48.09KF11

Precursive stage of nanocrystallization in niobium oxide-containing glass 査読有り

Yoshihiro Takahashi, Hirokazu Masai, Minoru Osada, Takumi Fujiwara

APPLIED PHYSICS LETTERS 95 巻 ( 7 ) 2009年8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

In situ observation of inelastic light scattering in Raman and Boson regions was performed in a niobiogermanate glass with a high nucleation ability during heating in order to examine its nanocrystallization dynamics. The relation of structural heterogeneity to the precursive stage of crystallization is also discussed. It is suggested that evolution of nuclei occurs in a nanometric niobate-rich region due to density fluctuation in the supercooled liquid phase prior to nanocrystallization.

DOI： 10.1063/1.3211989

Softer region at boundary of supercooled liquid-crystal in glassy fresnoite 査読有り

Yoshihiro Takahashi, Minoru Osada, Hirokazu Masai, Takumi Fujiwara

APPLIED PHYSICS LETTERS 94 巻 ( 24 ) 2009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：AMER INST PHYSICS

The transition between the supercooled liquid (SCL) and crystal phases was investigated by in situ observation of boson peak in a glassy fresnoite (Ba(2)TiSi(2)O(8)) with an extremely high nucleation ability. The glassy fresnoite revealed anomalous boson behavior, in that the boson peak's full width at half maximum diverged at T/T(g)similar to 1.2. This behavior suggests that an elastically softer region exists at the interface of the fresnoite nucleus/crystallite in the SCL state.

DOI： 10.1063/1.3156025

Crystallization and nanometric heterogeneity in glass: In situ observation of the boson peak during crystallization 査読有り

Yoshihiro Takahashi, Minoru Osada, Hirokazu Masai, Takumi Fujiwara

PHYSICAL REVIEW B 79 巻 ( 21 ) 2009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：AMER PHYSICAL SOC

In situ measurement of boson peak in several glasses was performed during the crystallization process to elucidate crystallization dynamics. In this study, it was experimentally illustrated that a drastic decrease in elasticity and damping of the boson peak occurred during the crystallization process when T/T(g)similar to 1.1-1.2. A possible mechanism for the crystallization precursive stage is also discussed, which integrates our boson peak observation results, Hikima's description [J. Mol. Struct. 479, 245 (1999)], Cabral's thermodynamic data [J. Non-Cryst. Solids 343, 85 (2004)], and other works.

DOI： 10.1103/PhysRevB.79.214204

Structural heterogeneity and homogeneous nucleation of 1BaO-2SiO(2) glass 査読有り

Yoshihiro Takahashi, Minoru Osada, Hirokazu Masai, Takumi Fujiwara

APPLIED PHYSICS LETTERS 94 巻 ( 21 ) 2009年5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

Structural relaxation was examined by in situ Boson peak observation in 1BaO-2SiO(2) glass with homogeneous nucleation tendency, in order to clarify the structural heterogeneity. The relation between the glass structure in the medium-range scale and nucleation feature is also discussed. From the results, it is predicted that a sheet-like structure with a network modifier in the resulting crystal is an essential condition for homogeneous nucleation.

DOI： 10.1063/1.3142394

Construction of Highly Ordered Lamellar Nanostructures through Langmuir-Blodgett Deposition of Molecularly Thin Titania Nanosheets Tens of Micrometers Wide and Their Excellent Dielectric Properties 査読有り

Kosho Akatsuka, Masa-aki Haga, Yasuo Ebina, Minoru Osada, Katsutoshi Fukuda, Takayoshi Sasaki

ACS NANO 3 巻 ( 5 ) 頁： 1097 - 1106 2009年5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

Exfoliated unilamellar titania nanosheets of Ti0.87O2 with a lateral size of 10-30 mu m were deposited layer-by-layer onto various substrates by Langmuir-Blodgett procedure to produce a highly ordered lamellar nanofilms. The nanosheets dispersed in an aqueous suspension containing quaternary ammonium ions as a supporting electrolyte floated spontaneously at the air/liquid interface, and they were successfully transferred onto the substrate after surface compression. Neat tiling of the nanosheets could be realized at an optimized surface pressure. The film thus obtained was exposed to UV light to turn the substrate surface hydrophilic, which was helpful for stable repetition of monolayer deposition. Layer-by-layer growth was confirmed by UV-visible absorption spectra, which showed progressive enhancement of an absorption band due to the nanosheet. Cross-sectional transmission electron microscopy images visualized the ultrathin film homogeneously deposited on the substrate surface and a lamellar fringe of the layer-by-layer assembled nanosheets was clearly resolved at a higher magnification. X-ray diffraction data on the films showed sharp basal reflections up to the seventh order, and Williamson-Hall analysis of the pattern indicated that the film was coherent across the total thickness with respect to X-ray and that the lattice strain was extremely small. In addition, the first basal reflection was accompanied by small satellite peaks, which are accounted for by the Laue interference function. All these features clearly indicate the formation of a highly ordered lamellar nanostructure of the titania nanosheets comparable to artificial lattice films produced via modern vapor-phase deposition processes. The obtained films showed superior dielectric and insulating properties as a reflection of the highly organized film nanoarchitecture.

DOI： 10.1021/nn900104u

Fabrication of novel composites of ZnO-nanoparticles and magadiite 査読有り

Kiyoshi Ozawa, Yasuhiro Nakao, Zhenxiang Cheng, Defa Wang, Minoru Osada, Reika Okada, Kazuhiko Saeki, Hiroyasu Itoh, Fumio Iso

MATERIALS LETTERS 63 巻 ( 3-4 ) 頁： 366 - 369 2009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：ELSEVIER SCIENCE BV

Novel composites of ZnO-nanoparticles and magadiite were Successfully prepared by a simple ion-exchange technique in an aqueous suspension of magadiite (Na(2)Si(14)O(29)center dot nH(2)O) and Zn(NO(3))(2). The TEM and STEM measurements showed that the composites have a structure in which ZnO-nanoparticles with relatively uniform particle sizes are well dispersed within the interlaminar spaces of the magadiite matrix. The particle sizes of the ZnO-nanoparticles were found to depend oil the heat-treatment temperature: the average particle sizes are similar to 2.6, similar to 2.8, similar to 4.4 and similar to 4.6 nm, respectively, for the temperatures of 40, 180, 300 and 600 degrees C. It Was also found that the ZnO nanoparticles crystallize and form a single-crystalline particle when the temperature exceeds similar to 300 degrees C. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.matlet.2008.10.038

Exfoliated oxide nanosheets: new solution to nanoelectronics 招待有り査読有り

M. Osada, T. Sasaki

J. Mater. Chem. 19 巻頁： 2503-2511 2009年

Anomalous Boson Behavior and Nanometric Heterogeneity in Glassy Fresnoite 査読有り

Yoshihiro Takahashi, Minoru Osada, Hirokazu Masai, Takumi Fujiwara

APPLIED PHYSICS EXPRESS 1 巻 ( 12 ) 2008年12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：JAPAN SOCIETY APPLIED PHYSICS

In-situ observation of the boson peak, omega(BP), Of as-quenched and annealed glassy Ba(2)TiGe(2)O(8) (BTG) and Ba(2)TiSi(2)O(8) (BTS) was performed during a heating process. Although annealed glassy BTG and BTS indicated a monotonous decrease in omega(BP) with temperature, the asquenched varieties, which included internal stress, revealed anomalous boson behavior at similar to 600 degrees C, lower than each one's glass-transition temperature. It was suggested that the omega(BP) anomaly was caused by beta-relaxation. This experimental result also supports the inhomogeneous structure (or cluster) model of glass. (C) 2008 The Japan Society of Applied Physics

DOI： 10.1143/APEX.1.121901

Raman spectroscopy study of oxygen vacancies in PbTiO3 thin films generated heat-treated in hydrogen atmosphere 査読有り

Ken Nishida, Minoru Osada, Hironari Takeuchi, Ishimoto Yosiaki, Joe Sakai, Nobuaki Ito, Rikyu Ikariyama, Takafumi Kamo, Takashi Fujisawa, Hiroshi Funakubo, Takashi Katoda, Takashi Yamamoto

JAPANESE JOURNAL OF APPLIED PHYSICS 47 巻 ( 9 ) 頁： 7510 - 7513 2008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：JAPAN SOC APPLIED PHYSICS

Raman spectroscopy is utilized to study the evaluation of vacancies in PbTiO3 thin films subjected to hydrogen atmosphere heat treatment. The B-1 mode consisted of only oxygen ion vibration was shifted to lower frequency with increasing heat treatment temperature. It was considered that the oxygen ions were lacking from PbTiO3, and that oxygen vacancies were generated. It was found that the frequency of the B-1 mode is proportional to oxygen ion content. Pb ions were also lacking in the PbTiO3 thin films with oxygen ions number of oxygen vacancies was larger than that of Pb ions. We suggest that the Raman spectroscopy is a suitable tool for the evaluation of oxygen vacancies in PbTiO3 thin films.

DOI： 10.1143/JJAP.47.7510

Interfacial modification for high-power solid-state lithium batteries 査読有り

Kazunon Takada, Narumi Ohta, Lianqi Zhang, Katsutoshi Fukuda, Isao Sakaguchi, Renzhi Ma, Minoru Osada, Takayoshi Sasaki

SOLID STATE IONICS 179 巻 ( 27-32 ) 頁： 1333 - 1337 2008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

Interfaces between LiCoO2 and sulfide solid electrolytes were modified in order to enhance the high-rate capability of solid-state lithium batteries. Thin films of oxide solid electrolytes, Li4Ti5O12, LiNbO3, and LiTaO3, were interposed at the interfaces as buffer layers. Changes in the high-rate performance upon heat treatment revealed that the buffer layer should be formed at low temperature to avoid thermal diffusion of the elements. Buffer layers of LiNbO3 and LiTaO3 can be formed at low temperature for the interfacial modification, because they show high ionic conduction in their amorphous states, and so are more effective than Li4Ti5O12 for high-power densities. (c) 2008 Elsevier BY All rights reserved.

DOI： 10.1016/j.ssi.2008.02.017

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