Faculty Profiles - OSADA Minoru

Papers - OSADA Minoru

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

Yoshihiro Takahashi, Minoru Osada, Hirokazu Masai, Takumi Fujiwara

PHYSICAL REVIEW B Vol. 79 ( 21 ) 2009.6

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

Yoshihiro Takahashi, Minoru Osada, Hirokazu Masai, Takumi Fujiwara

APPLIED PHYSICS LETTERS Vol. 94 ( 21 ) 2009.5

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

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

ACS NANO Vol. 3 ( 5 ) page： 1097 - 1106 2009.5

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

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

MATERIALS LETTERS Vol. 63 ( 3-4 ) page： 366 - 369 2009.2

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

M. Osada, T. Sasaki

J. Mater. Chem. Vol. 19 page： 2503-2511 2009

Anomalous Boson Behavior and Nanometric Heterogeneity in Glassy Fresnoite Reviewed

Yoshihiro Takahashi, Minoru Osada, Hirokazu Masai, Takumi Fujiwara

APPLIED PHYSICS EXPRESS Vol. 1 ( 12 ) 2008.12

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

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 Vol. 47 ( 9 ) page： 7510 - 7513 2008.9

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

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

SOLID STATE IONICS Vol. 179 ( 27-32 ) page： 1333 - 1337 2008.9

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

Langmuir-Blodgett fabrication of nanosheet-based dielectric films without an interfacial dead layer Reviewed

Minoru Osada, Kosho Akatsuka, Yasuo Ebina, Yoshinori Kotani, Kanta Ono, Hiroshi Funakubo, Shigenori Ueda, Keisuke Kobayashi, Kazunori Takada, Takayoshi Sasaki

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 47 ( 9 ) page： 7556 - 7560 2008.9

Language：English Publishing type：Research paper (scientific journal) Publisher：JAPAN SOC APPLIED PHYSICS

Langmuir-Blodgett (LB) deposition was employed to fabricate high-kappa dielectric nanofilms of titania nanosheets. The LB-based layer-by-layer approach using an atomically flat SrRuO(3) substrate is effective for the fabrication of atomically uniform and highly dense nanofilms. These films exhibited both high dielectric constant (kappa similar to 123) and low leakage current density (J < 10(-7) A cm(-2)) for thicknesses down to 5 nm, while eliminating the size-effect problems encountered in current high-kappa From analyses of interfacial structures by transmission electron microscopy and hard X-ray photoelectron spectroscopy. we have clarified that the films are composed of a well-ordered lamellar structure without an interfacial dead layer. According to first-principles calculations, a highly polarizable nature of titania nanosheets can bring improved dielectric properties. yielding high-kappa values even in an ultrathin geometry.

DOI： 10.1143/JJAP.47.7556

X-ray nanospectroscopic characterization of a molecularly thin ferromagnetic Ti(1-x)Co(x)O(2) nanosheet Reviewed

Yoshinori Kotani, Toshiyuki Taniuchi, Minoru Osada, Takayoshi Sasaki, Masato Kotsugi, F. Z. Guo, Yoshio Watanabe, Masato Kubota, Kanta Ono

APPLIED PHYSICS LETTERS Vol. 93 ( 9 ) 2008.9

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

We investigated the local electronic structures of a molecularly thin ferromagnetic Ti(0.8)Co(0.2)O(2) nanosheet by means of x-ray nanospectroscopy with spectroscopic photoemission and low energy electron microscopy. By analyzing the Co 2p x-ray absorption and photoemission spectra, the chemical state of doped Co ions in individual Ti(0.8)Co(0.2)O(2) nanosheet was found to be Co(2+) low-spin state, which is consistent with previous magnetization data and first-principles calculation [M. Osada , Phys. Rev. B 73, 153301 (2006)]. Furthermore, we employed photoelectron emission microscopy to image the variation in chemical states in Ti(0.8)Co(0.2)O(2) nanosheets with different stacking structures and clarified the identical Co(2+) low-spin state in monolayer and overlapped cases. (C) 2008 American Institute of Physics.

DOI： 10.1063/1.2976550

Gigantic magneto-optical effects induced by (Fe/Co)-cosubstitution in titania nanosheets Reviewed

Minoru Osada, Masayuki Itose, Yasuo Ebina, Kanta Ono, Shigenori Ueda, Keisuke Kobayashi, Takayoshi Sasaki

APPLIED PHYSICS LETTERS Vol. 92 ( 25 ) 2008.6

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

Magneto-optical Faraday effect has been investigated for 3d-transition-metal-substituted titania nanosheets Ti(1-x)M(x)O(2) (M=Fe,Co). In Ti(0.8)Co(0.2)O(2) and Ti(0.6)Fe(0.4)O(2) nanosheets, a strong magneto-optical response (similar to 10(4) deg/cm) appeared near the absorption edge at 260 nm. We find that tailoring magneto-optical properties could be achieved by (Fe/Co) cosubstitution and an optimally doped Ti(0.75)Fe(0.1)Co(0.15)O(2) nanosheet exhibits a gigantic magneto-optical response (similar to 10(5) deg/cm) over the wide wavelength region (400-750 nm). By analyzing electronic structures from first-principle calculations, we have clarified that the d-d transitions are responsible for the gigantic signal in (Fe/Co)-cosubstituted nanosheets. (C) 2008 American Institute of Physics.

DOI： 10.1063/1.2937094

Synthesis and electrochemistry of new layered (1-x) LiVO2 center dot xLi(2)TiO(3) (0 <= x <= 0.6) electrode materials Reviewed

Lianqi Zhang, Kazunori Takada, Narumi Ohta, Minoru Osada, Takayoshi Sasaki

JOURNAL OF POWER SOURCES Vol. 174 ( 2 ) page： 1007 - 1011 2007.12

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

Novel electrode materials with nominal compositions of (1 - x)LiVO2 center dot xLi(2)TiO(3) (0 <= x <= 0.6) were synthesized by carbothermal reduction reaction. All the materials were identified to have a layered structure and can be considered as a solid solution related to LiVO2-Li2TiO3 system, in which Li layers was alternately stacked with the layers made of mixture of Li, V, and Ti in a ccp array of oxygen. The redox reaction associated with vanadium ions was not reversible in LiVO2; however, introduction of the redox couple into Li2TiO3 made it much more reversible. A reversible capacity of about 120 mAh g(-1) remained after 90 cycles for the samples with x = 0.5 and 0.6, when they were cycled in the voltage range of 1.0-4.8 V. (c) 2007 Elsevier B.V All rights reserved.

DOI： 10.1016/j.jpowsour.2007.06.082

Hydration of sodium cobalt oxide Reviewed

Hiroya Sakurai, Minoru Osada, Eiji Takayama-Muromachi

CHEMISTRY OF MATERIALS Vol. 19 ( 25 ) page： 6073 - 6076 2007.12

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

It was found that Na+ ions in NaxCoO2 can be partially substituted by H3O+ ions while maintaining a constant Co valence simply by immersion in water. The Magnetic Susceptibility of Na-x(H3O)(z)CoO2 (X + z = 0.70) changed drastically from Curie-Weiss type to Pauli paramagnetic type, indicating that the electronic band structure was modified by the isovalent ion substitution of Na+/H3O+. Two possible origins of the change in the electronic structure are discussed.

DOI： 10.1021/cm0714786

Solution-based fabrication of high-kappa dielectric nanofilms using titania nanosheets as a building block Reviewed

Minoru Osada, Kosho Akatsuka, Yasuo Ebina, Hiroshi Funakubo, Takanori Kiguchi, Kazunori Takada, Takayoshi Sasaki

JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS Vol. 46 ( 10B ) page： 6979 - 6983 2007.10

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

We have demonstrated a novel procedure for fabricating high-kappa dielectric nanofilms by using a titania nanosheet as a building block. The layer-by-layer assembly of titania nanosheets using an atomically flat SrRuO3 substrate is advantageous as a means of fabricating atomically uniform multilayer high-kappa nanofilms. High-resolution transmission electron microscopy revealed that these multilayer nanofilms are composed of a well-ordered lamellar structure without an interfacial dead layer. These nanofilms exhibited both high dielectric constant (epsilon(r)similar to 125) and low leakage current density (J < 10(-7) A/cm(2)) even for thicknesses as low as 10nm. These results indicate that the titania nanosheet is a very promising candidate as a high-kappa nanoblock, and its bottom-up fabrication provides new opportunities for the development of high-kappa devices.

DOI： 10.1143/JJAP.46.6979

LiNbO3-coated LiCoO2 as cathode material for all solid-state lithium secondary batteries Reviewed

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

ELECTROCHEMISTRY COMMUNICATIONS Vol. 9 ( 7 ) page： 1486 - 1490 2007.7

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

The further enhancement of high-rate capabilities for all solid-state lithium secondary batteries is reported. A LiNbO3 layer of nanometer thickness was interposed between LiCoO2 and sulfide solid electrolyte as buffer layer. This greatly reduced the interfacial resistance in the cathode and enhanced the high-rate capabilities of solid-state lithium batteries, providing good prospects for practical application of lithium secondary batteries free from safety issues. (c) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.elecom.2007.02.008

AgI/Ag heterojunction nanowires: Facile electrochemical synthesis, photoluminescence, and enhanced ionic conductivity Reviewed

Changhao Liang, Kazuya Terabe, Tohru Tsuruoka, Minoru Osada, Tsuyoshi Hasegawa, Masakazu Aono

ADVANCED FUNCTIONAL MATERIALS Vol. 17 ( 9 ) page： 1466 - 1472 2007.6

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH

The construction of an electronic-conductor/ionic-conductor heterojunction in a well-defined nanostructure is the basis of studying interfacial and bulk transport and the reactions of ions and electrons at the nanoscale level. An ionic-conductor/metal (AgI/Ag) beterostructured nanowire array is easily fabricated by a template-confined, step-electrochemical technique. The structural and morphological evolution of the AgI/Ag heterostructure before and after its release from the anodic aluminum oxide (AAO) membrane is characterized by scanning electron microscopy, X-ray diffraction, and optical spectroscopy. The structural disordering of released AgI is suggested by the appearance of a broad photoluminescence emission band at longer wavelengths and a short-range-order-like Raman peak. The ionic conductivity of the AgI nanowire embedded inside the insulating AAO membrane is measured as being on the order of 10(-3) S cm(-1), which is an enhancement by two to three orders of magnitude compared with that of bulk polycrystalline AgI at room temperature. This electrochemical method could be useful in fabricating other pure and mixed ionic conductors in heterojunction nanostructures.

DOI： 10.1002/adfm.200600590

New misfit-layered cobalt oxide (CaOH)(1.14)CoO2 Reviewed

Mitsuyuki Shizuya, Masaaki Isobe, Yuji Baba, Takuro Nagai, Minoru Osada, Kosuke Kosuda, Satoshi Takenouchi, Yoshio Matsui, Eiji Takayama-Muromachi

JOURNAL OF SOLID STATE CHEMISTRY Vol. 180 ( 1 ) page： 249 - 259 2007.1

Language：English Publishing type：Research paper (scientific journal) Publisher：ACADEMIC PRESS INC ELSEVIER SCIENCE

We synthesized a new cobalt oxide (CaOH)(1.14)CoO2 by utilizing a high-pressure technique. X-ray and electron diffraction studies revealed that the compound has a layered structure that consists of Cdl(2)-type CoO2 layers and rock-salt-type double CaOH atomic layers. The two subcells have incommensurate periodicity along the a-axis, resulting in a misfit-layered structure. From resistivity and Seebeck coefficient measurements, we have shown that the two-dimensional (2-D) variable-range hopping (VRH) regime with hole conduction is dominant at low temperature for this compound. As temperature increases, the conduction mechanism undergoes crossover from the 2-D VRH regime to a thermal activation-energy-type regime. (c) 2006 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jssc.2006.10.014

Impacts of intrinsic defects on luminescence properties of CuAlS2 Reviewed

Yuichiro Kuroki, Tomoichiro Okamoto, Masasuke Takata, Minoru Osada

APPLIED PHYSICS LETTERS Vol. 89 ( 22 ) 2006.11

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

The authors report on Raman scattering of CuAlS2 in order to study the influences of intrinsic defects on luminescence properties. The A(1) mode is dominated in stoichiometric samples, whereas sulfur-poor conditions prepared at high temperatures (>= 800 degrees C) cause defect-specific shift and broadening. They also find that additional mode (at 330 cm(-1)) caused by antisite defects is resonated at 2.16 eV excitation, in accordance with visible luminescence attributed to donor-acceptor pair (DAP) emission in photoluminescence. These results suggest that the DAP emissions may be caused by the defect complexes such as Al-Cu-V-Cu and V-S-V-Cu, which reduces ultraviolet excitonic emission in this system. (c) 2006 American Institute of Physics.

DOI： 10.1063/1.2400101

Resonant two-phonon Raman scattering as a probe of hole crystal formation in Sr14-xCaxCu24O41 Reviewed

Joakim Holmlund, Jakob Andreasson, Christopher S. Knee, Joakim Backstrom, Mikael Kall, Minoru Osada, Takashi Noji, Yoji Koike, Masato Kakihana, Lars Borjesson

PHYSICAL REVIEW B Vol. 74 ( 13 ) 2006.10

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

The charge dynamics of the spin ladder compound Sr14-xCaxCu24O41 with x=0,6,13.6 has been investigated using wavelength- and temperature-dependent phonon Raman scattering on single crystals. In the unsubstituted, x=0, compound, a set of sharp two-phonon lines shows a strong increase in intensity below T similar to 200 K for light polarized along the ladder layer and with excitation energy close to the charge transfer gap similar to 1.9 eV. The temperature dependence of the strongly enhanced two-phonon bands below 200 K closely follows the recently reported formation of a standing charge density wave in the ladders [P. Abbamonte , Nature 431, 1078 (2004)]. Upon calcium substitution the polarized resonant Raman response rapidly decreases, signaling an increase of hole mobility in the ladder units. Temperature-dependent measurements of the x=13.6 sample indicate mobility of holes down to < 8 K.

DOI： 10.1103/PhysRevB.74.134502

Synthesis and electrochemical propeities of Li2S-B2S3-Li4SiO4 Reviewed

Yoshikatsu Seino, Kazunori Takada, Bong-Chull Kim, Lianqi Zhang, Narumi Ohta, Hiroaki Wada, Minoru Osada, Takayoshi Sasaki

SOLID STATE IONICS Vol. 177 ( 26-32 ) page： 2601 - 2603 2006.10

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

New Li+ ion-conductive glasses Li2S-B2S3-Li4SiO4 were synthesized by rapid quenching, and they were transformed into glass ceramics by heat treatment. The heat treatment increased the ionic conductivities of the Li4SO4-doped glasses, and the highest ionic conductivity observed in the system was 1.0 x 10(-3) S cm(-1) at room temperature. The glass ceramics were highly stable against electrochemical oxidation with a wide electrochemical window of 10 V. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ssi.2006.01.005

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