論文 - 長田　実

Extra-Large Mechanical Anisotropy of a Hydrogel with Maximized Electrostatic Repulsion between Cofacially Aligned 2D Electrolytes 査読有り

Sano Koki, Arazoe Yuka Onuma, Ishida Yasuhiro, Ebina Yasuo, Osada Minoru, Sasaki Takayoshi, Hikima Takaaki, Aida Takuzo

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   57 巻 ( 38 ) 頁： 12508 - 12513   2018年9月

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1002/anie.201807240

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PubMed

Extra‐Large Mechanical Anisotropy of a Hydrogel with Maximized Electrostatic Repulsion between Cofacially Aligned 2D Electrolytes

Koki Sano, Yuka Onuma Arazoe, Yasuhiro Ishida, Yasuo Ebina, Minoru Osada, Takayoshi Sasaki, Takaaki Hikima, Takuzo Aida

Angewandte Chemie   130 巻 ( 38 ) 頁： 12688 - 12693   2018年8月

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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  

Abstract

In our previous work, we have shown that “electrostatic forces”, when generated anisotropically in aqueous media by 2D electrolytes upon cofacial orientation, enable the formation of a hydrogel with an anisotropic parameter, as defined by the ratio of elastic moduli E_⊥/E_∥, of 3.0. Herein, we successfully developed the design strategy for a hydrogel with an anisotropic parameter of no less than 85. This value is not only 28 times greater than that of our previous anisotropic hydrogel but also 6 times larger than the current champion record in synthetic hydrogels (E_⊥/E_∥∼15). Firstly, we simply lowered ionic contaminants in the hydrogel and were able to enhance the anisotropic parameter from 3.0 to 18. Then, we chose a supporting polymer network allowing the hydrogel to carry a higher interior permittivity. Consequently, the anisotropic parameter was further enhanced from 18 to 85. Owing to the enhanced mechanical anisotropy, our new hydrogel displayed a superb ability of seismic isolation.

DOI： 10.1002/ange.201807240

High areal capacitance and rate capability using filled Ni foam current collector 査読有り

Zheyin Yu, Zhenxiang Cheng, George Tsekouras, Xiaolin Wang, Xiangyang Kong, Minoru Osada, Shi Xue Dou

Electrochimica Acta   281 巻   頁： 761 - 768   2018年8月

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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 Ltd  

A novel approach to achieving high areal capacitance and rate capability is demonstrated, whereby an active material is loaded onto a high surface area, filled Ni foam current collector. Micro/nano Ni-filled Ni foam (MNFNF) current collector was fabricated by initially filling commercial Ni foam with Ni slurry and sintering to yield micro Ni-filled Ni foam, followed by electrochemical deposition of nano Ni. This current collector has a greatly enhanced surface area compared to Ni foam, allowing for high mass loading of active material and thereby high areal capacitance and rate capability. Using NiCo2O4 prepared via hydrothermal reaction followed by annealing as the active material, an outstanding areal capacitance of 29.4 F cm-2 at 5 mA cm−2 discharge was achieved, while a high 80% of this capacitance (i.e. 23.5 F cm−2) was retained at 50 mA cm−2 discharge, ascribed to the high surface area and high conductivity of the MNFNF current collector. Regarding stability, only a 2% decrease in areal capacitance after 1000 charge/discharge cycles was observed. The approach employed here might be used to enhance the performance of other active materials besides NiCo2O4.

DOI： 10.1016/j.electacta.2018.06.007

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Scopus

Multifield Control of Domains in a Room-Temperature Multiferroic 0.85BiTi0.1Fe0.8Mg0.1O3-0.15CaTiO3 Thin Film 査読有り

Tingting Jia, Ziran Fan, Junxiang Yao, Cong Liu, Yuhao Li, Junxi Yu, Bi Fu, Hongyang Zhao, Minoru Osada, Ehsan Nasr Esfahani, Yaodong Yang, Yuanxu Wang, Jiang-Yu Li, Hideo Kimura, Zhenxiang Cheng

ACS Applied Materials and Interfaces   10 巻 ( 24 ) 頁： 20712 - 20719   2018年6月

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：American Chemical Society  

Single-phase materials that combine electric polarization and magnetization are promising for applications in multifunctional sensors, information storage, spintronic devices, etc. Following the idea of a percolating network of magnetic ions (e.g., Fe) with strong superexchange interactions within a structural scaffold with a polar lattice, a solid solution thin film with perovskite structure at a morphotropic phase boundary with a high level of Fe atoms on the B site of perovskite structure is deposited to combine both ferroelectric and ferromagnetic ordering at room temperature with magnetoelectric coupling. In this work, a 0.85BiTi0.1Fe0.8Mg0.1O3-0.15CaTiO3 thin film has been deposited by pulsed laser deposition (PLD). Both the ferroelectricity and the magnetism were characterized at room temperature. Large polarization and a large piezoelectric effective coefficient d33 were obtained. Multifield coupling of the thin film has been characterized by scanning force microscopy. Ferroelectric domains and magnetic domains could be switched by magnetic field (H), electric field (E), mechanical force (F), and, indicating that complex cross-coupling exists among the electric polarization, magnetic ordering and elastic deformation in 0.85BiTi0.1Fe0.8Mg0.1O3-0.15CaTiO3 thin film at room temperature. This work also shows the possibility of writing information with electric field, magnetic field, and mechanical force and then reading data by magnetic field. We expect that this work will benefit information applications.

DOI： 10.1021/acsami.8b05289

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PubMed

Vapour-liquid-solid growth of monolayer MoS₂ nanoribbons 査読有り

Li, SS; Lin, YC; Zhao, W; Wu, J; Wang, Z; Hu, ZH; Shen, YD; Tang, DM; Wang, JY; Zhang, Q; Zhu, H; Chu, LQ; Zhao, WJ; Liu, C; Sun, ZP; Taniguchi, T; Osada, M; Chen, W; Xu, QH; Wee, ATS; Suenaga, K; Ding, F; Eda, G

NATURE MATERIALS   17 巻 ( 6 ) 頁： 535 - +   2018年6月

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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 Materials  

Chemical vapour deposition of two-dimensional materials typically involves the conversion of vapour precursors to solid products in a vapour-solid-solid mode. Here, we report the vapour-liquid-solid growth of monolayer MoS2, yielding highly crystalline ribbons with a width of few tens to thousands of nanometres. This vapour-liquid-solid growth is triggered by the reaction between MoO3 and NaCl, which results in the formation of molten Na-Mo-O droplets. These droplets mediate the growth of MoS2 ribbons in the 'crawling mode' when saturated with sulfur. The locally well-defined orientations of the ribbons reveal the regular horizontal motion of the droplets during growth. Using atomic-resolution scanning transmission electron microscopy and second harmonic generation microscopy, we show that the ribbons are grown homoepitaxially on monolayer MoS2 with predominantly 2H- or 3R-type stacking. Our findings highlight the prospects for the controlled growth of atomically thin nanostructure arrays for nanoelectronic devices and the development of unique mixed-dimensional structures.

DOI： 10.1038/s41563-018-0055-z

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PubMed

Chemical synthesis of porous barium titanate thin film and thermal stabilization of ferroelectric phase by porosity-induced strain 査読有り

Norihiro Suzuki, Minoru Osada, Motasim Billah, Yoshio Bando, Yusuke Yamauchi, Shahriar A. Hossain

Journal of Visualized Experiments   2018 巻 ( 133 )   2018年3月

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Visualized Experiments  

Barium titanate (BaTiO3, hereafter BT) is an established ferroelectric material first discovered in the 1940s and still widely used because of its well-balanced ferroelectricity, piezoelectricity, and dielectric constant. In addition, BT does not contain any toxic elements. Therefore, it is considered to be an eco-friendly material, which has attracted considerable interest as a replacement for lead zirconate titanate (PZT). However, bulk BT loses its ferroelectricity at approximately 130 °C, thus, it cannot be used at high temperatures. Because of the growing demand for high-temperature ferroelectric materials, it is important to enhance the thermal stability of ferroelectricity in BT. In previous studies, strain originating from the lattice mismatch at hetero-interfaces has been used. However, the sample preparation in this approach requires complicated and expensive physical processes, which are undesirable for practical applications. In this study, we propose a chemical synthesis of a porous material as an alternative means of introducing strain. We synthesized a porous BT thin film using a surfactant-assisted sol-gel method, in which self-assembled amphipathic surfactant micelles were used as an organic template. Through a series of studies, we clarified that the introduction of pores had a similar effect on distorting the BT crystal lattice, to that of a hetero-interface, leading to the enhancement and stabilization of ferroelectricity. Owing to its simplicity and cost effectiveness, this fabrication process has considerable advantages over conventional methods.

DOI： 10.3791/57441

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PubMed

Self-Sensitization and Photo-Polymerization of Diacetylene Molecules Self-Assembled on a Hexagonal-Boron Nitride Nanosheet 査読有り

Verveniotis, E; Okawa, Y; Watanabe, K; Taniguchi, T; Taniguchi, T; Osada, M; Joachim, C; Aono, M

POLYMERS   10 巻 ( 2 )   2018年2月

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

Long poly-diacetylene chains are excellent candidates for planar, on-surface synthesized molecular electronic wires. Since hexagonal-Boron Nitride (h-BN) was identified as the best available atomically flat insulator for the deposition of poly-diacetylene precursors, we demonstrate the polymerization patterns and rate on it under UV-light irradiation, with subsequent polymer identification by atomic force microscopy. The results on h-BN indicate self-sensitization which yields blocks comprised of several polymers, unlike on the well-studied graphite/diacetylene system, where the polymers are always isolated. In addition, the photo-polymerization proceeds at least 170 times faster on h-BN, where it also results in longer polymers. Both effects are explained by the h-BN bandgap, which is larger than the diacetylene electronic excitation energy, thus allowing the transfer of excess energy absorbed by polymerized wires to adjacent monomers, triggering their polymerization. This work sets the stage for conductance measurements of single molecular poly-diacetylene wires on h-BN.

DOI： 10.3390/polym10020206

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Scopus

PubMed

Self-Assembly Atomic Stacking Transport Layer of 2D Layered Titania for Perovskite Solar Cells with Extended UV Stability 査読有り

Tzu-Pei Chen, Chung-Wei Lin, Shao-Sian Li, Yung-Han Tsai, Cheng-Yen Wen, Wendy Jessica Lin, Fei-Man Hsiao, Ya-Ping Chiu, Kazuhito Tsukagoshi, Minoru Osada, Takayoshi Sasaki, Chun-Wei Chen

Advanced Energy Materials   8 巻 ( 2 )   2018年1月

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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-VCH Verlag  

A novel atomic stacking transporting layer (ASTL) based on 2D atomic sheets of titania (Ti1−δO2) is demonstrated in organic–inorganic lead halide perovskite solar cells. The atomically thin ASTL of 2D titania, which is fabricated using a solution-processed self-assembly atomic layer-by-layer deposition technique, exhibits the unique features of high UV transparency and negligible (or very low) oxygen vacancies, making it a promising electron transporting material in the development of stable and high-performance perovskite solar cells. In particular, the solution-processable atomically thin ASTL of 2D titania atomic sheets shows superior inhibition of UV degradation of perovskite solar cell devices, compared to the conventional high-temperature sintered TiO2 counterpart, which usually causes the notorious instability of devices under UV irradiation. The discovery opens up a new dimension to utilize the 2D layered materials with a great variety of homostructrual or heterostructural atomic stacking architectures to be integrated with the fabrication of large-area photovoltaic or optoelectronic devices based on the solution processes.

DOI： 10.1002/aenm.201701722

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Nanoarchitectonics in dielectric/ferroelectric layered perovskites: From bulk 3D systems to 2D nanosheets 査読有り

Minoru Osada, Takayoshi Sasaki

Dalton Transactions   47 巻 ( 9 ) 頁： 2841 - 2851   2018年

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Royal Society of Chemistry  

We present an overview of recent investigations on the dielectric/ferroelectric properties of Dion-Jacobson-type perovskites, including bulk 3D layered systems and their exfoliated 2D nanosheets. In contrast to the Ruddlesden-Popper and Aurivillius phases, the Dion-Jacobson phases in bulk 3D systems have not been important targets for constructing dielectric/ferroelectric materials. However, recent investigations on Dion-Jacobson phases have provided new impetus to dielectric/ferroelectric materials. Dion-Jacobson perovskites can also facilitate delamination into 2D nanosheets. Layer-by-layer engineering of 2D perovskite nanosheets has a great potential for the rational design of new high-k dielectric/ferroelectric materials and nanodevices.

DOI： 10.1039/c7dt03719h

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Scopus

Elucidation of structure and conduction mechanism in Nd-Mn substituted Y-type strontium hexaferrites 査読有り

Bashir Ahmad, Muhammad Naeem Ashiq, Muhammad Shuaib Khan, Minoru Osada, Muhammad Najam-Ul-Haq, Irshad Ali

JOURNAL OF ALLOYS AND COMPOUNDS   723 巻   頁： 9 - 16   2017年11月

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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 SA  

Technologically important ferrites magnetic materials with nominal composition "Sr2-xNdxCo2MnyFe12-yO22" (x = 0.0 to 0.1 and y = 0.0 to 1.0) were fabricated by the simple sol-gel method. The X-ray diffraction analysis endorsed the formation of well-defined Y-type hexagonal single phase with crys-tallite size in range of 38-45 nm. Owing to reduction of Fe3+ ions at octahedral site, an increase in DC resistivity was observed from 4.083 x 10(8) to 2.376 x 10(9) Omega-cm with the increase in substituents content. The two conduction mechanisms operating in ferri- and paramagnetic regions were shown by Arrhenius plot. It was observed that conduction in ferrimagnetic and paramagnetic regions was governed by the hopping of electrons and polarons, respectively. The decrease in Curie temperature "Tc" (553-423 K) was detected as a factor of Nd-Mn content due to decrease in Fe-Fe interaction at octahedral site. The changes in the values of dielectric constant (epsilon'), dielectric loss factor (epsilon") and tan loss (delta) follow Maxwell-Wagner model. The relatively high resistivity (2.376 x 10(9) Omega-cm) and low dielectric constants (2.97 at 1 MHz) for the sample with x = 0.1 and y = 1.0 make this material as an excellent candidates for high frequency microwave devices. (C) 2017 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jallcom.2017.06.219

Web of Science

Origin of thermally stable ferroelectricity in a porous barium titanate thin film synthesized through block copolymer templating(vol 5, 076111, 2017) 査読有り

Norihiro Suzuki, Minoru Osada, Motasim Billah, Zeid Abdullah Alothman, Yoshio Bando, Yusuke Yamauchi, Md. Shahriar A. Hossain

APL MATERIALS   5 巻 ( 9 )   2017年9月

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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  

DOI： 10.1063/1.5000538

Web of Science

Layer-by-layer engineering of two-dimensional perovskite nanosheets for tailored microwave dielectrics 査読有り

Muhammad Shuaib Khan, Hyung-Jun Kim, Takaaki Taniguchi, Yasuo Ebina, Takayoshi Sasaki, Minoru Osada

APPLIED PHYSICS EXPRESS   10 巻 ( 9 )   2017年9月

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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  

We report an approach for constructing ultrathin microwave dielectrics using two-dimensional (2D) perovskite nanosheets (Ca2Nb3O10). The solution-based layer-by-layer assembly of Ca2Nb3O10 nanosheets enables the tailoring of dielectric responses and breakdown voltage in order to realize miniaturized capacitors with improved performances. Multilayer stacked nanosheet films showed a stable dielectric response of up to 10 GHz; the dielectric constant of similar to 200 is the highest among high-k perovskites in the ultrathin region (< 30 nm). Moreover, the nanosheet films realized a high capacitance density (similar to 20 mu F/cm(2)) with a robust thermal stability up to 250 degrees C. These superior dielectric properties of perovskite nanosheets offer a new solution for high-performance microwave devices. (C) 2017 The Japan Society of Applied Physics

DOI： 10.7567/APEX.10.091501

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Photoreduction Dependent p- and n-Type Semiconducting Field-Effect Transistor Properties in Undoped Reduced Graphene Oxide 査読有り

Hiroshi Takehira, Md Saidul Islam, Mohammad Razaul Karim, Yuta Shudo, Ryo Ohtani, Leonard F. Lindoy, Takaaki Taniguchi, Minoru Osada, Shinya Hayami

CHEMISTRYSELECT   2 巻 ( 24 ) 頁： 6941 - 6944   2017年8月

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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  

Both p- and n-type field effect transistors (FET) properties have been observed in undoped reduced graphene oxide (rGO). Short and long time exposure of GO during photo reduction results in the formation of respective p- and n-type rGO semiconductor. Achieving duel behavior of this type in an undoped material is exceedingly unusual. Herein we report the presence of such behavior in the reduced from of graphene oxide (rGO) for the first time.

DOI： 10.1002/slct.201701509

Web of Science

Atomic Layer Engineering of High-kappa Ferroelectricity in 2D Perovskites 査読有り

Bao-Wen Li, Minoru Osada, Yoon-Hyun Kim, Yasuo Ebina, Kosho Akatsuka, Takayoshi Sasaki

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   139 巻 ( 31 ) 頁： 10868 - 10874   2017年8月

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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  

Complex perovskite oxides offer tremendous potential for controlling their rich variety of electronic properties, including high-T-C superconductivity, high-kappa ferroelectricity, and quantum magnetism. Atomic-scale control of these intriguing properties in ultrathin perovskites is an important challenge for exploring new physics and device functionality at atomic dimensions. Here, we demonstrate atomic-scale engineering of dielectric responses using two-dimensional (2D) homologous perovskite nanosheets (Ca2Nam-3NbmO3m+1; m = 3-6). In this homologous 2D material, the thickness of the perovskite layers can be incrementally controlled by changing m, and such atomic layer engineering enhances the high-kappa dielectric response and local ferroelectric instability. The end member (m = 6) attains a high dielectric constant of similar to 470, which is the highest among all known dielectrics in the ultrathin region (<10 nm). These results provide a new strategy for achieving high-kappa ferroelectrics for use in ultrascaled high-density capacitors and post-graphene technology.

DOI： 10.1021/jacs.7b05665

Web of Science

Origin of thermally stable ferroelectricity in a porous barium titanate thin film synthesized through block copolymer templating 査読有り

Norihiro Suzuki, Minoru Osada, Motasim Billah, Zeid Abdullah Alothman, Yoshio Bando, Yusuke Yamauchi, Md. Shahriar A. Hossain

APL MATERIALS   5 巻 ( 7 )   2017年7月

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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  

A porous barium titanate (BaTiO3) thin film was chemically synthesized using a surfactant-assisted sol-gel method in which micelles of amphipathic diblock copolymers served as structure-directing agents. In the Raman spectrum of the porous BaTiO3 thin film, a peak corresponding to the ferroelectric tetragonal phase was observed at around 710 cm(-1), and it remained stable at much higher temperature than the Curie temperature of bulk single-crystal BaTiO3 (similar to 130 degrees C). Measurements revealed that the ferroelectricity of the BaTiO3 thin film has high thermal stability. By analyzing high-resolution transmission electron microscope images of the BaTiO3 thin film by the fast Fourier transform mapping method, the spatial distribution of stress in the BaTiO3 framework was clearly visualized. Careful analysis also indicated that the porosity in the BaTiO3 thin film introduced anisotropic compressive stress, which deformed the crystals. The resulting elongated unit cell caused further displacement of the Ti4+ cation from the center of the lattice. This displacement increased the electric dipole moment of the BaTiO3 thin film, effectively enhancing its ferro(piezo) electricity. (C) 2017 Author(s).

DOI： 10.1063/1.4995650

Web of Science

High-temperature dielectric responses in all-nanosheet capacitors 査読有り

Muhammad Shuaib Khan, Minoru Osada, Hyung-Jun Kim, Yasuo Ebina, Wataru Sugimoto, Takayoshi Sasaki

Japanese Journal of Applied Physics   56 巻 ( 6 )   2017年6月

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：Japan Society of Applied Physics  

We have investigated high-temperature dielectric responses of layer-by-layer assembled nanosheet capacitors. All-nanosheet capacitors are fabricated by stacking metallic Ru0.95O2 as electrodes and dielectric Ca2Nb3O10 nanosheets as insulators. Through in situ characterizations, we find that all-nanosheet capacitors exhibit a size-free high-k dielectric response (&gt
155) and a moderate insulation resistance (&gt
1 ' 10%5A/cm2) at high temperatures up to 200 °C. The concomitant presence of high ϵr, low leakage profile, and thermal stability in high-k nanocapacitors is critically important for application in high-temperature electronics.

DOI： 10.7567/JJAP.56.06GH09

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Neat monolayer tiling of molecularly thin two-dimensional materials in 1 min 査読有り

Kazuaki Matsuba, Chengxiang Wang, Kazuko Saruwatari, Yusuke Uesusuki, Kosho Akatsuka, Minoru Osada, Yasuo Ebina, Renzhi Ma, Takayoshi Sasaki

SCIENCE ADVANCES   3 巻 ( 6 )   2017年6月

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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 ASSOC ADVANCEMENT SCIENCE  

Controlled arrangement of molecularly thin two-dimensional (2D) materials on a substrate, particularly into precisely organized mono-andmultilayer structures, is a key to design a nanodevice using their unique and enhanced physical properties. Several techniques such as mechanical transfer process and Langmuir-Blodgett deposition have been applied for this purpose, but they have severe restrictions for large-scale practical applications, for example, limited processable area and long fabrication time, requiring skilled multistep operations. We report a facile one-pot spin-coating method to realize dense monolayer tiling of various 2D materials, such as graphene and metal oxide nanosheets, within 1 min over a wide area (for example, a 30-mmf substrate). Centrifugal force drives the nanosheets in a thin fluid layer to the substrate edgewhere they are packed edge to edge all the way to the central region, without forming overlaps. We investigated the relationship between precursor concentration, rotation speed, and ultraviolet-visible absorbance and developed an effective method to optimize the parameters for neat monolayer films. The multilayer buildup is feasible by repeating the spin-coating process combined with a heat treatment at moderate temperature. This versatile solution-based technique will provide both fundamental and practical advancements in the rapid large-scale production of artificial lattice-like films and nanodevices based on 2D materials.

DOI： 10.1126/sciadv.1700414

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Ferroelectric BaTiO3 dipole induced charge transfer enhancement in dye-sensitized solar cells 査読有り

Keyuan Feng, Xiaoyan Liu, Donghui Si, Xiao Tang, An Xing, Minoru Osada, Peng Xiao

JOURNAL OF POWER SOURCES   350 巻   頁： 35 - 40   2017年5月

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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  

BaTiO3/TiO2 nanocomposite films with varied amount of BaTiO3 are fabricated and applied as photo anodes for dye-sensitized solar cells (DSCs) and demonstrated enhanced power conversion efficiency. Ferroelectricity of BaTiO3 in the film after subjected to a annealing process up to 450 degrees C is examined by Switching Spectroscopy Piezoresponse Force Microscopy (SSPFM). The highest performance is achieved in 1.0 wt% BaTiO3 addition as a result of increased photocurrent density (J(sc)) and fill factor (FF), regardless of reduction of dye-loading. Electrochemical impedance spectroscopy (EIS) measurements at different bias voltages (<= Voc) in dark suggest that ferroelectric dipole induced electric field has positive effects on enhancing electron mobility and suppressing charge recombination. Although more detailed experiments are needed in designing of the nanocomposite films for compensating characteristics of dye-loading and electron mobility, introduction of ferroelectric dipole induced electric field into the photoanode would be a good strategy in achieving further improvement of power conversion efficiency of DSCs through improved charge transfer properties. (C) 2017 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jpowsour.2017.03.049

Web of Science

Mechanical force involved multiple fields switching of both local ferroelectric and magnetic domain in a Bi5Ti3FeO15 thin film 査読有り

Tingting Jia, Hideo Kimura, Zhenxiang Cheng, Hongyang Zhao, Yoon-Hyun Kim, Minoru Osada, Takao Matsumoto, Naoya Shibata, Yuichi Ikuhara

NPG ASIA MATERIALS   9 巻   2017年2月

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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  

Multiferroics have received intense attention due to their great application potential in multi-state information storage devices and new types of sensors. Coupling among ferroic orders such as ferroelectricity, (anti-) ferromagnetism, ferroelasticity and so on will enable dynamic interaction between these ordering parameters. Direct visualization of such coupling behavior in single-phase multiferroic materials is highly desirable for both applications and fundamental study. Manipulation of both ferroelectric and magnetic domains of Bi5Ti3FeO15 thin film using electric field and external mechanical force is reported, which confirms the magnetoelectric coupling in Bi5Ti3FeO15, indicates the electric and magnetic orders are coupled through ferroelasticity. Due to the anisotropic relaxation of ferroelastic strain, the back-switching of out-of-plane electric domains is not as obvious as in-plane. An inevitable destabilization of the coupling between elastic and magnetic ordering happens because of the elastic strain relaxation, which result in a subsequent decay of magnetic domain switching. Mechanical force applied on the surface of Bi5Ti3FeO15 film generates by an atomic force microscopy tip will effectively drive a transition of the local ferroelastic strain state, reverse both the polarization and magnetization in a way similar to an electric field. Current work provides a framework for exploring cross-coupling among multiple orders and potential for developing novel nanoscale functional devices.

DOI： 10.1038/am.2017.3

Web of Science

Atomic layer engineering of high-k ferroelectricity in 2D perovskites 査読有り

  139 巻   頁： 10868-10874   2017年

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）