論文 - 野田　啓

Photocatalytic hydrogen production from gas-phase methanol and water with nanocrystalline TiO₂ thin films in high vacuum

Noda Kei, Hattori Masashi, Amari Kouichi, Kobayashi Kei, Horiuchi Toshihisa, Matsushige Kazumi

Materials Research Society Symposium Proceedings 1056   7 - 12 2008年

　概要を見る

<p>Photocatalytic hydrogen production with gas-phase reactions in high vacuum was examined for nanocrystalline anatase-type titanium dioxide (TiO₂) thin films. The hydrogen generation process on platinized TiC₂ specimens was investigated using a quadrupole mass spectrometer at a real-time scale under various partial pressures of gaseous methanol and water. As a result, hydrogen generation was successfully detected under ultraviolet (UV) ray illumination even in high vacuum (-10^-7 Torr). And the amount of produced H₂ largely depends on the temperature of TiO₂ samples, probably due to different surface states of TiO₂. This study suggests the possibility of new high-speed H₂ production system with gas-phase photocatalytic reactions.</p>

Flexible programmable logic gate using organic ferroelectric multilayer

Horie, Satoshi, Noda, Kei, Yamada, Hirofumi, Matsushige, Kazumi, Ishida, Kenji, Kuwajima, Shuichiro

APPLIED PHYSICS LETTERS 91 （ 19 ） 193506-1 - 193506-3 2007年11月

研究論文（学術雑誌）,  ISSN  0003-6951

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Real-time detection of photocatalytic hydrogen production for platinized titanium dioxide thin films in high vacuum

野田 啓

JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS &amp; EXPRESS LETTERS 46 （ 29-32 ） L749 - L751 2007年08月

研究論文（学術雑誌）,  ISSN  0021-4922

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Self-assembly of metal-virus nanodumbbells

野田 啓

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 46 （ 17 ） 3149 - 3151 2007年

研究論文（学術雑誌）,  ISSN  1433-7851

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Switching characteristics in the ferroelectric organic molecular memories

Uemura H., Horie S., Noda K., Kuwajima S., Ishida K., Horiuchi T., Matsushige K.

Nanotechnology Materials and Devices Conference, 2006 (NMDC 2006) IEEE 1   148 - 149 2006年

　概要を見る

<p>Organic molecular memories are expected to become one of the essential key devices in the next-generation flexible digital instruments, and in this paper a novel non-volatile organic memory will be introduced. It is shown that the polarization switching characteristics in the ferroelectric films of vinylidene fluoride (VDF) oligomer and P(VDF/TrFE) copolymer change with their structural factors such as crystallinity and chain length of the materials, and the switching time becomes shorter and shorter with increasing applied electric field and reaches in the order of nano-second. Moreover, the possibilities of the application of such thin organic ferroelectric films to an infrared image sensor as well as the creation of the ultra high-density molecular memory by utilizing recent scanning probe microscopy (SPM) technique will be discussed.</p>

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Pyroelectricity of Ferroelectric Vinylidene Fluoride-Oligomer-Evaporated Thin Films

Noda Kei, Ishida Kenji, Horiuchi Toshihisa, Yamada Hirofumi, Matsushige Kazumi

Japanese Journal of Applied Physics, Part 2: Letters 42 （ 11 A ）  2003年11月

ISSN  0021-4922

　概要を見る

<p>The pyroelectricity of ferroelectric vinylidene fluoride (VDF)-oligomer [CF₃(CH₂CF₂)₁₇I]-evaporated film was investigated utilizing a low-frequency sinusoidal heat source. A current profile appeared as the summation of a fundamental sine wave with a frequency of the temperature change and its harmonic responses. The pyroelectric coefficient (p) of the 600-nm-thick VDF oligomer film was estimated to be -68 μC/m²K at 37°C, whose absolute value is larger than those reported for ferroelectric polymers. Various characteristics such as a large |p|, a small dielectric constant and suitability for preparation of thinner films suggest that the VDF oligomer is a promising material for application in pyroelectric thin-film infrared detectors.</p>

Remanent polarization of evaporated films of vinylidene fluoride oligomers

Noda Kei, Ishida Kenji, Kubono Atsushi, Horiuchi Toshihisa, Yamada Hirofumi, Matsushige Kazumi

Journal of Applied Physics 93 （ 5 ） 2866 - 2870 2003年03月

ISSN  0021-8979

　概要を見る

<p>Remanent polarization of evaporated films of vinylidene fluoride was investigated. Hysteresis curves were also realized. The film was found to have an extremely high crystallinity, and the electric dipoles arrange almost perpendicular to the film surface. The obtained value of coercive field was attributed to the steric hindrance.</p>

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Investigation of ferroelectric properties of vinylidene fluoride oligomer evaporated films

Noda K., Ishida K., Mochizuki K., Kubono A., Horiuchi T., Yamada H., Matsushige K.

Materials Research Society Symposium Proceedings 748   217 - 222 2003年

　概要を見る

<p>Structures and electrical properties of newly synthesized vinylidene fluoride (VDF) oligomer [CF₃(CH₂CF₂)₁₇I] films evaporated onto various substrates around liquid nitrogen temperature were investigated. As a result, the VDF oligomer films were mainly formed with ferroelectric phase (form I) crystals and the molecular chains were oriented parallel to the substrate surfaces regardless of both the kind of the substrates and the thickness of the VDF oligomer films. In addition to these properties, the VDF oligomer films showed polarization reversal due to 180° rotation of the polar VDF oligomer molecules according to the applied voltages. This ferroelectric behavior was verified by local poling and piezoresponse measurements with an atomic force microscope, and by measurements of D-E hysteresis curves.</p>

Molecular-scale non-contact AFM studies of ferroelectric organic thin films epitaxially grown on alkali halides

Fukuma T., Kobayashi K., Noda K., Ishida K., Horiuchi T., Yamada H., Matsushige K.

Surface Science 516 （ 1-2 ） 103 - 108 2002年09月

ISSN  0039-6028

　概要を見る

<p>Epitaxially grown vinylidene fluoride oligomer thin films formed on KCl(0 0 1) surfaces were investigated by ultrahigh vacuum non-contact AFM (UHV-NC-AFM). Molecularly resolved NC-AFM images of organic thin layers on insulating surfaces were successfully obtained for the first time, which revealed the epitaxial growth process on a molecular-scale. It was found that the first monolayer formed on KCl(0 0 1) surface was composed of characteristic honeycomb-like structures while the following upper molecular layers consist of molecular-scale stripe structures. In addition, NC-AFM images of the first monolayer suggest a strong electrostatic interaction between the molecule in the layer and the AFM probe tip.</p>

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Molecular ferroelectricity of vinylidene fluoride oligomer investigated by atomic force microscopy

Noda Kei, Ishida Kenji, Kubono Atsushi, Horiuchi Toshihisa, Yamada Hirofumi, Matsushige Kazumi

Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers 40 （ 6 B ） 4361 - 4364 2001年06月

ISSN  0021-4922

　概要を見る

<p>Nanometer-scale electrical properties of local ferroelectric domains formed in thin films of newly synthesized vinylidene fluoride (VDF) oligomer were investigated by atomic force microscopy (AFM). Local poling and observation of the piezoelectric response revealed that the polarized domains were reversibly formed and erased in a nanometer-thick film by applying dc or pulse voltages between the electrically conductive AFM tip and the bottom electrode. The formed domain size depends on the pulse poling conditions and increases when the magnitude and the duration of a pulse voltage are increased. A local domain with a diameter of 65 nm was successfully created. The results in this work are comparable to those of previous studies performed on ferroelectric polymer thin films, suggesting that this material is one of the promising candidates for ferroelectric applications such as high-density data storages, and for molecular controls of ferroelectric properties.</p>

Structures and ferroelectric natures of epitaxially grown vinylidene fluoride oligomer thin films

Noda Kei, Ishida Kenji, Kubono Atsushi, Horiuchi Toshihisa, Yamada Hirofumi, Matsushige Kazumi

Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers 39 （ 11 ） 6358 - 6363 2000年11月

ISSN  0021-4922

　概要を見る

<p>Structural and electrical properties of newly synthesized vinylidene fluoride (VDF) oligomer thin film have been investigated. The FTIR spectrum showed that the epitaxially grown film on KBr(001) substrate consists of form I (β phase) crystals and their c axes (molecular axes) and b axes (polar axes) are arranged parallel to the KBr substrate. To make electrical measurements possible, this film was transferred onto a gold bottom electrode without causing any changes in the crystalline structures. By using a modified atomic force microscope, we succeeded in the formation of local polarized domains as well as the clear observation of piezoresponse hysteresis curves in this sample. The coercive field and piezoelectric coefficient (d₃₃) for the 37-nm-thick film were about 200 MV/m and -3 pm/V, respectively. It was suggested that the b axis in the as-grown film rotated from the parallel to the perpendicular direction to the film surface during the poling process. This study reveals the ferroelectric characteristics in the VDF oligomer thin films for the first time.</p>

Structural and electronic characterization of epitaxially-grown ferroelectric vinylidene fluoride oligomer thin films

Ishida K., Noda K., Kubono A., Horiuchi T., Yamada H., Matsushige K.

Materials Research Society Symposium Proceedings 600   101 - 106 2000年

　概要を見る

<p>The structural and electric properties of newly synthesized vinylidene fluoride (VDF) oligomer thin films evaporated on various substrate were investigated. The structural behavior of the VDF oligomer thin films strongly depended on the kinds of substrate and substrate temperature during film preparation. In particular, the VDF oligomers epitaxially grew on KBr(001), aligned their molecular chain along the 〈110〉 direction of substrate surface, and were similar to polar Form I-type crystals of poly(VDF). While, the thin films evaporated on NaCl(001), SiO₂/Si were non-polar Form II-type or mixture of both Form I- and Form II-type crystals with their molecular chain normal to the surface. These facts indicated that crystal field of substrate, based on van der Waals and electrostatic interactions, strongly influenced to ferroelectric phase transition of the VDF oligomer. In addition, we demonstrate the formation of the local polarized domains in the epitaxial crystals by applying electric pulses from a conducting AFM probe used as a positionable top-electrode, and confirm their piezoelectricity of the VDF oligomers for the first time.</p>

Structures of vinylidene fluoride oligomer thin films on alkali halide substrate

Noda Kei, Ishida Kenji, Horiuchi Toshihisa, Matsushige Kazumi, Kubono Atsushi

Journal of Applied Physics 86 （ 7 ） 3688 - 3693 1999年10月

ISSN  0021-8979

　概要を見る

<p>Structures and crystal transformation of the newly synthesized vinylidene fluoride (VDF) oligomer with large electric dipoles evaporated on KCl (001) at various substrate temperatures have been investigated by an energy dispersive-grazing incidence x-ray diffraction system, Fourier transform infrared spectroscopy, and atomic force microscope (AFM). It was revealed that the molecules grow epitaxially and are influenced greatly by forces of the crystal surface field in terms of van der Waals or electrostatic potentials, and found that the phase transformation from form II (α phase) to form I (β phase) is induced by raising the temperature of the substrate from 50 to 80°C, accompanying the alternation in the crystal axes on the substrate from the a axis of form II to the polar b axis of the form I crystal. This fact suggests that the molecular chain of VDF oligomers aligns their c axes along the 〈110〉 row of K⁺ or Cl^- with the aid of electrostatic interaction under enough thermal movement. Moreover, in the transformation process, a pair of "rod-like" crystals, suggesting ferroelectric activity, were observed by AFM.</p>

エネルギー分散型斜入射 X 線分光法によるエピ成長強誘電性有機薄膜の構造評価

石田 謙司、野田 啓、久保野 敦史、堀内 俊寿、山田 啓文、松重 和美

電子情報通信学会技術研究報告（信学技報） 98 （ 27 ） 17 - 24 1998年

研究論文（研究会，シンポジウム資料等）, 共著,  ISSN  0913-5685