2022/08/10 更新

写真a

ミヤタ ヒロカツ
宮田 浩克
所属
理工学術院 各務記念材料技術研究所
職名
上級研究員(研究院教授)

経歴

  • 2021年04月
    -
    継続中

    早稲田大学   各務記念材料技術研究所   上級研究員   研究院教授

  • 2014年08月
    -
    2021年03月

    キヤノン株式会社   材料・分析技術開発センター   主席   Member of the Canon Academy of Technology

 

論文

  • Lithographically Formed Fine Wavy Surface Morphology for Universal Alignment Control of Mesochannels in Mesostructured Silica Films

    Hirokatsu Miyata, Masahiko Takahashi

    Langmuir   37 ( 6 ) 2179 - 2186  2021年02月

     概要を見る

    In-plane orientation of mesochannels in mesostructured silica films is fully controlled by a lithographically formed anisotropic surface morphology of a substrate. The orientation is determined simply by elastic properties of a liquid crystal phase, which appears in the course of the formation of mesostructured silica films through the sol-gel process. When an array of linear microscopic grooves with a round cross section is closely formed on the substrate surface, the cylindrical mesochannels in the films are entirely aligned strictly perpendicular to the grooves, as a consequence of minimization of the total elastic energy. When the surface morphology geometrically fits to the hexagonal arrangement of the mesochannels, the orientation abruptly changes into the direction parallel to the long axis of the grooves. The alignment control based on the elastic property of the liquid crystal phase described in this report does not require any specific chemical interactions between the surfactant molecules and the substrate surface. Therefore, aligned mesostructured silica films with a large structural periodicity can successfully be formed using block copolymer surfactants, which hardly form an aligned mesostructure without the support of external fields. The vapor-phase synthesis, which enables considerable retardation of the solidification process of siliceous species, is the most favorable way, and totally aligned mesostructured silica films with significantly large thickness, more than 1 μm, can be obtained. Appropriate combination of the bottom-up and the top-down nanoprocesses reported in this paper, that is, self-assembly and photolithography, will enable the formation of highly anisotropic nanostructured materials, which will find various practical applications.

    DOI PubMed

  • Films Consisting of Innumerable Tapered Nanopillars of Mesoporous Silica for Universal Antireflection Coatings

    Hirokatsu Miyata, Shin Kitamura, Masatoshi Watanabe, Masahiko Takahashi

    Chemistry - An Asian Journal   11 ( 10 ) 1618 - 1623  2016年05月

     概要を見る

    Films with a fine structure consisting of innumerable nanopillars of mesoporous silica (MPS) are formed by a reactive ion etching process with a fluorine-containing gas. Each nanopillar has a tapered shape with a uniform height, which effectively suppresses reflection by the formation of an ideal graded refractive index structure. The nanopillars are spontaneously formed under low-pressure conditions, wherein locally deposited Al-F compounds, originating from an alumina plate in the etching chamber, work as a fine etching mask. The high etching rate of the MPS film allows a very high aspect ratio of the nanopillars. The refractive index of the MPS nanopillars can be universally tuned by a controlled incorporation of TiO2 into the mesopores, which results in effective reduction of reflectance on a given substrate. The outstanding antireflection performance is experimentally demonstrated for glass substrates with a wide refractive index range. Don't bounce back! Films with a fine structure consisting of nanopillars of mesoporous silica (MPS) are formed by a reactive ion etching process with a fluorine-containing gas. These antireflection coatings enable fine-tuning of the refractive index (see figure).

    DOI

  • Mechanism of the activation process for the formation of a surface-conduction electron-emitter

    Takeo Tsukamoto, Masahiro Okuda, Yutaka Arai, Hirokatsu Miyata

    Japanese Journal of Applied Physics   55 ( 1 )  2016年01月

     概要を見る

    The major role of the chemical reaction between a silica substrate and deposited carbon in the activation process for the formation of a surfaceconduction electron emitter (SCE) is investigated. The SCE emits electrons by the tunneling effect when an electric field is applied across a nanoscale gap. The nanogap is spontaneously formed by the activation process, wherein a pulse voltage is applied between a pair of electrodes, which are separated by a narrow gap inside a vacuum chamber in the presence of hydrocarbons. At the gap, two elemental processes compete; the deposition of carbon by the electron-induced decomposition of hydrocarbons and the consumption of carbon by reaction with the silica substrate. The balance of the dynamics of the two processes, which simply depends on the temperature at the gap, is responsible for the spontaneous determination of the width of the nanogap. The calculation based on the model that involves the two competitive processes agrees with the experimental results on the activation process.

    DOI

  • Mesoporous TiO<inf>2</inf> films with regularly aligned slit-like nanovoids

    Hirokatsu Miyata, Yuta Fukushima, Yosuke Kanno, Saeko Hayase, Shintaro Hara, Masatoshi Watanabe, Shin Kitamura, Masahiko Takahashi, Kazuyuki Kuroda

    Journal of Materials Chemistry C   3 ( 16 ) 3869 - 3875  2015年04月

     概要を見る

    Novel mesoporous TiO2 films with regularly aligned slit-like nanovoids are prepared through structural transformation from a mesostructured TiO2 film with honeycomb-packed aligned cylindrical micelles by pyrolytic removal of the micelle template. The transformation takes place through interconnection of the TiO2 walls of the framework in the thickness direction by a heat-induced shrinkage and eventual collapse of the original channel structure. For the formation of this new structure, the preparation of a mesostructured titania film with cylindrical micelles aligned entirely in the plane of the film over the whole thickness is indispensable. This is achieved by coating a substrate, on which a rubbing-treated polyimide layer is formed, with a precursor solution containing two nonionic surfactants, Brij56 and P123. In the mixed surfactant system, Brij56 works as an alignment-controlling agent through selective and directional adsorption on the anisotropic polymer surface. On the other hand, P123 suppresses the formation of a surface layer without controlled in-plane alignment, which has been inevitable when Brij56 is used alone. This is caused by the retarded condensation of the TiO2 precursors due to increased coordination of oxyethylene moieties on titanium. P123 also increases the wall thickness of the framework, which also contributes to the formation of this mesoporous TiO2 film with oriented regular slit-like voids. The structural transformation takes place in a relatively low temperature range lower than 300 °C, which shows that the driving force is not crystallization. The mesoporous TiO2 films with aligned slit-like voids show optical anisotropy, birefringence, with a Δn value of ∼0.023 reflecting the structural anisotropy of the film. Calcination of the aligned mesostructured TiO2 film at 450 °C induces crystallization of TiO2, which deteriorates the meso-scale structural regularity by interconnection of the TiO2 walls. However, the partial retention of the regular structure is confirmed in the vicinity of the surface, which allows the retention of the optical anisotropy. The novel mesoporous TiO2 films in this paper have potential for optical applications by combining their unique anisotropic mesostructure, which enhances the accessibility to the inner surface, with various properties of TiO2 such as high refractive index and photocatalytic activity. This journal is

    DOI

  • Si substrate as a SiO<inf>2</inf> source for the preparation of mesoporous SiO<inf>2</inf>TiO<inf>2</inf> thin films

    Shintaro Hara, Hirokatsu Miyata, Masahiko Takahashi, Atsushi Shimojima, Kazuyuki Kuroda

    Chemistry Letters   44 ( 3 ) 372 - 374  2015年

     概要を見る

    A Si substrate has been proved to be used as a SiO2 source for the preparation of mesoporous silicatitania thin films with cylindrical mesochannels. Exposing mesostructured titaniasurfactant thin films to aqueous NH3 vapor reinforces the pore walls with uniformly distributed silicate species, which retain the mesostructure after calcination.

    DOI

  • Films with Tunable Graded Refractive Index Consisting of Spontaneously Formed Mesoporous Silica Nanopinnacles

    Shin Kitamura, Yosuke Kanno, Masatoshi Watanabe, Masahiko Takahashi, Kazuyuki Kuroda, Hirokatsu Miyata

    ACS Photonics   1 ( 1 ) 47 - 52  2014年01月

     概要を見る

    Coatings with surfaces packed with pointed projections with subwavelength sizes are known as "moth-eye", whose graded index structure gives superior antireflection (AR) properties with a small dependence on wavelength and incident angle. However, the optical interface between the AR coating and a substrate still causes reflection, unless the refractive index of the coating is matched to that of the substrate. Here, we show a new AR coating with both graded and tunable refractive index, which completely eliminates distinct optical interfaces. The coating is made of a mesoporous silica film, whose surface is spontaneously converted to an assembly of pointed nanostructure by reactive ion etching, and its refractive index is matched universally to that of a substrate by controlled incorporation of titanium dioxide into the mesopores. This AR coating enables universal ultralow reflection on a substrate over the index range from 1.2 to 1.8 and will be applied widely in practical optics. (Figure Presented).

    DOI

  • Improvement of flatness and structural regularity of mesostructured silica films having strictly aligned two-dimensional hexagonal structure

    Wataru Kubo, Kohei Okamoto, Atsushi Komoto, Masatoshi Watanabe, Hirokatsu Miyata

    Journal of Materials Chemistry C   1 ( 25 ) 4025 - 4034  2013年07月

     概要を見る

    Surface flatness and structural regularity of a uniaxially aligned mesostructured silica film (MSF) is significantly improved by a new EISA process which consists of separate water addition to the precursor solution and coating under low humidity (SL process). This process ensures the control of both the state of the siliceous species and the water concentration during the coating process by optimizing the composition of the precursor solution just before the coating. The SL process improves the surface flatness and the regularity of the uniaxially aligned film, which had a large anisotropic roughness. The improved flatness and regularity of the obtained film are evident through reduction of the surface roughness to 1/7 and ten times higher diffraction intensity compared to the film prepared by a reference process using the precursor solution with the same composition. 29Si NMR spectroscopy and in-plane X-ray diffraction (XRD) reveal that the independent control of the state of the siliceous species suppresses the formation of the branched siliceous species while maintaining the optimized water concentration to form the strictly aligned structure. The film with high structural regularity and a flat surface enables new practical precise optical devices utilizing its specific nano-scale anisotropy. © 2013 The Royal Society of Chemistry.

    DOI

  • Strict in-plane alignment control of block-copolymer-templated mesostructured silica films using an alignment-controlling agent

    Wataru Kubo, Masahiko Takahashi, Kohei Okamoto, Shin Kitamura, Hirokatsu Miyata

    Langmuir   29 ( 26 ) 8193 - 8196  2013年07月

     概要を見る

    An alkoxysilane with an alkyl chain is introduced as an alignment-controlling agent of a block-copolymer-templated mesostructured silica film. Use of the alkylalkoxysilane achieves the alignment of the mesochannels of a triblock-copolymer-templated film by an intermolecular interaction with a rubbing-treated polyimide film. Co-use of an alkoxysilane with a hydroxymethyl group as a hydrophobicity reducing agent improves the alignment close to that of the film prepared using an alkyl surfactant. This concept widens the range of the structural period of aligned mesoporous films and thus widens the useful range of the anisotropic optical properties. © 2013 American Chemical Society.

    DOI

  • Heteroepitaxial formation of aligned mesostructured silica films with large structural periodicities from mixed surfactant systems

    Saeko Hayase, Yosuke Kanno, Masatoshi Watanabe, Masahiko Takahashi, Kazuyuki Kuroda, Hirokatsu Miyata

    Langmuir   29 ( 23 ) 7096 - 7101  2013年06月

     概要を見る

    Liquid-crystal phases consisting of cylindrical micelles of amphiphilic block copolymers and silica precursors are epitaxially built up on aligned surface micelles formed by an alkyl-PEO surfactant, Brij56, irrespective of the large difference in the intrinsic structural periodicities resulting in the formation of fully aligned mesostructured silica films with large lattice constants. Brij56 works as an alignment controlling agent on rubbing-treated polyimide through selective adsorption from a precursor solution containing the two surfactants, a block copolymer and Brij56, through strong hydrophobic interactions to form an anisotropic surface micelle structure. Aligned mesostructured silica layers with larger periodicities, which dominantly consist of block copolymers, form on these aligned surface micelles by gradually changing the vertical periodicity keeping the lateral intermicelle distance constant. This can be regarded as a kind of heteroepitaxy because the lattice constant at the surface is different from that of the bulk of the film. On the basis of this new concept, highly aligned mesostructured silica films with structural periodicities as large as 10 nm are successfully formed, which has never been achieved when the block copolymers are used alone as the structure-directing agent. The periodicity of the aligned films can precisely be controlled by an appropriate choice of block copolymers and the mixing ratio of the two surfactants, which increases the opportunity for applications of these films with highly anisotropic mesoscale structure. © 2013 American Chemical Society.

    DOI PubMed

  • Lattice matching in the epitaxial formation of mesostructured silica films

    Hirokatsu Miyata, Shimon Kobori, Wataru Kubo, Masatoshi Watanabe, Kazuyuki Kuroda

    Langmuir   29 ( 2 ) 761 - 765  2013年01月

     概要を見る

    Crystallographic orientation of mesostructured silica films on a substrate drastically changes when the substrate is modified with an anisotropic surface. The «01» axis of a two-dimensional (2D) hexagonal structure of the film prepared on a polyimide surface using C22EO20 as a structure-directing agent changes from perpendicular to parallel with respect to the substrate after a rubbing treatment of polyimide, which is accompanied by the simultaneous unidirectional alignment of the cylindrical pores in the plane of the film. The normal direction of the film is «21», which has never been observed in the mesostructured silica films reported so far including those with controlled in-plane alignment of the mesochannels. The change of the orientation with respect to the substrate can be explained by the increased lateral distance between the adjacent surface micelles, which is caused by the elongation of the alkyl chains of the surfactant molecules induced by the adsorption onto the polymer surface with a molecular-level anisotropy. These results show that the total structural orientation of the mesostructured silica film is determined by the matching of the intrinsic lattice constant of the mesostructured silica with that of the surface micelle structure on a substrate. © 2012 American Chemical Society.

    DOI

  • PEO-b-PPO diblock copolymers for the preparation of 2D hexagonal mesoporous silica films with extremely large structural periods

    Masahiko Takahashi, Wataru Kubo, Hirokatsu Miyata

    Chemistry Letters   42 ( 8 ) 909 - 911  2013年

     概要を見る

    Use of poly(ethylene oxide)-b-poly(propylene oxide) (PEO-b-PPO) diblock copolymers with appropriate block ratios effectively increases the structural period of the mesoporous silica films with a two-dimensional hexagonal structure, which are prepared by the evaporation-induced self-assembly process. The number of the hydrophobic PPO block can control the periodicity over a wide range, which reaches even ca. 20 nm. © 2013 The Chemical Society of Japan.

    DOI

  • X-ray waveguide mode in resonance with a periodic structure

    K. Okamoto, T. Noma, A. Komoto, W. Kubo, M. Takahashi, A. Iida, H. Miyata

    Physical Review Letters   109 ( 23 )  2012年12月

     概要を見る

    We present a novel concept for x-ray waveguiding based on electromagnetism in photonic crystals, using a waveguide consisting of a pair of claddings sandwiching a core with a periodic structure. By confining the x rays undergoing multiple interference in the core by total reflection, a characteristic waveguide mode whose field distribution matches the periodicity of the core is formed. The distinctively low propagation loss enables the single-mode propagation of x rays. This concept opens broad application possibilities in x-ray physics from coherent imaging to x-ray quantum optics. © 2012 American Physical Society.

    DOI

  • Exceptionally strong Bragg diffraction from a mesoporous silica film pretreated with chlorotrimethylsilane toward application in X-ray optics

    Wataru Kubo, Masahiko Takahashi, Atsushi Komoto, Kohei Okamoto, Hirokatsu Miyata

    Physical Chemistry Chemical Physics   14 ( 4 ) 1418 - 1423  2012年01月

     概要を見る

    Exceptionally strong Bragg diffraction from a mesoporous silica film is achieved by exposing the as-deposited film to vapor of chlorotrimethylsilane (Me3SiCl) before extracting the surfactant. The intensity of the X-ray diffraction peak increased 7 times after the surfactant removal and it approached 30% reflectivity. This large increase of diffraction intensity cannot be explained simply by the improved contrast of the electron density, and rearrangement of the pore wall during the Me3SiCl vapor treatment is suggested. It is shown by infrared spectroscopy that Me3SiCl with a high grafting reactivity effectively caps the silanol groups and prevents the following condensation, which causes the structural degradation. The substitution of the hydrogen atom of hydroxyl groups with trimethylsilyl groups should help the improvement of the structural regularity by reducing the hydrogen bonds in the pore wall. The achieved strong diffraction opens the gate for the application of these regular mesoporous films prepared by a self-assembly process to optical elements in the X-ray region. © 2012 the Owner Societies.

    DOI

  • Control of periodicity in mesoporous silica films with aligned mesochannels prepared by a solgel process

    Atsushi Komoto, Wataru Kubo, Hirokatsu Miyata

    Chemistry Letters   41 ( 7 ) 741 - 743  2012年

     概要を見る

    Periodicity of mesoporous silica films with aligned cylindrical pores formed on a substrate with a rubbing-treated polyimide through a solgel process can be finely controlled using nonionic surfactants with different alkyl chains. The degree of alignment increases with the alkyl-chain length of the surfactant due to increase in anisotropic hydrophobic interaction between the oriented polyimide chains and the alkyl groups, which is responsible for the alignment. © 2012 The Chemical Society of Japan.

    DOI

  • Remarkable birefringence in a TiO<inf>2</inf>-SiO<inf>2</inf> composite film with an aligned mesoporous structure

    Hirokatsu Miyata, Yuta Fukushima, Kohei Okamoto, Masahiko Takahashi, Masatoshi Watanabe, Wataru Kubo, Atsushi Komoto, Shin Kitamura, Yosuke Kanno, Kazuyuki Kuroda

    Journal of the American Chemical Society   133 ( 34 ) 13539 - 13544  2011年08月

     概要を見る

    Mesoporous titania-silica composite films with highly aligned cylindrical pores are prepared by the sol-gel method using a substrate with structural anisotropy. The strong alignment effect of a rubbing-treated polyimide film on a substrate provides a narrow alignment distribution in the plane of the film regardless of the fast condensation rate of titania precursors. The collapse of the mesostructure upon the surfactant removal is effectively suppressed by the reinforcement of the pore walls with silica by exposing the as-deposited film to a vapor of a silicon alkoxide. The existence of a silica layer on the titania pore wall is proved from the distributions of Ti and Si estimated by the elemental analysis in high resolution electron microscopy. The obtained mesoporous titania-silica composite film exhibits a remarkable birefringence reflecting the highly anisotropic mesoporous structure and the high refractive index of titania that forms the pore wall. The δn value estimated from the optical retardation and the film thickness is larger than 0.06, which cannot be achieved with the conventional mesoporous silica films with uniaxially aligned mesoporous structure even though the alignment of the pores in the films is perfect. These inorganic films with mesoscopic structural anisotropy will find many applications in the field of optics as phase plates with high thermal/chemical/mechanical stabilities. © 2011 American Chemical Society.

    DOI

  • Electrooptic response of colloidal liquid crystals of inorganic oxide nanosheets prepared by exfoliation of a layered niobate

    Teruyuki Nakato, Koichiro Nakamura, Yasuhiro Shimada, Yuko Shido, Takeshi Houryu, Yasufumi Iimura, Hirokatsu Miyata

    Journal of Physical Chemistry C   115 ( 18 ) 8934 - 8939  2011年05月

     概要を見る

    Colloidally dispersed inorganic nanosheets prepared by exfoliation of layered crystals form lyotropic liquid crystals where highly anisotropic nanosheets with a constant thickness of ca. 1 nm and lateral dimension up to several micrometers work as mesogen. We investigated electrooptic properties of the niobate nanosheet colloids yielded by exfoliation of layered hexaniobate K4Nb6O17. The nanosheets initially oriented parallel to the surface of flat substrate were aligned parallel to the direction of the applied ac electric fields, resulting in electric birefringence of the colloids. The liquid crystalline colloids consisting of large nanosheets with an average lateral size around 2 μm showed a sharp response to an electric field with a low threshold voltage (<4 × 102 V cm -1) and the consequent remarkable electrooptic effect, which is in contrast to the isotropic colloid composed of a small sub-millimeter nanosheet that exhibited only a weak electrooptic effect with a high threshold (10 3 V cm-1). Retention of the electrically induced alignment was observed for the LC colloids with high nanosheet concentrations. The response much slower than conventional thermotropic liquid crystals reflects the micrometer-level size of the mesogenic nanosheets. Whereas the two-dimensional nature of the nanosheets did not induce the formation of monodomain by applying only one-dimensional electric field, repeated application and consequent backflow in the measurement cell reoriented the nanosheets into monodomain. © 2011 American Chemical Society.

    DOI

  • Epitaxial-like growth of anisotropic mesostructure on an anisotropic surface of an oblique nanocolumnar structure

    Hirokatsu Miyata, Wataru Kubo, Akira Sakai, Yohei Ishida, Takashi Noma, Masatoshi Watanabe, Avi Bendavid, Philip J. Martin

    Journal of the American Chemical Society   132 ( 27 ) 9414 - 9419  2010年07月

     概要を見る

    Tetrahedral amorphous carbon (ta-C) films with nanoscale structural anisotropy, which are obliquely deposited on a substrate by a filtered cathodic vacuum arc deposition (FAD) technique, allow anisotropic growth of mesostructured silica films thereon. The ta-C films have a uniformly tilted nanoscale columnar structure, which is caused by the self-shadowing effect during the oblique deposition, and consequently, the surface of the film can be morphologically anisotropic when the deposition angle is large enough. When silica films with a two-dimensional hexagonal mesostructure are grown under hydrothermal conditions on these ta-C films, the cylindrical mesochannels are aligned perpendicularly to the deposition direction of ta-C. The distribution of the in-plane alignment direction of the mesochannels can be controlled by the deposition angle of ta-C; it becomes narrower with the increase of the deposition angle and the consequent increase of the surface roughness. The observed alignment of the mesochannels is caused by the anisotropic accommodation of the surfactant molecules on the structurally anisotropic surface of the ta-C films, which is consistent with the fact that the ta-C films prepared at small deposition angles with smoother surface morphology have little alignment controllability. The ta-C film can be removed with the surfactant by calcination, allowing the formation of an aligned mesoporous silica film directly on a substrate. In contrast to this, obliquely evaporated SiO2 films with a distinct tilted columnar structure and an anisotropic surface morphology provide neither continuous film formation nor controlled alignment of mesochannels even after providing hydrophobicity by a silylation process. This suggests the specificity, in particular, intrinsic strong hydrophobicity, of the ta-C films for the aligned mesostructured silica film formation. © 2010 American Chemical Society.

    DOI

  • Formation of multinuclear metal-terpyridyl complexes covalently bound to carbon substrates

    Wataru Kubo, Masashi Nagao, Yoichi Otsuka, Tsutomu Homma, Hirokatsu Miyata

    Langmuir   25 ( 23 ) 13340 - 13343  2009年12月

     概要を見る

    Multinuclear complexes consisting of metal ions and a bis(terpyridyl) ligand were covalently bound to carbon substrates. The bonding of the complexes is initiated by the bonding of phenylterpyridine (PT) on the substrates using its in-situ-generated diazonium derivative, followed by stepwise coordination of the metal ions and the ligand on it. The bonding of the PT and the formation of the multinuclear complexes were confirmed by XPS, AFM, and CV measurements. The heterogeneous rate constant (k) at the Co complex-substrate interface was evaluated by chronoamperometry (CA). The estimated high k=(2.9-3.6) × 103 s-1) would be attributed to the C-C bond at the interface without interrupting the conjugation. These multinuclear complexes bound to the carbon substrates can facilitate electron transfer from redox species such as enzymes. © 2009 American Chemical Society.

    DOI PubMed

  • Alignment control of self-assembled organosiloxane films derived from alkyloligosiloxane amphiphiles

    Jenny Du, Madoka Fukushima, Shigeru Sakamoto, Mikako Sakurai, Takashi Suzuki, Atsushi Shimojima, Hirokatsu Miyata, Cathleen M. Crudden, Kazuyuki Kuroda

    Langmuir   25 ( 23 ) 13614 - 13618  2009年12月

     概要を見る

    Transparent and continuous organosiloxane films with macroscopically oriented mesostructures were prepared by dip-coating a substrate, on which a rubbing-treated polyimide film is formed, with hydrolyzed solutions of oligosiloxane precursors (CnH2n+1Si(OSi(OMe) 3)3). The structure of the films depends on the alkyl chain length of the precursors such that films with two-dimensional (2D) hexagonal and lamellar structures are obtained when n=10 and 16, respectively. In the 2D hexagonal film, the cylindrical organic moieties are aligned perpendicular to the rubbing direction in the plane of the film over the whole film thickness. On the other hand, the lamellar film changes its orientation with increased distance from the substrate surface. While the orientation of the lamellae at the surface of the film is parallel to the film-air interface, they are perpendicularly aligned in the vicinity of the substrate with the layer normal parallel to the rubbing direction. The observed unique orientation of the mesostructures is attributed to the anisotropic hydrophobic interactions between the alkyl chains of the hydrolyzed oligosiloxane molecules and the polymer chains of the polyimide layer oriented by the rubbing treatment. © 2009 American Chemical Society.

    DOI

  • Platinum thin film consisting of well-aligned nanowires and its optical behavior

    Takashi Suzuki, Hirokatsu Miyata, Takashi Noma, Kazuyuki Kuroda

    Journal of Physical Chemistry C   112 ( 6 ) 1831 - 1836  2008年02月

     概要を見る

    A nanostructured film composed of interconnecting aligned platinum nanowires is prepared by electrodeposition using a hard template of mesoporous silica film with uniaxially aligned mesochannels formed on a conductive substrate. Platinum is introduced into the mesopores through micropores, connecting adjacent mesopores, without influencing the mesoporous structure. The alignment of the nanowires is retained to some extent after the removal of the silica template, leading to the formation of a film with aligned platinum nanowires, although the structural regularity is largely degraded. Irrespective of the presence of the silica template, the obtained films show distinct macroscopic optical anisotropy in the visible region, reflecting the anisotropic localized surface plasmon resonance arising from individual nanowire, despite its interconnected structure. The aligned structure enables, the observation of such an axis-dependent optical property in a macroscopic scale. This versatile replication method can be extended to the preparation of aligned nanowire assemblies with various compositions. © 2008 American Chemical Society.

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  • Silica films having zigzag mesoporous structures with fixed kink angles

    Hirokatsu Miyata, Takashi Suzuki, Masatoshi Watanabe, Takashi Noma, Kazuhiro Takada, Taihei Mukaide, Kazuyuki Kuroda

    Chemistry of Materials   20 ( 3 ) 1082 - 1089  2008年02月

     概要を見る

    Mesoporous silica films with a highly controlled unique zigzag porous structure are prepared on a rubbing-treated polyimide film. The honeycomb-packed tubular pores in the films have two distinct in-plane alignment directions with respect to the rubbing direction; that is, the films have an in-plane zigzag mesoporous structure with a fixed kink angle. The kink angle is controllable by the molar ratio of tetraethoxysilane as a silica source to surfactant in the reactant solution, and the increase of the ratio results in larger kink angles. The zigzag structure is found to be formed through the formation of an initial immature mesostructured film with uniaxially aligned rodlike surfactant assemblies. It is highly probable that the observed in-plane bending of the pores is caused by the translations shift of the positions of the adsorbed surfactant molecules along the polyimide chains on the surface and that the shift is caused by the steric effects between the adjacent hydrophilic components consisting of surfactant head groups and silica oligomers. The present results show that a unique nanoscale structure, which can hardly be obtained through a reaction under homogeneous conditions, can be formed under the heterogeneous conditions in which the reaction takes place within a restricted environment. © 2008 American Chemical Society.

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  • Phenylene-bridged mesoporous organosilica films with uniaxially aligned mesochannels

    Takashi Suzuki, Hirokatsu Miyata, Kazuyuki Kuroda

    Journal of Materials Chemistry   18 ( 11 ) 1239 - 1244  2008年

     概要を見る

    The alignment of mesochannels in a phenylene-bridged mesoporous organosilica film is successfully controlled by using a substrate with a rubbing-treated polyimide film. The films are prepared by two different procedures: the hydrothermal deposition process and the so-called evaporation-induced self-assembly process. The narrow alignment distribution of mesochannels is achieved by the interfacial hydrophobic interactions between alkyl chains of surfactant and the elongated polymer chains of rubbing-treated polyimide. The molecular-scale ordering of the framework in the films is low, unlike those in mesoporous organosilica powders and films prepared under basic conditions, though the thickness of the pore walls is comparable to the molecular size. The emission behaviour in the ultraviolet region, which is sensitive to inter-phenylene interactions, is influenced by synthesis and thermal treatment temperatures, irrespective of the preparative methods. The changes in the spectra indicate that the major emissive species changes from the excited monomer to the excimer with the increase of temperature. These organic-inorganic hybrid films will find various applications by combining functionalities of organic and inorganic moieties and highly controlled nanospaces. © 2008 The Royal Society of Chemistry.

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  • Controlling optical gain in semiconducting polymers with nanoscale chain positioning and alignment

    Ignacio B. Martini, Ian M. Craig, William C. Molenkamp, Hirokatsu Miyata, Sarah H. Tolbert, Benjamin J. Schwartz

    Nature Nanotechnology   2 ( 10 ) 647 - 652  2007年10月

     概要を見る

    We control the chain conformation of a semiconducting polymer by encapsulating it within the aligned nanopores of a silica host. The confinement leads to polarized, low-threshold amplified spontaneous emission from the polymer chains. The polymer enters the porous silica film from only one face and the filling of the pores is therefore graded. As a result, the profile of the index of refraction in the film is also graded, in the direction normal to the pores, so that the composite film forms a low-loss, graded-index waveguide. The aligned polymer chains plus naturally formed waveguide are ideally configured for optical gain, with a threshold for amplified spontaneous emission that is twenty times lower than in comparable unoriented polymer films. Moreover, the optimal conditions for ASE are met in only one spatial orientation and with one polarization. The results show that nanometre-scale control of semiconducting polymer chain orientation and position leads to novel and desirable optical properties. © 2007 Nature Publishing Group.

    DOI PubMed

  • Chemically prepared silica films with single crystalline mesoporous structures

    Hirokatsu Miyata

    Optics InfoBase Conference Papers    2007年

     概要を見る

    Self-assembly of surfactant molecules and silica oligomers on various substrates with surface anisotropy leads to the formation of silica films in which in-plane arrangement of regular mesopores shows long range correlation on the macroscopic scale. © 2007 Optical Society of America.

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  • X-Ray diffraction properties of silica thin films having single crystalline mesoporous structures

    Takashi Noma, Hirokatsu Miyata, Kazuhiro Takada, Atsuo Iida

    Optics InfoBase Conference Papers    2007年

     概要を見る

    Detailed X-ray diffraction study of silica films with single crystalline mesoporous structures shows that the behavior of X-rays in these mesoporous materials with nano-scaled structural regularity is quite identical to that in real crystals. © 2007 Optical Society of America.

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  • Alignment and switching behaviors of liquid crystal on a-Si Ox thin films deposited by a filtered cathodic arc process

    P. J. Martin, A. Bendavid, C. Comte, H. Miyata, Y. Asao, Y. Ishida, A. Sakai

    Applied Physics Letters   91 ( 6 )  2007年

     概要を見る

    A new method is described for the preparation of silicon oxide layers, which produces vertical alignment of liquid crystal with controlled pretilt angles, by a reactive filtered cathodic arc deposition under oblique incidence geometry. The pretilt angle is dependent on the angle of deposition, but is not simply caused by the surface roughness. The achievable pretilt angle by this method is ∼5.5°, which allows uniform switching behavior under an applied electric field. © 2007 American Institute of Physics.

    DOI

  • Critical effect of surfactant concentration on the structure of mesoporous silica films prepared on a substrate coated with rubbing-treated polyimide

    Takashi Suzuki, Hirokatsu Miyata, Masatoshi Watanabe, Kazuyuki Kuroda

    Chemistry of Materials   18 ( 20 ) 4888 - 4893  2006年10月

     概要を見る

    The change of nonionic surfactant C16(EO)10 (Brij56) concentration has a critical effect on the structure of mesoporous silica films grown hydrothermally on a substrate coated with a rubbing-treated polyimide film. The uniaxially aligned two-dimensional (2D) hexagonal mesoporous structure changes into a "single-crystalline" three-dimensional (3D) hexagonal structure, which means that the in-plane arrangement of spherical pores of the 3D-hexagonal structure is fully controlled, by simply decreasing the surfactant concentration. The investigation of the early stages of the film formation suggests that the initial formation of the uniaxially aligned tubular micelles and the subsequent transformation to the spherical ones are included in the formation mechanism. It is considered that such a transformation is caused by the increase in the size of headgroups of the building units, consisting of the surfactants and silica oligomers, due to the progress of silica condensation. The small association number of surfactant molecules in the building units would allow the growth of silica oligomers in the headgroups to the level that induces the total restructuring. © 2006 American Chemical Society.

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  • Preparation of a mesoporous silica film with a strictly aligned porous structure through a sol-gel process

    Hirokatsu Miyata, Yasuhiro Kawashima, Miki Itoh, Masatoshi Watanabe

    Chemistry of Materials   17 ( 21 ) 5323 - 5327  2005年10月

     概要を見る

    A novel strategy for the preparation of a mesoporous silica film, in which the in-plane alignment of the honeycomb packed mesochannels is strictly controlled, is developed. The highly aligned porous structure is achieved by using a substrate with a rubbing-treated polyimide coating in the evaporation induced self-assembly process. It is shown that the controlled porous structure is formed over the entire thickness of the film and that the alignment distribution is much narrower than that in the films prepared by the conventional process based on a heterogeneous nucleation and growth mechanism. In the present process, the aligned porous structure would be formed through a directional lamellar-to-hexagonal phase transition from the substrate surface toward the air/film interface. The new formation mechanism as well as the lower process temperature enables the observed strict alignment control of the mesochannels. © 2005 American Chemical Society.

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  • Characterization of nanoporous Si thin films obtained by Al-Si phase separation

    Kazuhiko Fukutani, Youhei Ishida, Toshiaki Aiba, Hirokatsu Miyata, Tohru Den

    Applied Physics Letters   87 ( 25 ) 1 - 3  2005年

     概要を見る

    Nanoporous silicon films of ultrahigh pore densities and large surface areas have been fabricated by sputtering an Al-Si target and subsequent removal of the deposited film's Al regions by etching in a sulfuric acid solution. The resulting nanoporous films are mainly composed of amorphous silicon and have cylindrical pores with an average pore density exceeding 1016 pores m2. These nanoporous films can be crystallized by thermal annealing in a H2 atmosphere to improve their electrical properties. The electrical properties of the crystallized nanoporous films, which behave as p -type semiconductors, are very similar to those of electrochemically etched porous Si. © 2005 American Institute of Physics.

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  • Silica films with a single-crystalline mesoporous structure

    Hirokatsu Miyata, Takashi Suzuki, Ayumu Fukuoka, Takeshi Sawada, Masatoshi Watanabe, Takashi Noma, Kazuhiro Takada, Taihei Mukaide, Kazuyuki Kuroda

    Nature Materials   3 ( 9 ) 651 - 656  2004年09月

     概要を見る

    Films of mesoporous materials attract broad interest because of their wide applicability in the fields of optics and electronics. Although many of these films have a regular local porous structure, the structural regularity has not been used practically yet because of difficulties in its control on macroscopic scales. Here, we demonstrate the preparation of mesoporous silica films whose porous structure can be described as a single crystal, that is, a long-range order of cage-like pores is maintained over centimetre scales. These films have a three-dimensional hexagonal (space group P63/mmc) porous structure, and the in-plane arrangement of the pores is strictly controlled by a polymeric substrate surface that has been treated by rubbing. This new class of singie-crystalline films with rnesoscopic periodic structure is a significant breakthrough in bottom-up nanotechnology, and could lead to novel devices, for example, optics in a soft X-ray region, and quantum electronics.

    DOI PubMed

  • Highly Polarized Luminescence from Optical Quality Films of a Semiconducting Polymer Aligned within Oriented Mesoporous Silica

    William C. Molenkamp, Masatoshi Watanabe, Hirokatsu Miyata, Sarah H. Tolbert

    Journal of the American Chemical Society   126 ( 14 ) 4476 - 4477  2004年04月

     概要を見る

    In this Communication, we show that nanometer scale control of semiconducting polymer chain conformation is possible using host/guest chemistry in highly ordered and macroscopically oriented thin films of mesoporous silica. This control leads to a thin film composite material that is optically transparent, densely filled with polymer, and has highly polarized optical properties. Calculations of absorption and emission anisotropies further indicate full incorporation of the polymer into the nanoscale pore spaces. Such materials could serve as a useful tool for further investigations of polymer photophysics, as well as for device applications. Copyright © 2004 American Chemical Society.

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  • Preparation of highly ordered mesostructured tin oxide film with a microcrystalline framework through vapor-induced liquid-crystal templating

    Hirokatsu Miyata, Miki Itoh, Masatoshi Watanabe, Takashi Noma

    Chemistry of Materials   15 ( 6 ) 1334 - 1343  2003年03月

     概要を見る

    An optically transparent hexagonal mesostructured tin oxide film with a microcrystalline framework was prepared by combining dipcoating and a subsequent treatment with water vapor. After a substrate was coated with an alcoholic precursor solution containing tin tetrachloride and nonionic surfactant, the substrate was subject to a process to form a highly ordered mesostructured film on the substrate. Although the film after the simple drying process was opaque and showed only poor structural ordering, a short post-treatment with water vapor at low temperature significantly improved the transparency and the structural ordering of the film. It was proved that the longer low-temperature post-treatment induces the crystallization of the framework, preserving the ordered channel structure though vertical shrinkage of the periodic structure and degradation of the ordering were concomitantly observed. The post-treatment could not be replaced by the addition of water in the precursor solution. Though water was added to the system, the film was opaque and showed only poor structural ordering without the post-treatment. These results show that the present process cannot be a simple solvent evaporation process. It was shown that the formation of a lyotropic liquid-crystal phase induced by the exposure to water vapor before the completion of the condensation plays an essential role in the preparation process.

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  • Alignment control of a cyanine dye using a mesoporous silica film with uniaxially aligned mesochannels

    Ayumu Fukuoka, Hirokatsu Miyata, Kazuyuki Kuroda

    Chemical Communications   ( 2 ) 284 - 285  2003年

     概要を見る

    The feasibility of alignment control of low-molecular-weight guest species by controlling the orientation of mesochannels in a mesoporous silica host has been shown for the first time; spectroscopically anisotropic absorption behaviour of a cyanine dye was observed upon its incorporation into the mesochannels of a mesoporous silica film with uniaxially aligned porous structure, proving that the preferred alignment of the dye molecules was achieved on a macroscopic scale.

    DOI PubMed

  • Preparation of mesoporous silica films with fully aligned large mesochannels using nonionic surfactants

    Hirokatsu Miyata, Takashi Noma, Masatoshi Watanabe, Kazuyuki Kuroda

    Chemistry of Materials   14 ( 2 ) 766 - 772  2002年

     概要を見る

    Mesoporous silica films with uniaxially aligned large-sized mesochannels were prepared using nonionic alkyl poly(ethylene oxide) surfactants and a rubbing-treated polyimide coating. Although the increment of the pore size was small as long as conventional alkylammonium surfactants were used, the use of nonionic surfactants with poly(ethylene oxide) headgroups led to successful enlargement of the mesochannels. The directional distribution of the mesochannels in the films, which is estimated by in-plane X-ray diffraction, was very narrow and was comparable with that in the oriented mesostructured silica films prepared using hexadecyltrimethylammonium chloride as a templating agent. The distribution of the alignment direction of the mesochannels is nearly independent of the nature of the hydrophilic headgroup, but is slightly affected by the alkyl-chain length of the surfactants used. These results indicate that the alignment of the mesochannels is determined by the hydrophobic interactions between the oriented polymer chains of the rubbed polyimide and the surfactant tail groups.

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  • Film to fiber transformation of preferentially aligned mesostructured silica

    Hirokatsu Miyata, Kazuyuki Kuroda

    Advanced Materials   13 ( 8 ) 558 - 561  2001年04月

     概要を見る

    A new method for fabricating fibrous mesostructured silica on a glass substrate using rubbing-treated polyimide film is presented. By using this method, both continuous films and fibers with preferred mesochannel orientation can be formed. Self-supported fiber-like silica prepared by this method have smooth surfaces without branching or connecting.

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  • Characterization of the local layer structure of a narrow wall in a surface stabilized ferroelectric liquid crystal using synchrotron X-ray micro-diffraction

    Atsuo Iida, Takashi Noma, Hirokatsu Miyata

    Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers   40 ( 3 A ) 1345 - 1351  2001年03月

     概要を見る

    Synchrotron X-ray microbeam small angle diffraction experiments were carried out for the characterization of the local layer structure of the narrow wall of a zig-zag defect in a surface stabilized ferroelectric liquid crystal cell. A series of the rocking curve (ω) and the azimuthal (χ) intensity distribution profiles were measured as a function of the vertical position across the narrow wall. The local layer was deflected at the wall in the χ direction. For the inclined narrow wall making an angle of a few degrees to 10° with respect to the rubbing direction, the deflected layer bent in both ω and χ directions. At the narrow wall running parallel to the rubbing direction, the layer bent only in the ω direction. The local layer structure was discussed in relation to the surface anchoring effect and a uniformly bent layer structure was proposed to explain experimental results.

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  • X-ray micro diffraction study on mesostructured silica thin films

    Takashi Noma, Kazuhiro Takada, Hirokatsu Miyata, Atsuo Iida

    Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment   467-468 ( PART II ) 1021 - 1025  2001年

     概要を見る

    The local structure of highly ordered mesostructured silica films was investigated by using a synchrotron X-ray microbeam and a CCD X-ray detector. Two-dimensional X-ray diffraction patterns clearly showed the detailed arrangement of the mesostructures, in which the hexagonal mesochannels aligned uniaxially in the mesostructured silica films formed on a silica glass substrate with a rubbing-treated thin polyimide coating. The alignment direction was shown to be perpendicular to the rubbing direction. The grazing incidence condition revealed the structural anisotropy of the mesostructures, while normal incidence X-ray diffraction data indicated the in-plane structural uniformity of the films. Extra spots were observed in the diffraction patterns. This suggested that the X-ray beam reflected at the boundary of the mesostructured silica film and the substrate. © 2001 Elsevier Science B.V. All rights reserved.

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  • Formation of a continuous mesoporous silica film with fully aligned mesochannels on a glass substrate

    Hirokatsu Miyata, Kazuyuki Kuroda

    Chemistry of Materials   12 ( 1 ) 49 - 54  2000年

     概要を見る

    A continuous mesoporous silica film with uniaxially aligned hexagonal mesochannels was formed on a silica glass substrate using a rubbing-treated thin polyimide coating on the substrate. Polyimide which has a hexamethylene group per the repeating unit as a part of the main chain was used. The mesostructured silica film was grown on the polyimide-coated substrate through the hydrolysis of tetraethoxysilane under acidic conditions in the presence of hexadecyltrimethylammonium chloride. X-ray diffraction experiments show that the hexagonal mesochannels in the film run parallel to the substrate surface and are aligned normal to the rubbing direction with a very narrow distribution of ±6°. The hexagonal arrangement of the mesochannels over the whole film thickness was proved by cross-sectional transmission electron microscopy. This highly preferred alignment of the mesochannels is caused by strong interactions between the surfactant tail groups and the polymer chains.

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  • Alignment of mesostructured silica on a Langmuir-Blodgett film

    Hirokatsu Miyata, Kazuyuki Kuroda

    Advanced Materials   11 ( 17 ) 1448 - 1452  1999年12月

    DOI

  • Preferred alignment of mesochannels in a mesoporous silica film grown on a silicon (110) surface

    Hirokatsu Miyata, Kazuyuki Kuroda

    Journal of the American Chemical Society   121 ( 33 ) 7618 - 7624  1999年08月

     概要を見る

    It has been proved that surfactant-silicate supramolecular architecture formed on a silicon substrate is strongly affected by the crystal orientation of a silicon wafer, indicating the variation of the interactions between the surfactants and the silicon surfaces. The hexagonal mesoporous silica film with aligned mesochannels was grown on a (110) wafer, whereas the mesochannels were not aligned in the films grown on (100) and (111) wafers. The alignment direction of the mesochannels on the (110) wafer is parallel to the [001] direction. The Gaussian distribution of the alignment direction with a full width at half-maximum (fwhm) of 29°was shown by in-plane X-ray diffraction. The hexagonal packing of the mesochannels in the film is distorted. The strong anisotropy of the atomic arrangement of silicon on the (110) surface causes the preferential alignment of mesochannels.

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  • Direct observation of mesoporous silica by high resolution scanning electron microscopy

    Hirokatsu Miyata, Kazuyuki Kuroda

    Advanced Materials   11 ( 10 ) 857 - 860  1999年07月

    DOI

  • Alignment of mesoporous silica on a glass substrate by a rubbing method

    Hirokatsu Miyata, Kazuyuki Kuroda

    Chemistry of Materials   11 ( 6 ) 1609 - 1614  1999年

     概要を見る

    Alignment of hexagonal mesoporous silica particles was achieved by a simple rubbing method used for the alignment of liquid crystals on a very thin polyimide film coated on a silica glass substrate. Mesoporous silica was synthesized through the hydrolysis of tetraethoxysilane under acidic conditions in the presence of hexadecyltrimethylammonium chloride. The arrangement of the elongated particles was observed with their long axes parallel to the rubbing direction. The maximum aspect ratio of the particles reached ∼100. Both the elongation and alignment of the particles were not observed on the same substrate without the rubbing treatment. The hexagonal channel orientation was confirmed using in-plane X-ray diffraction and high-resolution scanning electron microscopy. The hexagonal mesoporous structure was retained over calcination in air and the adhesion of the particles onto the substrate was greatly improved. © 1999 American Chemical Society.

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  • Characterization of the local layer structure at a broad wall in a surface stabilized ferroelectric liquid crystal during electric field application using synchrotron X-ray microdiffraction

    Atsuo Iida, Takashi Noma, Hirokatsu Miyata

    Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers   38 ( 5 A ) 2845 - 2850  1999年

     概要を見る

    The local layer structure response to the electric field was characterized at and around the broad wall of a zig-zag defect in a surface stabilized ferroelectric liquid crystal cell by a synchrotron X-ray microbeam. The rocking curves were measured as a function of the applied voltage and the frequency. The broad peak appearing in the rocking curve at the broad wall changed into a single, sharp peak when the electric field was applied to the cell, while the rocking curve returned to the initial profile when the electric field was switched off. This observation suggests that the pseudo-bookshelf structure at the broad wall becomes the bookshelf structure with the application of electric field. The frequency dependence of the rocking curve profile indicates the relaxation time of the local layer response to the electric field. At a high electric field, a stripe texture comprised a pair of pseudo-bookshelf structures, each of which tilted in the opposite direction with respect to the rubbing direction, was generated from the broad wall. ©1999 Publication Board, Japanese Journal of Applied Physics.

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  • Characterization of the local layer structure of a broad wall in a surface stabilized ferroelectric liquid crystal using synchrotron X-ray micro-diffraction

    Atsuo Iida, Takashi Noma, Hirokatsu Miyata

    Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers   35 ( 1 A ) 160 - 167  1996年01月

     概要を見る

    The local layer structure of the broad wall of a zig-zag defect in a thin-surface stabilized ferroelectric liquid crystal cell was characterized using a synchrotron X-ray microbeam of less than 5 μm spatial resolution. By using a rocking curve measurement at the broad wall, multiple or broad peaks were observed between a pair of peaks due to a chevron structure. These new peaks are clear evidence of a modified pseudo-bookshelf structure at the wall. For 1.5 μm thick cells, a bookshelf layer is relatively flat, but is accompanied by small areas of inclined layer connecting the bookshelf and the chevron structures. For 10 μm thick cells, the pseudo-bookshelf structure bends or undulates both perpendicular and parallel to the rubbing direction. No appreciable change in the layer spacing was observed in the modified pseudo-bookshelf structure. The temperature dependence of the broad wall layer structure was also measured.

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  • Micro x-ray diffraction technique for analysis of the local layer structure in the ferroelectric liquid crystal

    A. Iida, T. Noma, H. Miyata, K. Hirano

    Review of Scientific Instruments   66 ( 2 ) 1373 - 1375  1995年

     概要を見る

    A hard x-ray microprobe has been developed for small-angle x-ray diffraction studies. The x-ray microprobe system consists of a multilayer monochromator in combination with x-ray focusing mirrors (Kirkpatrick-Baez type) and achieves both high spatial resolution (5×5 μm at the sample) and high angular resolution (about 0.6 and 0.2 mrad in horizontal and vertical directions, respectively). The local layer structure of the surface stabilized ferroelectric liquid crystals was determined, for the first time, directly with this arrangement. Advantages of x-ray microbeam topography are also discussed. © 1995 American Institute of Physics.

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  • Grazing Exit X-Ray Fluorescence Spectroscopy for Thin-Film Analysis

    Noma Takashi, Miyata Hirokatsu, Ino Shozo

    Jpn J Appl Phys   31 ( 7 ) L900 - L903  1992年07月

     概要を見る

    Under the grazing exit condition, X-ray fluorescence (XRF) experiments have been performed for metal thin films (Cu, Ni) on glass substrates. The XRF intensity was measured as a function of the exit angle for nearly normal X-ray incidence. The angular dependence of the grazing exit XRF intensity showed a sharp increase at the critical angle of Kα radiation for the metal film. A three-media model was used to calculate the angular dependence of the XRF intensity. The effects of the film thickness on the XRF intensity curve were also discussed. The applicability of the grazing exit XRF for thin-film analysis was clearly demonstrated.

    DOI CiNii

  • Synthesis of methylviologen-HTiNbO<inf>5</inf> intercalation compound and its photochemical behavior

    Teruyuki Nakato, Hirokatsu Miyata, Kazuyuki Kuroda, Chuzo Kato

    Reactivity of Solids   6 ( 2-3 ) 231 - 238  1988年12月

     概要を見る

    A novel intercalation compound composed of layered titanoniobic acid (HTiNbO5) and methylviologen was synthesized and its photochemical behavior was investigated. Although methylviologen could not be intercalated into the interlayer region of titanoniobic acid directly, the intercalation compound was obtained by guest exchange with the propylammonium-HTiNbO5 intercalation compound. When the viologen intercalated compound was irradiated by UV light under an N2 atmosphere or under a vacuum, the compound turned blue. Visible spectroscopy and ESR indicated the formation of viologen radical cations. The phenomenon was thought to be due to the electron transfer from the oxygen-deficient layered oxide to the viologen. The oxidation of the viologen radical cations did not occur under O2-free conditions; therefore the oxygen was responsible for the bleaching. © 1988.

    DOI

  • Synthesis of a viologen-tetratitanate intercalation compound and its photochemical behaviour

    Hirokatsu Miyata, Yoshiyuki Sugahara, Kazuyuki Kuroda, Chuzo Kato

    Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases   84 ( 8 ) 2677 - 2682  1988年

     概要を見る

    Methyl viologen has been intercalated into the interlayer space of layered tetratitanic acid by a method involving the displacement of guest molecules using an n-propylammonium tetratitanate intercalation compound. The viologen tetratitanate intercalation compound changed colour to blue when irradiated by a mercury lamp under vacuum conditions or a nitrogen atmosphere. The formation of radical cations was confirmed by visible and e.s.r. spectroscopy. The electron donor for the photoreduction is thought to originate from the tetratitanate layers. The colour was stable as long as the vacuum conditions were maintained, and fading did not occur rapidly even after the introduction of air, requiring > 1 h for the colour to fade completely. These results indicate remarkable stability of the viologen radical cations in this intercalation compound.

    DOI

  • Synthesis of montmorillonite-viologen intercalation compounds and their photochromic behaviour

    Hirokatsu Miyata, Yoshiyuki Sugahara, Kazuyuki Kuroda, Chuzo Kato

    Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases   83 ( 6 ) 1851 - 1858  1987年

     概要を見る

    The photochemical properties of four different viologen di-cations (V2+,1,1′-dipropyl-, 1,1′-diheptyl-, 1,1′-diphenylmethyl- and 1,1′-diphenylethyl-4,4′-bipyridinium di-cations) intercalated into the interlayer space of montmorillonite have been studied. The colour of the intercalation compounds which were co-intercalated by poly(vinyl pyrrolidone) (PVP) changed to blue when irradiated by a mercury lamp, showing the formation of the radical cations. Their characteristic absorptions appeared at ca. 610 and 400 nm in their visible spectra. Since the viologens were present in their cationic forms in the interlayer space it was thought that PVP acted as an electron donor for the photochemical reduction of the viologens. The intensity decay of the radical cations was very slow in comparison with the species in PVP matrices, indicating their remarkable stability.

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▼全件表示

Misc

  • Epitaxial growth of a surfactant-silica mesostructure on oriented polyimide films

    Hirokatsu Miyata

    Microporous and Mesoporous Materials   101 ( 1-2 SPEC. ISS. ) 296 - 302  2007年04月

    書評論文,書評,文献紹介等  

     概要を見る

    In this paper, I review our past works on macroscopic control of in-plane arrangement of mesopores in mesoporous silica films. Mesostructured silicas are grown epitaxially on polyimide coatings with surface anisotropy to provide silica films with fully controlled mesoporous structures over the whole of the substrate surface. The anisotropic polyimide coatings are formed by a mechanical rubbing post-treatment of isotropic polyimide coatings as well as by thermal imidation of a Langmuir-Blodgett (LB) film of the precursor polyamic acid. The chemical anisotropy of the polyimide underlayer is shown to be more important for the epitaxial growth than the morphological anisotropy. Not only the uniaxially aligned two-dimensional (2D) hexagonal mesostructure but also the single-crystalline three-dimensional (3D) hexagonal mesostructure, in which the in-plane arrangement of the spherical mesopores is entirely controlled, are formed on the anisotropic polyimide. The epitaxial growth takes place hydrothermally through heterogeneous nucleation and growth of mesostructured silica seeds on the anisotropic polymer surfaces. It is considered that the hydrophobic interactions between the anisotropic polymer chains and the alkyl chains of the surfactants cause the observed epitaxial growth. It is shown that, in contrast to the conventional epitaxial growth of crystals, the observed epitaxial growth of silica mesostructures does not require molecular-scaled size matching with the chemical structure of the underlying polyimide. © 2006 Elsevier Inc. All rights reserved.

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