論文
Li+ storage and transport in high-voltage spinel-type LiNi0.5Mn1.5O4 codoped with F− and Cu2+
Journal of Materials Chemistry A,11(2):838-848 2023
Author:Dae-wook Kim; Hiromasa Shiiba; Katsuya Teshima; Nobuyuki Zettsu
Abstract:Material design based on the F−/Cu2+-codoping into the spinel lattice of LiNi0.5Mn1.5O4 enable to attain high voltage durability and high reversible discharge capacity of >200 mA h g−1 at cut-off voltages of 4.8–2.0 V (vs. Li+/Li).
Passivating oxygen atoms in SiO through pre-treatment with Na- 2 CO (3) to increase its first cycle efficiency for lithium-ion batteries
ELECTROCHIMICA ACTA,404:139777 2022
Author:Tan, Tian; Lee, Pui-Kit; Zettsu, Nobuyuki; Teshima, Katsuya; Yu, Denis Y. W.;
Keywords:Lithium-ion battery; Silicon monoxide; first Coulombic efficiency; Pre-treatment; Reversibility;
(3-Aminopropyl)triethoxysilane as an Electrolyte Additive for Enhancing the Thermal Stability of Silicon Anode in Lithium-Ion Batteries
ACS APPLIED ENERGY MATERIALS 2022
Author:Tan, Tian; Lee, Pui-Kit; Mayeesha, Marium; Zettsu, Nobuyuki; Yu, Denis Y. W.;
Keywords:lithium-ion batteries; silicon anode; thermal stability; electrolyte additive; solid-electrolyte interphase;
Molecular gate effects observed in fluoroalkylsilane self-assembled monolayers grafted on LiNi0.5Mn1.5O4 cathodes: an application to efficient ion-exchange reactions
MATERIALS ADVANCES,2(16):5406-5414 2021(Aug.)
Author:Youn Charles-Blin; Hitomi Todoki; Nobuyuki Zettsu; Katsuya Teshima
Abstract:We demonstrated the role of fluoroalkylsilane (FAS) self-assembled monolayers in improving the high-voltage durability and C-rate capabilities of spinel LiNi0.5Mn1.5O4 (LNMO) cathodes. The influence of the cathode-electrolyte interface (CEI) layer formation was assessed and compared with various linear carbonates and fluoroethylenecarbon (FEC) additives using electrochemical impedance and X-ray photoemission spectroscopies. The densely grafted FAS monolayer provided a less resistive CEI with a nearly three times lower charge transfer resistance owing to the formation of lower amounts of Li2CO3 and LiPF6 salt degradation byproducts and the significant reduction of Mn dissolution by almost a third in full cells after cycling. Notably, high voltage stabilities dependent on non-cyclic carbonates were proportional to the depth of their HOMO-level positions. However, the addition of FEC drastically degraded the capacity retention in the FAS-grafted LNMO cathode systems during the cycles with the a thick CEI layer formation. This suggests that it was because of the enhancement of affinity, driven by the strong intermolecular interaction among fluorine-containing compounds. Furthermore, we found that the Li+ diffusion coefficient was larger than that for bare LNMO electrodes, which suggested significant changes in the kinetics of the Li+ exchange reaction (Li+ adsorption and diffusion processes) on the electrode/electrolyte associated with polarization mitigation. We believe that the grafted FAS layer plays a role as a molecular gate, and while blocking the diffusion of uncoordinated free-carbonate solvents to the electrode surface, it tends to preferentially permeate both solvated Li+ and counter PF6-, and partially permeate fluorine-substituted additives, which nearly eliminate the oxidation decomposition of free-carbonate solvents and promote an efficient Li+-exchange reaction.
Metastable oxysulfide surface formation on LiNi0.5Mn1.5O4 single crystal particles by carbothermal reaction with sulfur-doped heterocarbon nanoparticles: new insight into their structural and electrochemical characteristics, and their potential applications
JOURNAL OF MATERIALS CHEMISTRY A,8(42):22302-22314 2020(Nov.)
Author:Dae-Wook Kim; Nobuyuki Zettsu; Hiromasa Shiiba; Gabriel Sanchez-Santolino; Ryo Ishikawa; Yuichi Ikuhara; Katsuya Teshima
Abstract:Spinel LiNi0.5Mn1.5O4 (LNMO) and related compounds have attracted much attention as high voltage cathode material for lithium ion batteries. However, their strong Lewis basic characteristics shown at the surface promotes various side reactions in associating with the oxidative decomposition of the electrolyte, leading to significant capacity degradation with increasing cycle numbers. We proposed multi-anion surfaces (such as oxyfluoride) for the direct tuning of the electronic properties for the cathode surface. In this study, we report the synthesis of LNMO single crystals with an oxysulfide surface and characterization of their electrochemical properties. A carbothermal reaction at around 450 degrees C with sulfur-doped hydrocarbon (S-HC) nanoparticles as a solid-phase precursor made it possible to prepare the metastable oxysulfide surface without the excess-reduction of transition metals in the spinel frame. This systematic study, using experimental and theoretical approaches, revealed many new findings for understanding the oxysulfide surface effects. The incorporated S2- were preferentially occupied at O-24e-sites (P4(3)32), which are bonded with three transition metals containing single Ni2+ and double Mn4+, leading to mitigating the cation mixing of Li+/Ni2+ formed at the surface and reducing the surface energy of {100} faces, resulting in significant changes in the corresponding electric structures, large morphological changes and an increase of specific capacity, as well as significant cyclability enhancement. Furthermore, it was found that the S-3p orbital appeared newly at a higher level than the Ni-3d orbital, resulting in dramatic changes of their electrical properties, including the narrowing of band gap and lowering the overpotential for the redox reaction of Ni2+/Ni3+.
Effects of a solid electrolyte coating on the discharge kinetics of a LiCoO2 electrode: mechanism and potential applications
JOURNAL OF MATERIALS CHEMISTRY A,8(40):20979-20986 2020(Oct.)
Author:Youn Charles-Blin; Kazune Nemoto; Nobuyuki Zettsu; Katsuya Teshima
Abstract:The application of a Li+-conductive amorphous Li2B4O7 coating on a LiCoO2 electrode enhanced its discharge kinetics by increasing the local concentration of Li+ at the surface of LiCoO2 particles. The origin of internal resistance in Li+ intercalation steps was elucidated by electrochemical impedance spectroscopy (EIS)-based characterization of discharge kinetics for states of charges of 0, 50, and 100%, while the activation energies of intercalation steps were determined from EIS data collected at different temperatures (-10, 0, 20, and 40 degrees C). The activation energy of Li+ desolvation was smaller than that previously reported for bare LiCoO2 particles, which suggested that the significant changes in kinetics associated with polarization mitigation were due to the Li+ exchange reaction (Li+ adsorption and diffusion processes) on the surface of LiCoO2 particles. Finally, C-rate capability tests performed at -10 degrees C revealed that the capacity retention of the electrode comprising Li2B4O7-coated LiCoO2 particles exceeded that of the electrode comprising bare LiCoO2 particles (45% vs. 18%, respectively).
Highly stable lithium-ion battery anode with polyimide coating anchored onto micron-size silicon monoxide via self-assembled monolayer
JOURNAL OF POWER SOURCES,453 2020(Mar.)
Author:Tian Tan; Pui-Kit Lee; Nobuyuki Zettsu; Katsuya Teshima; Denis Y. W. Yu
Abstract:Silicon monoxide (SiO) with a high Li storage capacity is an attractive material for next-generation lithium-ion batteries. Though, micron-size SiO, which is easier to handle and manufacture, undergoes particle cracking during charge and discharge, leading to fast capacity fading. In this work, we design a robust coating system to accommodate the large volume change of the SiO particles using a self-assembled monolayer (SAM) to covalently bond the active material with a high-modulus polyimide (PI) coating. The SAM is essential as it enhances the adhesion between the particles and the coating, preventing the delamination of the PI coating. The SiO material with the coating demonstrates a stable capacity of 1310.7 mAh g(-1) under a current rate of 150 mA g(-1) for 100 cycles. The electrode is stable even for 300 cycles at a current rate of 1000 mA g(-1). Full cell test with LiFePO4 positive electrode also shows stable cycle performance with 86% capacity retention after 200 cycles.
Three-dimensional assembly of multiwalled carbon nanotubes for creating a robust electron-conducting network in silicon-carbon microsphere-based electrodes.
Scientific reports,10(1):2342-2342 2020(Feb. 11)
Author:Hyemin Kim; Dae-Wook Kim; Hitomi Todoki; Nobuyuki Zettsu; Katsuya Teshima
Abstract:We present a strategic approach to improve the cycle performance of a polymeric binder-free anode based on nano-Si@C microspheres by incorporating a multiwalled carbon nanotubes (MW-CNTs) network and performing carbodiimide-based condensation coupling to form a robust molecular-junction between MW-CNTs and nano-Si@C microspheres. Field-emission scanning electron microscopy reveals that one-dimensional MW-CNTs homogeneously wrapped the individual Si@C microspheres and they interwove through the intergranular nanospace. The incorporation of amide bonds at the junction primarily contributes to the stabilization and reinforcement of the hybrid electrodes. Their reversible capacity after 50 cycles with 0.5 A g-1 was significantly improved from 81 mAh·g-1 to 520 mAh·g-1. Such robustness associated with the supramolecularly assembled MW-CNTs is expected to facilitate electron conductivity and mass transfer kinetics, leading to enhanced electrochemical performance of the Si@C anode.
Effects of a solid electrolyte coating on the discharge kinetics of a LiCoO2 electrode: mechanism and potential applications
JOURNAL OF MATERIALS CHEMISTRY A,8(40):20979-20986 2020
Author:Charles-Blin, Youn; Nemoto, Kazune; Zettsu, Nobuyuki; Teshima, Katsuya;
Metastable oxysulfide surface formation on LiNi0.5Mn1.5O4 single crystal particles by carbothermal reaction with sulfur-doped heterocarbon nanoparticles: new insight into their structural and electrochemical characteristics, and their potential applications
JOURNAL OF MATERIALS CHEMISTRY A,8(42):22302-22314 2020
Author:Kim, Dae-Wook; Zettsu, Nobuyuki; Shiiba, Hiromasa; Sanchez-Santolino, Gabriel; Ishikawa, Ryo; Ikuhara, Yuichi; Teshima, Katsuya;
Three-dimensional assembly of multiwalled carbon nanotubes for creating a robust electron-conducting network in silicon-carbon microsphere-based electrodes
SCIENTIFIC REPORTS,10(1) 2020
Author:Kim, Hyemin; Kim, Dae-wook; Todoki, Hitomi; Zettsu, Nobuyuki; Teshima, Katsuya;
Highly stable lithium-ion battery anode with polyimide coating anchored onto micron-size silicon monoxide via self-assembled monolayer
JOURNAL OF POWER SOURCES,453 2020
Author:Tan, Tian; Lee, Pui-Kit; Zettsu, Nobuyuki; Teshima, Katsuya; Yu, Denis Y. W.;
Waterproof molecular monolayers stabilize 2D materials.
Proceedings of the National Academy of Sciences of the United States of America,116(42):20844-20849 2019(Oct. 15)
Author:Cong Su; Zongyou Yin; Qing-Bo Yan; Zegao Wang; Hongtao Lin; Lei Sun; Wenshuo Xu; Tetsuya Yamada; Xiang Ji; Nobuyuki Zettsu; Katsuya Teshima; Jamie H Warner; Mircea Dincă; Juejun Hu; Mingdong Dong; Gang Su; Jing Kong; Ju Li
Abstract:Two-dimensional van der Waals materials have rich and unique functional properties, but many are susceptible to corrosion under ambient conditions. Here we show that linear alkylamines n-C m H2m+1NH2, with m = 4 through 11, are highly effective in protecting the optoelectronic properties of these materials, such as black phosphorus (BP) and transition-metal dichalcogenides (TMDs: WS2, 1T'-MoTe2, WTe2, WSe2, TaS2, and NbSe2). As a representative example, n-hexylamine (m = 6) can be applied in the form of thin molecular monolayers on BP flakes with less than 2-nm thickness and can prolong BP's lifetime from a few hours to several weeks and even months in ambient environments. Characterizations combined with our theoretical analysis show that the thin monolayers selectively sift out water molecules, forming a drying layer to achieve the passivation of the protected 2D materials. The monolayer coating is also stable in air, H2 annealing, and organic solvents, but can be removed by certain organic acids.
Exclusive Growth of Low-Aspect Ratio, Polyhedral h-BN Crystals in Molten Li2CO3 as the Reactive Flux
CRYSTAL GROWTH & DESIGN,19(10):5720-5728 2019(Oct.)
Author:Tetsuya Yamada; Yuto Kamiya; Noriyuki Naruse; Nobuyuki Zettsu; Katsuya Teshima
Abstract:Hexagonal boron nitride (h-BN) exhibits a wide range of properties, including insulation and high thermal conduction. Despite these advantages, h-BN often forms with a plate-like morphology, with an aspect ratio much greater than 1, which gives ineffective thermal conduction at the particle interfaces. The problem arises because of the plate-like morphology that renders the crystal a high aspect ratio, much greater than 1, in its typical growth form. Herein, we used the flux method to grow and develop the morphology of h-BN crystals with a much smaller aspect ratio. After screening the flux and heating conditions, we found that crystals of h-BN grown in molten Li2CO3 had a new polyhedral structure that was over 3 mu m in size. These crystals had low aspect ratio (around 1), which was unusual, and nonequilibrium morphology. Crystallographic evaluation revealed that the polyhedral h-BN crystals were not single crystals but were polycrystals with oriented tablet-type single crystals. This unique morphology was further investigated by in situ thermal analyses of the phase transition, chemical reaction, and morphological change during the growth of h-BN in molten Li2CO3. Based on these results, we discuss the mechanism of the growth of the crystal and the role of the flux. Our observations could be explained based on the reactivity of the flux and its probable absorbed manner on h-BN, which is dependent on its crystal facets in the flux.
Exclusive Growth of Low-Aspect Ratio, Polyhedral h-BN Crystals in Molten Li2CO3 as the Reactive Flux
CRYSTAL GROWTH & DESIGN,19(10):5720-5728 2019(Oct.)
Author:Yamada, Tetsuya; Kamiya, Yuto; Naruse, Noriyuki; Zettsu, Nobuyuki; Teshima, Katsuya;
Three-dimensional SWCNT and MWCNT hybrid networks for extremely high-loading and high rate cathode materials
JOURNAL OF MATERIALS CHEMISTRY A,7(29):17412-17419 2019(Aug.)
Author:Dae-wook Kim; Nobuyuki Zettsu; Katsuya Teshima
Abstract:Extremely high-loading LiNi0.5Co0.2Mn0.3O2 (NCM523) cathode materials (up to 99.5 wt%) were achieved through self-organization of a three-dimensional network of multi-walled and single-walled CNT hybrids. The full cell using the NCM523 cathode/graphite without any conventionally used insulating binder exhibited superior C-rate capability (105 mA h g(-1) at 10C) and remarkably improved cycling stability (94% capacity after 300 cycles at 1C). The hybridization of a small amount of single-walled CNTs enabled a fast lithiation/delithiation reaction with less polarization and prevented intergranular cracking in both the individual NCM523 secondary particles and NCM523 electrodes during cycling.
Formation of silica nanolayer on titania surface by photocatalytic reaction
APPLIED CATALYSIS B-ENVIRONMENTAL,241:299-304 2019(Feb.)
Author:Hiromasa Nishikiori; Shingo Matsunaga; Moeko Iwasaki; Nobuyuki Zettsu; Mari Yamakawa; Ayaka Kikuchi; Tomohiko Yamakami; Katsuya Teshima
Abstract:Silica nanolayers were formed as adsorbents on anatase-type titania particles immersed in tetraethyl orthosilicate (TEOS) solutions during UV irradiation. The concentration of the basic OH groups on the titania surface increased during the UV irradiation. The basicity promoted hydrolysis and subsequent polymerization of the TEOS on the titania surface on which the silica layers were deposited. The titania particles loading a small amount of the thin silica layers exhibited a higher photocatalytic activity for organic molecule degradation and photofuel cell performance than the original titania. The silica-modified titania particles efficiently adsorbed, then degraded the molecules on the surface. Therefore, the photocatalyzed surface modification in this study was significantly useful to activate the titania surface.
Formation of silica nanolayer on titania surface by photocatalytic reaction
APPLIED CATALYSIS B-ENVIRONMENTAL,241:299-304 2019(Feb.)
Author:Nishikiori, Hiromasa; Matsunaga, Shingo; Iwasaki, Moeko; Zettsu, Nobuyuki; Yamakawa, Mari; Kikuchi, Ayaka; Yamakami, Tomohiko; Teshima, Katsuya;
Three-dimensional SWCNT and MWCNT hybrid networks for extremely high-loading and high rate cathode materials
JOURNAL OF MATERIALS CHEMISTRY A,7(29):17412-17419 2019
Author:Kim, Dae-wook; Zettsu, Nobuyuki; Teshima, Katsuya;
Waterproof molecular monolayers stabilize 2D materials
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA,116(42):20844-20849 2019
Author:Su, Cong; Yin, Zongyou; Yan, Qing-Bo; Wang, Zegao; Lin, Hongtao; Sun, Lei; Xu, Wenshuo; Yamada, Tetsuya; Ji, Xiang; Zettsu, Nobuyuki; Teshima, Katsuya; Warner, Jamie H.; Dinca, Mircea; Hu, Juejun; Dong, Mingdong; Su, Gang; Kong, Jing; Li, Ju;
Impact of trace extrinsic defect formation on the local symmetry transition in spinel LiNi0.5Mn1.5O4- systems and their electrochemical characteristics
JOURNAL OF MATERIALS CHEMISTRY A,6(45):22749-22757 2018(Dec.)
Author:Hiromasa Shiiba; Nobuyuki Zettsu; Satoru Kida; Dae-wook Kim; Katsuya Teshima
Abstract:Many fundamental studies have been conducted on the electrochemical and electronic structures in transition metal cation-substituted LiNi0.5Mn1.5O4 systems. These systems have potential use as 5 V-level high voltage cathode materials for lithium ion batteries, but there are only a few reports regarding the control of their symmetry transitions which contribute the electronic structures and Li+ transport efficiency. We address this solid chemistry and the corresponding electrochemical characteristics using both systematic experimental and theoretical approaches. Trace substitution of Cu2+ with Mn4+ (Cu-Mn) can promote the symmetry transition from Fd3m to P4(3)32 phase in oxygen-deficient LiNi0.5Mn1.5O4-. This behavior is detectable by Fourier-transform infrared and Raman spectroscopies but undetectable by X-ray diffraction, suggesting that the symmetry transition was localized in the space near the point of extrinsic defects Cu-Mn in the spinel framework. Notably, a very small amount of Cu2+ substitution not only affects the local atomic arrangement but also remarkably affects the macroscopic electrochemical redox responsiveness, including the inactivation of Mn3+/Mn4+ redox couples, suppression of Mn ion dissolution, and enhancing the C rate capability (increasing the electron conductivity, and reducing the activation barrier for lithium ion hopping along the most energetically preferable 8a-16c-8a route) and cyclability.
One-Dimensional Growth of Li2NiPO4F Single Crystals from Intermediate LiNiPO4 Crystal Surface Using KCl-KI Fluxes
CRYSTAL GROWTH & DESIGN,18(11):6777-6785 2018(Nov.)
Author:Tetsuya Yamada; Nobuyuki Zettsu; Hye-min Kim; Yuta Hagano; Nobuyuki Handa; Kunio Yubuta; Katsuya Teshima
Abstract:The shape of an inorganic material affects its luminescence, catalytic activity, surface energy, solubility, and conductivity, which are important properties of a functional inorganic material. Herein, we demonstrate the one-dimensional growth of Li2NiPO4F single crystals from a KCl-KI binary flux; these crystals are oriented along the b axis through the conversion of intermediate LiNiPO4. The crystal surface was assigned as {h0l} and included {100} and {001} as major faces. The formation mechanism and growth manner are discussed in terms of phase transitions and morphological changes. Since the LiNiPO4 surface was gradually converted into Li2NiPO4F by reacting with LiF, as evidenced from cross-sectional scanning electron microscopy observations, we speculate that the growth of one-dimensional crystals toward the exterior of LiNiPO4 was driven by the relaxation of compressive stresses formed on the surface as well as by the formation of a steep supersaturation gradient near the LiNiPO4 surface.
One-Dimensional Growth of Li2NiPO4F Single Crystals from Intermediate LiNiPO4 Crystal Surface Using KCl-KI Fluxes
CRYSTAL GROWTH & DESIGN,18(11):6777-6785 2018(Nov.)
Author:Yamada, Tetsuya; Zettsu, Nobuyuki; Kim, Hye-min; Hagano, Yuta; Handa, Nobuyuki; Yubuta, Kunio; Teshima, Katsuya;
Molecular Dynamics Studies on the Lithium Ion Conduction Behaviors Depending on Tilted Grain Boundaries with Various Symmetries in Garnet-Type Li7La3Zr2O12
JOURNAL OF PHYSICAL CHEMISTRY C,122(38):21755-21762 2018(Sep.)
Author:Hiromasa Shiiba; Nobuyuki Zettsu; Miho Yamashita; Hitoshi Onodera; Randy Jalem; Masanobu Nakayama; Katsuya Teshima
Abstract:Grain boundary (GB) structure is a critical parameter that significantly affects the macroscopic properties of materials; however, the evaluation of GB characteristics by modern analytical methods remains an extremely challenging task. In this work, Li+ conductivity degradation at the GBs of cubic Li7La3Zr2O12 (LLZO) with a garnet framework (which represents the most promising candidate material for solid electrolytes utilized in all-solid-state batteries) has been investigated by various molecular dynamics approaches combined with newly developed analytical techniques. It was found that the transboundary diffusion of Li ions was generally slower than their diffusion in the bulk regardless of the GB symmetry; however, this effect strongly depended on the concentration of Li-deficient sites (trapping Li vacancies) in the GB layer. Furthermore, the compactness and density of the combined GB regions represent the key parameters affecting the overall Li+ conductivity of polycrystalline LLZO films.
New Insight for Surface Chemistries in Ultra-thin Self-assembled Monolayers Modified High-voltage Spinel Cathodes.
Scientific reports,8(1):11771-11771 2018(Aug. 06)
Author:Dae-Wook Kim; Shuhei Uchida; Hiromasa Shiiba; Nobuyuki Zettsu; Katsuya Teshima
Abstract:The electrochemical properties of the interface between the spinel LiNi0.5Mn1.5O4-δ (LNMO4-δ) cathodes and ethylene carbonate-dimethyl carbonate (EC-DMC) electrolyte containing 1 M of LiPF6 have been investigated to achieve high-voltage durability of LNMO4-δ/graphite full cells. Coating the LNMO4-δ crystal surface by a fluoroalkylsilane self-assembled monolayer with a thickness below 2 nm resulted in a capacity retention of 94% after 100 cycles at a rate of 1 C and suppression of capacity fading for both the cathode and anode of the full cell. The observed effect is likely caused by the inhibited oxidative decomposition of EC-DMC electrolyte and vinylene carbonate (VC) species at the LNMO4-δ crystal surface and formation of a stable VC solid electrolyte interface near the anode. Moreover, the results obtained via photoelectron spectroscopy and density-functional calculations revealed that the increase in the work function of the LNMO4-δ crystal surface due to the formation of Si-O-Mn species primary contributed to the inhibition of the oxidative decomposition of the electrolyte and VC molecules at the cathode/electrolyte interface.
Flux-Mediated Topochemical Growth of Platelet-Shaped Perovskite LiNbO3 Single Crystals from Layered Potassium Niobate Crystals
CRYSTAL GROWTH & DESIGN,18(7):4111-4116 2018(Jul.)
Author:Dae-wook Kim; Tomohito Sudare; Takumi Nakanishi; Satoshi Yuasa; Kunio Yubuta; Nobuyuki Zettsu; Katsuya Teshima
Abstract:Well-defined, platelet-shaped LiNbO3 single crystals were prepared by a flux-mediated topochemical reaction from platelet K4Nb6O17 crystals with a mixture of LiNO3 solute and alkali metal nitrate (LiNO3, NaNO3, and KNO3) fluxes at 600 degrees C. Crystallographic structural characterizations revealed that the LiNbO3 crystals inherited the K4Nb6O17 crystal shape with well-developed {012} faces. The topochemical reaction in molten KNO3 promoted smooth surface formation, in contrast to LiNO3 and NaNO3, which formed rough surfaces. We further found that the dissolution and deposition reaction occurs repeatedly in the vicinity of the LiNbO3 crystal and KNO3 flux interface. It is considered that the KNO3 flux hybridized with the LiNO3 solute provides a moderate solubility and dissolution rate suitable for crystal growth. We also achieved reed-shaped LiNbO3 crystal growth by applying the same technique to the KNb3O8 crystal template.
Thin and Dense Solid-solid Heterojunction Formation Promoted by Crystal Growth in Flux on a Substrate
SCIENTIFIC REPORTS,8 2018(Jan.)
Author:Nobuyuki Zettsu; Hiromasa Shiiba; Hitoshi Onodera; Kazune Nemoto; Takeshi Kimijima; Kunio Yubuta; Masanobu Nakayama; Katsuya Teshima
Abstract:In this work, we demonstrate the direct growth of cubic Li5La3Nb2O12 crystal layer on the LiCoO2 substrate through the conversion of ultra-thin Nb substrate in molten LiOH flux. The initial thickness of the Nb layer determines that of the crystal layer. SEM and TEM observations reveal that the surface is densely covered with well-defined polyhedral crystals. Each crystal is connected to neighboring ones through the formation of tilted grain boundaries with Sigma 3 (2-1-1) = (1-21) symmetry which show small degradation in lithium ion conductivity comparing to that of bulk. Furthermore, the sub-phase formation at the interface is naturally mitigated during the growth since the formation of Nb2O5 thin film limits the whole reaction kinetics. Using the newly developed stacking approach for stacking solid electrolyte layer on the electrode layer, the grown crystal layer could be an ideal ceramic separator with a dense thin-interface for all-solid-state batteries.
Molecular Dynamics Studies on the Lithium Ion Conduction Behaviors Depending on Tilted Grain Boundaries with Various Symmetries in Garnet-Type Li7La3Zr2O12
JOURNAL OF PHYSICAL CHEMISTRY C,122(38):21755-21762 2018
Author:Shiiba, Hiromasa; Zettsu, Nobuyuki; Yamashita, Miho; Onodera, Hitoshi; Jalem, Randy; Nakayama, Masanobu; Teshima, Katsuya;
Impact of trace extrinsic defect formation on the local symmetry transition in spinel LiNi0.5Mn1.5O4- systems and their electrochemical characteristics
JOURNAL OF MATERIALS CHEMISTRY A,6(45):22749-22757 2018
Author:Shiiba, Hiromasa; Zettsu, Nobuyuki; Kida, Satoru; Kim, Dae-wook; Teshima, Katsuya;
Crystal growth of titania by photocatalytic reaction
APPLIED CATALYSIS B-ENVIRONMENTAL,217:241-246 2017(Nov.)
Author:Hiromasa Nishikiori; Shunpei Fujiwara; Syuhei Miyagawa; Nobuyuki Zettsu; Katsuya Teshima
Abstract:Substrate plates coated with anatase-type titania thin films were immersed in a solution of titanium (IV) chloride and lithium nitrate at 353 K during UV irradiation. About 20 nm-sized anatase-type titania crystals were formed on the original titania film consisting of almost the same sized particles. Nitrate ions in the solution were reduced to nitrite ions, and water was transformed into hydroxide ions by a photocatalytic reaction on the original titania film. The pH value increased on the titania surface, which caused the titanium hydroxide formation. The titanium hydroxide was then dehydrated and transformed into titania. The titania particles formed on the substrate exhibited a photocatalytic activity similar to the original titania. (C) 2017 Elsevier B.V. All rights reserved.
Three-dimensional electric micro-grid networks for high-energy-density lithium-ion battery cathodes
JOURNAL OF MATERIALS CHEMISTRY A,5(43):22797-22804 2017(Nov.)
Author:Dae-wook Kim; Nobuyuki Zettsu; Katsuya Teshima
Abstract:High-energy-density LiNi0.5Co0.2Mn0.3O2 (NCM523) cathodes are prepared by the reduction of carbon additive loading based on the self-organization of water-soluble multiwalled carbon nanotubes (MW-CNTs) into MW-CNT/NCM523 supramolecular assemblies. Field emission scanning electron microscopy reveals that the MW-CNTs homogeneously included NCM523 particles and formed a grid structure that bridges the NCM523 particles. These structural characteristics are quite different from those of conventional composite electrode systems in lithium-ion secondary batteries. The supramolecular assemblies enable the increase of the NCM523 particle concentration (up to 98 wt%) and tap density (up to 3.8 g cm(-3)), and eliminate the need for a binder. A higher C-rate capability and cyclability are achieved by improving the kinetic parameters of the composite electrode for the battery reactions. In particular, the maximum average discharge capacity based on the total mass of the composite is 171 mA h g(-1) in the MW-CNT/NCM523 (98 wt%) composite electrode within the cut-off voltage range of 2.5-4.3 V (vs. Li+/Li), which is much higher than those of conventional acetylene black systems (157 mA h g(-1)).
Intrinsic electrochemical characteristics of one LiNi0.5Mn1.5O4 spinel particle
JOURNAL OF ELECTROANALYTICAL CHEMISTRY,799:468-472 2017(Aug.)
Author:Kei Nishikawa; Nobuyuki Zettsu; Katsuya Teshima; Kiyoshi Kanamura
Abstract:A precise understanding of the intrinsic electrochemical characteristics of electrode active materials is significant for designing next-generation Li-ion batteries (LIBs). Spinel phase LiNi0.5M1.5O4 (LNMO) is a promising cathode material, because of its high operation voltage (similar to 4.7 V vs. Li+/Li). We demonstrate that the electrochemical characteristics of an LNMO particle electrode, without any interference additives, may be probed by the single particle measurement technique. This technique provides explicit evidence that single spherical LNMO particles with diameters of 10-20 mu m are reliably rechargeable, exhibit high discharge rate capability, and produce an exchange current density of similar to 0.2 mA cm(-2) for the Ni4+/Ni2+ redox couple in the depth of discharge (DOD) range of 10-40%, based on quasi-Tafel analysis. This work effectively demonstrates the efficacy of using the single particle measurement technique to evaluate the intrinsic properties of 5 V class cathode materials.
Full picture discovery for mixed-fluorine anion effects on high-voltage spinel lithium nickel manganese oxide cathodes
NPG ASIA MATERIALS,9 2017(Jul.)
Author:Dae-wook Kim; Hiromasa Shiiba; Nobuyuki Zettsu; Tetsuya Yamada; Takeshi Kimijima; Gabriel Sanchez-Santolino; Ryo Ishikawa; Yuichi Ikuhara; Katsuya Teshima
Abstract:Small amounts of fluorine substituting for oxygen deficiencies could reduce Mn dissolution, enhancing the cyclability in spinel-type lithium nickel manganese oxides (LiNi0.5Mn1.5O4). Fluorine anion incorporation simultaneously enhances the C-rate capability and specific capacity fading. We used experimental and theoretical approaches to obtain a full picture of the mixed-anion effects for LiNi0.5Mn1.5O4-xFx cathode materials. The fluorine anion reduced the activation barrier for lithium-ion hopping along the most energetically preferable 8a-16c-8a route, enhancing the C-rate capability. Simultaneously, the coordination bond of the linear F--Mn3+-F- (Mn@2F diagonal) arrangement increased the oxidation potential to 5.1 V (vs Li+/Li). This hampered full extraction of Li+ from the spinel lattice, which was triggered by the oxidation of Mn3+ below the cutoff voltage (3.5-4.8 V (vs Li+/Li)), leading to a capacity loss.
Intrinsic Electrochemical Characteristics in the Individual Needle-like LiCoO2 Crystals Synthesized by Flux Growth
ELECTROCHEMISTRY,85(2):72-76 2017(Feb.)
Author:Kei Nishikawa; Nobuyuki Zettsu; Katsuya Teshima; Kiyoshi Kanamura
Abstract:The intrinsic electrochemical characteristics of needle-like LiCoO2 crystals with a hexagonal cylindrical shape were studied by the single particle measurement technique. The needle-like LiCoO2 crystals were synthesized by the flux growth method. Single-particle Raman spectroscopy and galvanostatic charge-discharge tests at different electrical contact points in one needle-like LiCoO2 crystal revealed that the crystal has homogeneous intercalation/deintercalation characteristics throughout the long axis. This suggests that the electron conductivity is high on a 100 pm scale along that axis and that lithium ions are efficiently transferred from the electrolyte to the layer structure of the crystal. The charge rate characteristics of the needle-like LiCoO2 crystals were also evaluated and compared to those of powdered LiCoO2. The polarization curve analysis indicates that the needle-like LiCoO2 particles had almost same exchange current density, i(0), as powdered LiCoO2, which has a much smaller volume. These excellent electrochemical characteristics are considered to be due to the orientation of the {104} crystal face on the crystal sides, which is the preferential face for lithium ion transfer, and the larger effective surface area of the particles. (C) The Electrochemical Society of Japan, All rights reserved.
Growth of idiomorphic LiMnPO4 crystals in molten NaCl-KCl and LiF-NaCl-KCl fluxes
CRYSTENGCOMM,19(1):93-98 2017(Jan.)
Author:Tetsuya Yamada; Nobuyuki Zettsu; Shota Nozaki; Katsuya Teshima
Abstract:Olivine-type idiomorphic polyhedral LiMnPO4 crystals grown from a molten LiF-NaCl-KCl ternary flux at 700 degrees C are found to be surrounded with well-defined facets of major {100}, {101}, and {210} faces with minor {011} faces. The average size of these crystals of similar to 20.7 mu m was around ten times larger than those grown from a molten NaCl-KCl binary flux. In situ XRD and TG-DTA measurements revealed that LiMnPO4 crystals grew from the melt during heating and holding at 700 degrees C with little assistance from the supersaturation produced by flux evaporation. Time-dependent scanning electron microscopy observation found that Ostwald ripening caused by repeated partial dissolution and reprecipitation of the LiMnPO4 crystals is the dominant factor in both the development of crystal facets and the mean diameter of individual crystals. The addition of LiF is therefore considered to promote the development of well-defined polyhedral crystals by increasing the solubility of LiMnPO4 in the molten flux.
テンプレートを導入したフラックス法による無機結晶の形状制御育成
日本結晶成長学会誌,44(2):88-95 2017
Author:山田 哲也; 鈴木 清香; 是津 信行; 手嶋 勝弥
Abstract: Shape controls of primary and secondary particles, which mean the design of crystals, including atomic building, shape control, particle connection, and crystal alignment, is one of dominant factors to determine functional abilities of materials, since the material performances do not only depend on chemical compositions and structures, but also crystallographic characteristics. For improvements of advanced materials use, development of innovative morphologic-control techniques should be an important issue. We have studied crystal growths by using flux method, which is liquid-phase growth technique, to provide high crystalline, unconventional shape of functional materials. As one of strategic application of flux method for shape control, we introduced template-mediated flux crystal growths, which exhibit unique shapes in terms of their primary and secondary appearances.
Sub-2 nm Thick Fluoroalkylsilane Self-Assembled Monolayer-Coated High Voltage Spinel Crystals as Promising Cathode Materials for Lithium Ion Batteries
SCIENTIFIC REPORTS,6 2016(Aug.)
Author:Nobuyuki Zettsu; Satoru Kida; Shuhei Uchida; Katsuya Teshima
Abstract:We demonstrate herein that an ultra-thin fluoroalkylsilane self-assembled monolayer coating can be used as a modifying agent at LiNi0.5Mn1.5O4-delta cathode/electrolyte interfaces in 5V-class lithium-ion batteries. Bare LiNi0.5Mn1.5O4-delta cathode showed substantial capacity fading, with capacity dropping to 79% of the original capacity after 100 cycles at a rate of 1C, which was entirely due to dissolution of Mn3+ from the spinel lattice via oxidative decomposition of the organic electrolyte. Capacity retention was improved to 97% on coating ultra-thin FAS17-SAM onto the LiNi0.5Mn1.5O4 cathode surface. Such surface protection with highly ordered fluoroalkyl chains insulated the cathode from direct contact with the organic electrolyte and led to increased tolerance to HF.
Effect of Side-Plane Width on Lithium-Ion Transportation in Additive-Free LiCoO2 Crystal Layer-Based Cathodes for Rechargeable Lithium-Ion Batteries
JOURNAL OF PHYSICAL CHEMISTRY C,120(33):18496-18502 2016(Aug.)
Author:Dae-wook Kim; Nobuyuki Zettsu; Yusuke Mizuno; Katsuya Teshima
Abstract:Rechargeable lithium-ion batteries (LIBs) with improved performance, including higher power, higher energy density, and superior cycling performance, are in demand for highly specialized applications. The design and synthesis of cathode materials with effective shapes surrounded by suitable faces for Li-ion transportation are essential for high-performance LIBs. In the present work, we address the effects of side-plane width on the Li-ion diffusion coefficient and charge transfer resistance of additive-free LiCoO2 electrodes composed of highly controlled crystals with exposed {101}, {012}, and {104} faces. The changes in the shape and order of orientation in the LiCoO2 crystals were evaluated using electron microscopic observations and X-ray diffraction measurements. The discharge capacity drastically increased from 87.9 to 131.5 mA.h.g(-1) on increasing the width of the side plane in the LiCoO2 crystal from ca. 11 to ca. 59 nm. Further, electrochemical impedance spectroscopy revealed that the Li-ion diffusion coefficient and charge transfer resistance of the electrodes were related to the dimensions of the exposed {101}, {012}, and {104} faces. Thus, increasing the crystal faces available for Li-ion transfer provides layer-based cathode materials with increased discharge capacities.
Surface Modification of Titanium Metal Plate Using Alkali Metal Chlorides
CHEMISTRY LETTERS,45(7):729-731 2016(Jul.)
Author:Hiromasa Nishikiori; Tetsuya Akaozeki; Taisuke Hizumi; Nobuyuki Zettsu; Katsuya Teshima
Abstract:A titanium metal surface was heated with an alkali metal chloride in order to produce a phase transition from amorphous titania to crystalline titania. The anatase-type titania phase was formed by heating the surface with KCl at 550 degrees C for 3 h. Further heating and higher temperatures caused a transition to the rutile-type titania. The amorphous titania layer on the surface of the titanium metal was reduced with the assistance of alkali metal chloride and reoxidized to transform into the metastable anatasetype titania phase under certain conditions.
Formation of high electrical-resistivity thin surface layer on carbonyl-iron powder (CIP) and thermal stability of nanocrystalline structure and vortex magnetic structure of CIP
AIP ADVANCES,6(5) 2016(May)
Author:K. Sugimura; Y. Miyajima; M. Sonehara; T. Sato; F. Hayashi; N. Zettsu; K. Teshima; H. Mizusaki
Abstract:This study focuses on the carbonyl-iron powder (CIP) used in the metal composite bulk magnetic core for high-efficient/light-weight SiC/GaN power device MHz switching dc-dc converter, where the fine CIP with a mean diameter of 1.1 mu m is used to suppress the MHz band eddy current inside the CIP body. When applying the CIP to composite core together with the resin matrix, high electrical resistivity layer must be formed on the CIP-surface in order to suppress the overlapped eddy current between adjacent CIPs. In this study, tens nm thick silica (SiO2) was successfully deposited on the CIP-surface by using hydrolysis of TEOS (Si(OC2H5)(4)). Also tens nm thick oxidized layer of the CIP-surface was successfully formed by using CIP annealing in dry air. The SiC/GaN power device can operate at ambient temperature over 200 degree-C, and the composite magnetic core is required to operate at such ambient temperature. The as-made CIP had small coercivity below 800 A/m (10 Oe) due to its nanocrystalline-structure and had a single vortex magnetic structure. From the experimental results, both nanocrystalline and single vortex magnetic structure were maintained after heat-exposure of 250 degree-C, and the powder coercivity after same heat-exposure was nearly same as that of the as-made CIP. Therefore, the CIP with thermally stable nanocrystalline-structure and vortex magnetic state was considered to be heat-resistant magnetic powder used in the iron-based composite core for SiC/GaN power electronics. (C) 2016 Author(s).
Growth Manner of Octahedral-Shaped Li(Ni1/3Co1/3Mn1/3)O-2 Single Crystals in Molten Na2SO4
CRYSTAL GROWTH & DESIGN,16(5):2618-2623 2016(May)
Author:Takeshi Kimijima; Nobuyuki Zettsu; Katsuya Teshima
Abstract:The synthesis of shape-controlled crystals has been a highly attractive research topic in modern materials chemistry. In this work, the growth of Li(Ni1/3Co1/3Mn1/3)O-2 (NCM) crystals in molten sulfate or carbonate salts (flux) at 1000 degrees C was systematically studied under various conditions. In situ X-ray diffraction during the growth and thermogravimetry-differential thermal analysis revealed that the growth of NCM crystals in the flux was controlled by liquid-phase sintering according to the Ostwald ripening principle. We studied the effect of Na+ in the flux on the crystal shapes and found that Na+ was critical in forming octahedral crystals with well-developed facets. Single crystals with well-developed facets were obtained homogeneously from Na2SO4, while truncated polyhedral crystals of smaller size were obtained from Li2SO4. The shape-controlled NCM crystals showed discharge capacities approaching 160 mAh g(-1) in the operating voltage range of 2.8-4.4 V vs Li/Li+ under a low current density of 0.1 C, independent of flux composition. This suggests that the Lit and transition-metal ions in the individual NCM crystals were highly ordered into hexagonal arrangements belonging to the R (3) over barm space group, without cation mixing.
Growth of hollow-structured LiMn2O4 crystals starting from Mn metal in molten KCl through the microscale Kirkendall effect
CRYSTENGCOMM,18(12):2105-2111 2016
Author:N. Zettsu; T. Yoda; H. Onodera; N. Handa; H. Kondo; K. Teshima
Abstract:Hollow-structured LiMn2O4 crystals are grown in molten KCl (flux) for the first time via an oxidation reaction of metallic Mn followed by a lithiation reaction. Characterization of the formation process, which is achieved using thermogravimetric differential thermal analysis, X-ray diffraction, and scanning electron microscopy observation, reveals that the hollow structures are formed via a mechanism analogous to the microscale Kirkendall effect, which results from the difference between the solid-state diffusion rates of the core materials and the rate of O-2 diffusion through the shell at elevated temperatures occurring during oxidation. Interestingly, the development of well-defined crystal facets is observed on the surfaces of the LiMn2O4 crystals, implying that the crystal growth is driven by supersaturation in the same manner as the flux growth. We also examine two possible approaches to reduce the volume of the inner space in the crystal: crystal growth under O-2 flow for enhancement of the O-2 diffusion and insertion of a Co and Ni layer between Mn and the substrate to induce the formation of the LiNi1/3Co1/3Mn1/3O2 phase.
High-voltage capabilities of ultra-thin Nb2O5 nanosheet coated LiNi1/3Co1/3Mn1/3O2 cathodes
RSC ADVANCES,6(72):67514-67519 2016
Author:S. Uchida; N. Zettsu; K. Hirata; K. Kami; K. Teshima
Abstract:In this study, we propose coating the surface of LiNi1/3Co1/3Mn1/3O2 (NCM) electrodes with 1.1 nm Nb2O5 nanosheets as a new way for enhancing their high-voltage capabilities in galvanostatic charge-discharge performances and long-term storage of the charged state at 60 degrees C. The coatings suppress the oxidative decomposition of the electrolyte and the disordering of the layered structures on the NCM surface, which result in impedance growth. After 100 cycles at voltage ranges 4.6-2.8 V at 1 C rate, more than 70% of the initial discharge capacity was retained in the coated electrodes. In comparison, the discharge capacity completely faded in the bare NCM cathode. Furthermore, the nanosheet coatings stabilize the delithiated NCM lattice charged at 4.6 V and inhibit current generation based on the electrode reactions at 60 degrees C for 300 h.
Molybdate flux growth of idiomorphic Li(Ni1/3Co1/3Mn1/3)O-2 single crystals and characterization of their capabilities as cathode materials for lithium-ion batteries
JOURNAL OF MATERIALS CHEMISTRY A,4(19):7289-7296 2016
Author:T. Kimijima; N. Zettsu; K. Yubuta; K. Hirata; K. Kami; K. Teshima
Abstract:A Li2MoO4 flux enabled size-tunable idiomorphic Li(Ni1/3Co1/3Mn1/3)O-2 (NCM) crystal growth. The crystal size was controlled from 0.26 to 4.4 mm simply by changing the experimental conditions (i.e., solute concentration and reaction temperature). The obtained crystals individually dispersed in both water and N-methylpyrrolidone without unexpected agglomeration; however, Li deficiency and a thin amorphous-like layer formed on the NCM crystal surface during flux removal with water. We found that post-heattreatment with LiOH significantly improved the discharge capacity of NCM. Recovery of the surface quality of the NCM crystals was primarily responsible for the capacity improvement. The electrodes achieved a high capacity of 81 mA h g(-1) under a high current density of 2000 mA g(-1), while the electrodes prepared from commercially available NCM showed a maximum of 65 mA h g(-1). The rate and cycle performance of the flux-grown NCM crystals was highly dependent on the crystal size. Smaller crystals showed excellent discharge capacities at high C rates, whereas larger crystals showed better cycle performances.
Phase-selective hydrothermal synthesis of hydrous lithium titanates nanoparticles as a precursor to Li4Ti5O12 anode material for lithium ion rechargeable batteries
CERAMICS INTERNATIONAL,41(9):10988-10994 2015(Nov.)
Author:Takeshi Kimijima; Kiyoshi Kanie; Yusuke Tsujikawa; Masafumi Nakaya; Nobuyuki Zettsu; Katsuya Teshima; Atsushi Muramatsu
Abstract:The phase-selective synthesis of (Li1.81H0.19)Ti2O5 center dot 2H(2)O flakes and homogenous LiTiO2 spheres has been achieved by means of a hydrothermal method using a titanium triethanolamine complex. Compared with other Ti sources this offers the advantage of being more stable in water, though the crystal phases obtained depend on the growth conditions used, such as the initial Li/Ti ratio and aging time. The Ti2O5 center dot 2H(2)O flakes were obtained through aging at 250 degrees C for 3 h from an initial Li/Ti ratio of 1.0 and exhibited a large surface area of 135 m(2) g(-1). Subsequent heat treatment of these flakes yielded Li4Ti5O12 nanoparticles with an even larger surface area (141 m(2) g(-1)) and a discharge capacity of 164 mA h g(-1), making them suited for use as an active material in lithium-ion rechargeable batteries. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Unique Growth Manner of Li5La3Ta2O12 Crystals from Lithium Hydroxide Flux at Low Temperature
CRYSTAL GROWTH & DESIGN,15(10):4863-4868 2015(Oct.)
Author:Xiong Xiao; Hajime Wagata; Fumitaka Hayashi; Hitoshi Onodera; Kunio Yubuta; Nobuyuki Zettsu; Shuji Oishi; Katsuya Teshima
Abstract:Garnet-type Li(5+x)Ln(3)M(2-y)(IV)M(y)(V)O(12+z) (x, y = 0-2, z = 0-1; Ln = La, Pr, Nd; M = Ta, Zr, Nb) compounds are promising Li-ion conducting solid electrolytes, but their growth manner is still unclear. Herein, the analysis of the low-temperature growth of idiomorphic Li5La3Ta2O12 single crystals as a function of holding temperature and time, cooling rate, flux type, and solute concentration revealed a unique growth manner. Li5La3Ta2O12 crystals were grown at 500 degrees C from LiOH flux and transformed into Li7La3Ta2O13 at 700 degrees C. The pseudo-perovskite-type LiLa2TaO6 phase, initially formed during the holding at 500 degrees C, was efficiently transformed into the Li5La3Ta2O12 phase with increasing holding time. The growth of Li5La3Ta2O12 single crystals was independent of the cooling rate but was affected by the kind of flux and solute concentration. A low solute concentration (1 or 5 mol %) was the key to obtain well-dispersed and idiomorphic single crystals. The optimum growth conditions involved a holding temperature of 500 degrees C, a solute concentration of 1 or 5 mol %, and a holding time of 10 h. These findings indicate that formation and growth of Li5La3Ta2O12 single crystals are not only controlled by a general flux growth process but also involve chemical reactions between solutes and LiOH flux. Finally, high-resolution transmission electron microscopy image and selected area diffraction pattern highlighted products with high crystallinity and well-developed {110} and {211} facets.
Growth of Individual, Highly Oriented LiFePO4 Crystals on a SUS Substrate Using NaCI-KCI Flux Coating
CRYSTAL GROWTH & DESIGN,15(8):3922-3928 2015(Aug.)
Author:Tetsuya Yamada; Nobuyuki Zettsu; Nobuyuki Handa; Shuji Oishi; Katsuya Teshima
Abstract:Olivine-type LiFePO4 has been, an interesting material in the development of catalysts and lithium-ion rechargeable batteries. In this study, we propose a new method for,growing thin films of LiFePO4 crystals directly on SUS substrates using flint coating; Molten NaCI-KCI flux promoted the formation of individual LiFePO4 crystals with well-defined facets surrounded by {100}, {110}, and {201} faces and highly oriented along the [100] direction. The LiFePO4 crystals attached tightly to the SUS substrate, implying that crystal growth began directly at the SUS surface via heterogeneous nucleation, driven by supersaturation in the NaCI-KCI flux. We further demonstrated:the formation of LiPePO(4) crystal films using an infrared light heating furnace system, which reduced the fabrication time from several hours to less than 30 min. Rapid heating and cooling effectively suppressed the corrosion of the SUS substrate caused by the NaCl-KCI flux.
Defect Formation Energy in Spinel LiNi0.5Mn1.5O4-delta Using Ab Initio DFT Calculations
JOURNAL OF PHYSICAL CHEMISTRY C,119(17):9117-9124 2015(Apr.)
Author:Hiromasa Shiiba; Nobuyuki Zettsu; Masanobu Nakayama; Shuji Oishi; Katsuya Teshima
Abstract:Defect formation energies based on an oxygen vacancy model and a metal-excess model in Ni/Mn ordered P4(3)32 and disordered Fd (3) over barm LiNi0.5Mn1.5O4 (LNMO) were evaluated by using ab initio density functional theory (DFT) calculations. The defect formation energy for the metal excess model was lower than that for the oxygen vacancy model in both P4(3)32 and Fd (3) over barm. This indicates that oxygen vacancy formation reactions are unlikely, although interstitial cation occupation at the octahedral vacancies occurred in both P4(3)32 and Fd (3) over barm LNMO spinel compounds. In addition, the corresponding defect formation energy in Fd (3) over barm was lower than that in P4(3)32, indicating that the amount of defects is sensitive to the cation ordering/disordering in the spinel framework. This agrees with the experimental results that show that only Fd (3) over barm tends to possess oxygen defects.
Chloride Flux Growth of La2Ti2O7 Crystals and Subsequent Nitridation To Form LaTiO2N Crystals
CRYSTAL GROWTH & DESIGN,15(1):124-128 2015(Jan.)
Author:Hajime Wagata; Nobuyuki Zettsu; Akiko Yamaguchi; Hiromasa Nishikiori; Kunio Yubuta; Shuji Oishi; Katsuya Teshima
Abstract:Highly crystalline, platelike La(2)Ti(2)O7 were grown from a NaCl flux, and LaTiO2N crystals were obtained by subsequent nitridation under NH3 flow. The TEM analysis indicated that the flux-grown platelike La2Ti2O7 crystals are single-crystalline growing along the a axis. The shapes and sizes of the LaTiO2N crystals were almost unchanged from the La2Ti2O7 precursor. In addition, LaTiO2N crystals remained single-crystalline with a porous nanostructure. The optical absorption edges of the La2Ti2O7 and LaTiO2N crystals were approximately 320 and 600 nm.
Flux growth of hexagonal cylindrical LiCoO2 crystals surrounded by Li-ion conducting preferential facets and their electrochemical properties studied by single-particle measurements
JOURNAL OF MATERIALS CHEMISTRY A,3(33):17016-17021 2015
Author:N. Zettsu; K. Nishikawa; K. Yubuta; K. Sakurai; Y. Yamamoto; Y. Mizuno; S. Oishi; K. Teshime
Abstract:In this study, we demonstrate the template-mediated flux growth of one-dimensional LiCoO2 single crystals surrounded by {104} faces in a hot solution of LiCl-KCl. The reaction and growth processes were characterized by time-dependent X-ray diffraction and scanning electron microscopy. The transformation in the crystal shape from rectangular to hexagonal cylindrical was considered to be directly related to the gradual lithiation of the starting CoO whiskers. Single particle galvanostatic tests of the single-strand LiCoO2 crystals were carried out. The LiCoO2 crystals exhibited excellent rate performance and more than 65% of the full capacity was maintained under ca. 370C. These characteristics likely resulted from the exposure of the {104} faces, since they were electrochemically active in layered LiCoO2 with an a-NaFeO2 structure and favored fast Li+ transportation. This finding will facilitate the development of new materials for advanced lithium ion rechargeable batteries.
Flux growth of patterned LiCoO2 crystal arrays directly on a Pt substrate in molten LiNO3
RSC ADVANCES,5(116):96002-96007 2015
Author:T. Yoda; N. Zettsu; H. Onodera; Y. Mizuno; H. Kondo; K. Teshima
Abstract:We demonstrate a new way to prepare hollow-structured LiCoO2 crystals directly on a Pt substrate for the first time through a combination of semi-additive electrodeposition of a Co core and subsequent flux growth in molten LiNO3. The reaction process was characterized by time-dependent X-ray diffraction and scanning electron microscopy. The vertically oriented crystals having a platelet shape grew densely on the Co dot surface. The crystal growth was driven by supersaturation in the same manner as the flux growth. Significantly slower oxidation of the Co core and rapid lithiation of Co3O4 lead to pore formation, which suggests that slow oxygen diffusion in the Co core is rate limiting. Galvanostatic tests revealed that the LiCoO2 crystal array exhibited typical capacity-voltage profiles with no heavy capacity loss during the first three cycles without any additives.
Low-temperature growth of idiomorphic cubic-phase Li7La3Zr2O12 crystals using LiOH flux
CRYSTENGCOMM,17(18):3487-3492 2015
Author:Takeshi Kimijima; Nobuyuki Zettsu; Hitoshi Onodera; Kunio Yubuta; Shuji Oishi; Katsuya Teshima
Abstract:Micrometer-sized Li7La3Zr2O12 crystals with well-developed facets were grown from a LiOH flux at 700 degrees C. Supersaturation-controlled crystallization driven by the cooling of a homogeneous hot solution with a Li/Zr ratio of 70 achieved one-step formation of cubic-phase Li7La3Zr2O12 that potentially exhibits high lithiumion conductivity. Excess LiOH flux decreased the reaction temperature dramatically to 700 degrees C, lower than that of solid-state-reaction processes. The flux growth of the Li7La3Zr2O12 crystals in response to varying reaction conditions was studied systematically and indicated that the initial Li/Zr ratio and the holding temperature significantly affected the crystal phase, shape, and size. We further demonstrated Li7La3Zr2O12 crystal growth at 500 degrees C, beginning with La2Zr2O7 powders that dissolve readily in hot LiOH. This will be examined in greater depth in the near future.
Direct Fabrication of Densely Packed Idiomorphic Li4Ti5O12 Crystal Layers on Substrates by Using a LiCI-NaCI Mixed Flux and Their Additive-Free Electrode Characteristics
CRYSTAL GROWTH & DESIGN,14(11):5634-5639 2014(Nov.)
Author:Nobuyuki Zettsu; Yusuke Mizuno; Hiroki Kojima; Kunio Yubuta; Takuya Sakaguchi; Toshiya Saito; Hajime Wagata; Shuji Oishi; Katsuya Teshima
Abstract:Thin layers of densely packed idiomorphic Li4Ti5O12 crystals were prepared directly on a Pt substrate by using a LiClNaCl mixed flux. The thin film of colloidal anatase nanoparticles with an similar to 30 nm diameter was fully converted into Li4Ti5O12 crystals with a diameter of 100-200 nm having polyhedral shapes with well-defined {111} faces during the evaporation-driven flux growth. Cross-sectional structure analysis revealed that the interface between the crystals and the substrate seemed to be atomically bonded. Galvanometric charge and discharge properties strongly supported our consideration of interface formation. The Li4Ti5O12 crystal layer exhibited a large capacity close to its theoretical value under 0.1C rate with no assistance from additional electroconductive materials and binders, meaning that the interfaces provide seamless charge transportation pathways. We also addressed the formation mechanism of the Li4Ti5O12 crystal layer accompanied by the experimental results of in situ X-ray diffraction, thermogravimetric and differential thermal analysis, and scanning electron microscopy observation.
Direct Fabrication of Densely Packed Idiomorphic Li4Ti5O12 Crystal Layers on Substrates by Using a LiCI-NaCI Mixed Flux and Their Additive-Free Electrode Characteristics
CRYSTAL GROWTH&DESIGN,14(11):5634-5639 2014(Nov.)
Author:Zettsu, Nobuyuki; Mizuno, Yusuke; Kojima, Hiroki; Yubuta, Kunio; Sakaguchi, Takuya; Saito, Toshiya; Wagata, Hajime; Oishi, Shuji; Teshima, Katsuya
Nature-mimetic flux innovation of functional inorganic crystals and layers for green energy & environmental materials
Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy,61(9):454-459 2014(Sep. 01)
Author:Katsuya Teshima; Nobuyuki Zettsu; Hajime Wagata; Shuji Oishi
Abstract:Functional devices for energy and environmental applications have been attracted increasing attention in recent decades. Those devices are usually composed of a bunch of sophisticated materials which are often prepared by complex fabrication processes. It is important to prepare high-quality materials and connect them with good interfaces which don't interrupt the diffusion of atoms and energy carriers by simple procedures. In this regards, our group has focused on growing high quality inorganic crystals by flux method. The advantages of flux method are growth of high-quality crystals without thermal strain, relatively low-temperature process, and simple experimental equipment. These advantages match with crystal growth not only in lab scale but also to industrial scale. In fact, we have grown many inorganic crystals for energy and environmental applications, and some of them are being tried to scaling up for industrial production. Our group has recently developed the flux method to thin film fabrication process which is named "flux coating method", and fabricated many crystal layers with good interfaces between crystals and substrates. In this report, we introduce the series of grown crystals and fabricated crystal layers in addition to their future applications.
次世代環境・エネルギー材料のための機能性無機結晶および薄膜のネイチャーミメティックフラックス創成 (特集 省エネルギー・低環境負荷プロセスによるナノマテリアル創製と機能開発)
粉体および粉末冶金 : 粉体粉末冶金協会誌,61(9):454-459 2014(Sep.)
Author:手嶋 勝弥,是津 信行,我田 元
TEM observation for low-temperature grown spinel-type LiMn2O4 crystals
ACTA CRYSTALLOGRAPHICA A-FOUNDATION AND ADVANCES,70:C749-C749 2014(Aug.)
Author:K. Yubuta; Y. Mizuno; N. Zettsu; S. Komine; K. Kami; H. Wagata; S. Oishi; K. Teshima
プラズマプロセスを援用した高密着性ポリテトラフルオロエチレン/エポキシ樹脂/SUS304界面形成技術
表面技術,65(5):227-233 2014(May)
Author:是津信行; 山村和也; 井筒祐志; 我田元; 大石修治; 手島勝弥
プラズマプロセスを援用した高接着性ポリテトラフルオロエチレン/エポキシ樹脂/SUS304界面形成技術
表面技術 = Journal of the Surface Finishing Society of Japan,65(5):227-233 2014(May)
Author:是津 信行,山村 和也,井筒 祐志
Coherent Diffraction Imaging Analysis of Shape-Controlled Nanoparticles with Focused Hard X-ray Free-Electron Laser Pulses (vol 13, pg 6028, 2013)
NANO LETTERS,14(4):2231-2231 2014(Apr.)
Author:Yukio Takahashi; Akihiro Suzuki; Nobuyuki Zettsu; Tomotaka Oroguchi; Yuki Takayama; Yuki Sekiguchi; Amane Kobayashi; Masaki Yamamoto; Masayoshi Nakasako
Fabrication of LiCoO2 Crystal Layers Using a Flux Method and Their Application for Additive-Free Lithium-Ion Rechargeable Battery Cathodes
CRYSTAL GROWTH & DESIGN,14(4):1882-1887 2014(Apr.)
Author:Yusuke Mizuno; Nobuyuki Zettsu; Kunio Yubuta; Takuya Sakaguchi; Toshiya Saito; Hajime Wagata; Shuji Oishi; Katsuya Teshima
Abstract:Higher performance active materials containing cathodes have been strongly required for the achievement of advanced lithium-ion rechargeable batteries. We report the formation of a densely packed and idiomorphic LiCoO2 crystal layer directly on a substrate surface using flux coating with a LiNO3-LiOH mixed flux and their applications as an additive-free cathode to enhance gravimetric energy density per single cell as well as durability. The formation mechanism of LiCoO2 nanocrystals from high temperature melt of the mixed flux was controlled under evolution selection growth, driven by supersaturation. The as-grown crystals formed a petal-shape with well-developed {001} faces. After annealing treatment, the crystal shape transformed into hexagonal plates with vertical orientation. The hexagonal plate-shaped crystal arrays were identified to be homogeneous LiCoO2 having a rhombohedral crystal system. Their lattice parameters were a = 0.2784 and c = 1.4248 nm, and the Li/Co ratio in the crystals was 1.00. Furthermore, transmission electron microscopic images and selected area electron diffraction patterns revealed that the interface between the crystal layer and the substrate was smoothly connected and free of impurities. In fact, the LiCoO2 nanoplate layer exhibited desirable properties such as a large discharge capacity close to its theoretical value, higher rate performance, and high cyclability over 500 cycles with no assistance of additional electroconductive materials and binders, meaning that the interfaces provide seamless charge transportation pathways.
Fabrication of LiCoO2 Crystal Layers Using a Flux Method and Their Application for Additive-Free Lithium-Ion Rechargeable Battery Cathodes
CRYSTAL GROWTH&DESIGN,14(4):1882-1887 2014(Apr.)
Author:Mizuno, Yusuke; Zettsu, Nobuyuki; Yubuta, Kunio; Sakaguchi, Takuya; Saito, Toshiya; Wagata, Hajime; Oishi, Shuji; Teshima, Katsuya
Coherent Diffraction Imaging Analysis of Shape-Controlled Nanoparticles with Focused Hard X-ray Free-Electron Laser Pulses (vol 13, pg 6028, 2013)
NANO LETTERS,14(4):2231-2231 2014(Apr.)
Author:Takahashi, Yukio; Suzuki, Akihiro; Zettsu, Nobuyuki; Oroguchi, Tomotaka; Takayama, Yuki; Sekiguchi, Yuki; Kobayashi, Amane; Yamamoto, Masaki; Nakasako, Masayoshi
高出力・高エネルギー密度リチウムイオン二次電池を実現する高品質結晶材料の創成 : フラックス結晶育成技術の可能性 (特集 二次電池用材料製造における技術的課題)
化学装置,56(3):54-57 2014(Mar.)
Author:手嶋 勝弥,是津 信行,水野 祐介
Low-temperature growth of spinel-type Li1+xMn2-xO4 crystals using a LiCl-KCl flux and their performance as a positive active material in lithium-ion rechargeable batteries
CRYSTENGCOMM,16(6):1157-1162 2014
Author:Yusuke Mizuno; Nobuyuki Zettsu; Hikaru Inagaki; Shigeki Komine; Kenichiro Kami; Kunio Yubuta; Hajime Wagata; Shuji Oishi; Katsuya Teshima
Abstract:Low-temperature growth of idiomorphic spinel-type Li1+xMn2-xO4 (x = 0.09, 0.14) crystals was achieved by using a LiCl-KCl flux. The flux growth driven by rapid cooling resulted in truncated octahedral Li1+xMn2-xO4 crystals surrounded by both dominating {111} and minor {100} faces. The chemical compositions, sizes, and shapes of the Li1+xMn2-xO4 crystals could be tuned by simply changing the growth conditions. Among the various products, the crystals grown at a low temperature of 600 degrees C showed a small average size of 0.2 mu m. The small Li1+xMn2-xO4 crystals grown at 600 degrees C showed better rate properties than the large crystals grown at 900 degrees C, when used as a positive active material in lithium-ion rechargeable batteries.
フラックスコーティング法による結晶相界面デザイン (特集 表面・界面のメゾスコピックサイエンス)
材料の科学と工学 : 日本材料科学会誌,51(4):126-129 2014
Author:手嶋 勝弥,是津 信行,我田 元
Low-temperature growth of spinel-type Li1+xMn2-xO4 crystals using a LiCl-KCl flux and their performance as a positive active material in lithium-ion rechargeable batteries
CRYSTENGCOMM,16(6):1157-1162 2014
Author:Mizuno, Yusuke; Zettsu, Nobuyuki; Inagaki, Hikaru; Komine, Shigeki; Kami, Kenichiro; Yubuta, Kunio; Wagata, Hajime; Oishi, Shuji; Teshima, Katsuya
Coherent Diffraction Imaging Analysis of Shape-Controlled Nanoparticles with Focused Hard X-ray Free-Electron Laser Pulses
NANO LETTERS,13(12):6028-6032 2013(Dec.)
Author:Takahashi, Yukio; Suzuki, Akihiro; Zettsu, Nobuyuki; Oroguchi, Tomotaka; Takayama, Yuki; Sekiguchi, Yuki; Kobayashi, Amane; Yamamoto, Masaki; Nakasako, Masayoshi
Fabrication of Combined One-Dimensional and Three-Dimensional Structure of Potassium Tungstate Crystal Layers by Spray Deposition with Polystyrene Colloidal Crystal Templates
CRYSTAL GROWTH & DESIGN,13(8):3294-3298 2013(Aug.)
Author:Hajime Wagata; Maki Fujisawa; Yusuke Mizuno; Nobuyuki Zettsu; Shuji Oishi; Katsuya Teshima
Abstract:Well-aligned honeycomb-designed layers of potassium tungstate (K0.33WO3.165) were successfully fabricated by spray deposition and microsphere lithography using polystyrene (PS) colloidal crystals as templates. A densely packed monolayer of monodisperse PS microspheres was formed on a silica glass surface, using the Langmuir-Blodgett thin film technique. Subsequently, a (NH4)(10)W12O41 center dot 5H(2)O-KCl aqueous solution was sprayed as a micromist on the PS templates. While the K0.33WO3.165 crystal layers were synthesized by chemical reaction between W and K sources during the heating, the PS templates were thermally decomposed, generating an inverse opal surface structure where the interstitial space of the densely hexagonal packed PS microspheres had been. Numerous hexagonal rodlike crystals were grown on the honeycomb-designed layer of K0.33WO3.165. X-ray diffraction analysis, energy-dispersive X-ray spectroscopy analyses, and X-ray photoelectron spectroscopy were performed to analyze the combined one-dimensional and three-dimensional honeycomb-designed structure.
Fabrication of Combined One-Dimensional and Three-Dimensional Structure of Potassium Tungstate Crystal Layers by Spray Deposition with Polystyrene Colloidal Crystal Templates
CRYSTAL GROWTH&DESIGN,13(8):3294-3298 2013(Aug.)
Author:Wagata, Hajime; Fujisawa, Maki; Mizuno, Yusuke; Zettsu, Nobuyuki; Oishi, Shuji; Teshima, Katsuya
Fundamental research on the label-free detection of protein adsorption using near-infrared light-responsive plasmonic metal nanoshell arrays with controlled nanogap.
Nanoscale research letters,8(1):274-274 2013(Jun. 07)
Author:Shuhei Uchida; Nobuyuki Zettsu; Katsuyoshi Endo; Kazuya Yamamura
Abstract:In this work, we focused on the label-free detection of simple protein binding using near-infrared light-responsive plasmonic nanoshell arrays with a controlled interparticle distance. The nanoshell arrays were fabricated by a combination of colloidal self-assembly and subsequent isotropic helium plasma etching under atmospheric pressure. The diameter, interparticle distance, and shape of nanoshells can be tuned with nanometric accuracy by changing the experimental conditions. The Au, Ag, and Cu nanoshell arrays, having a 240-nm diameter (inner, 200-nm polystyrene (PS) core; outer, 20-nm metal shell) and an 80-nm gap distance, exhibited a well-defined localized surface plasmon resonance (LSPR) peak at the near-infrared region. PS@Au nanoshell arrays showed a 55-nm red shift of the maximum LSPR wavelength of 885 nm after being exposed to a solution of bovine serum albumin (BSA) proteins for 18 h. On the other hand, in the case of Cu nanoshell arrays before/after incubation to the BSA solution, we found a 30-nm peak shifting. We could evaluate the difference in LSPR sensing performance by changing the metal materials.
Fundamental research on the label-free detection of protein adsorption using near-infrared light-responsive plasmonic metal nanoshell arrays with controlled nanogap
NANOSCALE RESEARCH LETTERS,8 2013(Jun. 07)
Author:Uchida, Shuhei; Zettsu, Nobuyuki; Endo, Katsuyoshi; Yamamura, Kazuya
Solution Plasma Sputtering Processes for the Synthesis of PtAu/C Catalysts for Li-Air Batteries
INTERNATIONAL JOURNAL OF ELECTROCHEMICAL SCIENCE,8(4):5407-5420 2013(Apr.)
Author:Chiaki Terashima; Yujiro Iwai; Sung-Pyo Cho; Tomonaga Ueno; Nobuyuki Zettsu; Nagahiro Saito; Osamu Takai
Abstract:Clean, nanosized PtAu/C catalysts were fabricated, using a simple one-step synthesis technique that involved sputtering discharge in liquid, and did not require the use of chemical species such as surfactants and/or reductants. This solution plasma sputtering was driven by a pulsed power supply, and was performed on the discharge between Pt and Au targets in a liquid dispersion of carbon black. Fine PtAu nanoparticles with an average diameter of 5.7 nm were uniformly deposited on the carbon support. The production and composition of the PtAu nanoparticles could be controlled via changes in the sputtering conditions. The Au-rich Pt19Au81/C (atomic %) catalysts provided higher specific capacity, even in carbonate-based electrolyte Li-air batteries, reducing the amount of Li2CO3 that was deposited on the bare carbon.
Solution Plasma Sputtering Processes for the Synthesis of PtAu/C Catalysts for Li-Air Batteries
INTERNATIONAL JOURNAL OF ELECTROCHEMICAL SCIENCE,8(4):5407-5420 2013(Apr.)
Author:Terashima, Chiaki; Iwai, Yujiro; Cho, Sung-Pyo; Ueno, Tomonaga; Zettsu, Nobuyuki; Saito, Nagahiro; Takai, Osamu
ソリューションプラズマにより作製したシリカの化学結合状態と形態
表面技術 = The journal of the Surface Finishing Society of Japan,64(3):180-184 2013(Mar. 01)
Author:山本 泰望,上野 智永,是津 信行,高井 治,齋藤 永宏
The adsorption mechanism of titanium-binding ferritin to amphoteric oxide.
Colloids and surfaces. B, Biointerfaces,102:435-40 2013(Feb. 01)
Author:Megumi Fukuta; Nobuyuki Zettsu; Ichiro Yamashita; Yukiharu Uraoka; Heiji Watanabe
Abstract:We investigated the origin of selective adsorption of titanium-binding ferritin (TBF), the outer surface of which is genetically modified with titanium-binding peptides (TBPs). By varying pH conditions (7-9), TBF adsorption behavior onto amphoteric and acidic oxide substrates was observed using atomic force microscopy, and the zeta potential of substrates was measured. This suggests that a TBP interacted with local charges such as -O(-), -OH(+), and -OH(2)(+) on substrates regardless of the constituent elements of the substrate, which makes it possible for TBF to adsorb on TiO(X), ZrO(2), Fe(2)O(3), and SiO(2) substrates despite the presence of an overall electrostatic repulsive force between TBF and the substrates. This also suggests that a surfactant, TWEEN20, can completely hamper attractive interaction between TBF and acidic oxide, but amphoteric oxide can withstand TWEEN20 interference.
The adsorption mechanism of titanium-binding ferritin to amphoteric oxide
COLLOIDS AND SURFACES B-BIOINTERFACES,102:435-440 2013(Feb. 01)
Author:Fukuta, Megumi; Zettsu, Nobuyuki; Yamashita, Ichiro; Uraoka, Yukiharu; Watanabe, Heiji
Coherent diffraction imaging analysis of shape-controlled nanoparticles with focused hard X-ray free-electron laser pulses.
Nano letters,13(12):6028-32 2013
Author:Yukio Takahashi; Akihiro Suzuki; Nobuyuki Zettsu; Tomotaka Oroguchi; Yuki Takayama; Yuki Sekiguchi; Amane Kobayashi; Masaki Yamamoto; Masayoshi Nakasako
Abstract:We report the first demonstration of the coherent diffraction imaging analysis of nanoparticles using focused hard X-ray free-electron laser pulses, allowing us to analyze the size distribution of particles as well as the electron density projection of individual particles. We measured 1000 single-shot coherent X-ray diffraction patterns of shape-controlled Ag nanocubes and Au/Ag nanoboxes and estimated the edge length from the speckle size of the coherent diffraction patterns. We then reconstructed the two-dimensional electron density projection with sub-10 nm resolution from selected coherent diffraction patterns. This method enables the simultaneous analysis of the size distribution of synthesized nanoparticles and the structures of particles at nanoscale resolution to address correlations between individual structures of components and the statistical properties in heterogeneous systems such as nanoparticles and cells.
Flux growth of Sr2Ta2O7 crystals and subsequent nitridation to form SrTaO2N crystals
CRYSTENGCOMM,15(40):8133-8138 2013
Author:Yusuke Mizuno; Hajime Wagata; Kunio Yubuta; Nobuyuki Zettsu; Shuji Oishi; Katsuya Teshima
Abstract:Highly crystalline, idiomorphic Sr2Ta2O7 and SrTaO2N crystals were successfully grown by a SrCl2 flux cooling method and followed by a nitriding treatment using NH3 gas, respectively. The flux-grown Sr2Ta2O7 crystals had a columnar structure with flat and well-developed {010}, {061}, and {150} faces. The lattice parameters of the Sr2Ta2O7 crystals were determined to be a = 0.398, b = 2.716, and c = 0.570 nm. The TEM images indicated that the flux-grown Sr2Ta2O7 crystals had a mature columnar structure with high crystallinity. The shapes and sizes of the SrTaO2N crystals were in good agreement with the original Sr2Ta2O7 crystals, and they consisted of numerous small crystals with approximate dimensions of 50 nm and high crystallinity. The lattice parameters of the SrTaO2N crystals were a = 0.570 and c = 0.809 nm. The optical absorption edges of the Sr2Ta2O7 and SrTaO2N crystals were approximately 275 and 600 nm, respectively, and the band gaps were estimated to be located at 4.5 and 2.1 eV, respectively.
ナノギャップ構造を有する金属ナノシェルアレイを用いた生体分子検出
精密工学会学術講演会講演論文集,2013:337-338 2013
Author:内田 修平; 是津 信行; 遠藤 勝義; 山村 和也
Abstract:ユビキタス社会実現のため、安心・安全・簡便な健康診断を可能とするセンシング手法の確立が希求されている。我々は金属ナノシェル構造において発現する局在型表面プラズモン共鳴現象に注目し、自己組織化現象を用いた大面積アレイ化を実現することでセンシングプレートの実現を目指している。ナノシェル材料の最適化をおこない、作製した金属ナノシェルアレイを用いた生体分子検出に取り組み、5fMの検出感度を達成した。
ナノギャップ構造を有する金属ナノシェルアレイを用いた生体分子検出
精密工学会学術講演会講演論文集,2013:337-338 2013
Author:内田 修平,是津 信行,遠藤 勝義,山村 和也
Flux growth of Sr2Ta2O7 crystals and subsequent nitridation to form SrTaO2N crystals
CRYSTENGCOMM,15(40):8133-8138 2013
Author:Mizuno, Yusuke; Wagata, Hajime; Yubuta, Kunio; Zettsu, Nobuyuki; Oishi, Shuji; Teshima, Katsuya
Nanometer-level self-aggregation and three-dimensional growth of copper nanoparticles under dielectric barrier discharge at atmospheric pressure
CURRENT APPLIED PHYSICS,12:S63-S68 2012(Dec.)
Author:Yuto Yamamoto; Hiroki Akiyama; Kento Ooka; Kazuya Yamamura; Yasushi Oshikane; Nobuyuki Zettsu
Abstract:We have recently demonstrated an approach to the surface activation of fluoropolymers, based on the plasma-induced decomposition and reduction of an organo-copper precursor. Although a surface densely and homogeneously seeded with copper nanoparticles enables the initiation of the autocatalytic electroless deposition of a copper layer at 40 degrees C with a time lag of less than 2 s, the formation mechanism of Cu nanoparticles under this plasma process is yet to be elucidated. Here we report some progress on this matter: scanning electron, and atomic force microscopic experiments revealed that the total population of Cu nanoparticles on the surface clearly decreased with time while the particles continued to grow. Furthermore, their growth behavior strongly depended on the plasma intensity. These results imply that the thermodynamically driven spontaneous migration of Cu atoms occurred from the initially formed smaller particles to the larger ones by the Ostwald ripening mechanism. (c) 2012 Elsevier B.V. All rights reserved.
Relationship between peroxide radical species on plasma-treated PFA surface and adhesion strength of PFA/electroless copper-plating film
CURRENT APPLIED PHYSICS,12:S38-S41 2012(Dec.)
Author:Yasuhiro Hara; Kento Ooka; Nobuyuki Zettsu; Kazuya Yamamura
Abstract:Surface metallization process for fluoropolymers with lower environmental impact was studied as a replacement for conventionally used sodium processing with a Pd catalyst. We demonstrated the surface modification of a fluoropolymer to enhance the adhesion of an electroless Cu layer on a poly(-tetrafluoroethylene-co-perfluoropropyl vinyl ether) (PFA) surface by combining atmospheric-pressure plasma modification and the grafting of a polymer film. This process allows a high-adhesion interface to be formed without degrading the surface roughness through the graft copolymerization of a poly (4-vinylpyridine) (P4VP) layer as a metal-ion-trapping layer on a PFA substrate. The effect of the plasma treatment time on the adhesion strength was systematically investigated. We found that the surface radical species on the plasma-treated PFA strongly affected the adhesion strength. We achieved a maximum adhesion strength of 0.44 N/mm through the selective formation of side-chain radicals on the PFA surface. It was confirmed that the plasma treatment combined with the plasma-grafting process can be used as an alternative to the conventional copper-plating process with a Pd catalyst. (c) 2012 Elsevier B.V. All rights reserved.
Relationship between peroxide radical species on plasma-treated PFA surface and adhesion strength of PFA/electroless copper-plating film
CURRENT APPLIED PHYSICS,12:S38-S41 2012(Dec.)
Author:Hara, Yasuhiro; Ooka, Kento; Zettsu, Nobuyuki; Yamamura, Kazuya
Nanometer-level self-aggregation and three-dimensional growth of copper nanoparticles under dielectric barrier discharge at atmospheric pressure
CURRENT APPLIED PHYSICS,12:S63-S68 2012(Dec.)
Author:Yamamoto, Yuto; Akiyama, Hiroki; Ooka, Kento; Yamamura, Kazuya; Oshikane, Yasushi; Zettsu, Nobuyuki
次世代自動車への開発戦略とそこに求められるマテリアルとは?
Material stage,12(8):1-3 2012(Nov.)
Author:是津 信行
自己組織化材料とバイオミメティック応用
材料の科学と工学 = Materials science and technology,49(4):157-161 2012(Aug. 20)
Author:上野 智永,是津 信行,石崎 貴裕,齋藤 永宏
Practical protein removal using atmospheric-pressure helium plasma for densely packed gold nanoparticle arrays assembled by ferritin-based encapsulation/transport system
APPLIED PHYSICS LETTERS,101(7) 2012(Aug. 13)
Author:Hashimoto, Tatsuya; Zettsu, Nobuyuki; Zheng, Bin; Fukuta, Megumi; Yamashita, Ichiro; Uraoka, Yukiharu; Watanabe, Heiji
Practical protein removal using atmospheric-pressure helium plasma for densely packed gold nanoparticle arrays assembled by ferritin-based encapsulation/transport system
APPLIED PHYSICS LETTERS,101(7) 2012(Aug.)
Author:Tatsuya Hashimoto; Nobuyuki Zettsu; Bin Zheng; Megumi Fukuta; Ichiro Yamashita; Yukiharu Uraoka; Heiji Watanabe
Abstract:We propose using atmospheric-pressure helium (AP He) plasma to efficiently remove the ferritin protein shells surrounding gold nanoparticles (GNPs). The high density GNPs assembled on a substrate by using a ferritin-based encapsulation/transport system were exposed to He radicals with a high internal energy to decompose their outer protein shells. In contrast to the conventional methods, AP-plasma treatment was found to suppress the aggregation of adjacent GNPs and produce densely packed and isolated GNP arrays. Consequently, we obtained an intense and sharp surface plasmon band from the plasma-treated GNP arrays. The clear response of their plasmonic behavior according to a refractive index of the surrounding media demonstrated that the proposed method had a significant advantage when fabricating GNP-based plasmonic devices. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4745508]
自己組織化材料とバイオミメティック応用
材料の科学と工学,49(4):157-161 2012(Aug.)
Author:上野 智永 , 是津 信行 , 石崎 貴裕 , 齋藤 永宏
ソリューションプラズマによるナノクラスター合成 (特集 大気圧プラズマと注目の応用)
オプトロニクス,31(6):94-97 2012(Jun.)
Author:上野 智永,是津 信行,齋藤 永宏
ソリューションプラズマによるナノクラスター合成
オプトロニクス,31(6):94-97 2012(Jun.)
Author:上野 智永 , 是津 信行 , 齋藤 永宏
Effect of Si interlayers on the magnetic and mechanical properties of Fe/Ge neutron polarizing multilayer mirrors
JOURNAL OF APPLIED PHYSICS,111(6) 2012(Mar. 15)
Author:Maruyama, R.; Yamazaki, D.; Okayasu, S.; Takeda, M.; Zettsu, N.; Nagano, M.; Yamamura, K.; Hayashida, H.; Soyama, K.
Effect of Si interlayers on the magnetic and mechanical properties of Fe/Ge neutron polarizing multilayer mirrors
JOURNAL OF APPLIED PHYSICS,111(6) 2012(Mar.)
Author:R. Maruyama; D. Yamazaki; S. Okayasu; M. Takeda; N. Zettsu; M. Nagano; K. Yamamura; H. Hayashida; K. Soyama
Abstract:The neutron polarizing supermirror is one of the most important optical devices for polarizing neutron beams. To meet a variety of research demands, neutron polarizing supermirrors need to display high polarization efficiencies at low external magnetic fields. Fe/Si and Fe/Ge multilayers are typically used in neutron polarizing supermirrors because the contrast in scattering length densities almost vanishes for spin-down neutrons. The Fe/Si/Ge/Si multilayer, obtained by adding thin interlayers of Si to an Fe/Ge multilayer, is effective in reducing the external field strength necessary to achieve efficient neutron polarization. To gain insight into the mechanism that controls the required external field strength for a neutron polarizing supermirror, we investigated the magnetic and mechanical properties of Fe/Si, Fe/Ge, and Fe/Si/Ge/Si multilayers. The external field strength required to achieve efficient neutron polarization was found to be proportional to the compressive film stress. The compressive stress of the Fe/Si/Ge/Si multilayer was smaller by a factor of 4.4 and 2.7 than that of Fe/Si and Fe/Ge multilayers, respectively. These measurements and analyses showed that a reduction in the compressive film stress in the Fe/Si/Ge/Si multilayer permits the use of lower external field strength to achieve efficient neutron polarization. X-ray photoelectron spectroscopic studies showed that the formation of a Ge-Si solid solution in the Ge layer may explain the marked reduction in compressive stress in the case of the Fe/Si/Ge/Si multilayer. This study confirmed that a reduction in compressive film stress is very important for a high-performance neutron polarizing supermirror. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3694001]
Synthesis of gold nanoparticles on petal-shaped silica by solution plasma
2011 Int. Symp. on Micro-NanoMechatronics and Human Science, Symp. on "COE for Education and Research of Micro-Nano Mechatronics", Symposium on "Hyper Bio Assembler for 3D Cellular System Innovation",:186-191 2012
Author:Taibou Yamamoto; Tomonaga Ueno; Nobuyuki Zettsu; Osamu Takai; Nagahiro Saito
Abstract:Spherical silica and gold nanoparticles were attempted to be prepared by solution plasma. The silica was prepared from the following solutions by solution plasma treatment. Those are (a) tetraethoxysilane, ethanol, water and hexadecylamine (TEOS-EtOH-H2O-HDA) system and (b) tetraethoxysilane, ethanol, water, hexade-cylamine and aurochloric acid (TEOS-EtOH-H2O-HDA-HAuCl4 ) system. In the system (a), the spherical silica was produced. While, in the system (b), gold nanoparticles supported petal-shaped silica were produced. These shapes differs from the one prepared from the conventional acid and base solutions stober method. © 2011 IEEE.
Fabrication of Precise Asymmetric Nanoshells Array with Nanogaps for A Label-Free Immunoassay Based on NIR-light Responsive LSPR
EMERGING TECHNOLOGY IN PRECISION ENGINEERING XIV,523-524:680-+ 2012
Author:Shuhei Uchida; Kazuya Yamamura; Nobuyuki Zettsu
Abstract:Localized surface plasmon resonance (LSPR) based sensors are a well established technology utilized for label-free biochemical sensing in immunoassay, medical diagnostics and environmental monitoring. The understanding of asymmetric metal nanoparticles, new object for complex, coupled plasmon systems providing localized significantly enhanced E-field, is central to a wide range of novel applications and processes in science of higher sensitive sensing systems. However, few methods are available for actual characterization of such nanostructures at the single particle level. Here we propose a precise and large sized scale fabrication technique for asymmetric nanoshells array with nanogaps of several tens of nanometers for LSPR sensor through atmospheric pressure plasma etching processes. A nanoshell was simply constructed by laminating thin Au films on periodic isolated polymer nanoparticles template. This nanoshells array was expected to exhibit specific near-infrared plasmonic properties. When measuring the sensitivity, nanoshells array exhibited a high sensitivity to changes of surrounding refractive index and showed a higher sensor figure of merit than the alternative structures. This indicated that the enhanced plasmon E-field in the asymmetric nanostructures improved sensor performance. Our fabrication technique and the optical properties of the arrays will provide useful information for developing new plasmonic applications.
Adhesion strength of electroless copper plated layer on fluoropolymer surface modified by medium pressure plasma
EMERGING TECHNOLOGY IN PRECISION ENGINEERING XIV,523-524:262-+ 2012
Author:Kento Ooka; Yuto Yamamoto; Yasuhiro Hara; Nobuyuki Zettsu; Kazuya Yamamura
Abstract:We demonstrated high adhesive fluoropolymer/copper interface through combination of atmospheric pressure plasma with liquid phase self-assembly. However, there are some disadvantages in atmospheric pressure plasma technique, such as small processing area due to the localized plasma and high gas temperature. Medium pressure plasma process has some advantages over atmospheric pressure plasma systems. A large plasma volume and low gas temperature, available for surface treatment of polymer material, can be easier obtained at medium pressure than at atmospheric pressure, which can result in a higher overall productivity. In this paper, we investigated the adhesion strength of electroless copper plated layer formed on poly(tetrafluoroethylene-co-perfluoropropyl vinyl ether) (PFA) surface modified by combination of medium pressure helium plasma irradiation and aminated acrylic polymer grafting. The 90 degrees peel test result for copper plating film formed on the treated PFA films showed the adhesion strength of 0.44 N/mm without increasing the surface roughness.
自己組織化材料とバイオミメティック応用 (特集 生物に学ぶ材料開発)
材料の科学と工学 : 日本材料科学会誌,49(4):157-161 2012
Author:上野 智永,是津 信行,石崎 貴裕
Control of selective adsorption behavior of Ti-binding ferritin on a SiO2 substrate by atomic-scale modulation of local surface charges
APPLIED PHYSICS LETTERS,99(26) 2011(Dec. 26)
Author:Hashimoto, Tatsuya; Gamo, Kentaro; Fukuta, Megumi; Zheng, Bin; Zettsu, Nobuyuki; Yamashita, Ichiro; Uraoka, Yukiharu; Watanabe, Heiji
Control of selective adsorption behavior of Ti-binding ferritin on a SiO2 substrate by atomic-scale modulation of local surface charges
APPLIED PHYSICS LETTERS,99(26) 2011(Dec.)
Author:Tatsuya Hashimoto; Kentaro Gamo; Megumi Fukuta; Bin Zheng; Nobuyuki Zettsu; Ichiro Yamashita; Yukiharu Uraoka; Heiji Watanabe
Abstract:We have systematically investigated the influence of local surface potential distribution on selective adsorption of Ti-binding ferritin (TBF) on SiO2 substrates. We found that the TBF exhibits the adsorption ability onto Ti-decorated SiO2 surface of less than one atomic layer coverage. This experimental finding enabled us to propose a model in which the positively charged sites and their nanometer-scale interval are the dominant factors that determine bond strength between TBF and SiO2 surfaces. Furthermore, on the basis of this model, the adsorption behavior of TBF onto bare SiO2 surfaces was controlled by generation and/or recovery of electrical defects in SiO2. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3672043]
Noncontact figuring of millimeter-thick elliptical mirror substrate by numerically controlled local wet etching
Abstracts of 4th International Conference of Asian Society for Precision Engineering and Nanotechnology, 72.,516:361-+ 2011(Nov.)
Author:M. Nagano; F. Yamaga; K. Yamasaki; N. Zettsu; D. Yamazaki; R. Maruyama; H. Hayashida; K. Soyama; K. Yamamura
Abstract:Aspherical supermirrors are some of the most useful neutron-focusing optics. We aim to develop multiple aspherical supermirror devices using high-precision figured aspherical focusing supermirrors to focus neutron beams with high intensities, because multiple mirrors collect a very large beam divergence. Thin mirrors with millimetre thickness are required to minimize the absorption loss of incident neutron beams since the thickness of a mirror shadows the reflective area of other mirrors. However, it is difficult to fabricate thin mirror substrates with a form accuracy at the sub-micrometre level by conventional machining. Conventional machining deforms a substrate by machining force and spring back after machining causes figure error. Furthermore the deposition of supermin-ors deforms the mirror substrate by film stress. Thus, we developed a new process of fabricating a precise millimetre-thick elliptical supermirror. This process consists of non-contact figuring by the numerically controlled local wet etching technique, the minimization of surface roughness without degrading form accuracy by low-pressure polishing with a polishing pressure less than about 7 kPa (lpsi), and the ion beam sputter deposition of NiC/Ti multilayers on both sides of the mirror substrate to compensate for film stress. In this paper, we report on the fabrication results of aplano-elliptical mirror substrate with a thickness of 1 mm.
Multiscale element mapping of buried structures by ptychographic x-ray diffraction microscopy using anomalous scattering
APPLIED PHYSICS LETTERS,99(13) 2011(Sep. 26)
Author:Takahashi, Yukio; Suzuki, Akihiro; Zettsu, Nobuyuki; Kohmura, Yoshiki; Yamauchi, Kazuto; Ishikawa, Tetsuya
プラズマ援用研磨による4H-SiC(0001)表面の高品位仕上げ加工
砥粒加工学会誌 = Journal of the Japan Society of Grinding Engineers,55(9):534-539 2011(Sep. 01)
Author:山村 和也,瀧口 達也,上田 真己,〓 輝,服部 梓,是津 信行
Multiscale element mapping of buried structures by ptychographic x-ray diffraction microscopy using anomalous scattering
APPLIED PHYSICS LETTERS,99(13) 2011(Sep.)
Author:Yukio Takahashi; Akihiro Suzuki; Nobuyuki Zettsu; Yoshiki Kohmura; Kazuto Yamauchi; Tetsuya Ishikawa
Abstract:We propose an element mapping technique of nano-meso-microscale structures buried within large and/or thick objects by ptychographic x-ray diffraction microscopy using anomalous scattering. We performed quantitative imagings of both the electron density and Au element of Au/Ag nanoparticles at the pixel resolution of better than 10 nm in a field of view larger than 5 x 5 mu m(2) by directly phasing ptychographic coherent diffraction patterns acquired at two x-ray energies below the Au L-3 edge. This method provides us with multiscale structural and elemental information for understanding the element/property relationship linking nanoscale structures to macroscopic functional properties in material and biological systems. (C) 2011 American Institute of Physics. [doi:10.1063/1.3644396]
Damage-Free Dry Polishing of 4H-SiC Combined with Atmospheric-Pressure Water Vapor Plasma Oxidation
JAPANESE JOURNAL OF APPLIED PHYSICS,50(8) 2011(Aug.)
Author:Hui Deng; Tatsuya Takiguchi; Masaki Ueda; Azusa N. Hattori; Nobuyuki Zettsu; Kazuya Yamamura
Abstract:A dry polishing technique combined with the atmospheric-pressure water vapor plasma oxidation has been proposed for the high-integrity smoothing of SiC materials. Optical emission spectra revealed the composition of the plasma, and strong emission from OH, which has a high oxidation-reduction potential (ORP), was observed. X-ray photoelectron spectroscopy (XPS) measurements indicated that the irradiation of water vapor plasma efficiently oxidized the surface of SiC because of the reactive species in plasma such as OH radicals. Swell-like structures were also observed along scratches on the SiC surface. Plasma-assisted polishing using CeO2 abrasive enabled us to reduce the surface roughness of SiC without introducing crystallographical subsurface damage, and an atomically flat scratch-free surface with an rms roughness of less than 0.1 nm was obtained. (C) 2011 The Japan Society of Applied Physics
Damage-Free Dry Polishing of 4H-SiC Combined with Atmospheric-Pressure Water Vapor Plasma Oxidation
JAPANESE JOURNAL OF APPLIED PHYSICS,50(8) 2011(Aug.)
Author:Deng, Hui; Takiguchi, Tatsuya; Ueda, Masaki; Hattori, Azusa N.; Zettsu, Nobuyuki; Yamamura, Kazuya
Towards high-resolution ptychographic x-ray diffraction microscopy
PHYSICAL REVIEW B,83(21) 2011(Jun. 13)
Author:Takahashi, Yukio; Suzuki, Akihiro; Zettsu, Nobuyuki; Kohmura, Yoshiki; Senba, Yasunori; Ohashi, Haruhiko; Yamauchi, Kazuto; Ishikawa, Tetsuya
Towards high-resolution ptychographic x-ray diffraction microscopy
PHYSICAL REVIEW B,83(21) 2011(Jun.)
Author:Yukio Takahashi; Akihiro Suzuki; Nobuyuki Zettsu; Yoshiki Kohmura; Yasunori Senba; Haruhiko Ohashi; Kazuto Yamauchi; Tetsuya Ishikawa
Abstract:Ptychographic x-ray diffraction microscopy is a lensless imaging technique with a large field of view and high spatial resolution, which is also useful for characterizing the wavefront of an x-ray probe. The performance of this technique is degraded by positioning errors due to the drift between the sample and illumination optics. We propose an experimental approach for correcting the positioning errors and demonstrate success by two-dimensionally reconstructing both the wavefront of the focused x-ray beam and the complex transmissivity of the weakly scattering objects at the pixel resolution of better than 10 nm in the field of view larger than 5 mu m. This method is applicable to not only the observation of organelles inside cells or nano-mesoscale structures buried within bulk materials but also the characterization of probe for single-shot imaging with x-ray free electron lasers.
Versatile protein-based bifunctional nano-systems (encapsulation and directed assembly): Selective nanoscale positioning of gold nanoparticle-viral protein hybrids
CHEMICAL PHYSICS LETTERS,506(1-3):76-80 2011(Apr. 11)
Author:Zheng, Bin; Zettsu, Nobuyuki; Fukuta, Megumi; Uenuma, Mutsunori; Hashimoto, Tatsuya; Gamo, Kentaro; Uraoka, Yukiharu; Yamashita, Ichiro; Watanabe, Heiji
Development of fabrication process for aspherical neutron focusing mirror using numerically controlled local wet etching with low-pressure polishing
NUCLEAR INSTRUMENTS&METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT,634:S112-S116 2011(Apr. 01)
Author:Nagano, M.; Yamaga, F.; Zettsu, N.; Yamazaki, D.; Maruyama, R.; Soyama, K.; Yamamura, K.
Versatile protein-based bifunctional nano-systems (encapsulation and directed assembly): Selective nanoscale positioning of gold nanoparticle-viral protein hybrids
CHEMICAL PHYSICS LETTERS,506(1-3):76-80 2011(Apr.)
Author:Bin Zheng; Nobuyuki Zettsu; Megumi Fukuta; Mutsunori Uenuma; Tatsuya Hashimoto; Kentaro Gamo; Yukiharu Uraoka; Ichiro Yamashita; Heiji Watanabe
Abstract:We demonstrate a selective nanoscale positioning of targeted Au nanoparticles (NPs) through a bifunctional protein-based encapsulation/delivery system. The newly designed recombinant bifunctional protein, appended with both gold-binding peptide (GBP) and Ti/Si-binding peptide (TBP) at the C-and N-termini efficiently encapsulated 15-20 nm-diameter Au NPs during the pH-controlled reversible reassembly process, and showed the ability of the internalized Au NPs in selective binding to nanometer-scale Ti islands without overshooting. This highly controlled placement of the Au NPs on substrates can be employed to make both large scale devices and point-contact devices. (C) 2011 Elsevier B.V. All rights reserved.
Finishing of AT-Cut Quartz Crystal Wafer with Nanometric Thickness Uniformity by Pulse-Modulated Atmospheric Pressure Plasma Etching
JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY,11(4):2922-2927 2011(Apr.)
Author:Kazuya Yamamura; Masaki Ueda; Masafumi Shibahara; Nobuyuki Zettsu
Abstract:Quartz resonator is a very important device to generate a clock frequency for information and telecommunication system. Improvement of the productivity of the quartz resonator is always required because a huge amount of the resonator is demanded for installing to various electronic devices. Resonance frequency of the quartz resonator is decided by the thickness of the quartz crystal wafer. Therefore, it is necessary to uniform the thickness distribution of the wafer with nano-metric level. We have proposed the improvement technique of the thickness distribution of the quartz crystal wafer by numerically controlled correction using atmospheric pressure plasma which is non-contact and chemical removal technique. Heating effects of the quartz wafer in the removal rate and the correction accuracy were investigated. The heating of the substrate and compensate of the scanning speed of the worktable according to the variation of the surface temperature enabled an increase of 50% in the etching rate and 10-nanometric-level accuracy in the correction of the thickness distribution of the quartz wafer, respectively.
Improvement in Thickness Uniformity of Thick SOI by Numerically Controlled Local Wet Etching
JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY,11(4):2910-2915 2011(Apr.)
Author:Kazuya Yamamura; Kazuaki Ueda; Mao Hosoda; Nobuyuki Zettsu
Abstract:Silicon-on-insulator (SOI) wafers are promising semiconductor materials for high-speed LSIs, low-power-consumption electric devices and micro electro mechanical systems (MEMS). The thickness distribution of an SOI causes the variation of threshold voltage in electronic devices manufactured on the SOI wafer. The thickness distribution of a thin SOI, which is manufactured by applying a smart cut technique, is comparatively uniform. On the other hand, a thick SOI has a large thickness distribution because a bonded wafer is thinned by conventional grinding and polishing. For a thick SOI wafer with a thickness of 1 mu m, it is required that the tolerance of thickness variation is less than 50 nm. However, improving the thickness uniformity of a thick SOI layer to a tolerance of +/- 5% is difficult by conventional machining because of the fundamental limitations of these techniques. We have developed numerically controlled local wet etching (NC-LWE) technique as a novel deterministic subaperture figuring and finishing technique, which utilizes a localized chemical reaction between the etchant and the surface of the workpiece. We demonstrated an improvement in the thickness distribution of a thick SOI by NC-LWE using an HF/HNO3 mixture, and thickness variation improved from 480 nm to 200 nm within a diameter of 170 mm.
Fabrication of discrete polystyrene nanoparticle arrays with controllable their structural parameters.
Journal of nanoscience and nanotechnology,11(4):2956-61 2011(Apr.)
Author:Shuhei Uchida; Kazuya Yamamura; Nobuyuki Zettsu
Abstract:We have demonstrated the fabrication of two-dimensionally periodic non-close packed arrays of spherical polystyrene nanoparticles with controllable their structural parameters including diameter and interpartcile distance. The principle of this procedure relies on stepwise integration of spin-coat-assisted colloidal self-assembly of the single layer of close-packed polystyrene nanoparticle on a substrate, and subsequent etching of the particle under atmospheric pressure helium plasma. The plasma process converted the close-packed nanoparticle array into non-close-packed arrangement remaining with unchanged their original spherical shape and periodicity. Owing to the etching process underwent isotropically, the structural parameters could be controlled with nanometric accuracy by the treatment time. The etching rate strongly depended on the working pressure conditions, and the etching rate under 250 Torr was ca. 3 times faster than that of the 760 Torr. The effects of the working pressure indicated the neutral helium radicals and photons diffused from the plasma might be primarily responsible for the etching.
Simple and versatile route to high yield face-to-face dimeric assembly of Ag nanocubes and their surface plasmonic properties.
Journal of nanoscience and nanotechnology,11(4):2890-6 2011(Apr.)
Author:Shuhei Uchida; Atsushi Taguchi; Munehisa Mitani; Taro ichimura; Satoshi Kawata; Kazuya Yamamura; Nobuyuki Zettsu
Abstract:We have demonstrated the higher yield dimerization of single-crystalline Ag nanocubes through preciously controlled face-selective functionalization. With the achievement of the higher yield dimerization, we could thus observe some interesting optical properties of the dimer. Both experimental and theoretical studies revealed that the 50-nm-diameter Ag nanocubes dimers with a ca. 3.3 nm gap at their junction exhibited two plasmon peaks centered at 446 nm and 600 nm, which contributed to transverse and longitudinal plasmon resonances, respectively. Elctromagnetic calculations based on the FDTD method clearly showed that a greater enhancement of the local field occurred, with an average amplitude of the electric field of 22, at the fractal space between the aggregated Ag nanocubes when the dimer was illuminated under longitudinally polarized light.
Development of fabrication process for aspherical neutron focusing mirror using numerically controlled local wet etching with low-pressure polishing
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT,634:S112-S116 2011(Apr.)
Author:M. Nagano; F. Yamaga; N. Zettsu; D. Yamazaki; R. Maruyama; K. Soyama; K. Yamamura
Abstract:The aspherical supermirror is among the most useful optics to focus a neutron beam with a wide wavelength range. The improvement of surface roughness and enlargement of mirror size are essential for increasing the focusing gain. A highly efficient and high-precision fabrication process for the substrate of a large aspherical mirror combining conventional precision grinding, numerically controlled local wet etching (NC-LWE) figuring and low-pressure polishing was developed. Using this new fabrication process, a 400 mm-long plano-elliptical neutron focusing mirror substrate was successfully fabricated with a figure error of 0.39 mu m p-v and an rms surface roughness of less than 0.2 nm. (C) 2010 Elsevier B.V. All rights reserved.
触媒フリー無電解銅めっきプロセスによるフッ素樹脂表面の高密着性銅メタライジング
大阪大学低温センターだより,154:20-26 2011(Apr.)
Author:是津 信行,山村 和也
Finishing of AT-Cut Quartz Crystal Wafer with Nanometric Thickness Uniformity by Pulse-Modulated Atmospheric Pressure Plasma Etching
JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY,11(4):2922-2927 2011(Apr.)
Author:Yamamura, Kazuya; Ueda, Masaki; Shibahara, Masafumi; Zettsu, Nobuyuki
Improvement in Thickness Uniformity of Thick SOI by Numerically Controlled Local Wet Etching
JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY,11(4):2910-2915 2011(Apr.)
Author:Yamamura, Kazuya; Ueda, Kazuaki; Hosoda, Mao; Zettsu, Nobuyuki
Simple and Versatile Route to High Yield Face-to-Face Dimeric Assembly of Ag Nanocubes and Their Surface Plasmonic Properties
JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY,11(4):2890-2896 2011(Apr.)
Author:Uchida, Shuhei; Taguchi, Atsushi; Mitani, Munehisa; Ichimura, Taro; Kawata, Satoshi; Yamamura, Kazuya; Zettsu, Nobuyuki
Fabrication of Discrete Polystyrene Nanoparticle Arrays with Controllable Their Structural Parameters
JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY,11(4):2956-2961 2011(Apr.)
Author:Uchida, Shuhei; Yamamura, Kazuya; Zettsu, Nobuyuki
Enhanced Red-Light Emission by Local Plasmon Coupling of Au Nanorods in an Organic Light-Emitting Diode
APPLIED PHYSICS EXPRESS,4(3) 2011(Mar.)
Author:Takuya Tanaka; Yuji Totoki; Aya Fujiki; Nobuyuki Zettsu; Yusuke Miyake; Megumi Akai-Kasaya; Akira Saito; Takuji Ogawa; Yuji Kuwahara
Abstract:A significant increase in the quantum efficiency of an organic red-light-emitting diode was achieved through coupling with localized surface plasmons of Au nanorods with a length of 50-60 nm embedded on the substrate anode. We used 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM)-doped tris(8-hydroxylquinolianato) aluminum(III) (Alq3) as an emission layer. The fabricated diode structure consists of an indium tin oxide (ITO) anode, a Cu phthalocyanine (CuPc) hole transport layer, an Alq3 electron transport layer, a LiF electron injection layer, and an Al cathode. We observed a 3-fold increase in the intensity of molecular fluorescence compared with that of a conventional diode structure. (C) 2011 The Japan Society of Applied Physics
Enhanced Red-Light Emission by Local Plasmon Coupling of Au Nanorods in an Organic Light-Emitting Diode
APPLIED PHYSICS EXPRESS,4(3) 2011(Mar.)
Author:Tanaka, Takuya; Totoki, Yuji; Fujiki, Aya; Zettsu, Nobuyuki; Miyake, Yusuke; Akai-Kasaya, Megumi; Saito, Akira; Ogawa, Takuji; Kuwahara, Yuji
金属ナノ結晶の形状制御と機能(<特集>ナノ結晶の成長と新機能)
日本結晶成長学会誌,37(4):281-290 2011(Jan.)
Author:是津 信行
Plasma assisted polishing of single crystal SiC for obtaining atomically flat strain-free surface
CIRP ANNALS-MANUFACTURING TECHNOLOGY,60(1):571-574 2011
Author:K. Yamamura; T. Takiguchi; M. Ueda; H. Deng; A. N. Hattori; N. Zettsu
Abstract:A novel polishing technique combined with the irradiation of atmospheric pressure plasma was proposed for the finishing of a silicon carbide material. The irradiation of helium-based water vapor plasma efficiently oxidized the surface of single-crystal 4H-SiC (0 0 0 1), and a nanoindentation test revealed that the hardness of SiC decreased by one order of magnitude compared with that of the unprocessed surface. Plasma-assisted polishing using a CeO2 abrasive enabled us to improve the surface roughness of a commercially available SiC wafer without introducing crystallographical subsurface damage, and a scratch-free atomically flat surface with an rms roughness of 0.1 nm level was obtained. (C) 2011 CIRP.
Evaluation of Surface Roughness of Quartz Glass Substrate in Fabrication Process for Neutron Focusing Mirror
ADVANCES IN ABRASIVE TECHNOLOGY XIV,325:647-+ 2011
Author:Mikinori Nagano; Fumiya Yamaga; Kenta Yamasaki; Nobuyuki Zettsu; Dai Yamazaki; Ryuji Maruyama; Kazuhiko Soyama; Kazuya Yamamura
Abstract:The aspherical supermirror is among the most useful optics for focusing a neutron beam with a wide wavelength range. The improvement in surface roughness is essential for increasing the focusing gain. A highly efficient and high-precision fabrication process for the substrate of the aspherical mirror combining conventional precision grinding, numerically controlled local wet etching (NC-LWE) figuring, and low-pressure polishing was developed. Using this new fabrication process, piano-elliptical neutron-focusing mirror substrates were successfully fabricated with a figure error of submicrometer order and an rms surface roughness of less than 0.3 nm. In this report, the surface roughness of a quartz glass substrate for a neutron focusing supermirror was evaluated.
プラズマ援用研磨による4H-SiC (0001)表面の高品位仕上げ加工
砥粒加工学会誌,55(9):534-539 2011
Author:山村 和也,瀧口 達也,上田 真己,トウ 輝,服部 梓,是津 信行
リング型PS@Auプラズモニックナノシェルアレイの作製
精密工学会学術講演会講演論文集,2011:519-520 2011
Author:山本 悠人,内田 修平,山村 和也,是津 信行
大気開放下におけるプラズマ化学液相堆積法によるフッ素ポリマー表面の銅メタライジング:過酸化物ラジカルの存在形態と無電解銅めっき膜の密着強度の相関
精密工学会学術講演会講演論文集,2011:537-538 2011
Author:大岡 健人,秋山 弘貴,山本 悠人,是津 信行,山村 和也
Plasma assisted polishing of single crystal SiC for obtaining atomically flat strain-free surface
CIRP ANNALS-MANUFACTURING TECHNOLOGY,60(1):571-574 2011
Author:Yamamura, K.; Takiguchi, T.; Ueda, M.; Deng, H.; Hattori, A. N.; Zettsu, N.
High-resolution projection image reconstruction of thick objects by hard x-ray diffraction microscopy
PHYSICAL REVIEW B,82(21) 2010(Dec. 02)
Author:Takahashi, Yukio; Nishino, Yoshinori; Tsutsumi, Ryosuke; Zettsu, Nobuyuki; Matsubara, Eiichiro; Yamauchi, Kazuto; Ishikawa, Tetsuya
High-resolution projection image reconstruction of thick objects by hard x-ray diffraction microscopy
PHYSICAL REVIEW B,82(21) 2010(Dec.)
Author:Yukio Takahashi; Yoshinori Nishino; Ryosuke Tsutsumi; Nobuyuki Zettsu; Eiichiro Matsubara; Kazuto Yamauchi; Tetsuya Ishikawa
Abstract:Hard x-ray diffraction microscopy enables us to observe thick objects at high spatial resolution. The resolution of this method is limited, in principle, by only the x-ray wavelength and the largest scattering angle recorded. As the resolution approaches the wavelength, the thickness effect of objects plays a significant role in x-ray diffraction microscopy. In this paper, we report high-resolution hard x-ray diffraction microscopy for thick objects. We used highly focused coherent x rays with a wavelength of similar to 0.1 nm as an incident beam and measured the diffraction patterns of a similar to 150-nm-thick silver nanocube at the scattering angle of similar to 3 degrees. We observed a characteristic contrast of the coherent diffraction pattern due to only the thickness effect and collected the diffraction patterns at nine incident angles so as to obtain information on a cross section of Fourier space. We reconstructed a pure projection image by the iterative phasing method from the patched diffraction pattern. The edge resolution of the reconstructed image was similar to 2 nm, which was the highest resolution so far achieved by x-ray microscopy. The present study provides us with a method for quantitatively observing thick samples at high resolution by hard x-ray diffraction microscopy.
Three-dimensional electron density mapping of shape-controlled nanoparticle by focused hard X-ray diffraction microscopy.
Nano letters,10(5):1922-6 2010(May 12)
Author:Yukio Takahashi; Nobuyuki Zettsu; Yoshinori Nishino; Ryosuke Tsutsumi; Eiichiro Matsubara; Tetsuya Ishikawa; Kazuto Yamauchi
Abstract:Coherent diffraction microscopy using highly focused hard X-ray beams allows us to three-dimensionally observe thick objects with a high spatial resolution, also providing us with unique structural information, i.e., electron density distribution, not obtained by X-ray tomography with lenses, atom probe microscopy, or electron tomography. We measured high-contrast coherent X-ray diffraction patterns of a shape-controlled Au/Ag nanoparticle and successfully reconstructed a projection and a three-dimensional image of the nanoparticle with a single pixel (or a voxel) size of 4.2 nm in each dimension. The small pits on the surface and a hollow interior were clearly visible. The Au-rich regions were identified based on the electron density distribution, which provided insight into the formation of Au/Ag nanoboxes.
Two-dimensional measurement of focused hard X-ray beam profile using coherent X-ray diffraction of isolated nanoparticle
NUCLEAR INSTRUMENTS&METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT,616(2-3):266-269 2010(May 01)
Author:Takahashi, Yukio; Kubo, Hideto; Tsutsumi, Ryosuke; Sakaki, Shigeyuki; Zettsu, Nobuyuki; Nishino, Yoshinori; Ishikawa, Tetsuya; Yamauchi, Kazuto
Fabrication of damage-free Johansson-type doubly curved crystal spectrometer substrate by numerically controlled local wet etching
NUCLEAR INSTRUMENTS&METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT,616(2-3):281-284 2010(May 01)
Author:Yamamura, K.; Ueda, K.; Nagano, M.; Zettsu, N.; Maeo, S.; Shimada, S.; Utaka, T.; Taniguchi, K.
High-reflectivity (m=4) elliptical neutron focusing supermirror fabricated by numerically controlled local wet etching with ion beam sputter deposition
NUCLEAR INSTRUMENTS&METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT,616(2-3):193-196 2010(May 01)
Author:Yamamura, K.; Nagano, M.; Zettsu, N.; Yamazaki, D.; Maruyama, R.; Soyama, K.
Fabrication of damage-free Johansson-type doubly curved crystal spectrometer substrate by numerically controlled local wet etching
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT,616(2-3):281-284 2010(May)
Author:K. Yamamura; K. Ueda; M. Nagano; N. Zettsu; S. Maeo; S. Shimada; T. Utaka; K. Taniguchi
Abstract:A doubly curved crystal spectrometer with Johansson-type geometry is very effective for focusing and monochromatizing an X-ray beam. In this study, numerically controlled local wet etching (NC-LWE) was used to form the curvature of the Si(1 1 1) substrate. NC-LWE figuring reduced the inclination of the crystal plane to less than 0.01 degrees by applying the controlled etching of the surface, and achieved error of the figured curvature radius R of 6.7%. The reflectivity and the full width at half maximum (FWHM) of the rocking curve of the processed surface were almost the same as those of the unprocessed surface. (C) 2009 Elsevier B.V. All rights reserved.
High-reflectivity (m=4) elliptical neutron focusing supermirror fabricated by numerically controlled local wet etching with ion beam sputter deposition
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT,616(2-3):193-196 2010(May)
Author:K. Yamamura; M. Nagano; N. Zettsu; D. Yamazaki; R. Maruyama; K. Soyama
Abstract:High-performance neutron-focusing supermirror devices with both high figure accuracy and high reflectivity are essential to effectively collect and focus a neutron beam on a sample without scattering loss. To fabricate these devices, numerically controlled local wet etching and ion beam sputter deposition techniques were developed for the figuring of an aspherical mirror substrate and for the deposition of NiC/Ti multilayers, respectively. By applying these techniques, a piano-elliptical supermirror with a clear aperture size of 90 mm x 40 mm was fabricated to focus a cold neutron beam. Focusing performance and reflectivity were evaluated using a neutron reflectometer and a focusing gain of 4.4 and a reflectivity of 0.64-0.7 in the near-critical-angle region for m=4 were achieved. (C) 2009 Elsevier B.V. All rights reserved.
Two-dimensional measurement of focused hard X-ray beam profile using coherent X-ray diffraction of isolated nanoparticle
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT,616(2-3):266-269 2010(May)
Author:Yukio Takahashi; Hideto Kubo; Ryosuke Tsutsumi; Shigeyuki Sakaki; Nobuyuki Zettsu; Yoshinori Nishino; Tetsuya Ishikawa; Kazuto Yamauchi
Abstract:A method for evaluating the two-dimensional photon density distribution in focused hard X-ray beams is proposed and demonstrated in a synchrotron experiment at SPring-8. A synchrotron X-ray beam of 11.8 key is focused to a similar to 1 mu m spot by Kirkpatrick-Baez mirrors. The two-dimensional intensity distribution of the focused beam is derived by monitoring the forward diffracted intensity from an isolated silver nanocube with an edge length of similar to 150 nm positioned in the beam waist, which is two-dimensionally scanned. Furthermore, the photon density of X-rays illuminated onto the nanocube is estimated by utilizing coherent X-ray diffraction microscopy. This method is useful for evaluating the photon density distribution of hard X-ray beams focused to a spot size of less than a few micrometers. (C) 2009 Elsevier B.V. All rights reserved.
Three-Dimensional Electron Density Mapping of Shape-Controlled Nanoparticle by Focused Hard X-ray Diffraction Microscopy
NANO LETTERS,10(5):1922-1926 2010(May)
Author:Takahashi, Yukio; Zettsu, Nobuyuki; Nishino, Yoshinori; Tsutsumi, Ryosuke; Matsubara, Eiichiro; Ishikawa, Tetsuya; Yamauchi, Kazuto
Fabrication of discrete array of metallodielectric nanoshells and their surface plasmonic properties
THIN SOLID FILMS,518(13):3581-3584 2010(Apr. 30)
Author:Uchida, Shuhei; Yamamura, Kazuya; Zettsu, Nobuyuki
Atmospheric pressure plasma liquid deposition of copper nanoparticles on poly(4-vinylpyridine)-grafted-poly(tetrafluoroethylene) surface and their autocatalytic properties
THIN SOLID FILMS,518(13):3551-3554 2010(Apr. 30)
Author:Akiyama, Hiroki; Zettsu, Nobuyuki; Yamamura, Kazuya
Fabrication of discrete array of metallodielectric nanoshells and their surface plasmonic properties
THIN SOLID FILMS,518(13):3581-3584 2010(Apr.)
Author:Shuhei Uchida; Kazuya Yamamura; Nobuyuki Zettsu
Abstract:In this paper we describe the fabrication of two-dimensionally periodic non-close-packed nanoshell arrays, consisting of a spherical polystyrene core coated with a thin gold shell, as well as their surface plasmonic properties. The principle of this procedure relies on stepwise integration of spin-coat-assisted colloidal self-assembly of the single layer of close-packed polystyrene nanoparticle, atmospheric pressure plasma-induced isotropic etching, and deposition of gold thin film by thermal evaporation. The plasma process converted the close-packed nanoparticle array into non-close-packed arrangement without changing their original spherical shape and periodicity. Both experimental and theoretical studies revealed that the densely packed nanoshell array with a 160 nm inner core diameter and a 20 nm thick shell strongly scattered and absorbed near infrared light, due to the interaction between primitive plasmon modes associated with the surface of the nanoparticle. Furthermore, the resultant nanoshell array was utilized for near infrared light responsible localized surface plasmon resonance based sensor. The bulk refractive index sensitivity was 220 nm RIU-1. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.
Atmospheric pressure plasma liquid deposition of copper nanoparticles on poly(4-vinylpyridine)-grafted-poly(tetrafluoroethylene) surface and their autocatalytic properties
THIN SOLID FILMS,518(13):3551-3554 2010(Apr.)
Author:Hiroki Akiyama; Nobuyuki Zettsu; Kazuya Yamamura
Abstract:We demonstrate catalyst-free electroless deposition of copper on a poly(4-vynylpyrridine)-grafted-poly (tetrafluoroethylene) surface. The principle of this process relies on deposition of an organo-copper(II) precursor film on the functionalized polymer surface and on subsequent plasma-assisted reduction of the copper ion to form nanoparticles. A polymer surface densely and homogeneously seeded with copper nanoparticles enable to initiate autocatalytic electroless deposition of copper layer without need for any prior sensitizing the surface with conventionally used SnCl2 and Pd species. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.
Enhanced fluorescence by surface plasmon coupling of Au nanoparticles in an organic electroluminescence diode
APPLIED PHYSICS LETTERS,96(4) 2010(Jan. 25)
Author:Fujiki, A.; Uemura, T.; Zettsu, N.; Akai-Kasaya, M.; Saito, A.; Kuwahara, Y.
Enhanced fluorescence by surface plasmon coupling of Au nanoparticles in an organic electroluminescence diode
APPLIED PHYSICS LETTERS,96(4) 2010(Jan.)
Author:A. Fujiki; T. Uemura; N. Zettsu; M. Akai-Kasaya; A. Saito; Y. Kuwahara
Abstract:A significant increase in electroluminescence was achieved through coupling with localized surface plasmons in a single layer of Au nanoparticles. We fabricated a thin-film organic electroluminescence diode, which consists of an indium tin oxide (ITO) anode, a Au nanoparticle array, a Cu phthalocyanine hole transport layer, a tris(8-hydroxylquinolianato) aluminum (III) electron transport layer, a LiF electron injection layer, and an Al cathode. The device structure, with size-controlled Au particles embedded on ITO, can be used to realize the optimum distance for exciton-plasmon interactions by simply adjusting the thickness of the hole transport layer. We observed a 20-fold increase in the molecular fluorescence compared with that of a conventional diode structure.
High-integrity finishing of 4H-SiC (0001) by plasma-assisted polishing
ADVANCES IN ABRASIVE TECHNOLOGY XIII,126-128:423-428 2010
Author:Kazuya Yamamura; Tatsuya Takiguchi; Masaki Ueda; Azusa N. Hattori; Nobuyuki Zettsu
Abstract:A novel machining method combined with the irradiation of atmospheric pressure plasma was proposed for the finishing of difficult-to-machine materials. The irradiation of helium-based water vapor plasma efficiently oxidized the surface of single-crystal 4H-SiC (0001), and a ball-on-disc test using an alumina ceramic ball revealed that the wear rate of SiC, the surface of which was modified by the irradiation of water vapor plasma, is 20-fold higher than that of the surface without plasma irradiation. Plasma-assisted polishing using CeO2 abrasives enabled us to improve the surface roughness of SiC without introducing crystallographical subsurface damage, and a scratch-free surface with a roughness of less than 0.3 nm rms was obtained.
Fabrication of Ultraprecision Millimeter-thick Elliptical Neutron Focusing Mirror Substrate by Local Wet Etching
ADVANCED PRECISION ENGINEERING,447-448:208-+ 2010
Author:Fumiya Yamaga; Mikinori Nagano; Nobuyuki Zettsu; Dai Yamazaki; Ryuji Maruyama; Kazuhiko Soyama; Kazuya Yamamura
Abstract:Numerically controlled local wet etching (NC-LWE) is a novel technique to fabricate the ultraprecision optical components and/or finishing the functional materials. In this technique, a figuring is performed by controlling the dwelling time of the combination nozzle, which consists of a supply and a suction part of an etchant, on the workpiece. In this paper, we proposed fabrication process of millimeter-thick elliptical neutron focusing mirror substrate by applying NC-LWE figuring involving CeO2 slurry polishing. We fabricated a millimeter-thick elliptical neutron focusing mirror substrate with a figure error of less than 0.2 mu m and obtained a surface roughness of less than 0.15 nm rms.
Effect of Substrate Heating in Thickness Correction of Quartz Crystal Wafer by Plasma Chemical Vaporization Machining
ADVANCED PRECISION ENGINEERING,447-448:218-+ 2010
Author:Masaki Ueda; Masafumi Shibahara; Nobuyuki Zettsu; Kazuya Yamamura
Abstract:Quartz resonator is a very important device to generate a clock frequency for information and telecommunication system. Improvement of the productivity of the quartz resonator is always required because huge amounts of resonator are demanded to install to various electronic devices. Resonance frequency of the quartz resonator is determined by the thickness of the quartz crystal wafer. Therefore it is essential to uniform the thickness distribution of the quartz crystal wafer with nanometric level. We propose the improvement process of the thickness distribution of the quartz crystal wafer by numerically controlled correction using atmospheric pressure plasma which is noncontact and chemical removal technique. We have already succeeded in obtaining a thickness uniformity of 33.1nm within 2 min in the thickness correction of an AT-cut quartz crystal wafer with an area of 24 mm x 24 mm. However, increase of removal rate and improvement of correction accuracy are required for industrial manufacturing. Heating effects of the quartz crystal wafer in the removal rate and the correction accuracy were investigated. The heating of the substrate and compensate of the scanning speed of the worktable in accordance with the variation of the surface temperature enabled an increase of 50% in removal rate and 10-nanometric-level accuracy in correction of the thickness distribution of the quartz crystal wafer.
Fabrication of Damage-free Curved Silicon Crystal Substrate for a Focusing X-ray Spectrometer by Plasma Chemical Vaporization Machining
ADVANCED PRECISION ENGINEERING,447-448:213-+ 2010
Author:Mao Hosoda; Kazuaki Ueda; Mikinori Nagano; Nobuyuki Zettsu; Shoichi Shimada; Kazuo Taniguchi; Kazuya Yamamura
Abstract:In the X-ray fluorescence analysis on sub-micron particle, application of the doubly curved crystal (DCC) spectrometer with Johansson-type geometry is effective to improve the lowest limit of detection because DCC makes it possible to focus and monochromatize an X-ray beam simultaneously. A strain-free crystal is essential for the high-performance focusing crystal spectrometer. We propose the application of the open-air type numerically controlled plasma chemical vaporization machining (NC-PCVM), which utilizes neutral reactive species generated by atmospheric pressure plasma, to fabricate the DCC substrate. By applying NC-PCVM technique, a curvature radius error of 0.08% was obtained, and there was no degradation of the crystallinity of the Si (111) substrate.
Atmospheric pressure plasma liquid deposition of copper nanoparticles onto poly(4-vinylpyrdine)-grafted-poly(tetrafluoroethylene) surface
Transactions of the Materials Research Society of Japan,35(4):817-820 2010
Author:Akiyama Hiroki; Yamamura Kazuya; Zettsu Nobuyuki
Abstract:We have demonstrated systematic studies of plasma-induced copper nanoparticle deposition onto a poly(4-vinylpyridine)-grafted-poly(tetrafluoroethylene) surface, as well as their autocatalytic characteristics for the initiation of the following electroless copper plating. The plasma-induced reduction of the organo-copper precursor gradually increased the surface copper concentration owing to the formation of the copper nanoparticles with treatment time. The concentration became maximal at 300 s of treatment, and then it progressively decreased with further plasma treatment. XPS, SEM, and AFM experiments revealed that the total population of nanoparticles on the surface was clearly decreased, while the particles continued to grow. We found that thermodynamically driven spontaneous migration of Cu atoms occurred from the initially formed smaller particles to the larger ones, by the Ostwald ripening mechanism. The polymer surface densely and homogeneously seeded with copper nanoparticles enable the initiation of autocatalytic electroless deposition of copper layer at 40℃ with less than 5 s time lag.
Figuring of millimeter-thick elliptical mirror substrate using numerically controlled local wet etching with low-pressure polishing
Proceedings - ASPE 2010 Annual Meeting,50:21-24 2010
Author:Nagano M; Yamaga F; Zettsu N; Yamazaki D; Maruyama R; Soyama K; Yamamura K
大気開放型プラズマCVMによるATカット水晶ウエハの厚さ修正加工:基板加熱による加工速度の向上
精密工学会学術講演会講演論文集,2010:307-308 2010
Author:上田 真己,永野 幹典,柴原 正文,是津 信行,山村 和也
低コスト・大面積の能動的超精密ナノ粒子配列制御装置およびプロセスの開発
旭硝子財団助成研究成果報告,:1-8 2010
Author:是津 信行
High-resolution diffraction microscopy using the plane-wave field of a nearly diffraction limited focused x-ray beam
PHYSICAL REVIEW B,80(5) 2009(Aug.)
Author:Yukio Takahashi; Yoshinori Nishino; Ryosuke Tsutsumi; Hideto Kubo; Hayato Furukawa; Hidekazu Mimura; Satoshi Matsuyama; Nobuyuki Zettsu; Eiichiro Matsubara; Tetsuya Ishikawa; Kazuto Yamauchi
Abstract:X-ray waves in the center of the beam waist of nearly diffraction limited focused x-ray beams can be considered to have amplitude and phase that are both almost uniform, i.e., they are x-ray plane waves. Here we report the results of an experimental demonstration of high-resolution diffraction microscopy using the x-ray plane wave of the synchrotron x-ray beam focused using Kirkpatrik-Baez mirrors. A silver nanocube with an edge length of similar to 100 nm is illuminated with the x-ray beam focused to a similar to 1 mu m spot at 12 keV. A high-contrast symmetric diffraction pattern of the nanocube is observed in the forward far field. An image of the nanocube is successfully reconstructed by an iterative phasing method and its half-period resolution is 3.0 nm. This method does not only dramatically improve the spatial resolution of x-ray microscopy but also is a key technology for realizing single-pulse diffractive imaging using x-ray free-electron lasers.
High-resolution diffraction microscopy using the plane-wave field of a nearly diffraction limited focused x-ray beam
PHYSICAL REVIEW B,80(5) 2009(Aug.)
Author:Takahashi, Yukio; Nishino, Yoshinori; Tsutsumi, Ryosuke; Kubo, Hideto; Furukawa, Hayato; Mimura, Hidekazu; Matsuyama, Satoshi; Zettsu, Nobuyuki; Matsubara, Eiichiro; Ishikawa, Tetsuya; Yamauchi, Kazuto
Highly Efficient Damage-Free Correction of Thickness Distribution of Quartz Crystal Wafers by Atmospheric Pressure Plasma Etching
IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL,56(6):1128-1130 2009(Jun.)
Author:Kazuya Yamamura; Tetsuya Morikawa; Masaki Ueda; Mikinori Nagano; Nobuyuki Zettsu; Masafumi Shibahara
Abstract:A new finishing method was developed to correct the thickness distribution of a quartz crystal wafer by the numerically controlled scanning of a localized atmospheric pressure plasma. The thickness uniformity level of a commercially available AT-cut quartz crystal wafer was improved to less than 50 nm without any subsurface damage by applying one correction process. Furthermore, applying a pulse-modulated plasma markedly decreased the correction time of the thickness distribution without breaking the quartz crystal wafer by thermal stress.
Highly Efficient Damage-Free Correction of Thickness Distribution of Quartz Crystal Wafers by Atmospheric Pressure Plasma Etching
IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL,56(6):1128-1130 2009(Jun.)
Author:Yamamura, Kazuya; Morikawa, Tetsuya; Ueda, Masaki; Nagano, Mikinori; Zettsu, Nobuyuki; Shibahara, Masafumi
Figuring of plano-elliptical neutron focusing mirror by local wet etching
OPTICS EXPRESS,17(8):6414-6420 2009(Apr. 13)
Author:Yamamura, Kazuya; Nagano, Mikinori; Takai, Hiroyuki; Zettsu, Nobuyuki; Yamazaki, Dai; Maruyama, Ryuji; Soyama, Kazuhiko; Shimada, Shoichi
Improvement of thickness uniformity of bulk silicon wafer by numerically controlled local wet etching
JOURNAL OF CRYSTAL GROWTH,311(8):2560-2563 2009(Apr. 01)
Author:Nagano, Mikinori; Mitani, Takuro; Ueda, Kazuaki; Zettsu, Nobuyuki; Yamamura, Kazuya
Figuring of plano-elliptical neutron focusing mirror by local wet etching
OPTICS EXPRESS,17(8):6414-6420 2009(Apr.)
Author:Kazuya Yamamura; Mikinori Nagano; Hiroyuki Takai; Nobuyuki Zettsu; Dai Yamazaki; Ryuji Maruyama; Kazuhiko Soyama; Shoichi Shimada
Abstract:Local wet etching technique was proposed to fabricate high-performance aspherical mirrors. In this process, only the limited area facing to the small nozzle is removed by etching on objective surface. The desired objective shape is deterministically fabricated by performing the numerically controlled scanning of the nozzle head. Using the technique, a plano-elliptical mirror to focus the neutron beam was successfully fabricated with the figure accuracy of less than 0.5 mu m and the focusing gain of 6. The strong and thin focused neutron beam is expected to be a useful tool for the analyses of various material properties. (C) 2009 Optical Society of America
Improvement of thickness uniformity of bulk silicon wafer by numerically controlled local wet etching
JOURNAL OF CRYSTAL GROWTH,311(8):2560-2563 2009(Apr.)
Author:Mikinori Nagano; Takuro Mitani; Kazuaki Ueda; Nobuyuki Zettsu; Kazuya Yamamura
Abstract:We have developed numerically controlled local wet etching (NC-LWE) as a novel deterministic subaperture figuring and finishing method, which is suitable for fabricating various optical components and for finishing functional materials. In this method, a chemical reaction between the etchant and the surface of the workpiece removes the surface without degrading the physical properties of the workpiece material. Furthermore, the processing properties of NC-LWE are insensitive to external disturbances, such as the vibration or thermal deformation of the machine or the workpiece, because of its noncontact removal mechanism. By applying the NC-LWE process using a HF/HNO3 mixture to etch silicon, we corrected the thickness distribution of a bulk silicon wafer with a diameter of 200 mm and achieved a total thickness variation of less than 0.23 mu m within a diameter of 190 mm. (C) 2009 Elsevier B.V. All rights reserved.
Improvement of Thickness Uniformity of Bulk Silicon Wafer by Numerically Controlled Local Wet Etching
PROGRESS OF MACHINING TECHNOLOGY,407-408:372-375 2009
Author:Kazuya Yamamura; Takuro Mitani; Kazuaki Ueda; Mikinori Nagano; Nobuyuki Zettsu
Abstract:We have developed numerically controlled local wet etching (NC-LWE) as a novel deterministic subaperture figuring and finishing technique, which is suitable for fabricating various optical components and finishing functional materials. In this technique, a chemical reaction between the etchant and the surface of the workpiece removes the surface without causing the degradation of the physical properties of the workpiece material. Furthermore, the processing properties of NC-LWE are insensitive to external disturbances, such as the vibration or thermal deformation of the machine or the workpiece, because of its noncontact removal mechanism. By applying the NC-LWE process using HF/HNO3 mixtures to etch the silicon, we corrected the thickness distribution of the bulk silicon wafer with a diameter of 200 mm and achieved the total thickness variation of less than 0.23 mu m within the diameter of 190 mm.
数値制御ローカルウェットエッチング法による高精度光学素子の作製:中性子集光用楕円面ミラーの作製 第V報
精密工学会学術講演会講演論文集,2009:153-154 2009
Author:永野 幹典,山家 史也,山本 悠人,是津 信行,山崎 大,丸山 龍治,曽山 和彦,山村 和也
数値制御ローカルウエットエッチングによるSOI膜厚の均一化加工（第二報）
精密工学会学術講演会講演論文集,2009:157-158 2009
Author:植田 和晃,細田 真央,永野 幹典,是津 信行,山村 和也
大気圧プラズマを援用した難加工材料加工プロセスの開発（第1報）
精密工学会学術講演会講演論文集,2009:163-164 2009
Author:瀧口 達也,是津 信行,山村 和也
大気圧プラズマ化学液相堆積法によるフッ素ポリマー表面の高密着性銅メタライジング
精密工学会学術講演会講演論文集,2009:579-580 2009
Author:秋山 弘貴,是津 信行,山村 和也
Surface functionalization of PTFE sheet through atmospheric pressure plasma liquid deposition approach
SURFACE&COATINGS TECHNOLOGY,202(22-23):5284-5288 2008(Aug. 30)
Author:Zettsu, Nobuyuki; Itoh, Hiroto; Yamamura, Kazuya
Plasma-chemical surface functionalization of flexible substrates at atmospheric pressure
THIN SOLID FILMS,516(19):6683-6687 2008(Aug. 01)
Author:Zettsu, Nobuyuki; Itoh, Hiroto; Yamamura, Kazuya
Surface functionalization of PTFE sheet through atmospheric pressure plasma liquid deposition approach
SURFACE & COATINGS TECHNOLOGY,202(22-23):5284-5288 2008(Aug.)
Author:Nobuyuki Zettsu; Hiroto Itoh; Kazuya Yamamura
Abstract:We demonstrated here fascicle copper (Cu) metallization of poly(tetrafluoroethylene) [PTFE] surface through an atmospheric pressure plasma liquid deposition [APPLD] technique to design the interface for high frequency electronic devices. We found that exposing with atmospheric pressure helium plasma to the PTFE surface covered with thin liquid film, containing both poly(4-vinylpyridine) as a metal ion trapping polymer and copper acetate, simultaneously offered the plasma-induced direct graft polymerization and the reduction of Cu2+. The modified surface was characterized by using several analytical techniques, including water contact angle measurement, X-ray photoelectron spectroscopy, and atomic force microscopy. (C) 2008 Elsevier FIN. All rights reserved.
Plasma-chemical surface functionalization of flexible substrates at atmospheric pressure
THIN SOLID FILMS,516(19):6683-6687 2008(Aug.)
Author:Nobuyuki Zettsu; Hiroto Itoh; Kazuya Yamamura
Abstract:We demonstrated here fascicle surface functionalization of poly(tetrafluoroethylene) [PTFE] sheet through an atmospheric pressure plasma liquid deposition [APPLD] technique to design the interface for improvement of copper plated layer adhesion. We found that radiation with atmospheric pressure plasma to the PTFE sheet covered with thin liquid film, containing both an ion trapping polymer and copper ion (Cu2+), simultaneously brought about the direct polymer grafting onto the PTFE surface and Cu2+ ion reduction to metallic Cu. The treated surface was characterized by water contact angle measurement, X-ray photoelectron spectroscopy, and atomic force microscopy. (C) 2007 Elsevier B.V. All rights reserved.
Photo-triggered surface relief grating formation in supramolecular liquid crystalline polymer systems with detachable azobenzene units
ADVANCED MATERIALS,20(3):516-+ 2008(Feb. 04)
Author:Zettsu, Nobuyuki; Ogasawara, Toshinobu; Mizoshita, Norihiro; Nagano, Shusaku; Seki, Takahiro
Photo-triggered surface relief grating formation in supramolecular liquid crystalline polymer systems with detachable azobenzene units
ADVANCED MATERIALS,20(3):516-+ 2008(Feb.)
Author:Nobuyuki Zettsu; Toshinobu Ogasawara; Norihiro Mizoshita; Shusaku Nagano; Takahiro Seki
Abstract:The efficient photo-triggered surface relief formation in the H-boned supramolecular liquid crystalline system was performed for the first time. This supramolecular framework leads to facile and successful detachment of azobenzene unit from the SRG inscribed film with exact retention of the morphological periodicity.
貴金属ナノ粒子の精密形状制御合成とその光機能 (特集 光・電子機能材料の新展開)
科学と工業,82(1):30-44 2008(Jan.)
Author:是津 信行
サブメートル級ナノ粒子配列膜製造技術の開発（５）
精密工学会学術講演会講演論文集,2008:689-690 2008
Author:真鍋 享平,是津 信行,山村 和也,遠藤 勝義
数値制御ローカルウエットエッチングによる二重湾曲分光結晶の加工:単結晶シリコン薄板の加工
精密工学会学術講演会講演論文集,2008:809-810 2008
Author:植田 和晃,是津 信行,山村 和也,前尾 修司,島田 尚一,宇高 忠,谷口 一雄
Highly photosensitive surface relief gratings formation in a liquid crystalline azobenzene polymer: New implications for the migration process
MACROMOLECULES,40(13):4607-4613 2007(Jun. 26)
Author:Zettsu, Nobuyuki; Ogasawara, Toshinobu; Arakawa, Ryusuke; Nagano, Susaku; Ubukata, Takashi; Seki, Takahiro
Highly photosensitive surface relief gratings formation in a liquid crystalline azobenzene polymer: New implications for the migration process
MACROMOLECULES,40(13):4607-4613 2007(Jun.)
Author:Nobuyuki Zettsu; Toshinobu Ogasawara; Ryusuke Arakawa; Susaku Nagano; Takashi Ubukata; Takahiro Seki
Abstract:We have recently demonstrated a markedly photosensitive surface relief gratings (SRG) formation in thin films of liquid crystalline azobenzene-containing polymers, which proceeds from a cis-rich state of the azobenzene [Zettsu et al. Adv. Mater. 2001, 13, 1693; Macromolecules 2004, 37, 8692]. Such polymers exhibited unexpected enhancements in the sensitivity to light for the completion of SRG formation, the required energy dose being similar to 10(3)-fold lower than that for other azobenzene polymers systems widely employed. Here we report detailed results on the systematic explorations for understanding the migration mechanism. The cis-isomer content at the initial state and irradiation intensity crucially influenced the migration efficiency and the resulting relief structure in nonlinear manners. The Zisman plot showed that the light irradiation leads to a large change in the critical surface tension. Such results strongly suggest that the photochemically induced phase transition and the resulting spatial modulations in the physical properties in the film play the essential roles for the SRG formation. On the basis of this knowledge, the SRG formation via a sensitized excitation was demonstrated for the first time by incorporation of a near-infrared absorbing dye.
Dual luminophore polystyrene microspheres for pressure-sensitive luminescent imaging
MEASUREMENT SCIENCE AND TECHNOLOGY,17(6):1254-1260 2006(Jun.)
Author:Fletcher Kimura; Gamal Khalil; Nobuyuki Zettsu; Younan Xia; James Callis; Martin Gouterman; Larry Dalton; Dana Dabiri; Miguel Rodriguez
Abstract:Polystyrene microspheres containing both an oxygen-sensitive platinum porphyrin luminescence and a pressure-insensitive silicon porphyrin luminescence are prepared in high yield. The ratio of these two luminescences responds reversibly in aerodynamic flows over a wide dynamic range of oxygen concentrations, with a response time of < 10 ms. These microspheres have been used in a non-intrusive imaging method to potentially obtain the pressure distributions in three-dimensional aerodynamic flows.
Dual luminophore polystyrene microspheres for pressure-sensitive luminescent imaging
MEASUREMENT SCIENCE&TECHNOLOGY,17(6):1254-1260 2006(Jun.)
Author:Kimura, Fletcher; Khalil, Gamal; Zettsu, Nobuyuki; Xia, Younan; Callis, James; Gouterman, Martin; Dalton, Larry; Dabiri, Dana; Rodriguez, Miguel
Synthesis, stability, and surface plasmonic properties of rhodium multipods, and their use as substrates for surface-enhanced Raman scattering.
Angewandte Chemie (International ed. in English),45(8):1288-92 2006(Feb. 13)
Author:Nobuyuki Zettsu; Joseph M McLellan; Benjamin Wiley; Yadong Yin; Zhi-Yuan Li; Younan Xia
Synthesis, stability, and surface plasmonic properties of rhodium multipods, and their use as substrates for surface-enhanced Raman scattering
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION,45(8):1288-1292 2006
Author:Zettsu, N; McLellan, JM; Wiley, B; Yin, YD; Li, ZY; Xia, YN
Spontaneous motion observed in highly sensitive surface relief formation system
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS,257-58:123-126 2005(May 05)
Author:Ubukata, T; Higuchi, T; Zettsu, N; Seki, T; Hara, M
Spontaneous motion observed in highly sensitive surface relief formation system
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS,257-58:123-126 2005(May)
Author:T Ubukata; T Higuchi; N Zettsu; T Seki; M Hara
Abstract:Surface relief ratings formed on a liquid-crystalline azobenzene polymer film known as a highly sensitive system were investigated to FF obtain deeper insights into polymer migration on the micrometer scale. A surface relief formation was induced with incoherent nonpolarized patterned blue-light using a photomask instead of interference patterns of a coherent laser. Spontaneous lateral migration was observed under the edge of the grating photomask at room temperature even after terminating light irradiation. It was found that interfacial tension and the living cis form of azobenzene are essential for inducing spontaneous motion. (c) 2004 Published by Elsevier B.V.
Light-driven organized layer materials
MOLECULAR CRYSTALS AND LIQUID CRYSTALS,430:107-+ 2005
Author:T Seki; S Nagano; Y Kawashima; N Zettsu; T Ubukata
Abstract:Organized molecular systems provide alluring light-driven actuation systems. They can be migrated or deformed themselves or control states of other ordered materials. This paper presents our two recent topics on light-driven organized monolayers and thin films comprising photochromic azobenzene-containing liquid crystalline polymers; i) photo- alignment of nanochannels in mesoporous silica film, and ii) light-triggered instant mass migration in a thin film state, which can be utilized as a conveyance system for micropatterning of light-inert molecules and materials.
Light-driven organized layer materials
MOLECULAR CRYSTALS AND LIQUID CRYSTALS,430:107-+ 2005
Author:Seki, T; Nagano, S; Kawashima, Y; Zettsu, N; Ubukata, T
Highly efficient photogeneration of surface relief structure and its immobilization in cross-linkable liquid crystalline azobenzene polymers
MACROMOLECULES,37(23):8692-8698 2004(Nov. 16)
Author:Zettsu, N; Seki, T
Highly efficient photogeneration of surface relief structure and its immobilization in cross-linkable liquid crystalline azobenzene polymers
MACROMOLECULES,37(23):8692-8698 2004(Nov.)
Author:N Zettsu; T Seki
Abstract:A new family of azobenzene containing polymer applicable for photoinduced surface relief formation is reported. An azobenzene containing acrylate was copolymerized with methacrylate monomers bearing an oligo(ethylene oxide) chain via free radical copolymerization, yielding soft liquid crystalline polymers. These copolymers displayed a smectic liquid crystal phase at room temperature. After preexposure to ultraviolet light, thin films of the liquid crystalline polymers showed highly sensitive photoinduced material transfer to generate the surface relief structures. The typical exposure dose required for full polymer migration was as low as 50 mJ cm(-2). The inscribed surface relief structures could be rapidly and fully erased either upon incoherent nonpolarized ultraviolet light irradiation or by heating close to the clear point of the soft liquid crystalline polymers. On the other hand, the chemical cross-linking, using a mixed vapor of hydrogen chloride and formaldehyde after surface relief inscription, resulted in a drastic improvement of the shape stability, maintaining the structure at high temperatures up to 250 degreesC. After cross-linking, the trans-to-cis photoisomerization readily proceeded without any modification of the surface morphology and can therefore be applied to the photoswitchable alignment of nematic liquid crystals.
高感度光誘起表面レリーフ形成とその応用
高分子加工,53(11):488-494 2004(Nov.)
Author:是津 信行,生方 俊,関 隆広
Two-dimensional manipulation of poly(3-dodecylthiophene) using light-driven instant mass migration as a molecular conveyer
JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS&EXPRESS LETTERS,43(9A-B):L1169-L1171 2004(Sep. 15)
Author:Zettsu, N; Ubukata, T; Seki, T
Two-dimensional manipulation of poly(3-dodecylthiophene) using light-driven instant mass migration as a molecular conveyer
JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS,43(9A-B):L1169-L1171 2004(Sep.)
Author:N Zettsu; T Ubukata; T Seki
Abstract:Microrelief structures were optically inscribed on binary polymer blend films which consist of a liquid crystalline azobenzene polymer as a host matrix and pi-conjugated poly(3-dodecylthiophene) as a guest functional polymer. In this process, full migrations occurred to a level where the bare substrate surface was exposed within only 20 s. The inscribed film exhibited a high-contrast fluorescent pattern corresponding to the relief structure. We can conclude that poly(3-dodecylthiophene) is transferred together with the active migration of the azobenzene polymer. The light-driven mass migration technique which works as a molecular conveyer is useful in the two-dimensional patterning of functional materials.
液晶性アゾベンゼン高分子における高感度な光誘起物質移動
液晶 : 日本液晶学会誌 = Ekisho,8(2):94-105 2004(Apr. 25)
Author:生方 俊,是津 信行,関 隆広
Unconventional polarization characteristic of rapid photoinduced material motion in liquid crystalline azobenzene polymer films
APPLIED PHYSICS LETTERS,83(24):4960-4962 2003(Dec. 15)
Author:Zettsu, N; Fukuda, T; Matsuda, H; Seki, T
Unconventional polarization characteristic of rapid photoinduced material motion in liquid crystalline azobenzene polymer films
APPLIED PHYSICS LETTERS,83(24):4960-4962 2003(Dec.)
Author:N Zettsu; T Fukuda; H Matsuda; T Seki
Abstract:We carried out double-beam interference experiments using an argon ion laser with controlled polarization in order to cause the formation of photoinduced surface relief in liquid crystalline azobenzene polymer films. The irradiation was undertaken on a film in the cis-rich state obtained by a pre-exposure to ultraviolet light. In this procedure, the efficiency of the photoinduced mass transfer was high, more than 1000 times greater than hitherto reported for amorphous azobenzene polymers. This approach revealed the unusual nature of the migration process. Rapid mass migration is promoted by intensity holographic recording, independent of the polarization of the light used for the irradiation. This insensitivity with respect to the polarization of the light led us to the conclusion that rapid mass migration starting from a cis-rich azobenzene polymer is predominately driven by phototriggered elemental processes such as local dewetting, self-organizing motion, and translation diffusion. (C) 2003 American Institute of Physics.
Liquid crystal-assisted engineering of polymer thin films
LIQUID CRYSTALS VII,5213:154-168 2003
Author:T Seki; S Nagano; N Zettsu; T Ubukata
Abstract:The hybridization of different types of materials frequently leads to specific performances and structure formation. Our current interest is focused onto dynamic performances photofunctional polymers assisted by hybridized liquid crystal molecules. In this paper, two current topics undergoing in our laboratory are presented. In the former part, monolayer formation of hydrophobic polysilanes assisted by polar calamitic liquid crystal molecules is described, This is the first example of monolayer formation of a fully dydrophobic polymer on water. The latter part shows the marked acceleration of lateral mass migration promoted by photoirradiation in azobenzene-containing polymers. Both systems utilize common and general features of liquid crystals, namely, dynamic properties (fluidity) maintaining orientational order in the molecular assemblies. We show herein the high validity of liquid crystals for thin film processing of polymers.
Soft crosslinkable azo polymer for rapid surface relief formation and persistent fixation
ADVANCED MATERIALS,13(22):1693-1697 2001(Nov. 16)
Author:Zettsu, N; Ubukata, T; Seki, T; Ichimura, K
Soft crosslinkable azo polymer for rapid surface relief formation and persistent fixation
ADVANCED MATERIALS,13(22):1693-1697 2001(Nov.)
Author:N Zettsu; T Ubukata; T Seki; K Ichimura
Photoinduced reorientation of azo-dyes covalently linked to a styrene copolymer in bulk state
JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY,143(1):31-38 2001(Oct. 01)
Author:Tawa, K; Zettsu, N; Minematsu, K; Ohta, K; Namba, A; Tran-Cong, Q
Photoinduced reorientation of azo-dyes covalently linked to a styrene copolymer in bulk state
JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY,143(1):31-38 2001(Oct.)
Author:K Tawa; N Zettsu; K Minematsu; K Ohta; A Namba; Q Tran-Cong
Abstract:Polarized light-induced orientation in azo-dyes covalently bonded to styrene copolymer (Azo-PSCMS) was investigated by using polarized UV-VIS spectroscopy. It was found that thermal isomerization and photoisomerization was slower and a photoinduced dichroism was larger than azo-dyes doped in polystyrene. The covalent linkage to a polymer chain may suppress both the mobility required for the isomerization and the rotational diffusion of the azo-moiety. The trans --> cis photoisomerization was induced by ultraviolet (UV) light, whereas light with visible wavelength was used to drive the trans <----> cis photoisomerization. A high repetition of "trans-cis-trans" isomerization cycles achieved under visible light plays an important role for the photoinduced reorientation. Therefore, the high repetition of the "trans-cis-trans" cycle and suppression of the rotational diffusion by the covalent linkage to a polymer are the two important factors for the photoinduced reorientation of azo-dyes in bulk polymer matrix. (C) 2001 Elsevier Science B.V. All rights reserved.
Azo Polymers with Oligo(ethylene oxide) Side Chain for Rapid Surface Relief Formation.
Journal of Photopolymer Science and Technology,14(2):193-194 2001
Author:Zettsu Nobuyuki; Ubukata Takashi; Seki Takahiro; Ichimura Kunihiro
MISC
車載テクノロジー最前線 リチウムイオン二次電池の高電圧作動を可能にする電極表面処理技術
車載テクノロジー = Automotive technology,4(3):41-45 2017(Feb.)
Author:手嶋 勝弥; 是津 信行
全固体型リチウムイオン二次電池応用を目指した高結晶性固体電解質材料のフラックス育成
加工技術 = Textile processing technology,51(10):544-550 2016(Oct.)
Author:手嶋 勝弥; 是津 信行
フラックス概念を導入した環境調和プロセスによる機能性結晶薄膜の創成 (特集 セラミックスウェットコーティングの新たな潮流)
Ceramics Japan = セラミックス : bulletin of the Ceramic Society of Japan,51(8):478-482 2016(Aug.)
Author:手嶋 勝弥; 大石 修治; 是津 信行
フラックス法と先進リチウムイオン二次電池材料の出会い (特集 結晶構造・結晶薄膜デザインによる次世代エネルギー関連材料開発)
日本結晶成長学会誌 Journal of the Japanese Association for Crystal Growth,43(1):41-46 2016
Author:是津 信行; 手嶋 勝弥
エレワザ×エレザイ : エレクトロニクス関連のちょっとイイ技術&材料ファイル(FILE20)新しい結晶層作製&デザイン技術 : フラックスコーティング法の提案
コンバーテック,43(1):76-81 2015(Jan.)
Author:手嶋 勝弥; 是津 信行; 我田 元
フラックスコーティング法による結晶相界面デザイン (特集 表面・界面のメゾスコピックサイエンス)
材料の科学と工学 : 日本材料科学会誌,51(4):126-129 2014
Author:手嶋 勝弥; 是津 信行; 我田 元
金属ナノ結晶の形状制御と機能
日本結晶成長学会誌,37(4):281-290 2011(Jan. 31)
Author:是津 信行
Abstract:近年,液相中におけるナノ結晶合成技術が目まぐるしい発展を続けている.ナノ結晶のサイズや幾何学形状が材料固有の化学的・物理的性質だけに限らず,光・電子・磁気特性にまで影響を及ぼすことが実験的・理論的に明らかになっている.ナノ結晶の形状を制御することにより目的用途に適した機能を実現できる可能性が現実的なものとなってきた.本稿では,液相中における貴金属ナノ結晶の形状制御合成に焦点を当てて,当該領域における最近の研究報告を紹介する.さらに,形状制御された貴金属ナノ結晶によって創出された光機能として,銀ナノキューブの光学特性についてハイライトする.
局在表面プラズモン共鳴を利用した有機電界発光素子の高効率化
応用物理学会学術講演会講演予稿集(CD-ROM),71st 2010
Author:藤喜彩; 植村隆文; 是津信行; 赤井恵; 齊藤彰; 齊藤彰; 齊藤彰; 桑原裕司; 桑原裕司
局在表面プラズモン共鳴を用いた有機電界発光素子の色相制御
応用物理学会学術講演会講演予稿集(CD-ROM),71st 2010
Author:田中琢也; 藤喜彩; 是津信行; 赤井恵; 齋藤彰; 齋藤彰; 齋藤彰; 桑原裕司; 桑原裕司
有機電界発光素子のドーピングを用いた色相制御-ドーピング層の膜厚制御による-
精密工学会関西地方定期学術講演会講演論文集,2010 2010
Author:田中琢也; 藤喜彩; 是津信行; 赤井恵; 齋藤彰; 桑原裕司
Uniformalization of AT cut quartz crystal wafer thickness using open-air type plasma CVM process
Surface and Interface Analysis,40(6-7):1007-1010 2008(Jun.)
Author:Kazuya Yamamura; Tetsuya Morikawa; Masafumi Shibahara; Nobuyuki Zettsu; Yuzo Mori
Abstract:Improvement of thickness variation of the AT cut quartz crystal wafer is very important to advance the performance of the quartz resonator and to improve the productivity. However, conventional machining cannot exceed its technical limit any more, because quartz crystal is brittle and the wafer having thickness less than several tens of micrometers is required. We have newly developed the chemical finishing process to correct the thickness variation of the quartz crystal wafer, which utilizes localized atmospheric pressure plasma without gas replacing process. In the case of the atmospheric pressure plasma, high-density plasma region is localized in the vicinity of the electrode because of its small mean free path. Removal volume is proportional to the dwelling time of the plasma on the workpiece surface. Therefore, free figuring without mask pattern is realized by numerically controlled scanning of the localized reactive area. By applying our proposed correcting process, thickness variation of the commercially available AT cut quartz crystal wafer was improved from 270 to 40 nm. Copyright (C) 2008 John Wiley & Sons, Ltd.
高感度光誘起表面レリーフ形成とその応用
高分子加工,53(11):488-494 2004(Nov.)
Author:是津 信行; 生方 俊; 関 隆広
液晶性アゾベンゼン高分子における高感度な光誘起物質移動
液晶 : 日本液晶学会誌 = Ekisho,8(2):94-105 2004(Apr. 25)
Author:生方 俊; 是津 信行; 関 隆広
研究者総覧
