[in Japanese]

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In this work, we aimed at the preparation of a micro-pattern of a functional thin film using photocatalyst. For example, a TiO2 coating agent was spin-coated on a photomask and dried to produce a photomask with the photocatalyst. Next, a photomask with photocatalyst was placed over the substrate with the photocatalyst layer facing the water-repellent layer. The photomask was then irradiated with UV light. As a result, a wettable pattern formed due to the photocatalytic oxidized decomposition of the water-repellent layer.

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Some carbon compound materials, such as diamond, diamond-like carbon and polyimide, are promising materials, especially in electronics and photonics field. However, they are so mechanically hard and chemically inactive that it is not easy to machine their surface by conventional chemical or physical processes. Recently, we reported that a porous TiO2 wire, which was prepared by utilizing two-liquid phase separation in a TiO2-SiO2 system and selective leaching the SiO2-rich phase, could machine the surfaces of polyimide thin film and a PMMA plate under UV light irradiation. In this study, the mechanism of the photocatalytic decomposition of some carbon compound materials was investigated by the examinations of chemical conditions of their machined surfaces.

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[in Japanese]

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Our recent study revealed that nitrogen and fluorine codoped anatase is appropriate to obtain high activity of photo-catalytic activity under visible light illumination. However, the electronic structure of N- and/or F-doped ZnO is still unclear. Although we observed some defect related light emission form doped anatase, the assignments for the luminescence lines were not completed. In order to explain the properties of N- and/or F-doped anatase, we carried out first principle calculations to evaluate stability of N- and/or F-doped anatase and to estimate the activation energy for donors and acceptors introduced by N- and/or F-doping.

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Titanium oxide clusters doping nitrogen were prepared by the reaction of titanium tetrachloride vapor and NH3 gas on porous silica glass surface. The sample showed absorption in visible light region and photocatalytic activity depended on the amount of doped nitrogen atoms. The reaction mechanism on the glass surface was investigated by the measurements of in situ FT-IR spectra. The size of the cluster on the glass surface was estimated from the peak widths of X-ray diffraction pattern.

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Starting materials such as TiO2(TTO-55(N)) were mixed with PVA powder in various mass ratios and them heated up to 1100 degree C : Ar gas. Fine particles of photocatalytic TiO2 were coated by carbon, and reduced phase, such as Ti3O5 and Ti4O7 were formed through interaction between TiO2 and coated carbon. The photocatalytic activity was evaluated from the decomposition of IT in its aqueous solution under irradiation of visible light. Under visible irradiation, the carbon coated TinO2n-1 were confirmed to have photocatalytic activity.

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[in Japanese]

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Amorphous titanium oxide films were formed on metallic titanium by conventional anodization processes. The conventional anodized films hardly showed photocatalytic activities. High performance-titanium oxide films were sucessfully formed on metallic titanium by anodization process in acidic electrolytes after a pre-nitridation treatment. The anodized films showed high photocatalytic activities.

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[in Japanese]

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The composite with fiber assembled structure was fabricated by hot-pressing of green body composed with one-directionally aligned Al₂O₃ fiber. ZrO₂ as inter-fiber layer was coated on the surface of the fiber. Effects of ZrO₂ layer thickness or sintering temperature was evaluated. Sintering temperature for densification was more than 1773 K. All composites were fractured with non-brittle manner. Though the composite sintered at 1873K showed high strength, fracture manner became more brittle one.

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Highly oriented hydroxyapatite (HA) coatings were successfully obtained on titanium (Ti) through a radio-frequency thermal plasma spraying method. XRD patterns showed that the topmost HA layer of the coatings had an apatite structure with (00l) preferred orientation.

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Fluidized-bed reaction of niobium oxide powder was carried out at 1000 to 1400 C for 60 to 120 min in gas mixture of nitrogen, ammonia and hexane. Fine NbC powder was synthesized at 1400 C for 60 min in gas mixture of nitrogen, ammonia and hexane. Specific surface area and powder size of NbC powder was larger than raw powder.

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Several kinds of α-Fe fine powder were nitrided by ammonia treatment. The formation of Fe₁₆N₂ was found in the product by nitridation of α-Fe fine powder derived from γ-Fe₂O₃.

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Many Fe-Mn spinel-type oxides were synthesized and their magnetic properties were studied. The magnetic resistivity of 4.96% was obtained for FeMn2O4 spinel oxide.

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The effect of ethanol on the formation of magnetite (Fe3O4) was stsudied. Magnetite nanoparticles were synthesized from an Fe(OH)2 suspension (green rust) by oxidation with oxygen dissolved in an ethanol-water solution. There were no Fe3O4 cubic particles instead of needle-like crystal obtained when the pH value was up to 14.2 in 50% ethanol-water solution. The particle size was ~20nm as revealed by TEM photograph. The decrease of ethanol ratio in ethanol-water solution caused the increase of magnetite particle size. It was found that the formation of magnetite was slower in the high ethanol ratio solution.

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The preparation of gold nanoparticles has attracted much attention and has been intensively investigated in recent years because of their unique shape-dependent optical, catalytic, electrical and thermal properties. Recently, we have developed an efficient approach to morphology control of gold nanoparticles with icosahedrons on the basis of chemical reduction using ascorbic acid in the presence of polyvinylpyrrolidone (PVP) with addition of sodium hydroxide (NaOH). Detailed investigation on their formation process indicated that the growth of the icosahedrons was, in fact, a result of temperature change in the hydrothermal method. Besides gold icosahedrons, other well-crystallized gold nanoparticles including truncated triangles, rods, and wires were also obtained by adjusting synthesis parameters, in particular reaction temperature.

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Silver nanoparticles were prepared by reduction of silver nitrate by sodium borohydride in water, in the presence of 2-phosphonobutane-1,2,4-tricarboxylic acid(PBTCA). UV-vis spectroscopy was employed to characterize the silver colloids, and transmission electron microscopy (TEM) and dynamic light scattering (DLS) was used to determine the particle sizes. It is found that the presence of PBTCA can effectively protect the silver particles from aggregation. The mechanism for the protecting effect was investigated using FTIR analysis and zeta potential measurements.

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Rutile TiO2 absorbs more energy from solar irradiation compared to anatase TiO2. We previous reported that rutile TiO2 nanocrystals showed the significantly enhanced efficiency for the photocatalytic degradation of phenol solution. In this paper, we present the preparation of rutile TiO2 and tuning its pore size by thermal hydrolysis and hydrothermal treatment of TiCl4 solution. It is found that mesoporous rutile aggregated particles were formed in the presence of excessive chloride ions. Furthermore, monodispersed rutile particles with size of 500 nm were prepared by hydrothermal treatment of TiCl4 solution in the presence of NaCl or NH4Cl.

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Coal fly ash includes silica and alumina. They can be converted into zeolite by alkaline treatment. The fly ash was mixed with NaOH solution and heated at about 100 C. Zeolite synthesized from the fly ash was coated with TiO₂ by hydrolysis of titanium iso-propoxide. The XRD peaks of anatase phase were detected after the thermal treatment at 250 C. TiO₂ coated zeolite was effective for the decomposition of metylene-blue aqueous solution.

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The acidic amino acid, such as aspartic acid(L-Asp)and glutamic acid, are the molecules of the glycoprotein primarilyacting on the organic/inorganic interfaces of biomineralizedissue. Mimicking this biological phenomenon, we have investigated the effectsof several types of amino acid and water-soluble polymers on the morphogenesisof BaTiO₃ precursor particles that are useful for electronicproducts. BaTiO₃ has been synthesized by the liquid phase depositionmethod. Clear differences in size and shape of BaTiO₃ precursorparticles were found for different organic substances.

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Blue phosphors for PDP have been researched to solve low brightness and short lifetime occurred due to luminance degradation by heating process. Synthetic routes of phosphor materials have been developed by sol-gel, solid state reaction, etc.. To solve the above demerits of blue phosphors, we first syntheized nanosized BaMgAl₁₀O₁₇:Eu²⁺(BAM) in the range of 40-100 nm by using pulp or crystalline cellulose precursor process. The precursor impregnated with mixed metal salts was calcined in flowing air at 850 ^oC and then reduced under 5% H₂/N₂ flow at 1300-1500 ^oC. The nanosized BAM was characterized by XRD, TEM, photoluminescence, etc..

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The (Y,Gd)2O3:Eu phosphors were synthesized using impregnation method in order to improve the performance of red emitting phosphors for plasma display panel(PDP). (Y,Gd)2O3:Eu phosphor exhibits a strong red emission around 615nm. The particle size is in the range between 150 and 200nm. The emission intensity and particle size of powders were controlled by sintering temperature and raw material composition. As a result, we have found that particle size was very uniform and PL luminance characteristic was excellent about twice than commercial red phosphor.

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The Zn2SiO4:Mn phosphors were prepared using polymer matrix technique in order to improve the performance of green emitting phosphors for plasma display panel(PDP). Zn2SiO4:Mn phosphor exhibits a strong green emission around 520-530nm. The emission intensity and particle size of powders were controlled by sintering temperature and raw material composition. The zinc silicate Zn2SiO4:Mn single phase were obtained lower temperature than solid-state reaction method. PL luminance of Zn2SiO4:Mn phosphor was similar to the commercial material.

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Beta gallium oxide (β-Ga₂O₃) ceramics was reacted with alpha aluminum oxide (α-Al₂O₃) ceramics and zinc oxide (ZnO) ceramics. Energy dispersive X-ray spectroscopy (EDS) analysis revealed gradual distribution of Al, Zn and Ga around the boundary. In order to evaluate the microscopic domain of these reacted boundaries, the novel evaluation method was utilized. This evaluation method has combined cathodoluminescence (CL) and EDS, and it can analyze luminescence and elemental composition with simultaneously. The boundaries among these materials showed various emissions from visible to deep ultraviolet, and these emissions were strongly correlated to elemental composition of the samples.

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We report an electrochemical deposition of single-crystal-like ZnO thin films on a conductive substrate. The as-deposited film was ZnO with the wurzite structure of which crystallites highly oriented along (002) plane. The specific crystalline property may be attributed to the growth mechanism through the orientation attachment mode, which is one of the characteristics peculiar to the present process, because the terrace has been clearly observed in high-resolution AFM images. The film shows high transmittance and optical band gap energy of 3.3 eV. After annealing in N₂ or Ar, strong green emission was observed, which should be related to the generation of singly ionized oxygen defects. Improving emission intensity further by optimizing of the annealing conditions, this method may be promising to replace the traditional method for preparation of ZnO green phosphor.

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NASICON (Na3Zr2Si2PO12)-based solid-state ionic conductor as a host ceramic with a guest ion, such as Cu+, Eu3+ ions, have been produced as a noble phosphor powders and/or thick-films by using sol-gel method and/or electrophoretic deposition (EPD) method.

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Perovskite-type oxide thin films were prepared using polymer precurser or mixed organic solution. We study about calcination temperature effect on chemical property of the oxide thin film. Furthermore, we estimated the oxide thin-film for hydrogen-phosphate ion sensor.

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A high performance SOFC single cell with La0.9Sr0.1Ga0.8Mg0.2O3-d (LSGM)thin film (5 micron in thickness) as electrolyte, working at 400-700C willbe demonstrated. A Ce0.8Sm0.2O2-d (SDC) interlayer (400 nm in thickness)was introduced between the anode substrate of NiO-Fe2O3-SDC and the LSGMthin film to prohibit the reaction between LSGM and NiO and also to promotethe electrode processes. Both SDC and LSGM films were deposited by pulsedlaser deposition. The peak power density reached 3270 mW/cm2, 1951 mW/cm2,612 mW/cm2 and 80 mW/cm2 at 700, 600, 500 and 400C, respectively, which maybroaden the SOFC application to the mobile field.

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Polycrystalline silicon (poly-Si) has been received a great deal of attention for use in high resolution active matrix liquid crystal displays (AMLCDs), because of its high carrier mobility compared with amorphous silicon (a-Si) [1]. For the application of poly-Si TFTs on flexible substrate, all of the process temperature has to be come down below 200^oC. In this study, we propose the field aided rapid thermal annealing (FARTA) process to reduce the crystallization temperature of the amorphous silicon [2]. In this FARTA process, a pulse-type rapid thermal annealing was carried out periodically and the electric field was applied at the same time. Base temperature was maintained as low as possible during the crystallization process, and the temperature was rapidly heated up to peak temperature for few seconds periodically. Due to the low thermal conductivity of a-Si, pulse type heat streak could prevent the substrate from degradation during thermal heating. Upon heating, the metal catalyst treated area of silicon film was crystallized first, and it propagated into the metal free region with directionality because of electric field. By adopting the FARTA process, crystallization temperature could be reduced efficiently down to 200^oC. Without electric field during thermal annealing, however, we could not observe the crystallization of a-Si film at the same annealing condition of FARTA. These results imply that the electric field effect plays an important role in FARTA process. The effect of electric field and crystallization mechanism of FARTA process will be discussed.

References
[1] K. Sera et al., IEEE Trans. Electron Dev., 36(12), 2868 (1989)
[2] M.S.Kang et al., J. Vac. Sci. Technol. B, 21(5), 2076 (2003)

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