Advanced Micro-Device Engineering IV

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Authors: Kenta Hiiragi, Masahiro Naito, Hiromi Watanabe, Hiroshi Maruyama, Masahisa Ito
Abstract: Diffraction intensities of a single crystal of Fe3Pt alloy have been measured by using white X-rays of synchrotron radiation. The observed intensities have been compared with the calculated ones for fundamental and superlattice reflections. By normalizing the calculated intensities of fundamental reflections to the observed ones and evaluating the ratio of the observed intensity of superlattice reflection to the calculated ones, we have estimated the order parameter as 0.82±0.03. The obtained order parameter has been applied to an analysis of the X-ray magnetic diffraction data to estimate the spin moment of Fe and Pt atoms in this alloy.
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Authors: Kosuke Suzuki, Masaki Hayata, Katsuhiko Minegishi, Ryosuke Kondoh, Tadashi Kato, Kazushi Hoshi, Masayoshi Itou, Yoshiharu Sakurai, Hiroshi Sakurai
Abstract: Magnetic Compton profiles (MCPs) of Co/Au multilayers have been measured and analyzed by DV-Xα cluster model calculations from a viewpoint of perpendicular magnetic anisotropy (PMA). The PMA and the MCPs are discussed for the presently obtained results for Co/Au, along with the previously obtained results for Co/Pd and Co/Pt. A Co/Au multilayer shows a weak PMA which is caused by |m|=1 states of Co 3d electrons at a smooth Co/Au interface. The increase of the interface-to-volume ratio plays the main role in determining the perpendicular anisotropy in Co/Au multilayers. The strain of a Co layer can have a secondary role in determining the magnetic anisotropy in Co/Au multilayers, although the strain dominates PMA in the case of Co/Pd and Co/Pt multilayers.
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Authors: Shinichi Furusawa, Takao Tsurui, Kouhei Shimizu
Abstract: Thin-film samples of the lithium ionic conductor Li2SiO3 (LSO) were deposited on an A-plane sapphire substrate via the pulsed laser deposition (PLD) method, and the irreversible temperature dependence of the ionic conductivity in the thin-film samples was studied. Via transmission electron microscopy (TEM) observations of annealed LSO thin-film, it was found that the as-prepared LSO thin-film was amorphous over the temperature range T 490 K, and that nanocrystals existed in the annealed LSO thin-film in the temperature range T 550 K. Further more, it was clarified the irreversible temperature dependence of the ionic conductivity is due to the generation of nanocrystals.
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Authors: Tamihiro Gotoh, Kosuke Yazawa, Kento Imai
Abstract: Electrical properties of SnS films deposited by a thermal evaporation method have been investigated using the resistivity and thermopower measurements. The SnS films show p-type conduction at room temperature, and electrical activation energy of ~0.3 eV. Resistivity and Seebeck coefficient at room temperature were ~4×101 Ωm and +0.2 mV/K for as-deposited sample. The resistivity decreased ~1×100 Ω·m and the Seebeck coefficient increased +0.27 mV/K when the sample was annealed at 400 °C. Crystallization and structural change cause the improvement of electronic transport with annealing treatment.
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Authors: Toru Kyomen, Takumi Nozawa, Minoru Hanaya
Abstract: La1-xBaxCoO3 single crystals were grown from KOH melt at 873 K under H2O/O2 mixed gas flow. The grown crystals had a parallelepiped form with the edges of about 60 μm. Streaks indicating twin boundaries were observed on the surface planes of the crystals. The crystals showed magnetic anisotropy and anomalous MH hysteresis loops. The magnetocrystalline anisotropy and coupling of ferroelasticity and ferromagnetism were discussed based on the magnetic properties.
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Authors: Yusuke Ogiwara, Kimiko Dejima, Toru Kyomen, Minoru Hanaya
Abstract: In order to obtain information about the structure of a typical Li+-ion conducting glass of (LiCl)x(LiPO3)1-x, 31P MAS NMR measurements were performed for the glass samples with different LiCl compositions x from 0 to 0.4. NMR spectra of the samples indicated the existence of two kinds of P atoms; one is that within the-P-O-P-O-P-chain of LiPO3, P(Q2), and the other is that at the ends of the chain, P(Q1). The ratio of the amount of P(Q1) to that of P(Q2) was observed to increase with the increment of x. The result shows that the addition of LiCl to the glass former of LiPO3 changes the glass network structure by cutting P-O bonds in one-dimensional phosphate chain, and the increment of the Li+-ion conductivity with the increase of x is concluded to be brought not only by the increase of the amount of LiCl dissolved into the interstices between the phosphate glass networks but also by the dispersion of the phosphate glass network structure.
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Authors: Kenji Kakiage, Emi Fujimura, Yoshinori Nakada, Takashi Ogino, Toru Kyomen, Minoru Hanaya
Abstract: In dye-sensitized solar cells (DSSCs) fabricated with azobenzene and azulene derivatives as the photosensitizing dyes, the replacement of the conventional I3-/I- redox mediator with Br3-/Br- redox mediator possessing more positive redox potential has been examined to improve open-circuit photovoltages (Voc) of the cells. The cells with the Br3-/Br- redox mediator exhibited high Voc of ~0.8 V, resulting in higher light-to-electric energy conversion efficiencies (η) than the cells with the I3-/I- redox mediator by a factor of 1.7 under the simulated sunlight irradiation (AM-1.5G, 100 mW cm-2). The results indicate a high potential of the Br3-/Br- redox mediator in DSSCs.
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Authors: Shinnosuke Noguchi, Toru Tokutome, Shinji Iwamoto
Abstract: Niobium modified titania samples were prepared by thermal reaction of titanium tetraisopropoxide and niobium pentaethoxide in 1,4-butanediol at 300 °C (solvothermal method), and the products were nitrified in an NH3 flow at 600 °C. The physicochemical property of the thus-obtained N-and Nb-co-doped titanias and visible-light response photocatalytic activity of FeOx-loaded N-and Nb-co-doped titanias were investigated. The N-and Nb-co-doped titanias had larger absorptions in the visible-light range as compared to the only N-doped titania samples. In ESR spectra of the Nb-modified TiO2 samples annealed at 300 °C after the nitrification, signals due to Ti3+ and oxygen vacancies, which accelerate the recombination of the photo-generated electrons and holes, were clearly observed. On the other hand, for the N-and Nb-co-doped titanias annealed at 500 °C, the signals due to Ti3+ and oxygen vacancies decreased significantly. Actually, the FeOx-loaded N-and Nb-co-doped samples annealed at 500 °C exhibited a higher photocatalytic activity for a photocatalytic decomposition of acetaldehyde under visible-light irradiation.
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Authors: Hiroki Uehara, Masaki Kakiage, Hidekazu Tanaka, Takeshi Yamanobe
Abstract: Structural deformation during uniaxial drawing of polyethylene-block-polystyrene (PE-b-PS) copolymer film was analyzed by in-situ small angle X-ray scattering (SAXS) measurement. The PE-b-PS film was prepared by solution casting, followed by isothermally crystallizing from melt. The obtained film exhibits the characteristic bicontinuous crystalline/amorphous morphology. Initial stage of uniaxial drawing induces the orientation of such crystalline/amorphous phases, but these phase separation is destroyed in the latter stage. In contrast, solvent swelling treatment successfully induces the orientation of crystalline/amorphous phases with keeping the phase continuity.
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Authors: Takayuki Ishikawa, Mohammad Ali Abdelkareem, Takuya Tsujiguchi, Nobuyoshi Nakagawa
Abstract: Tungsten carbide nanofibers for the anode catalyst of direct methanol fuel cells (DMFCs) were prepared from the precursor nanofibers with the diameter around 250 nm using an electrospinning technique. The electrospun nanofibers from the mixture of ammonium metatungstate and polyvinylpyrrolidone were dried and calcined in air at 700 °C to form tungsten oxide nanofibers, and reduced in 20 vol.% CH4/H2 atmosphere at 700 °C for 2 h. Surface morphology and crystalline structure of the prepared nanofibers were investigated using FE-SEM and XRD. The methanol oxidation reaction (MOR) activity of the prepared samples was evaluated by cyclic voltammetry (CV). The FE-SEM and XRD analyses showed that beaded nanofibers of tungsten carbide were successfully obtained. The WC nanofiber electrocatalyst exhibited a MOR activity suggesting it can be a candidate of the catalyst for DMFC. The presence of impurities, carbon and tungsten oxide, which may affect the activity, were detected at the surface.
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