Volume 790

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Authors: Shin Ichi Furusawa, Tomosato Ida
Abstract: Tensile stress was applied to β-AgI thin film prepared on a polyethylene terephthalate film, and the ion conduction response in the direction of the tensile extension was investigated. The ionic conductivity of the β-AgI thin film decreases and the activation energy for ionic conduction increases with increasing extension ratio. This behaviour is attributed to the modulation of the crystal framework by the extension of the AgI thin film.
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Authors: Shin Ichi Furusawa, Yohei Minami
Abstract: MAlSi3O8 (M = Li, Na, K) was synthesized by solid-phase reaction at 1000 °C using M2CO3 (M = Li, Na, K), Al2O3, and SiO2 as the starting materials, and its ionic conduction was studied in the temperature range 475–800 K. It was confirmed from powder X-ray diffraction profiles that the crystalline phases of the prepared MAlSi3O8 were the same as those of orthoclase. Moreover, the ionic conductivity of NaAlSi3O8 was about 10 times higher than that of LiAlSi3O8 and KAlSi3O8. The activation energies for ionic conduction were estimated to be in the range of 0.70–0.77 eV, with NaAlSi3O8 exhibiting the lowest activation energy. The result suggests that the magnitude of the activation energy cannot be determined only from the ionic radius.
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Authors: Kosuke Suzuki, Ayumu Terasaka, Tomoya Abe, Hiroshi Sakurai
Abstract: In this study, we calculate electronic structures for Mn2O4 and LiMn2O4 by using CRYSTAL14 ab-initio calculation code in order to understand electrode reaction mechanism of LixMn2O4 by lithiation/delithiation. Mulliken population analysis for all electrons show that the redox orbitals with lithiation and delithiation is O 2p orbitals. However, difference charge densities between majority and minority electrons indicate the change of distribution in Mn 3d orbitals by lithiation. This modification of distribution in Mn 3d orbitals suggests the change of electron configuration because the number of electrons at Mn atom is almost constant in Mulliken population analysis for all electrons. As a result, this modification of distribution in Mn 3d orbitals improves electron conductivity of this material.
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Authors: Yoshiharu Suzuki, Teruo Kanki, Hidekazu Tanaka, Tomotaka Inoue, Naoki Wada, Kiyohiko Matsubara, Naoki Asakawa
Abstract: Stochastic resonance (SR) phenomenon is emerged in organic field effect transistors (OFETs) using $\pi$-conjugated polymer, where application of external noise to the OFET system enhances signal/information processing performance which is often found in biological systems.The channel conductivity of the OFET is slightly increased by spin-coating using heated semiconductor polymer solution with heated glass substrate.In order to improve frequency responses of OFET, optimal width of the gate electrode is explored. Furthermore, it turns out that scratching and removing semiconductor film outside the source-drain electrodes and the channel enhances the On-Off current ratio of the device. These fabrication processes lead to steeper nonlinearity on the $I_{\rm DS}$ {\it vs.} $V_{\rm GS}$ curve, resulting in emergence of SR, which is fingerprinted in increase of correlation value between input and output signals with increase of intensity of external noise.
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Authors: Tashiro Tomoya, Hui Zhang, Kakeru Oshima, Yuya Sakurai, Takaaki Suzuki, Noriyasu Ohshima, Takashi Izumi, Hayato Sone
Abstract: A simple fabrication process of an n-type silicon nanowire (SiNW) biosensor for sub-10 femtomolar (fM) concentration immunoglobulin detection was presented in this work. The SiNWs with different widths of 80-190 nm were fabricated using electron beam lithography and reaction ion etching techniques. The electrical characteristics of SiNWs with various widths were measured. And it can be observed that thin SiNW has high resistance, which is in agreement with electrical resistance theory. Furthermore, the surface of the fabricated SiNW was functionalized by 3-aminopropyltriethoxysilane for making the biosensor device to detect the binding of immunoglobulin G (IgG) molecules. The responsivity of the biosensor was investigated by observing electrical performance in response due to IgG with various concentration from 6 fM to 600 nanomolar (nM). The resistance changing ratio based on the current voltage (I-V) characteristics was analyzed and it increased with increasing of the IgG concentration. As a result, it demonstrated that the n-type SiNW biosensor has the ability to detect the IgG molecules with low concentration of 6 fM.
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Authors: Koichi Tanaka, Kanami Okamoto
Abstract: We fabricated Si:SiO2 films including silicon nanocrystallites as one of nanoscale materials, which were prepared by co-sputtering of silicon and silicon dioxide. Optical properties of these films were analyzed by photoluminescence spectroscopy. Specimens fabricated at higher pressure between 0.3 Pa to 0.9 Pa emitted photoluminescence strongly. Photoluminescence was strong at shorter wavelength. In case fabricated in same Ar gas pressure, specimens that had composition ratio, 0.04, of the silicon for target emitted the photoluminescence strongly. Peaks existed on some PL spectra of specimen fabricated by the Ar gas pressure 0.3, 0.5 Pa and the composition ratio 0.04. Suppose that silicon nanocrystallites were fabricated, these size were few nm.
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Authors: Masahiro Kanakubo, Kenta Miura, Keisuke Shimada, Ryosuke Fujii, Katsuya Noguchi, Wataru Kada, Osamu Hanaizumi
Abstract: We prepared ytterbium and silver co-doped tantalum-oxide (Ta2O5:Yb,Ag) thin films using a simple co-sputtering method and evaluated photoluminescence (PL) properties of the films after annealing. We found that a PL peak at a wavelength of 980 nm due to Yb3+ can be strongly enhanced by Ag doping. From X-ray diffraction measurements, we found that Ag2Ta8O21 and orthorhombic Ta2O5 crystalline phases are very important in order to enhance the 980-nm peak observed from our Ta2O5:Yb,Ag thin films. Because of the human-body transmittability of the 980-nm wavelength, such films are applicable to a novel real-time X-ray dosimeter system.
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Authors: Moriyoshi Haruyama, Yoshinori Suda, Wataru Kada, Shinobu Onoda, Takeshi Ohshima, Kenta Miura, Osamu Hanaizumi
Abstract: Micrometer-scale patterning was performed using the particle beam writing technique with a focused heavy-ion microbeam, allowing the creation of a unique two-dimensional distribution of fluorescent centers in single-crystalline diamond. The focused nitrogen microbeam was scanned over the target of single-crystalline diamond prepared by chemical vapor deposition to create nitrogen-vacancy (NV) centers at defined positions. Imaging using a custom-built confocal fluorescence microscopy system revealed that the desired NV distribution was generated in the target crystal with a spatial resolution similar to the beam resolution. A two-dimensional matrix barcode test pattern was successfully generated in a diamond substrate to demonstrate the encryption of information inside a solid-state target.
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Authors: Shunji Ozaki, Kazuya Matsumoto
Abstract: Zinc selenide (ZnSe) nanowires were grown on Si and fused quartz substrates by a simple vapor transport method of heating the ZnSe powder at 1100 °C in a tube of the furnace. The obtained yellow colored product has indicated to be the high density of ZnSe nanowires with diameters ranging from 50 to 200 nm. Low-temperature photoluminescence spectra for ZnSe nanowires show near band-edge emissions. The free excitonic emissions were observed at ~2.8 eV.
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