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    Provided is a method which enables observation of a minor crystal defect in a visible light region and which comprises: irradiating a substrate with polarized parallel light; and evaluating the crystal quality of at least one portion of the substrate through an image obtained from the light having transmitted through or been reflected by the substrate. The half value of width HW, the divergence angle DA, and the central wavelength CWL of the parallel light satisfy the following conditions, respectively. 3 ≤ HW ≤ 100, 0.1 ≤ DA ≤ 5, 250 ≤ CWL ≤ 1600, wherein the units of the central wavelength CWL and the half value of width HW are each nm, and the unit of the divergence angle DA is mrad.
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    The purpose of the present invention is to provide a method for polishing a silicon carbide substrate that allows the silicon carbide substrate to be polished at high speed and warping of the polished silicon carbide substrate surface to be minimized. The present invention is a method for polishing a silicon carbide substrate in which the surface of the silicon carbide substrate to be polished is disposed so as to face an electroconductive surface plate with an electrolyte solution containing a gap-forming material, abrasive grains, and an electrolyte interposed therebetween. At least a part of the surface of the silicon carbide substrate to be polished is electrolytically polished while in contact with the electrolyte solution, the surface of the silicon carbide substrate serving as positive electrode and the electroconductive surface plate serving as negative electrode.
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  • Raman characterization of damaged layers of 4H-SiC induced by scratching

    Nakashima, Shin-ichi   Mitani, Takeshi   Tomobe, Masaru   Kato, Tomohisa   Okumura, Hajime  

    Recent development of device fabrication of SiC is awaiting detailed study of the machining of the surfaces. We scratched 4H-SiC surfaces with a sliding microindenter made of a SiC chip, and characterized machining affected layers by micro-Raman spectroscopy. The results of the Raman measurement of the scratching grooves revealed that there were residual stress, defects, and stacking faults. Furthermore, with heavy scratching load, we found clusters of amorphous SiC, Si, amorphous carbon, and graphite in the scratching grooves. Analysis of the Raman spectra showed that SiC amorphization occurs first and surface graphitization (carbonization) is subsequently generated through the phase transformation of SiC. We expect that the Raman characterization of machined surfaces provides information on the machining mechanism for compound semiconductors. (C) 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (
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  • Development of Ultrahigh-Voltage SiC Devices

    Fukuda, Kenji   Okamoto, Dai   Okamoto, Mitsuo   Deguchi, Tadayoshi   Mizushima, Tomonori   Takenaka, Kensuke   Fujisawa, Hiroyuki   Harada, Shinsuke   Tanaka, Yasunori   Yonezawa, Yoshiyuki   Kato, Tomohisa   Katakami, Shuji   Arai, Manabu   Takei, Manabu   Matsunaga, Shinichiro   Takao, Kazuto   Shinohe, Takashi   Izumi, Toru   Hayashi, Toshihiko   Ogata, Syuuji   Asano, Katsunori   Okumura, Hajime   Kimoto, Tsunenobu  

    Ultrahigh-voltage silicon carbide (SiC) devices [p-i-n diodes and insulated-gate bipolar transistors (IGBTs)] and switching test have been investigated. As a result, we have succeeded in developing a 13-kV p-i-n diode, 15-kV p-channel IGBT, and 16-kV flip-type n-channel implantation and epitaxial IGBT with a low differential specific on-resistance (R-diff,R-on). It was revealed that a power module fabricated using a nanotech resin, Si3N4 ceramic substrate, and W base plate was suitable for ultrahigh voltage and high temperature. A switching test was carried out using a clamped inductive load circuit, which indicated that the energy loss of a circuit with ultrahigh-voltage SiC devices is lower than that of Si devices.
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    Provided is a silicon carbide powder which, when used as a raw material for a sublimation recrystallization method, is capable of improving productivity of a silicon carbide single crystal and of producing a large silicon carbide single crystal (for example, a single crystal wafer) since the powder has a high sublimation rate and the amount of residual silicon carbide that is not sublimed is small. The silicon carbide powder has a Blaine specific surface area of 250 to 1000 cm2/g and the ratio of the silicon carbide powder with a particle size of over 0.70 mm and 3.00 mm or less is 50 volume% or more of the total amount of the silicon carbide powder. By heating and subliming the silicon carbide powder (5) contained in a crucible (1), a single crystal (6) of silicon carbide can be formed on a seed crystal (4) provided on a bottom face portion of an upper lid (3).
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  • A Case of Ganglion Cyst in the Retropharyngeal Region

    Kato, Tomohisa   Kasuya, Norikuni   Takezawa, Kumiko   Shimizu, Takeshi  

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    Provided is a bathtub including: a back rest part which has an angle of inclination of 45° or less relative to the horizontal direction; a left shoulder rest part and a right shoulder rest part which are provided on the left and right sides of the upper portion of the back rest part; a left hand rest part and a right hand rest part which are provided on the left and right sides of the lower portion of the back rest part; and a left groove part and a right groove part which are provided on the left and right sides of the center of the backrest part in the up-down direction, which are recessed, more than the back rest part, to the rear of a user whose back is resting against the backrest part, and which enable the bather's elbows to be positioned rearward of the back rest part when the bather pushes the left hand rest part and the right hand rest part with his or her hands to sit up.
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  • Enlargement Growth of Large 4H-SiC Bulk Single Crystal

    Kato, Tomohisa   Miura, Tomonori   Nagai, Ichiro   Taniguchi, Hiroyoshi   Kawashima, Hideaki   Ozawa, Tetsuya   Arai, Kazuo   Okumura, Hajime  

    In this study, we suggest the effective enlargement method of (0001) 4H-SiC bulk crystals grown by the sublimation method using long length growth technique (LLG). This method could achieve low thermal strain and rapid enlargement growth comparing with conventional c-axis growth technique. We also demonstrated high quality enlargement growth from Phi 2inch to Phi 4inch of (0001) 4H-SiC by LLG.
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  • AlN bulk crystal growth by sublimation method

    Kato, Tomohisa   Nagai, Ichiro   Miura, Tomonori   Kamata, Hiroyuki   Naoe, Kunihiro   Sanada, Kazuo   Okumura, Hajime  

    In this study, we report the growth of aluminum nitride (AlN) bulk single crystals by the sublimation method. The crystals were grown in a newly designed TaC crucible. The crucible has a TaC guard ring around the seed crystal to protect against polycrystal deposition around the seed crystal during the initial growth stage. The ring enhances lateral enlargement growth because it protects against the polycrystal deposition. The (0001) oriented AlN crystals were grown on (0001) SiC and (0001) AlN seed crystals. The largest grown crystal was 43 mm in diameter. The best quality area on the grown AlN crystal had the lowest etch pit density of 1x10(-4)cm(-2). (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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  • The effect of calprotectin on TSLP and IL-25 production from airway epithelial cells

    Kato, Tomohisa   Kouzaki, Hideaki   Matsumoto, Koji   Hosoi, Junichi   Shimizu, Takeshi  

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  • AlN bulk single crystal growth on 6H-SiC substrates by sublimation method

    Nagai, Ichiro   Kato, Tomohisa   Miura, Tomonori   Kamata, Hiroyuki   Naoe, Kunihiro   Sanada, Kazuo   Okumura, Hajime  

    Large and thick AlN bulk single crystals up to 43 mm in diameter and 10 mm in thickness have been successfully grown on 6H-SiC (0 0 0 1) substrates by the sublimation method using a TaC crucible. Raman spectrum indicates that the polytype of the grown AlN single crystals is a Wurtzite-2H type structure, and the crystals do not include any impurity phases. The quality at the top of the crystal improves as crystal thickness increases along the < 0 0 0 1 > direction during growth: a low etch pit density (7 x 10(4) cm(-2)) and a small full width at half maximum for a 0002 X-ray rocking curve (58 arcsec) have been achieved at a thickness of similar to 8 mm. The possible mechanism behind the improvement in the AlN crystal quality is also discussed. (C) 2010 Elsevier B.V. All rights reserved.
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  • Alkane inducible proteins in Geobacillus thermoleovorans B23

    Kato, Tomohisa   Miyanaga, Asuka   Kanaya, Shigenori   Morikawa, Masaaki  

    Background: Initial step of beta-oxidation is catalyzed by acyl-CoA dehydrogenase in prokaryotes and mitochondria, while acyl-CoA oxidase primarily functions in the peroxisomes of eukaryotes. Oxidase reaction accompanies emission of toxic by-product reactive oxygen molecules including superoxide anion, and superoxide dismutase and catalase activities are essential to detoxify them in the peroxisomes. Although there is an argument about whether primitive life was born and evolved under high temperature conditions, thermophilic archaea apparently share living systems with both bacteria and eukaryotes. We hypothesized that alkane degradation pathways in thermophilic microorganisms could be premature and useful to understand their evolution. Results: An extremely thermophilic and alkane degrading Geobacillus thermoleovorans B23 was previously isolated from a deep subsurface oil reservoir in Japan. In the present study, we identified novel membrane proteins (P16, P21) and superoxide dismutase (P24) whose production levels were significantly increased upon alkane degradation. Unlike other bacteria acyl-CoA oxidase and catalase activities were also increased in strain B23 by addition of alkane. Conclusion: We first suggested that peroxisomal beta-oxidation system exists in bacteria. This eukaryotic-type alkane degradation pathway in thermophilic bacterial cells might be a vestige of primitive living cell systems that had evolved into eukaryotes.
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  • Morphology Improvement of Step Bunching on 4H-SiC Wafers by Polishing Technique

    Kato, Tomohisa   Kinoshita, Akimasa   Wada, Keisuke   Nishi, Takashi   Hozomi, Eiji   Taniguchi, Hiroyoshi   Fukuda, Kenji   Okumura, Hajime  

    In this paper, we report a new polishing technique regarding the elimination of step bunching on the silicon carbide (SiC) surface. The step bunching generation is often observed as frequent phenomenon on the surface of SiC epilayers grown on low off-angle (0001) SiC wafers and on SiC devices after annealing to activate the dopants. We polished the step bunching surface using a chemical mechanical polishing (CMP) technique reported in a previous study, and we succeeded to improve the morphology with a flat and smooth surface which showed a small Rms value of around 0.1nm. We especially found an excellent polishing effect for the control of leakage current in reverse I-V characteristics of SiC Schottky barrier diodes (SBD).
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    Disclosed is a toner for electrophotography which is excellent in low-temperature fixability, hot offset resistance and image stability. Also disclosed is a toner binder used therefor. Specifically disclosed is a toner binder for electrophotography which contains a styrene (co)polymer, wherein the acid value of the component (P) [AV (P)] is 9-30, the acid value of the component (Q) [AV (Q)] is 2-26, and the acid value of the component (R) [AV (R)] is 0-6, when the component having a molecular weight as determined by gel permeation chromatography of less than 25,000 is taken as a component (P), the component having a molecular weight as determined by gel permeation chromatography of not less than 25,000 but not more than 300,000 is taken as a component (Q) and the component having a molecular weight as determined by gel permeation chromatography of more than 300,000 is taken as a component (R). In addition, AV (P), AV (Q) and AV (R) satisfy the following relation (1). AV (P) > AV (Q) > AV (R) (1)
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    Provided is a shower bath system, which comprises a recessed seat unit and a water discharge unit disposed above the back of the seat unit for discharging water forward of the seat unit. The shower bath system is characterized in that the direction of the discharged water from the water discharge unit and the positional relation between the water discharge unit and the seat unit are so adjusted that at least a portion of the discharged water may shower the seat unit directly when a user is not seated on the seat unit. The shower bath system thus provided can enhance a bathing feel and a warming effect while the user is receiving the shower flow in the comfortable seated position, so that the user can warm the whole body in the seated position.
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  • Dendritic Cells Pre-Pulsed with Wilms' Tumor 1 in Optimized Culture for Cancer Vaccination

    Koya, Terutsugu   Date, Ippei   Kawaguchi, Haruhiko   Watanabe, Asuka   Sakamoto, Takuya   Togi, Misa   Kato, Tomohisa   Yoshida, Kenichi   Kojima, Shunsuke   Yanagisawa, Ryu   Koido, Shigeo   Sugiyama, Haruo   Shimodaira, Shigetaka  

    With recent advances in cancer vaccination therapy targeting tumor-associated antigens (TAAs), dendritic cells (DCs) are considered to play a central role as a cell-based drug delivery system in the bioactive immune environment. Ex vivo generation of monocyte-derived DCs has been conventionally applied in adherent manufacturing systems with separate loading of TAAs before clinical use. We developed DCs pre-pulsed with Wilms' tumor (WT1) peptides in low-adhesion culture maturation (WT1-DCs). Quality tests (viability, phenotype, and functions) of WT1-DCs were performed for process validation, and findings were compared with those for conventional DCs (cDCs). In comparative analyses, WT1-DCs showed an increase in viability and recovery of the DC/monocyte ratio, displaying lower levels of IL-10 (an immune suppressive cytokine) and a similar antigen-presenting ability in an in vitro cytotoxic T lymphocytes (CTLs) assay with cytomegalovirus, despite lower levels of CD80 and PD-L2. A clinical study revealed that WT1-specific CTLs (WT1-CTLs) were detected upon using the WT1-DCs vaccine in patients with cancer. A DC vaccine containing TAAs produced under an optimized manufacturing protocol is a potentially promising cell-based drug delivery system to induce acquired immunity.
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