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Now showing items 1 - 16 of 35

  • 3C-SIC SINGLE CRYSTAL AND PRODUCTION METHOD THEREFOR

    The purpose of the present invention is to provide a method for producing a 3C-SiC single crystal, while prioritizing the growth of one of two types of 3C-SiC. A 6H-SiC or a 4H-SiC having an off angle formed so as to be in a range of the [1-100] direction ±15° from the (0001) surface is used as a seed crystal, and a 3C-SiC single crystal is step-flow grown upon this seed crystal. Alternately, a 3C-SiC having an off angle formed so as to be in the range of the [11-2] or the [-1-12] direction ±15° from the (111) surface is used as a seed crystal, and a 3C-SiC single crystal is step-flow grown upon this seed crystal.
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  • Dislocation Conversion During SiC Solution Growth for High-Quality Crystals

    Harada, Shunta   Yamamoto, Yuji   Xiao, Shi Yu   Koike, Daiki   Mutoh, Takuya   Murayama, Kenta   Aoyagi, Kenta   Sakai, Takenobu   Tagawa, Miho   Ujihara, Toru  

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  • High-speed prediction of computational fluid dynamics simulation in crystal growth

    Tsunooka, Yosuke   Kokubo, Nobuhiko   Hatasa, Goki   Harada, Shunta   Tagawa, Miho   Ujihara, Toru  

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  • Detection of edge component of threading dislocations in GaN by Raman spectroscopy

    Kokubo, Nobuhiko   Tsunooka, Yosuke   Fujie, Fumihiro   Ohara, Junji   Hara, Kazukuni   Onda, Shoichi   Yamada, Hisashi   Shimizu, Mitsuaki   Harada, Shunta   Tagawa, Miho   Ujihara, Toru  

    We succeeded in measuring the density and direction of the edge component of threading dislocations (TDs) in c-plane (0001) GaN by micro-Raman spectroscopy mapping In the micro-Raman spectroscopy mapping of the E-2(H) peak shift between 567.85 and 567.75 cm(-1), six different contrast images are observed toward directions of (1100) By comparing X-ray topography and etch pit images, the E-2(H) peak shift is observed where the edge component of TDs exists in contrast, the E-2(H) peak is not observed where the screw component of TDs exists (C) 2018 The Japan Society of Applied Physics.
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  • Direct Growth of AlN Single Crystal on Sapphire by Solution Growth Method

    Matsubara, Hiroaki   Mizuno, Kohei   Takeuchi, Yukihisa   Harada, Shunta   Kitou, Yasuo   Okuno, Eiichi   Ujihara, Toru  

    AlN was directly grown on a sapphire substrate by the solution growth method with the Cu-Si-Al-Ti solvent under a nitrogen gas flow. X-ray diffraction measurements revealed that the grown AlN was single crystal. The AlN layer was epitaxially formed on the sapphire substrate with the orientation relationships: (0001)(AlN) parallel to (0001)(sapphire) and [(1) over bar 100](AlN) parallel to [<(1over bar>120](sapphire). The full widths at half maximum (FWHMs) of X-ray rocking curves for tilt and twist components were 414 and 2031 arcsec, respectively. (C) 2013 The Japan Society of Applied Physics
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  • Nondestructive visualization of threading dislocations in GaN by micro raman mapping

    Kokubo, Nobuhiko   Tsunooka, Yosuke   Fujie, Fumihiro   Ohara, Junji   Onda, Shoichi   Yamada, Hisashi   Shimizu, Mitsuaki   Harada, Shunta   Tagawa, Miho   Ujihara, Toru  

    Threading dislocations (TDs) in a HVPE-grown c-plane (0001) GaN single crystal were analyzed by micro Raman spectroscopy mapping. The mapping image exhibited the pairs of higher and lower wavenumber regions of E-2(H) peak shift of GaN, which corresponded to the compressive and tensile strains due to TDs. By comparing X-ray topography and etch pit images, the contrasts are considered as the edge component of TDs. By analyzing the existing 290 TDs in 80 x 80 mu m(2), the directions of the contrast were mainly dominant toward < 10 (1) over bar0 >. A few brighter contrasts toward < 11 (2) over bar0 > were also observed. These TDs are affiliated with Burgers vectors b =3D a/3 < 11 (2) over bar0 >, and b =3D a < 01 (1) over bar0 >, respectively. Judging from experimental and simulated result, it is confirmed that the contrast in the Raman mapping image of the b - a < 0 (1) over bar 10 > has a larger magnitude than the b =3D a/3 < 11 (2) over bar0 >. (C) 2019 The Japan Society of Applied Physics
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  • Polytype-selective growth of SiC by supersaturation control in solution growth

    Seki, Kazuaki   Alexander   Kozawa, Shigeta   Harada, Shunta   Ujihara, Toru   Takeda, Yoshikazu  

    We realized the polytype-selective growth of 3C-SiC and 6H-SiC on a 6H-SiC (0 0 0 1) seed crystal by controlling the supersaturation. Both 6H-SiC and 3C-SiC grew on the 6H-SiC seed crystal at low supersaturation, but 3C-SiC increased with increasing supersaturation. At high supersaturation, 3C-SiC grew so rapidly that it completely covered the 6H-SiC seed crystal. The growth rates of 3C-SiC and 6H-SiC have different dependences on supersaturation. In the present case, the growth rate of 3C-SiC in 2D nucleation mode is compared with that of 6H-SiC in spiral growth mode. The present kinetic polytype-control technique is based on polytypes having different growth rates and it differs considerably from the conventional technique that is based on "inheritance" of stacking sequence, which is well known as "step-controlled epitaxy". (C) 2011 Elsevier B.V. All rights reserved.
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  • CRYSTAL PRODUCTION DEVICE, PRODUCTION METHOD FOR SIC SINGLE CRYSTALS, AND SIC SINGLE CRYSTAL

    To provide a crystal production device capable of producing single crystals having excellent quality. A crystal production device that causes single crystals to grow on the crystal growth surface of a seed crystal in a raw material solution by using a liquid-phase growth method has a configuration comprising: a liquid tower (20) that houses the raw material solution (29); a crystal holding element (3) that holds the seed crystal (1); and a solution flow element (25) that causes the raw material solution (29) in the liquid tower (20) to flow. The crystal holding element (3) is configured so as to be capable of holding the seed crystal (1) inside the liquid tower (20) and capable of moving in at least part of an area in the xy plane orthogonal to the z axis extending in the depth direction of the liquid tower (20).
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  • Crystal structure refinement of ReSi(1.75) with an ordered arrangement of silicon vacancies

    Harada, Shunta   Hoshikawa, Hiroaki   Kuwabara, Kosuke   Tanaka, Katsushi   Okunishi, Eiji   Inui, Haruyuki  

    The crystal structure and microstructure of ReSi(1.75) were investigated by synchrotron X-ray diffraction combined with scanning transmission electron microscopy. ReSi(1.75) contains an ordered arrangement of vacancies in Si sites in the underlying tetragonal C11(b) lattice of the MoSi(2)-type and the crystal structure is monoclinic with the space group Cm. Atomic positions of Si atoms near vacancies are considerably displaced from the corresponding positions in the parent C11(b) structure, and they exhibit anomalously large local thermal vibration accompanied by large values of atomic displacement parameter. There are four differently-oriented domains with two of them being related to each other by the 90 degrees rotation about the c-axis of the underlying C11(b) lattice and the other two being their respective twins. The habit planes for domain boundaries observed experimentally are consistent with those predicted with ferroelastic theory.
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  • Crystal Structure and Thermoelectric Properties of ReSi1.75 Based Alloys

    Harada, Shunta   Tanaka, Katsushi   Kishida, Kyosuke   Inui, Haruyuki  

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  • Direct Observation of Vacancies and Local Thermal Vibration in Thermoelectric Rhenium Silicide

    Harada, Shunta   Tanaka, Katsushi   Kishida, Kyosuke   Okamoto, Norihiko L.   Endo, Noriaki   Okunishi, Eiji   Inui, Haruyuki  

    The crystal structure of rhenium silicide with an anomalous ordered arrangement of vacancies has been investigated by utilizing spherical-aberration (C-s)-corrected scanning transmission electron microscopy (STEM). Using C-s-corrected STEM imaging, we directly observe for the first time ordered silicon vacancies in thermoelectric rhenium silicide accompanied by anomalously large local thermal vibration ("rattling" motion) of silicon atoms in their adjacent sites. (C) 2012 The Japan Society of Applied Physics
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  • Direct Observation of Vacancies and Local Thermal Vibration in Thermoelectric Rhenium Silicide

    Harada, Shunta   Tanaka, Katsushi   Kishida, Kyosuke   Okamoto, Norihiko L.   Endo, Noriaki   Okunishi, Eiji   Inui, Haruyuki  

    The crystal structure of rhenium silicide with an anomalous ordered arrangement of vacancies has been investigated by utilizing spherical-aberration (C-s)-corrected scanning transmission electron microscopy (STEM). Using C-s-corrected STEM imaging, we directly observe for the first time ordered silicon vacancies in thermoelectric rhenium silicide accompanied by anomalously large local thermal vibration ("rattling" motion) of silicon atoms in their adjacent sites. (C) 2012 The Japan Society of Applied Physics
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  • Effect of Crystal Orientation of Cu Current Collectors on Cycling Stability of Li Metal Anodes

    Ishikawa, Kohei   Harada, Shunta   Tagawa, Miho   Ujihara, Toru  

    Li metal anodes are plagued by low coulombic efficiency due to their interfacial instability. Many approaches were proposed to cope with this problem; however, little attention has been given to the current collector of Li anodes. In this study, we investigate the crystal orientation dependence of the cycling stability of Li anodes on single-crystal Cu(111), (101), and (001) and polycrystalline Cu current collectors. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) show that (111) and (001) achieved high current efficiency and low interfacial resistance, while (101) and polycrystalline Cu exhibited low cyclabilities. X-ray photoelectron spectroscopy (XPS) and auger electron spectroscopy (AES) analysis revealed that the thickness of the solid electrolyte interphase (SEI) varies with the Cu crystal orientation, and the SEI is the thinnest on the single-crystal Cu(111). This tendency can be explained by the orientation dependence of the surface energy of Cu, which corresponds to the chemical activity of the surfaces. Our result advocates the importance of considering Cu orientation for interfacial engineering of Li metal anodes.
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  • Achiral Metastable Crystals of Sodium Chlorate Forming Prior to Chiral Crystals in Solution Growth

    Niinomi, Hiromasa   Yamazaki, Tomoya   Harada, Shunta   Ujihara, Toru   Miura, Hitoshi   Kimura, Yuki   Kuribayashi, Takahiro   Uwaha, Makio   Tsukamoto, Katsuo  

    Chiral symmetry breaking in NaClO3 crystallization from an aqueous solution with perturbations has been of great interest. To understand the mechanism, several models focusing on the early stage of the crystallization have been proposed. However, they are ambiguous because the early stage has been barely explored directly. Here, we investigate the early stages of the crystallization process driven by droplet evaporation using a combination of direct in situ microscopic observations and cryogenic single-crystal XRD experiments. We demonstrate that an achiral crystal having P2(1)/a symmetry, which is newly discovered for a solution growth, first appears in the droplet and then transforms into the chiral crystals. Additionally, determination of the lattice constants by XRD experiments (a =3D 8.42 angstrom, b =3D 5.26 angstrom, c =3D 6.70 angstrom, beta =3D 109.71 degrees) revealed that the achiral phase should be identical to Phase III (a =3D 8.78 angstrom, b =3D 5.17 angstrom, c =3D 6.83 angstrom, beta =3D 110 degrees), which is a high-temperature phase from a melt growth of NaClO3. We advocate further assessment of the achiral crystal and a new pathway for the formation of chiral crystals via crystalline phase transition from achiral Phase III.
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  • Low-dislocation-density 4H-SiC crystal growth utilizing dislocation conversion during solution method

    Yamamoto, Yuji   Harada, Shunta   Seki, Kazuaki   Horio, Atsushi   Mitsuhashi, Takato   Koike, Daiki   Tagawa, Miho   Ujihara, Toru  

    We report a marked reduction in the dislocation density of a 4H-SiC crystal using a high-efficiency dislocation conversion phenomenon. During the solution growth, threading dislocations were efficiently converted to basal plane defects by the step flow of macrosteps. Utilizing this dislocation conversion phenomenon, we achieved the marked reduction of threading dislocation density. Consequently, the threading screw dislocation density was only 30 cm(-2), which was two orders of magnitude lower than that of the seed crystal. The 4H-SiC polytype of the seed crystal was replicated in the grown crystal, which was attributed to the spiral growth owing to a few remaining threading screw dislocations upstream of the step flow. (C) 2014 The Japan Society of Applied Physics
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  • Reduction of Threading Screw Dislocation Utilizing Defect Conversion during Solution Growth of 4H-SiC

    Harada, Shunta   Yamamoto, Yuji   Seki, Kazuaki   Ujihara, Toru  

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