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Now showing items 1 - 16 of 56


    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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  • Plasmonic Trapping-Induced Crystallization of Acetaminophen

    Niinomi, Hiromasa   Sugiyama, Teruki   Uda, Satoshi   Tagawa, Miho   Ujihara, Toru   Miyamoto, Katsuhiko   Omatsu, Takashige  

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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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  • Conversion Mechanism of Threading Screw Dislocation during SiC Solution Growth

    Ujihara, Toru   Kozawa, Shigeta   Seki, Kazuaki   Alexander,    Yamamoto, Yuji   Harada, Shunta  

    Solution growth is considered to be a powerful method for high quality SiC crystals. This work reports that the conversion process from a threading screw dislocation into a few Frank partial dislocations in basal planes was investigated by synchrotron X-ray topography. This process was effectively assisted by step-flow growth on off-oriented (0001) seed crystals. The Frank partials were not extended into the crystal grown toward the [0001] direction perpendicular to the basal plane. Thus, the conclusion of this study suggests the use of off-orientcd seed crystal is important to improve crystal quality.
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  • Phase-locking of oscillating images using laser-induced spin-polarized pulse TEM

    Kuwahara, Makoto   Nambo, Yoshito   Kusunoki, Soichiro   Jin, Xiuguang   Saitoh, Koh   Asano, Hidefumi   Ujihara, Toru   Takeda, Yoshikazu   Nakanishi, Tsutomu   Tanaka, Nobuo  

    Pulse-mode operation was realized in spin-polarized transmission electron microscopy (SP-TEM) using a laser-driven electron gun with a GaAs-GaAsP strained-layer-superlattice photocathode. TEM images were acquired with a pulsed electron beam with a 5-mu s pulse duration. Phase locking of wobbling TEM images was demonstrated using a pulsed beam with a 1-kHz repetition frequency, which matched the image wobbling frequency. It was found that in composite images formed by superimposing 2 x 10(4) separate single-pulse exposures, the amount of image blurring due to wobbling was a linear function of the pulse duration. These results suggest the possibility of pump-probe measurements in SP-TEM using the pulsed electron beam as a probe, allowing nanometer-scale time-resolved spin mapping.
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    An AlN crystal preparation method, in which: at least one element excluding Si is used that fulfills the condition that a compound is not formed with either Al or N or the condition that a compound is formed with either Al or N but the standard free energy of formation of said compound is greater than the standard free energy of formation of AlN; a composition including at least Al and the element is melted; Al vapor and nitrogen gas are reacted at a prescribed reaction temperature; and AlN crystals are formed.
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  • Substrate dependence of the superconducting properties of NdFeAs(O,F) thin films

    Uemura, Hiroki   Kawaguchi, Takahiko   Ohno, Toshiya   Tabuchi, Masao   Ujihara, Toru   Takeda, Yoshikazu   Ikuta, Hiroshi  

    NdFeAs(O,F) superconducting thin films were grown on MgO, GaAs, CaF2, and LaAlO3 single crystal substrates by molecular beam epitaxy. All thin films exhibited a clear superconducting transition, while the critical temperature T-c showed a distinct substrate dependence, although the same growth condition was employed for all samples. The difference in T-c can be attributed to the lattice strain effect and how susceptible the substrate is to fluorine. The thin film grown on CaF2 substrate showed the highest T-c with an onset T-c of 56 K and zero resistance at 52 K. A correlation between T-c and the lattice constant ratio c/a was observed similar to what was reported for other iron-based superconductors, suggesting an intimate relation between the crystal structure and the superconducting properties. (C) 2012 Elsevier Ltd. All rights reserved.
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  • Stability Growth Condition for 3C-SiC Crystals by Solution Technique

    Ujihara, Toru   Maekawa, Ryosuke   Tanaka, Ryo   Sasaki, Katsuhiro   Kuroda, Kotaro   Takeda, Yoshikazu  

    A solution growth of 3C-SiC was performed on (111)Si-face or (111) C-face of 3C-SiC seed crystal at around 1700 degrees C by dipping method. The polytype of the crystal grown on the Si-face immediately changed to 6H-SiC. On the other hand, 3C-SiC stably grew on the C-face except for a small number of 6H-SiC precipitates. The polytype transition phenomenon can be explained by the difference of the chemical potential and the solution-crystal interfacial energy between 3C-SiC and 6H-SiC. To grow a larger 3C-SiC crystal, we carried out a long-term growth for 30 hours on the C-face. In the first 10 hours, the polytype of the grown crystal was 3C-SiC. In the next 10 hours, however, the polytype changed from 3C-SiC to 6H-SiC. According to our studies, 6H-SiC tends to grow on 6H-SiC at around 1700 degrees C, while both of 3C-SiC and 6H-SiC can grow on 3C-SiC at around the same temperature. In this case, 6H-SiC grows on 6H-SiC precipitates and then the dominant polytype changes to 6H-SiC after several 6H-SiC precipitations. To grow 3C-SiC crystal stably, it is necessary to surpress completely the polytype transition by the growth on C-face at lower growth temperatures.
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  • Epitaxial Growth of NdFeAsO Thin Films by Molecular Beam Epitaxy

    Kawaguchi, Takahiko   Uemura, Hiroki   Ohno, Toshiya   Watanabe, Ryotaro   Tabuchi, Masao   Ujihara, Toru   Takenaka, Koshi   Takeda, Yoshikazu   Ikuta, Hiroshi  

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  • Solution growth of high-quality 3C-SiC crystals

    Ujihara, Toru   Maekawa, Ryosuke   Tanaka, Ryo   Sasaki, Katsuhiro   Kuroda, Kotaro   Takeda, Yoshikazu  

    3C (cubic)-silicon carbide (SiC) bulk crystals that are stable at relatively low temperatures are difficult to grow by the sublimation method, which requires relatively high growth temperatures. This study focused on growth from the solution, which has the advantage that low growth temperatures are applied and the resulting crystals are mostly of high crystalline quality. Firstly, a large number of 3C-SiC crystals were grown by solution growth via spontaneous nucleation in a large temperature gradient. A relatively high yield of 6.4% was achieved from the charged Si solvent. Transmission electron microscopy and X-ray topography observations indicated that the stacking fault density of these crystals was much lower than that of the substrates grown by chemical vapor deposition methods. A dipping solution technique was then applied for 3C-SiC growth, using 3C-SiC seed crystals grown via spontaneous nucleation. Growth was performed on the (1 1 1)Si or ((1) over bar (1) over bar 1 (1) over bar )C faces. As a result, 3C-SiC grew on the ((1) over bar (1) over bar 1 (1) over bar )C face, but 6H-SiC crystals grew on the (1 1 1)Si face. For the stable growth of 3C-SiC crystals without 6H-SiC precipitation, growth on the ((1) over bar (1) over bar 1 (1) over bar )C faces is necessary. (C) 2007 Elsevier B.V. All rights reserved.
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  • Analysis of thickness modulation in GaAs/GaAsP strained superlattice by TEM observation

    Jin, Xiuguang   Nakahara, Hirotaka   Saitoh, Koh   Saka, Takashi   Ujihara, Toru   Tanaka, Nobuo   Takeda, Yoshikazu  

    GaAsP buffer layers grown on (001) just oriented GaP substrate show an undulated vicinal surface morphology and a thickness modulated GaAs/GaAsP strained superlattice layer grew on the vicinal GaAsP buffer layer. Structural characteristics of the thickness modulated superlattice have been carried out by transmission electron microscopy (TEM). In the thickness modulated structure, the first GaAs layer grown on the vicinal GaAsP buffer layer consisted of (001) and (117) facets, and thicker GaAsP grew on thinner GaAs and vice versa. Nano-beam electron diffraction revealed that an inhomogeneous residual strain distribution existed in the first GaAs layer. Therefore, the value of strain introduced in subsequent superlattice layers should be different from place to place and the strains in GaAs and GaAsP superlattice layers are also different from each other. The nucleus formation rate is inversely proportional to the value of the strain. So it is understood that the strain distribution in the first GaAs layer results in the successive thickness modulation of GaAs/GaAsP superlattice layers. (C) 2012 Elsevier B.V. All rights reserved.
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    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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