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71.
Takahiro Yamada Hisanori Yamane Takenari Goto Takafumi Yao Yongzhao Yao Takashi Sekiguchi 《Crystal Research and Technology》2007,42(7):713-717
Colorless transparent prismatic crystals (0.5‐2.0 mm long) and hopper crystals (1.0‐2.5 mm long) of GaN were prepared by heating a Ga melt at 800°C in Na vapor under N2 pressures of 7.0 MPa for 300 h. The photoluminescence (PL) spectrum of a prismatic crystal at 4 K showed the emission peaks of neutral donor‐bound exciton (D0‐X) and free exciton (XA) at 3.472 eV and 3.478 eV, respectively, in the near band edge region. The full‐width at half‐maximum (FWHM) of (D0‐X) peak was 1.9 meV. The emission peaks of a donor–acceptor pair transition (D0‐A0) and its phonon replicas were observed in a lower energy range (2.9‐3.3 eV). The emission peaks of the D0‐A0 and phonon replicas were also observed in the cathodoluminescence (CL) spectrum at 20 K. The (D0‐X) PL peak of a hopper crystal at 4 K was at 3.474 eV (2.1 meV higher), having a FWHM of 6.1 meV which was over 3 times larger than that of the prismatic crystal. A strong broad band with a maximum intensity around 1.96 eV was observed for the hopper crystals in the CL spectrum at room temperature. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
72.
Takahiro Yamada Hisanori Yamane Takaaki Ohta Takenari Goto Takafumi Yao 《Crystal Research and Technology》2007,42(1):13-17
GaN crystals were prepared by heating a Ga melt with 1 at% Li3N against Ga at 750 °C in Na vapor under N2 pressures of 0.4–1.0 MPa. The GaN crystals grown at 1.0 MPa of N2 were colorless and transparent prismatic, having a size of approximately 0.7 mm in length. A secondary ion mass spectrometry (SIMS) showed the contaminant of lithium in the obtained crystals. A large broad yellow band emission peak of 2.28 eV was observed at room temperature in the photoluminescence spectrum in addition to the near band emission peak of GaN at 3.39 eV and a small broad satellite emission at 3.24 eV. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
73.
Hideshi Yamane 《Proceedings of the American Mathematical Society》2007,135(11):3659-3667
We construct solutions to nonlinear wave equations that are singular along a prescribed noncharacteristic hypersurface, which is the graph of a function satisfying not the Eikonal but another partial differential equation of the first order. The method of Fuchsian reduction is employed.
74.
The root systems appearing in the theory of Lie superalgebras and Nichols algebras admit a large symmetry extending properly
the one coming from the Weyl group. Based on this observation we set up a general framework in which the symmetry object is
a groupoid. We prove that in our context the groupoid is generated by simple reflections and Coxeter relations. In a broad
sense this answers a question of Serganova. Our weak version of the exchange condition allows us to prove Matsumoto’s theorem.
Therefore the word problem is solved for the groupoid. 相似文献
75.
76.
A red-emitting Y2(WO4)3: Eu3+ phosphor (orthorhombic high temperature phase, anhydride) is prepared by two different methods: the firing of mixtures of constituent oxides and that of precipitates from aqueous solutions. After optimizing preparation conditions, the cathodoluminescence brightness reaches 56% that of Y2O2S: Eu3+, a commercial red phosphor for color TV. Formation of a high temperature phase below the reported transition temperature is noted in the fired precipitates. This phase occurrence is shown to depend on the treatment of the precipitates to be fired. Reflection difference measurement of Eu-doped and undoped samples assigns an excitation band of about 245 nm to the Eu-O charge transfer band. Different by-products in the two preparation methods are identified by measuring emission spectra under selective excitation. Reversible hydration-dehydration of the phosphor is demonstrated by successively measuring photoluminescence first in vacuum and then in air at various temperatures. No deterioration of luminescence efficiency is observed after repeating this reversible structural change. 相似文献
77.
78.
79.
Toshio Kinoshita Yukihiro Watanabe Setsuko Nakao Sunao Furukawa 《Journal of heterocyclic chemistry》1992,29(7):1785-1788
The following 5-nitro-2,4(1H,3H)-pyrimidinediones possessing bromo substituted side chains at the 1- and 6-positions were prepared by bromination of 3,6-dimethyl-1-(ω-hydroxyalkyl)-5-nitro-2,4(1H,3H)-pyrimidinediones 4a and 4b and its nitrates 2a and 2b . The three of mono-bromo derivatives are: 1-(ω-acetoxyalkyl and ω-hydroxyalkyl)-6-bromomethyl-3-methyl. 6a, 6b, 7a and 7b and 1-(ω-bromoalkyl)-3,6-dimethyl-2,4(1H,3H)- pyrimidinediones 8a and 8b . The one type dibromo derivatives are: 1-(ω-bromoalkyl)-6-bromomethyl-3-methyl-2,4(1H,3H)-pyrimidinediones 5a and 5b . 相似文献
80.
Hisanori Yamane Shinya SasakiShun-ichi Kubota Ryo InoueMasahiko Shimada Takashi Kajiwara 《Journal of solid state chemistry》2002,163(2):449-454
Single crystals of the quaternary compound Ba8Cu3In4N5 were prepared by heating Ba, Cu, and In in a Na flux at 1023 K under 7 MPa of N2, and by slow cooling from this temperature. The crystal structure was analyzed by single-crystal X-ray diffraction. It crystallizes in an orthorhombic cell (space group Immm (No. 71), Z=2) with a=4.0781(6), b=12.588(2), and c=19.804(3) Å at 298 K. The structural formula is expressed as Ba8[CuN2]2 [CuN]In4. Nitridocuprates of one-dimensional chains 1∞[CuN2/2] and isolated units 0[CuN2], and one-dimensional indium clusters 1∞[In2In4/2] are contained in the structure. A split-site model applied for the arrangement of 1∞[CuN2/2] chains suggested that there is a short-bond, long-bond alternation of the Cu-N bondings. The electrical resistivity of Ba8Cu3In4N5 was 3.44 mΩ·cm at 298 K. A metallic temperature dependence of the resistivity was observed down to 10 K. 相似文献