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Engineering Design of High Quality GaN Epitaxy on Silicon Substrate Using Varying GaN/AlGaN composite Buffer Structures

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稀有金属材料与工程 2012年第S1期41卷 57-60页

作者： Wu, G. M. Tu, K. N. Kuo, c. c. Univ calif Los Angeles Dept Mat Sci & Engn Los Angeles CA 90095 USA chang Gung Univ Inst Electroopt Engn Tao Yuan 333 Taiwan

High quality GaN epitaxy thin films have been desired for the energy-efficient,solid-state semiconductor illuminating *** substrates offer high crystal quality,low wafer cost,large wafer size,and potential integration with the well-established silicon processing ***,due to the large mismatch in lattice constants and thermal expansion coefficients,it is still challenging to grow high quality GaN on silicon *** this study,high quality GaN epitaxy has been engineering designed to grow on Si(111)substrate using varying GaN/AlGaN composite buffer structures by an Axitron 200 metal-organic vapor phase epitaxy deposition system.A thin AlN seed layer of 25 nm was firstly grown at 720℃.AlGaN layer of different thickness was then grown at 1050℃with subsequent GaN thin film until the total thickness reached 500 *** thickness of the subsequent GaN thin film could be increased by reducing the AlGaN thickness in the composite buffer *** results have shown that the lower GaN/AlGaN thickness ratio would decrease the dislocation density and provide crack-free,mirror-like upper GaN crystal thin *** the other hand,the GaN/AlGaN thickness ratio could be designed to be 2-6 to balance the processing cost and the thin film quality for engineering *** dislocation density has been about 2×10 9 *** addition,dislocation close loop was observed near the GaN/AlGaN *** annihilation mechanism could be depicted by the reduction in dislocation strain energy.

关键词： gallium nitride dislocation density silicon substrate buffer layer

Interfacial fracture analysis for a two-dimensional decagonal quasi-crystal coating layer structure

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Applied Mathematics and Mechanics(English Edition) 2021年第11期42卷 1633-1648页

作者： Minghao ZHAO cuiying FAN c.S.LU Huayang DANG School of Mechanics and Safety Engineering Zhengzhou UniversityZhengzhou 450001China School of Mechanical Engineering Zhengzhou UniversityZhengzhou 450001China School of civil and Mechanical Engineering Curtin UniversityWestern Australia 6845Australia

The interface crack problems in the two-dimensional(2D)decagonal quasicrystal(Qc)coating are theoretically and numerically investigated with a displacement discontinuity *** 2D general solution is obtained based on the potential *** analogy method is proposed based on the relationship between the general solutions for 2D decagonal and one-dimensional(1D)hexagonal *** to the analogy method,the fundamental solutions of concentrated point phonon displacement discontinuities are obtained on the *** using the superposition principle,the hypersingular boundary integral-differential equations in terms of displacement discontinuities are determined for a line interface ***,Green’s functions are found for uniform displacement discontinuities on a line *** oscillatory singularity near a crack tip is eliminated by adopting the Gaussian distribution to approximate the delta *** stress intensity factors(SIFs)with ordinary singularity and the energy release rate(ERR)are ***,a boundary element method is put forward to investigate the effects of different factors on the fracture.

关键词： two-dimensional(2D)decagonal quasi-crystal(Qc)coating interface crack analogy method displacement discontinuity stress intensity factor(SIF) energy release rate(ERR)

Synthesis and crystal Structure of complex: [co（cdm）2（H2O）4].2H2O （cdm=carbamyldicyanomethanide Anion）

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chinese Journal of Structural chemistry 2002年第2期21卷 178-181页

作者： SHI Jing-Min②1 YIN Hai-Liang1 SUN Li-Jing1 YU Wen-Tao2 XU Wen1 ZHAO Ming-Gen3 1(Department of chemistry, Shandong Normal University, Jinan 250014, china) 2(Institute of crystal Matrials, Shandong University, Jinan 250010, china) 3(Department of che Shandong Normal Univ Dept Chem Jinan 250014 Peoples R China Shandong Univ Inst Crystal Mat Jinan 250010 Peoples R China Xinzhou Normal Inst Dept Chem Xinzhou 034000 Peoples R China

Mononuclear complex [co(cdm)2(H2O)4]?H2O was synthesized by sodium carbamyldicyanomethanide (Nacda) and cobalt perchlorate. The crystal belongs to monoclinic system, space group P21/n with a = 9.366(3), b = 7.392(3), c = 12.039(4)? = 108.335(4)? V = 791.2(5)?, Z = 2, Mr (c8H16coN6O8) = 383.2, Dc = 1.608 g/cm3, F(000) = 394, = 1.135 mm-1, = 0.71073 ? The structure was refined to R = 0.0240 and wR = 0.0632 for 1267 observed reflections (I > 2(I)). The cobalt(II) atom in the complex is coordinated by two nitrile-nitrogen atoms and four oxygen atoms of H2O, which forms a slightly distorted coordination octahedron around the cobalt(II) ion. The mononuclear complexes are connected by hydrogen bondings and in the crystal there exists a cavity where the uncoordinated H2O molecules are trapped.

关键词： synthesis crystal structure cobalt complex

The Design and Synthesis of Trger's Base for Luminescent Applications

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The Design and Synthesis of Trger's Base for Luminescent A...

OPTIcAL ABSORPTION OF cO-DOPED SILIcA GEL-DERIVED GLASSES

全国第八届有机固体电子过程暨华人有机光电功能材料学术讨论会

作者： Xutang Tao~*,chunxue Yuan,Qian Xin,Minhua Jiang (State Key Laboratory of crystal Materials,Shandong University,Jinan,250100)

Trger’s base(TB),first synthesized by Trger in 1887,has gained steady interest in recent years because of its c symmetry,chirality,and rigid concave *** special twistedΛ-shaped configuration is theoretically disadvantageous to the formation ofπ-πclose stacking,which commonly results in fluorescence quenching in the

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OPTICAL ABSORPTION OF CO-DOPED SILICA GEL-DERIVED GLASSES

Tectono-magmatic evolution of Tethyan oceanic lithosphere in supra subduction zone fore arc regime:Geochemical fingerprints from crust-mantle sections of Naga Hills Ophiolite

第8届国际材联电子材料国际研讨会

作者： XX.Duan, D.R.Yuan State Key Laboratory of crystal Materials, Shandong University, Jinan 250100, china

Materials doped with transition metal cobalt (Ⅱ) ions (co) present different colors when co ions located in different symmetry sites, so cobalt can be used as a "color indicator". Furthermore, co ions can act as one kind of active ions in many materials. A number of materials doped with co ions are used as passive Q switches or tunable laser in the near-infrared region because they possess saturable absorption or exhibit strong and broad luminescence hands In this paper we mainly discussed the (?)

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Geoscience Frontiers 2021年第3期12卷 19-41页

作者： Anisha Verencar Abhishek Saha Sohini Ganguly Manikyamba c. cSIR-National Institute of Oceanography Dona PaulaGoa 403004India School of Earth Ocean and Atmospheric SciencesGoa UniversityTaleigão PlateauGoa 403206India cSIR-National Geophysical Research Institute Uppal RoadHyderabad 500007India

The Naga Hills Ophiolite(NHO)belt in the Indo-Myanmar range(IMR)represents a segment of Tethyan oceanic crust and upper mantle that was involved in an eastward convergence and collision of the Indian Plate with the Burmese Plate during the Late ***,we present a detailed petrological and geochemical account for the mantle and crustal sections of NHO,northeastern India to address(i)the mantle processes and tectonic regimes involved in their genesis and(ii)their coherence in terms of the thermo-tectonic evolution of Tethyan oceanic crust and upper *** NHO suite comprises well preserved crustal and mantle sections discretely exposed at Moki,Ziphu,Molen,Washelo and Lacham *** ultramafic-mafic lithologies of NHO are mineralogically composed of variable proportions of olivine,orthopyroxene,clinopyroxene and *** primary igneous textures for the mantle peridotites have been overprinted by extensive serpentinisation whereas the crustal section rocks reflect crystal cumulation in a magma *** normalised REE profiles for the cumulate peridotite-olivine gabbro-gabbro assemblage constituting the crustal section of NHO show flat to depleted LREE patterns consistent with their generation from depleted MORB-type precursor melt in an extensional tectonic setting,while the mantle peridotites depict U-shaped REE patterns marked by relative enrichment of LREE and HREE over *** features collectively imply a dual role of depleted MORB-type and enriched arc-type mantle components for their genesis with imprints of melt-rock and fluid-rock ***,studied lithologies from NHO correspond to a boninitic to slab-proximal Island Arc Tholeiite affinity thereby conforming to an intraoceanic supra subduction zone(SSZ)fore-arc regime coherent with the subduction initiation *** geochemical attributes for the crustal and mantle sections of NHO as mirrored by Zr/Hf,Zr/Sm,Nb/Ta,Zr/Nb,Nb/U,Ba/Nb,Ba/Th,Ba/La and Nd/

关键词： Tethyan Ocean Naga Hills Ophiolite Suprasubduction Zone Subduction initiation Fore arc extension Mantle refertilisation

Low symmetry aspects in spectroscopic and magnetic susceptibility studies of Tb^(3+)(4f^8) in TbAlO_3

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Journal of Rare Earths 2009年第4期27卷 627-632页

作者： c.Rudowicz P.Gnutek M.G.Brik Modeling in Spectroscopy Group Institute of Physics West Pomeranian University of Technology Institute of Physics University of Tartu

The three sets of crystal field parameters （cFPs） obtained from spectroscopic and magnetic susceptibility studies of Tb3＋（4f^8） ions in TbAlO3 by Gruber et al. （J. Lumin. 128 （2008） 1271） were reanalyzed. These sets, fitted from experimental energy levels, are physically equivalent and correspond to specific choices of the axis system. Proper interpretation of experimental data for Tb3＋ ions at monoclinic c8 symmetry sites in TbAlO3 crystal requires clarification of several intricate low syrmnetry aspects, namely, （a） three equivalent forms of monoclinic cF Hamiltouian, （b） relative orientation of the crystallographic axis system w.r.t, the symmetry-adapted axis system, （c） monoclinic standardization of cFPs, （d） distinction between the actual and apparent low symmetry effects exhibited by cFPs, and （e） nominal nature of all fitted cFP sets. For this purpose, modeling of cFPs for Tb3＋ in TbAlO3 was carried out using at the first stage only the coulomb, i.e. point charge, eonlribntions in the exchange charge model. The point charge model calculated cFPs disagree with the experimental cFPs, especially the rank k=6 cFPs. To explain this discrepancy and to verify the correcmess of the theoretical cFP calculations additionally the superposition model was employed. The methods of analysis and modeling of cFP sets for monoclinic symmetry cases proposed here proved useful for the studied case as well as might be used for other ion-host systems exhibiting monoclinic or triclinic local site symmetry. Partial results for Tb3＋ ions in TbAlO3 were presented here, whereas detailed results were given in a follow-up paper.

关键词： Tb3+ ions TbAlO3 spectroscopy crystal-field magnetic susceptibility low symmetry aspects rare earths

Growth,Structural and Microhardness Studies on New Semiorganic Single crystals of calcium Para Nitrophenolate Dihydrate

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Journal of Materials Science & Technology 2007年第6期23卷 855-859页

作者： c.Vesta R.Uthrakumar c.Justin Raj A.Jonie Varjula J.Mary Linet S.Jerome Das Department of Physics Loyola CollegeChennai-34India

Good quality crystals of calcium p-nitrophenolate （NPca） were grown from saturated solution by slow evaporation method. The crystal structure analysis and the molecular arrangement of these crystals were determined using X-ray diffraction （XRD）. From Single crystal XRD studies, NPca is found to be crystallized in the mon- oclinic system with a space group P21/n. The functional groups of the material were confirmed qualitatively by F-FIR （Fourier transform infrared spectroscopy） spectral analysis. Optical absorption studies reveal the absorption region and microhardness studies were carried out to confirm the mechanical behaviour of the crystals.

关键词： characterization crystal growth Structural analysis FTIR spectral analysis Microhardness UV-Vis analysis

crystal morphology of sucrose influenced by rotation axes parallel to growth planes

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chinese Science Bulletin 2000年第16期45卷 1468-1471页

作者： c.Silber H.Follner Institut Für Mineralogie und Mineralische Rohstoffe der Technischen Universitat clausthal Adolph-Roemer-Str.2AD-38678 Clausthal-ZellerfeldDeutschlandInstitut Für Mineralogie und Mineralische Rohstoffe der Technischen Universitat ClausthalAdolph-Roemer-Str.2AD-38678 Clausthal-ZellerfeldDeutschland

Three different types of growth forms of sucrose (P21) were found by calculating with the Fourier transform method of crystal morphology. The observed central distances of the (100) and (001) faces are smaller than those calculated. It will be shown that the two-fold screw axis, which runs parallel to these faces, influences the rate of growth. The effectiveness of these symmetry elements is relative to the rotation angle around the face normal.

关键词： sucrose crystal growth mechanism symmetry dependent growth Fourier transform method of morphology.