8,957 research outputs found

    Formation of high-quality Ag-based ohmic contacts to p-type GaN

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    Low resistance and high reflectance ohmic contacts on p-type GaN were achieved using an Ag-based metallization scheme. Oxidation annealing was the key to achieve ohmic behavior of Ag-based contacts on p-type GaN. A low contact resistivity of similar to 5x10(-5) Omega cm(2) could be achieved from Me (=Ni, Ir, Pt, or Ru)/Ag (50/1200 angstrom) contacts after annealing at 500 degrees C for 1 min in O(2) ambient. Oxidation annealing promoted the out-diffusion of Ga atoms from the GaN layer, and Ga atoms dissolved in the in-diffused Ag layer with the formation of Ag-Ga solid solution, resulting in ohmic contact formation. Using Ru/Ni/Au (500/200/500 angstrom) overlayers on the Me/Ag contacts, the excessive incorporation of oxygen molecules into the contact interfacial region, and the out-diffusion and agglomeration of Ag, were effectively prevented during oxidation annealing. As a result, a high reflectance of 87.2% at the 460 nm wavelength and a smooth surface morphology could be obtained simultaneously. (C) 2008 The Electrochemical Society.open111618sciescopu

    Atmospheric Argon Free burning Arcs with a Simplified Unified Model Using CFD-Arc Modeling

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    Free burning arcs, where the work piece acts as an anode, are frequently used for a number of applications. Our investigation is exclusively concerned with a simplified unified model of arcs and their electrodes under steady state conditions at atmospheric pressure. The model is used to make predictions of arc and electrode temperatures and arc voltage for a 200 A arc in argon. The computed temperatures along the axis between the cathode tip and the anode surface compare well the measured data

    Generic Lightlike Submanifolds of an Indefinite Cosymplectic Manifold

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    Lightlike geometry has its applications in general relativity, particularly in black hole theory. Indeed, it is known that lightlike hypersurfaces are examples of physical models of Killing horizons in general relativity (Galloway, 2007). In this paper, we introduce the definition of generic lightlike submanifolds of an indefinite cosymplectic manifold. We investigate new results on a class of generic lightlike submanifolds of an indefinite cosymplectic manifold

    Effect of Phosphatic Fertilizer Rates Level on Growth, Crude Protein Content and Nitrogen Fixation Ability of Alfalfa at Sowing Year

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    The experiment was conducted to determine effects of phosphate fertilizers on growth characteristics, crude protein content and nitrogen fixation ability of alfalfa (Medicago sativa L) in the sowing year. Two rates of phosphate (200 and 400 kg/ha P) were applied to phosphorus -deficient native soil in Korea and samples were taken every 7 days from the 30th to the 93rd day. Number of branches, root length and dry matter weight at phosphate fertilizer level of 400kg in sowing year more increased than those at 200kg/ha. The number of nodules did not differ due to phosphate fertilizer rate. The crude protein contents of leaves, stems and roots were not significantly affected by the phosphate fertilizer levels, except for those of leaves with 400kg/ha at 72 days after sowing that were higher. The crude protein contents of each plant along the growing stages were higher at the 44th and 72nd day after sowing. The dry weight of roots did not significantly respond to phosphate rates from 30 days to 51 days after sowing, but that was increased at phosphate fertilizer level of 400kg/ha from 51 days after sowing. The amount of ethylene evolved by samples during 2 hours and the calculated amount of nitrogen fixed were higher on phosphate fertilizer level of 400kg/ha from 30 days to 58 days after sowing, but decreased that