Papers by Keyword: Stacking Fault

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Authors: Kevin M. Speer, David J. Spry, Andrew J. Trunek, Philip G. Neudeck, M.A. Crimp, J.T. Hile, C. Burda, P. Pirouz
Abstract: pn diodes have recently been fabricated from 3C-SiC material heteroepitaxially grown atop on-axis 4H-SiC mesa substrate arrays [1,2]. Using an optical emission microscope (OEM), we have investigated these diodes under forward bias, particularly including defective 3C-SiC films with in-grown stacking faults (SFs) nucleated on 4H-SiC mesas with steps from screw dislocations. Bright linear features are observed along <110> directions in electroluminescence (EL) images. These features have been further investigated using electron channeling contrast imaging (ECCI) [3]. The general characteristics of the ECCI images—together with the bright to dark contrast reversal with variations of the excitation error—strongly suggest that the bright linear features are partial dislocations bounding triangular SFs in the 3C-SiC films. However, unlike partial dislocations in 4H-SiC diodes whose recombination-enhanced dislocation motion serves to expand SF regions, all the partial dislocations we observed during the electrical stressing were immobile across a wide range of current injection levels (1 to 1000 A/cm2).
Authors: Hisaomi Iwata, Sven Öberg, Patrick R. Briddon
Authors: A. Zywietz, P. Käckell, J. Furthmüller, Friedhelm Bechstedt
Authors: Syunsuke Izumi, Isaho Kamata, Takeshi Tawara, Hiroyuki Fujisawa, Hidekazu Tsuchida
Authors: B. Barbaray, V. Potin, Piere Ruterana, Gerard Nouet
Authors: Akila Derardja
Abstract: Nickel based super alloys are promising materials for high temperature structural applications because of their low density. The single grain super alloys are extremely creep resistant at high temperature, due to the fraction of Ni3Al based ' precipitates coherent with a Ni based  matrix [1, 3]. The cuboids group together and form semi-coherent interfaces after a long annealing at high temperature. The ' precipitate growths in nickel base super alloys often favor the parallelism of (111) planes between cubic dissimilar crystals [4]. In consequences, a hexagonal network of dislocations, that covers the hetero-interphase, is arranged by accommodation of the angular misfit between two semi coherent crystals ( ). In this work, the magnitude of the distortions is simulated as arising from a trigonal network of subsurface misfit dislocations partly dissociated in Shockley dislocations limiting intrinsic and /or extrinsic stacking faults. The results derived from a previous explicit formulation using double Fourier series [5]. Each harmonic term of the series depends on the anisotropic elastic constants and the thickness of each phase. The program built is in a double precision Fortran language and it shows the magnitude and the aspect of the distortions of the free surfaces when the dissociation change in the hetero-interphase. Also, the program has the advantage to fully apply to hetero-epitaxial systems, whatever is the thickness of the free surfaces.
Authors: M. Benaissa, P. Humbert, H. Lefakis, G. Ehret, V.S. Speriosu, B.A. Gurney
Authors: Tomáš Kekule, Martin Vlach, Hana Kudrnova, Veronika Kodetova, Bohumil Smola, Ivana Stulíková
Abstract: Response to isochronal annealing up to 440°C was investigated in squeeze cast Mg2Y1Zn alloy and in the same alloy prepared by powder metallurgy and extrusion at 280°C (PM). Electrical resistivity measurements at 77 K and at room temperature after each annealing step and differential scanning calorimetry performed at various heating rates characterized phase changes proceeding during the heat treatments. Transmission and scanning electron microscopy and optical microscopy revealed ribbons of a long-period ordered structure and a relatively high density of stacking faults in grain interiors of the cast alloy having the grain size of ~50 μm. Well pronounced subgrains were observed in the PM prepared alloy. Secondary phase particles decorate grain boundaries in this alloy. Electrical resistivity response of the cast alloy to isochronal annealing up to 440°C shows three precipitation processes, whereas one significant process was revealed in the PM alloy. Activation energies of precipitation processes were determined. Microhardness exhibits good thermal stability in the whole temperature range in the cast alloy and up to 360°C in the PM alloy.
Authors: Joseph J. Sumakeris, Mrinal K. Das, H. McD. Hobgood, Stephan G. Müller, Michael J. Paisley, Seo Young Ha, Marek Skowronski, John W. Palmour, Calvin H. Carter Jr.
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