Twin boundary energy and characterization of charge redistribution near the twin boundaries of cupperate superconductors

2014 ◽  
Vol 507 ◽  
pp. 41-46 ◽  
Author(s):  
Mahnaz Mohammadi ◽  
Bahram Khoshnevisan ◽  
S. Javad Hashemifar
Keyword(s):  
Twin Boundary ◽  
Boundary Energy ◽  
Charge Redistribution ◽  
Twin Boundaries

Mechanical and Optical Properties Characterization of C-Plane (0001) and M-Plane (10−10) GaN by Nanoindentation and Luminescence

2015 ◽  
Vol 1792 ◽  
Author(s):  
Toshiya Yokogawa ◽  
Masaki Fujikane ◽  
Shijo Nagao ◽  
Roman Nowak
Keyword(s):  
Plastic Deformation ◽  
Shear Stress ◽  
Dislocation Density ◽  
Twin Boundary ◽  
Boundary Energy ◽  
Dynamics Simulation ◽  
Dark Spot ◽  
Yield Shear Stress ◽  
Gan Crystal

ABSTRACTYield shear stress dependence on dislocation density and crystal orientation was studied in bulk GaN crystals by nanoindentation examination. The yield shear stress decreased with increasing dislocation density which is estimated by dark spot density in cathodoluminescence, and it decreased with decreasing nanoindentation strain-rate. It reached and coincided at 11.5 GPa for both quasi-static deformed c-plane (0001) and m-plane (10-10) GaN. Taking into account theoretical Peierls–Nabarro stress and yield stress for each slip system, these phenomena were concluded to be an evidence of heterogeneous mechanism associated plastic deformation in GaN crystal. Transmission electron microscopy and molecular dynamics simulation also supported the mechanism with obtained r-plane (-1012) slip line right after plastic deformation, so called pop-in event. The agreement of the experimentally obtained atomic shuffle energy with the calculated twin boundary energy suggested that the nucleation of the local metastable twin boundary along the r-plane concentrated the indentation stress, leading to an r-plane slip. This nanoindentation examination is useful for the characterization of crystalline quality because the wafer mapping of the yield shear stress coincided the photoluminescence mapping which shows increase of emission efficiency due to reduction of non-radiative recombination process by dislocation.

Characterization of the Structure and Polarity of Twin Boundaries in GaP

1998 ◽  
Vol 510 ◽  
Author(s):  
Dov Cohent ◽  
D.L. Medlin ◽  
C. Barry Carter
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Twin Boundary ◽  
Atomic Structure ◽  
Twin Boundaries ◽  
Planar Defects ◽  
Transmission Electron ◽  
Crystallographic Planes

AbstractThe structure of planar defects in GaP films grown by MBE on Si (110) was investigated by transmission electron microscopy. Growth of GaP films on the (110) surface produced numerous microtwins which formed both first and second order twin boundaries. Using high-resolution transmission electron microscopy, the atomic structure of Σ=3 and Σ=9 twin boundaries were studied. Both the Σ=3 and Σ=9 interfaces were observed to facet along specific crystallographic planes. Geometric models of the Σ=9 {221} twin boundary accounting for different polar bonding configurations were proposed and compared with experimental observations.

SEM Characterization of Silicon Layers Grown on Carbon Foil

2009 ◽  
Vol 156-158 ◽  
pp. 473-476 ◽  
Author(s):  
Sergei K. Brantov ◽  
A.V. Eltzov ◽  
Olga V. Feklisova ◽  
Eugene B. Yakimov
Keyword(s):  
Dislocation Density ◽  
Defect Structure ◽  
Growth Direction ◽  
Carbon Foil ◽  
Twin Boundaries ◽  
X Ray ◽  
Electron Backscattering Diffraction ◽  
Silicon Ribbon ◽  
Selective Chemical

Characterization of defect structure in silicon ribbon grown on carbon foil has been carried out. The structure of grown Si layers and a dislocation density in these layers have been studied using selective chemical etching and the Electron Backscattering Diffraction. It is observed that the layers consist of rather large grains, the majority of which is elongated along the growth direction with a similar surface orientation and with a misorientation angle between neighboring grains of 60º. This means that such grains are separated by the (111) twin boundaries. The dislocation density in different grains is found to vary from 102 to 107cm-2. The energy dispersive X-Ray microanalysis has shown that some twin boundaries are enriched with carbon.

Mechanism of Stress-Driven Grain Boundary Migration in Nanotwinned Materials

2018 ◽  
Vol 55 (1) ◽  
pp. 21-25 ◽  
Author(s):  
N.V. Skiba
Keyword(s):  
Theoretical Model ◽  
Grain Boundary ◽  
Twin Boundary ◽  
Boundary Migration ◽  
Grain Boundary Migration ◽  
High Angle ◽  
Twin Boundaries ◽  
Critical Stresses ◽  
Ultrafine Grained ◽  
Ultrafine Grained Materials

Abstract Stress-driven grain boundary (GB) migration in ultrafine-grained materials with nanotwinned structure is theoretically described. In the framework of the theoretical model, the stress-driven high-angle GB migration is accompanied by migration of twin boundaries which adjoin this GB. Energetic characteristics and critical stresses of the GB migration accompanied by the twin boundary migration are calculated.

DFT study of hydrogen and helium defects at the (112̄1) twin boundary in hcp scandium

2017 ◽  
Vol 31 (11) ◽  
pp. 1750080
Author(s):  
Kaimin Fan ◽  
Jing Tang ◽  
Li Yang ◽  
Yongqing Hu ◽  
Qingqiang Sun ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Twin Boundary ◽  
Density Functional ◽  
Nearest Neighbor ◽  
Boundary Energy ◽  
Boundary Plane ◽  
Octahedral Interstice ◽  
Tetrahedral Interstice ◽  
Densities Of States ◽  
Formation Energies

We have investigated the grain boundary energy of ([Formula: see text]) twin boundaries, the formation energies of hydrogen (H) and helium (He) defects in tetrahedral (T) and octahedral (O) interstitial sites at the ([Formula: see text]) twin boundary in hcp scandium (Sc) by first-principles calculations based on density functional theory. It is found that the formation energies of the tetrahedral and octahedral interstices H, and tetrahedral interstice He increase significantly towards the ([Formula: see text]) twin boundary plane, while the formation energy of the octahedral interstice He atom near the ([Formula: see text]) twin boundary plane decreases. To analyze these results, we present the electronic densities of states (DOSs) of H, He and their nearest-neighbor Sc (NN-Sc) atoms in several tetrahedral and octahedral configurations. We have also calculated the formation energies of He-vacancy clusters (He[Formula: see text]V) in the Sc grain boundary, which indicates the stabilities of He[Formula: see text]V clusters depend on the variations of the relaxed vacancy volume near the ([Formula: see text]) twin boundary plane.

The Morphology of Grain Boundary Interactions with Twins in YBa2Cu3O7−δ

1993 ◽  
Vol 319 ◽  
Author(s):  
Jenn-Yue Wang ◽  
A. H. King
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Twin Boundary ◽  
Interfacial Energy ◽  
Coincidence Site Lattice ◽  
The Other ◽  
Twin Boundaries ◽  
Site Lattice ◽  
Dislocation Arrays

AbstractVarious morphologies are observed where twins meet grain boundaries in YBa2Cu3O7−δ. Twins may be “correlated” at the boundary (i.e. twin boundaries from one grain may meet a twin boundary from the other grain in a quadruple junction) and the twins may be narrowed or “constricted” at the boundary. These effects are determined by the interfacial energy. We estimate the energy of the various interfaces by determining the dislocation arrays they contain, using the constrained coincidence site lattice (CCSL) model and Bollmann's O2-lattice formalism. Our approach indicates that there are significant changes in the energy of the interfaces and is thus able to explain the variety of observed morphologies.

Elimination of Twin Boundaries when Growing 3C-SiC Heteroepitaxial by Vapour-Liquid-Solid Mechanism on Patterned 4H-SiC Substrate

2012 ◽  
Vol 711 ◽  
pp. 11-15
Author(s):  
Jean Lorenzzi ◽  
Nikoletta Jegenyes ◽  
Mihai Lazar ◽  
Dominique Tournier ◽  
Davy Carole ◽  
...  
Keyword(s):  
Twin Boundary ◽  
Heteroepitaxial Growth ◽  
Twin Boundaries ◽  
Hexagonal Shape

In this work we report on the study of twin boundary (TB) evolution during heteroepitaxial growth of 3C-SiC on patterned 4H-SiC(0001) substrate by vapour-liquid-solid (VLS) mechanism. Ge50Si50 melt was used at a temperature of 1450°C. 3C-SiC deposit was obtained on top and outside the mesas. Some lateral enlargement of these mesas was observed but it was systematically homoepitaxial. Elimination of TBs inside the 3C-SiC deposit on top of the mesas was observed for specific mesa shape and/or orientation of the sidewalls. Though three–fold or six-fold symmetry mesas are recommended for TB elimination, originally circular mesas lead also to the same result due to initial faceting toward hexagonal shape.

Characterization of twin boundaries in an Fe–17.5Mn–0.56C twinning induced plasticity steel

2013 ◽  
Vol 85 ◽  
pp. 100-110 ◽  
Author(s):  
Erin E. Patterson ◽  
David P. Field ◽  
Yudong Zhang
Keyword(s):  
Twin Boundaries

On the Mechanism of Twin Boundary Elimination in 3C-SiC(111) Heteroepitaxial Layers on α-SiC Substrates

2011 ◽  
Vol 679-680 ◽  
pp. 71-74 ◽  
Author(s):  
Gabriel Ferro ◽  
Olivier Kim-Hak ◽  
Jean Lorenzzi ◽  
Nikoletta Jegenyes ◽  
Maya Marinova ◽  
...  
Keyword(s):  
Twin Boundary ◽  
Propagation Direction ◽  
Twin Boundaries ◽  
Crystalline Defects ◽  
Cvd Growth ◽  
Heteroepitaxial Layers

This paper deals with the formation and propagation of twin boundaries (TBs) inside 3C-SiC layers grown heteroepitaxially on -SiC substrate. The equivalent probability of nucleating 60° rotated 3C islands on such substrate lead to the systematic formation of TB upon coalescence of these islands. Elimination of these defects should occur by bending of the propagation direction. Bending through incoherent TBs is usually encountered during both VLS and CVD growth and it generates crystalline defects due to high built-in energy. One would prefer coherent TBs, formed by two-by-two annihilation of neighbouring TBs, which do not form new defect except microtwin inclusion at the interface. Such TB annihilation seems to be a specificity of growth by VLS mechanism. The mechanism of such bending is discussed

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