The Core Structure of Dislocations in GaAs

1985 ◽  
Vol 62 ◽  
Author(s):  
B. C. De Cooman ◽  
K.-H. Kuesters ◽  
C. B. Carter
Keyword(s):  
High Stress ◽  
Dislocation Core ◽  
Core Structure ◽  
Screw Dislocations ◽  
The Core ◽  
Resolution Electron ◽  
Model Structures ◽  
High Resolution Electron Micrographs ◽  
Structural Aspects ◽  
Strong Asymmetry

ABSTRACTThe structural aspects of dislocations in GaAs which had been plastically deformed at high stress were studied by TEM. The glide of well-defined dislocations in their slip-plane was observed during the recombination-enchanced relaxation of the dislocations from their high-stress configuration. The strong asymmetry of dislocation velocity previously observed by other techniques is confirmed. High-resolution, electron micrographs of dissociated end-on screw dislocations were compared to computer simulated micrographs of model structures of the dislocation core. No definite conclusion regarding the exact core structure could be made due to the movement of the defects during the observation.

scholarly journals Evaluation of Aberration-corrected Optical Sectioning for Exploring the Core Structure of ½[111] Screw Dislocations in BCC Metals

2017 ◽  
Vol 23 (S1) ◽  
pp. 432-433
Author(s):  
D. Hernandez-Maldonado ◽  
R. Groger ◽  
Q. M. Ramasse ◽  
P. B. Hirsch ◽  
P.D. Nellist
Keyword(s):  
Core Structure ◽  
Optical Sectioning ◽  
Screw Dislocations ◽  
The Core ◽  
Bcc Metals ◽  
Aberration Corrected

A dislocation core in titanium dioxide and its electronic structure

RSC Advances ◽  
2015 ◽  
Vol 5 (24) ◽  
pp. 18506-18510 ◽  
Author(s):  
Rong Sun ◽  
Zhongchang Wang ◽  
Naoya Shibata ◽  
Yuichi Ikuhara
Keyword(s):  
Titanium Dioxide ◽  
Electronic Structure ◽  
Electric Conductivity ◽  
Dislocation Core ◽  
Core Structure ◽  
Atomic Resolution ◽  
The Core ◽  
Resolution Imaging

We provide a direct atomic-resolution imaging of the core structure of a dislocation in technologically important TiO2 and predict that every individual impurity-free dislocation exhibits electric conductivity in an otherwise insulating TiO2.

The core structure of ½(111) screw dislocations in b.c.c. crystals

1970 ◽  
Vol 21 (173) ◽  
pp. 1049-1073 ◽  
Author(s):  
V. Vítek ◽  
R. C. Perrin ◽  
D. K. Bowen
Keyword(s):  
Core Structure ◽  
Screw Dislocations ◽  
The Core

Computer Simulation Study of the Effects of Copper Precipitates on Dislocation Core Structure in Ferritic Steels

1996 ◽  
Vol 439 ◽  
Author(s):  
T. Harry ◽  
D. J. Bacon
Keyword(s):  
Dislocation Core ◽  
Alloy System ◽  
Lattice Parameter ◽  
Transformation Process ◽  
Core Structure ◽  
Metastable Equilibrium ◽  
Precipitate Size ◽  
Ferritic Steels ◽  
Interatomic Potentials ◽  
The Core

AbstractThe small, coherent BCC precipitates of copper that form during fast neutron irradiation of ferritic steels are an important component of in-service irradiation hardening. Many-body interatomic potentials for the Fe-Cu alloy system have been developed and used to simulate the atomic structure of the ½<111> screw dislocation in both pure a-iron and the metastable BCC phase of copper. In iron, the core has the well-known 3-fold form of atomic disregistry. In BCC copper, however, the core structure depends on the lattice parameter. At the metastable equilibrium value, the core is similar to that in iron, but as the lattice parameter is reduced, as in a precipitate, the core becomes delocalised by transformation of the copper. Simulation of dislocated crystals containing precipitates shows that the extent of this effect depends on precipitate size. The energy changes indicate a significant dislocation pinning effect due to this dislocation-induced precipitate transformation process.

HREM imaging of screw dislocation core structures in bcc metals

2004 ◽  
Vol 839 ◽  
Author(s):  
B.G. Mendis ◽  
Y. Mishin ◽  
C.S. Hartley ◽  
K.J. Hemker
Keyword(s):  
Screw Dislocation ◽  
Dislocation Core ◽  
High Resolution Electron Microscopy ◽  
Core Region ◽  
Surface Relaxation ◽  
Hrem Image ◽  
The Core ◽  
Bcc Metals ◽  
Atomic Displacements ◽  
Resolution Electron

ABSTRACTQuantitative High Resolution Electron Microscopy (HREM) is used to characterize the in-plane displacements of atoms around a screw dislocation core in bcc molybdenum. The in-plane displacements have an important effect on the bulk mechanical properties of bcc metals and alloys. However, the largest displacements are predicted to be less than 10 pm, requiring that the atom positions in an HREM image be determined to sub-pixel accuracy. In order to calculate the displacements the positions of the atom columns in the undistorted crystal must be determined precisely from the information available in the HREM image. An algorithm for such a task is briefly discussed and the technique applied to several HREM images. It is seen that the atomic displacements are predominantly due to surface relaxation (i.e. Eshelby twist) of a thin TEM foil, thereby masking the finer displacements of the dislocation core. Nye tensor plots, which map the resultant Burgers vector at each point of a distorted crystal, are also used to characterize the core structure. Although the large displacements from the Eshelby twist were completely removed, no signal from the dislocation core region was observed.

Mixed partial dislocation core structure in GaN by high resolution electron microscopy

2006 ◽  
Vol 203 (9) ◽  
pp. 2156-2160 ◽  
Author(s):  
J. Kioseoglou ◽  
G. P. Dimitrakopulos ◽  
Ph. Komninou ◽  
Th. Kehagias ◽  
Th. Karakostas
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Partial Dislocation ◽  
Dislocation Core ◽  
High Resolution Electron Microscopy ◽  
Core Structure ◽  
Resolution Electron ◽  
Dislocation Core Structure

On non-glide stresses and their influence on the screw dislocation core in body-centred cubic metals. II. The core structure

1984 ◽  
Vol 392 (1802) ◽  
pp. 175-197 ◽  
Keyword(s):  
Stress Tensor ◽  
Screw Dislocation ◽  
Applied Stress ◽  
Elastic Strain ◽  
Elastic Anisotropy ◽  
Dislocation Core ◽  
Core Structure ◽  
Peierls Stress ◽  
The Core ◽  
Anisotropic Elastic

The change in core structure of the screw dislocation in a body-centred cubic lattice subjected to a general applied stress tensor is studied by means of computer simulation. The large variations observed are found not to be correlated with the applied stress, in that the same deformed core structure can be realized by many different combinations of stress components. Instead, the core structure is found to be characterized almost exclusively by the magnitude and orientation of the induced glide strain, with a much smaller dependence on the glide stress. This means that while the force acting on a dislocation is defined by the applied stress, it is the elastic strain within the lattice that determines the resistance to motion. This explains the anomalously large dependence of the Peierls stress upon non-glide components of the applied stress tensor. The Peierls stress varies strongly with the shape of the dislocation core, which depends upon the glide strain. However, the glide strain is in turn dependent on non-glide components of the applied stress by way of anisotropic elastic couplings. Therefore the Peierls stress is itself dependent on the non-glide stresses, to an extent governed by the elastic anisotropy. The possible origin of the strain-dependence of the core structure in elastic strain multiplet forces (equal and opposite generalized forces acting on the dislocation) is discussed briefly, as are implications for the phenomenon of ductile fracture.

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