CORE STRUCTURE OF 90° PARTIAL DISLOCATIONS IN DIAMOND

1983 ◽  
Vol 44 (C4) ◽  
pp. C4-37-C4-42 ◽  
Author(s):  
K. W. Lodge ◽  
A. Lapiccirella ◽  
N. Tomassini ◽  
S. L. Altmann
Keyword(s):  
Core Structure ◽  
Partial Dislocations

Core structure and properties of partial dislocations in silicon carbide p-i-n diodes

2003 ◽  
Vol 83 (24) ◽  
pp. 4957-4959 ◽  
Author(s):  
S. Ha ◽  
M. Benamara ◽  
M. Skowronski ◽  
H. Lendenmann
Keyword(s):  
Silicon Carbide ◽  
Core Structure ◽  
Structure And Properties ◽  
Partial Dislocations

Lattice Imaging of Stacking Faults in (011) Silicon

1977 ◽  
Vol 35 ◽  
pp. 20-21
Author(s):  
Ondrej L. Krivanek ◽  
Dennis M. Maher
Keyword(s):  
Thermal Oxidation ◽  
Surface Defects ◽  
Stacking Faults ◽  
High Density ◽  
Core Structure ◽  
Lattice Imaging ◽  
Partial Dislocations ◽  
Boron Implantation ◽  
P Type

Thermal oxidation of silicon containing surface defects results in the formation of extrinsic stacking faults inhabiting the (111) planes. The faults are bound by Frank partial dislocations, and oxygen may be closely associated with them. The present work aims to explore the fault core structure by lattice imaging.The p-type, 4 Ω-cm Si was boron implanted (50kV, 1x1015/cm2), annealed for 30 min at 1000°C and steam oxidized for 2 hours at 1050°C. The boron implantation prior to oxidation serves to produce a high density of stacking faults to facilitate their observation. The polished and thinned (011) foils were examined at 125kV in a Siemens 102 EM with a goniometer stage at magnifications of 500 000 to 800 000x, using axial illumination and no objective aperture.

Characterization of the dislocation core structure of partial dislocations in SiC(011) using HRTEM: a theoretical study

1993 ◽  
Vol 51 ◽  
pp. 992-993
Author(s):  
T. Geipel ◽  
P. Pirouz
Keyword(s):  
Chemical Composition ◽  
Chemical Characterization ◽  
Analytical Techniques ◽  
Dislocation Core ◽  
Core Structure ◽  
Chemical Mapping ◽  
Hrtem Image ◽  
Partial Dislocations ◽  
Constituent Elements

The mobility of a dislocation in compound semiconductors of zincblende or wurtzite structure depends on its core structure i.e. its chemical composition. Present analytical techniques are not able to resolve the nature of the atomic species at the dislocation core and although HRTEM is capable of resolving the atomic arrangement in the core, its chemical characterization is difficult. In single crystalline regions the chemical composition can be determined using chemical mapping but this method cannot be applied to dislocations, viewed end-on, because these are non-periodic features. In a HRTEM image of a compound material, different scattering factors of the constituent elements may lead to spots of different brightness, but these contrast differences are very small. The only distinct characteristic of a HRTEM image is the spacings between bright or dark spots which can be measured easily. In this paper a practical concept for chemical distinction between Si and C in the cores of partial dislocations in SiC(011) is presented.

A Many-Beam Technique for Enhanced Resolution of Partial Dislocations

1972 ◽  
Vol 30 ◽  
pp. 646-647
Author(s):  
J. M. Oblak ◽  
B. H. Kear
Keyword(s):  
Phase Shift ◽  
Field Method ◽  
Dark Field ◽  
Bright Field ◽  
Field Technique ◽  
Weak Beam ◽  
Partial Dislocations ◽  
Enhanced Resolution ◽  
Nickel Base ◽  
Beam Technique

The “weak-beam” and systematic many-beam techniques are the currently available methods for resolution of closely spaced dislocations or other inhomogeneities imaged through strain contrast. The former is a dark field technique and image intensities are usually very weak. The latter is a bright field technique, but generally use of a high voltage instrument is required. In what follows a bright field method for obtaining enhanced resolution of partial dislocations at 100 KV accelerating potential will be described.A brief discussion of an application will first be given. A study of intermediate temperature creep processes in commercial nickel-base alloys strengthened by the Ll2 Ni3 Al γ precipitate has suggested that partial dislocations such as those labelled 1 and 2 in Fig. 1(a) are in reality composed of two closely spaced a/6 <112> Shockley partials. Stacking fault contrast, when present, tends to obscure resolution of the partials; thus, conditions for resolution must be chosen such that the phase shift at the fault is 0 or a multiple of 2π.

Evidence for a shear mechanism for the precipitation of γ-zirconium hydride in zirconium

1978 ◽  
Vol 36 (1) ◽  
pp. 658-659
Author(s):  
G.J.C. Carpenter
Keyword(s):  
Elevated Temperature ◽  
Strain Field ◽  
Zirconium Hydride ◽  
Zirconium Atom ◽  
Atom Diffusion ◽  
Solvus Temperature ◽  
Hexagonal Close Packed ◽  
Partial Dislocations ◽  
The Face

In zirconium-hydrogen alloys, rapid cooling from an elevated temperature causes precipitation of the face-centred tetragonal (fct) phase, γZrH, in the form of needles, parallel to the close-packed <1120>zr directions (1). With low hydrogen concentrations, the hydride solvus is sufficiently low that zirconium atom diffusion cannot occur. For example, with 6 μg/g hydrogen, the solvus temperature is approximately 370 K (2), at which only the hydrogen diffuses readily. Shears are therefore necessary to produce the crystallographic transformation from hexagonal close-packed (hep) zirconium to fct hydride.The simplest mechanism for the transformation is the passage of Shockley partial dislocations having Burgers vectors (b) of the type 1/3<0110> on every second (0001)Zr plane. If the partial dislocations are in the form of loops with the same b, the crosssection of a hydride precipitate will be as shown in fig.1. A consequence of this type of transformation is that a cumulative shear, S, is produced that leads to a strain field in the surrounding zirconium matrix, as illustrated in fig.2a.

On effects of non-systematic reflections on weak-beam images of partial dislocations

1991 ◽  
Vol 49 ◽  
pp. 688-689
Author(s):  
K. Z. Botros ◽  
S. S. Sheinin
Keyword(s):  
High Precision ◽  
Stacking Fault ◽  
Important Application ◽  
Stacking Fault Energy ◽  
Sharp Peak ◽  
Weak Beam ◽  
Partial Dislocations ◽  
Deviation Parameter ◽  
Beam Diffraction

The main features of weak beam images of dislocations were first described by Cockayne et al. using calculations of intensity profiles based on the kinematical and two beam dynamical theories. The feature of weak beam images which is of particular interest in this investigation is that intensity profiles exhibit a sharp peak located at a position very close to the position of the dislocation in the crystal. This property of weak beam images of dislocations has an important application in the determination of stacking fault energy of crystals. This can easily be done since the separation of the partial dislocations bounding a stacking fault ribbon can be measured with high precision, assuming of course that the weak beam relationship between the positions of the image and the dislocation is valid. In order to carry out measurements such as these in practice the specimen must be tilted to "good" weak beam diffraction conditions, which implies utilizing high values of the deviation parameter Sg.

Structure of stacking faults in pyrite using TEM techniques

1992 ◽  
Vol 50 (1) ◽  
pp. 358-359
Author(s):  
Raja Subramanian ◽  
Kenneth S. Vecchio
Keyword(s):  
Lattice Structure ◽  
Stacking Faults ◽  
Covalent Bond ◽  
Group Symmetry ◽  
Iron Pyrite ◽  
Dislocation Glide ◽  
Partial Dislocations ◽  
Transmission Electron ◽  
Contrast Analysis ◽  
Chlorine Ions

The structure of stacking faults and partial dislocations in iron pyrite (FeS2) have been studied using transmission electron microscopy. Pyrite has the NaCl structure in which the sodium ions are replaced by iron and chlorine ions by covalently-bonded pairs of sulfur ions. These sulfur pairs are oriented along the <111> direction. This covalent bond between sulfur atoms is the strongest bond in pyrite with Pa3 space group symmetry. These sulfur pairs are believed to move as a whole during dislocation glide. The lattice structure across these stacking faults is of interest as the presence of these stacking faults has been preliminarily linked to a higher sulfur reactivity in pyrite. Conventional TEM contrast analysis and high resolution lattice imaging of the faulted area in the TEM specimen has been carried out.

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