Synchrotron Topography Studies of Growth and Deformation-Induced Dislocations in 4H-SiC

2012 ◽  
Vol 1433 ◽  
Author(s):  
M. Dudley ◽  
H. Wang ◽  
F. Wu ◽  
S. Byrappa ◽  
S. Shun ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Single Crystals ◽  
Basal Plane ◽  
Partial Dislocation ◽  
Reversible Process ◽  
Burgers Vector ◽  
Shockley Partial ◽  
Partial Dislocations ◽  
Equilibrium Concentrations ◽  
Dislocation Multiplication

ABSTRACTSynchrotron topography studies are presented of the behavior of growth dislocations and deformation-induced dislocations in 4H-SiC single crystals. The growth dislocations include those in threading orientation with line directions approximately along c with Burgers vectors of a, c, and na+mc (where n and m are integers) while the deformation-induced dislocations include those with line directions confined to the basal plane with Burgers vectors of a and Shockley partial dislocations with Burgers vectors of 1/3<1-100> as well as those with line directions in the {1-100} prismatic planes with Burgers vectors of a. Processes leading to the nucleation of the growth dislocations are discussed as well as their deflection onto the basal plane during crystal growth in a reversible process. This latter process can lead to the conversion of segments of the deflected growth dislocations into deformation induced dislocations. In some cases this can lead to dislocation multiplication via the Hopping Frank-Read source mechanism and in others to the motion of single Shockley partial dislocations leading to Shockley stacking fault expansion. Studies are also presented of interactions between threading growth dislocations with c-component of Burger’s vector facilitated by climb processes which are mediated by interactions with non-equilibrium concentrations of vacancies. This can lead to reactions whereby complete or partial dislocation Burgers vector annihilation occurs.

scholarly journals Twinning in Czochralski-Grown 36°-RY LiTaO3 Single Crystals

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1009
Author(s):  
Yutaka Ohno ◽  
Yuta Kubouchi ◽  
Hideto Yoshida ◽  
Toshio Kochiya ◽  
Tomio Kajigaya
Keyword(s):  
Single Crystals ◽  
Slip Plane ◽  
Edge Dislocation ◽  
Lithium Tantalate ◽  
Initiation Site ◽  
The Other ◽  
Burgers Vector ◽  
Partial Dislocations ◽  
Dislocation Arrays ◽  
Extension Direction

The origin of twinning during the Czochralski (CZ) growth of 36°-RY lithium tantalate (LiTaO3) single crystals is examined, and it is shown that lineages composed of dislocation arrays act as an initiation site for twinning. Two types of lineages expand roughly along three different {12¯10} planes and two different {11¯00} planes. The former lineages and some latter lineages are composed of two types of mixed-dislocations with different Burgers vectors, while the other lineages are composed of only one type of edge-dislocation. All the dislocations have the Burgers vector of ⟨12¯10⟩ type with the compression side at the +Z side. Twin lamellae on {101¯2} are generated at a lineage during the CZ growth. We have hypothesized that dislocations in the lineage with b = 1/3⟨12¯10⟩ change their extension direction along a slip plane of {101¯2}, and they dissociate into pairs of partial dislocations with b = 1/6⟨22¯01⟩and 1/6⟨02¯21¯⟩ forming twin lamellae on {101¯2}.

scholarly journals Dissociation Behavior of Dislocations in Ice

Crystals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 386
Author(s):  
Takeo Hondoh
Keyword(s):  
Basal Plane ◽  
Dislocation Line ◽  
Stacking Faults ◽  
Physical Models ◽  
Time Constants ◽  
Burgers Vector ◽  
Partial Dislocations ◽  
Perfect Dislocation ◽  
Low Energies ◽  
Dissociated State

Dislocations in ice behave very differently from those in other materials due to the very low energies of stacking faults in the ice basal plane. As a result, the dislocations dissociate on the basal plane, from a perfect dislocation into two partial dislocations with equilibrium width we ranging from 20 to 500 nm, but what is the timescale to reach this dissociated state? Using physical models, we estimate this timescale by calculating two time-constants: the dissociation-completing time td and the dissociation-beginning time tb. These time constants are calculated for two Burgers vectors as a function of temperature. For perfect dislocations with Burgers vector <c + a>, td is more than one month even at the melting temperature TM, and it exceeds 103 years below −50 ℃, meaning that the dissociation cannot be completed during deformation over laboratory timescales. However, in this case the beginning time tb is less than one second at TM, and it is within several tens of minutes above −50 ℃. These dislocations can glide on non-basal planes until they turn to the dissociated state during deformation, finally resulting in sessile extended dislocations of various widths approaching to the equilibrium value we. In contrast, for perfect dislocations with Burgers vector <a>, td is less than one second above −50 ℃, resulting in glissile extended dislocations with the equilibrium width we on the basal plane. This width is sensitive to the shear stress τ exerted normal to the dislocation line, leading to extension of the intervening stacking fault across the entire crystal grain under commonly accessible stresses. Also, due to the widely dissociated state, dislocations <a> cannot cross-slip to non-basal planes. Such behavior of extended dislocations in ice are notable when compared to those of other materials.

Effect of Ta on the Structure and Dynamics of γ/α2 Interfaces in Tial

1990 ◽  
Vol 213 ◽  
Author(s):  
S. R. Singh ◽  
J. M. Howe
Keyword(s):  
Partial Dislocation ◽  
Growth Mechanisms ◽  
Tial Alloys ◽  
Shockley Partial ◽  
Structure And Dynamics ◽  
Partial Dislocations ◽  
Α2 Phase ◽  
Atomically Flat ◽  
Ledge Mechanism ◽  
Image Simulations

ABSTRACTThe structure of γ/α interfaces in binary and Ta-containing TiAl alloys were analyzed by HRTEM and image simulations. Growth of α2 was found to be due to a ledge mechanism, consisting of Shockley partial dislocations on alternate (111)γ planes. The interface is atomically flat between the ledges and addition of Ta was found to transform arrays of growth ledges in the binary alloy into islands on the plate faces in the Ta-containing alloy. These islands of α2 on the γ/α2 interfaces were 4–7nm wide and increased in size with decreasing ageing temperature. The height of the ledges and islands were always a multiple of the c-parameter (0.46nm) of the α2 phase. The islands were bounded by 90°(edge) and 30° screw) Shockley partial dislocations. The 30° partial dislocation cores were localized whereas the 90° partial dislocation cores appeared to be highly delocalized due to presence of a high density of kinks, which in one case was found to be about 0.65nm−1.These results are interpreted in terms of the growth mechanisms and morphology of the α2 phase.

Observation of dislocation reactions in CDTE at lattice resolution

1983 ◽  
Vol 41 ◽  
pp. 112-113
Author(s):  
T. Yamashita ◽  
R. Sinclair
Keyword(s):  
Partial Dislocation ◽  
Video Recording ◽  
Dislocation Motion ◽  
Video Tape ◽  
Exposure Rate ◽  
Shockley Partial Dislocation ◽  
Shockley Partial ◽  
Partial Dislocations ◽  
Lattice Resolution ◽  
Obvious Extension

Recently, lattice resolution video-recording of dislocation motion in CdTe has been reported by Sinclair et al, using the Cambridge 500 keV microscope equipped with a TV camera. Phenomena such as the motion of Shockley partial dislocations and climb of Frank dislocations were recorded onto a video tape which has an exposure rate of 50 half-frames per second. An obvious extension of this work is to study the dislocation reactions. An example of such a reaction which was detected in CdTe is shown in Fig. 1. The micrographs were taken several seconds apart in a JEOL 200CX microscope, and they show dissociation of a Frank dislocation into a Shockley partial dislocation and a Lomer dislocation (ie., a sessile lock).

CBED analysis of extended defects in melt-grown GaSe single crystals

1990 ◽  
Vol 48 (4) ◽  
pp. 494-495
Author(s):  
C. De Blasi ◽  
D. Manno
Keyword(s):  
Single Crystals ◽  
Displacement Vector ◽  
Stacking Faults ◽  
Convergent Beam Electron Diffraction ◽  
Extended Defects ◽  
Burgers Vector ◽  
First Order ◽  
Partial Dislocations ◽  
Kinematical Condition ◽  
Convergent Beam

The study of dislocations and stacking faults in melt grown GaSe single crystals has been carried out by the Convergent Beam Electron Diffraction (CBED) technique.The presence of stacking faults induces distortions in the Kikuchi lines observed in the CBED transmitted disk. According to the kinematical condition of the stacking fault visibility, such lines show modifications when g·R is not integer, The displacement vector R has been determined by the analysis of the visibility and invisibility conditions in the transmitted disk, recorded according to the Tanaka method, The Burgers vector b of dislocations has been determined by the analysis of the modifications induced both in Kikuchi lines and in the First Order Laue Zone (FOLZ) reflections, observed in low camera length CBED patterns. Splitting and unsplitting of the reflections correspond to the visibility and invisibility of the dislocations in the kinematical approximation of diffraction contrast, The condition g·b = 0 is not strictly a sufficient condition for the vanishing of the modifications induced by the dislocation, neverthless it is generally very useful as a criterion for determining the direction of b, Moreover, some reflections g give g·b = ⅓ in the case of partial dislocations. This condition does not produce enough contrast to be detected, so that it is one more for the defect invisibility. The Thompson construction has been used in order to calculate the amplitude of b and to discriminate perfect or partial dislocations.

Characterization of Defect Structures in Lely 6H-SiC Single Crystals Using Synchrotron White Beam X-Ray Topography

1994 ◽  
Vol 375 ◽  
Author(s):  
W. Huang ◽  
S. Wang ◽  
M. Dudley ◽  
P. Neudeck ◽  
J. A. Powell ◽  
...  
Keyword(s):  
Single Crystals ◽  
Basal Plane ◽  
Stacking Faults ◽  
Defect Structures ◽  
Dislocation Generation ◽  
X Ray ◽  
Partial Dislocations ◽  
White Beam ◽  
Generation Mechanisms

AbstractDefect structures in Lely SiC single crystals have been studied using synchrotron white beam X-ray topography. Basal plane dislocations and stacking faults probably generated during post-growth cooling are clearly revealed. For both perfect dislocations and partial dislocations bounding the stacking faults, Burgers vectors and line directions are determined from contrast extinction analysis as well as projected direction analysis on different topographic images. The fault planes and fault vectors of the stacking faults were determined using contrast extinction analysis. Possible dislocation generation mechanisms are briefly discussed.

Stacking faults and dislocations in titanium dioxide, with special reference to non-stoichiometry

1963 ◽  
Vol 276 (1367) ◽  
pp. 542-552 ◽  
Keyword(s):  
Titanium Dioxide ◽  
Partial Dislocation ◽  
Stoichiometric Composition ◽  
Stacking Faults ◽  
Dislocation Loops ◽  
Microscopical Investigation ◽  
Burgers Vector ◽  
Vacancy Clusters ◽  
Partial Dislocations ◽  
Electron Microscopical

A detailed electron microscopical investigation has been made of the stacking faults and dislocations observed in thin films of titanium dioxide grown on the (100) faces of titanium carbide crystals. The large stacking faults formed during the growth process lie on a {101} plane, but they often change from one plane to another of the same family, sometimes on too fine a scale to be clearly resolved. The fault is terminated by a partial dislocation having a vector of the 1/2<101>-type; if the specimen is heated in the microscope, when it becomes non-stoichiometric, the fault anneals out by one of two mechanisms. The first mechanism involves the glide of the partial dislocation terminating the fault, and the second the growth of small dislocation loops formed by the condensation of vacancies introduced as a result of deviations from the stoichiometric composition. Contrast experiments show that the observed dislocations are of two types. The first are dissociated dislocations having a partial 1/2<101> vector, glissile on {101} planes and associated with a stacking fault. The second type of dislocation are undissociated and have a <001> Burgers vector. A sessile configuration is also formed by an interaction between dislocations with 1/2<101> and <001> and Burgers vector. An interaction between glissile partial dislocations and vacancy clusters also occurs, and it is suggested that this is a possible mechanism for the increased yield stress produced when TiO 2 becomes substoichiometric.

Misfit Dislocations in Epitaxial Layers of SI on Gap (001) Substrates

1984 ◽  
Vol 37 ◽  
Author(s):  
M. P. A. Viegers ◽  
C. W. T. Bulle Lieuwma ◽  
P. C. Zalm ◽  
P. M. J. Maree
Keyword(s):  
Strain Field ◽  
Stacking Faults ◽  
Misfit Strain ◽  
Epitaxial Layers ◽  
Misfit Dislocations ◽  
Biaxial Strain ◽  
Burgers Vector ◽  
Shockley Partial ◽  
Partial Dislocations ◽  
Geometrical Effect

AbstractMisfit dislocations in epitaxial layers of Si grown by MBE at 570°C on GaP(001) substrates have been studied by TEM. It is found that layers as thick as 500 Å at least reside coherently on the substrate without misfit dislocations. In 1000 Å layers of Si the misfit strain is accommodated in part by 60-degree type dislocations with their Burgers vector inclined with respect to the interface, and by stacking faults intersecting the Si layer. The dislocations are dissociated into 30- and 90-degree Shockley partial dislocations. It is shown that in the case of a biaxial strain field, which is tensile in a (001)-plane, the 90-degree partial must be nucleated first. Only then can the 30-degree partial follow on the same glide plane. This geometrical effect explains the presence of dislocations as well as stacking faults in the Si layer.

Creation of Dislocations in a Shall Copper Single Crystal

1992 ◽  
Vol 278 ◽  
Author(s):  
Masao Doyama
Keyword(s):  
Single Crystal ◽  
Yield Stress ◽  
Partial Dislocation ◽  
Stacking Fault ◽  
Copper Single Crystal ◽  
Shockley Partial ◽  
Partial Dislocations ◽  
Edge Dislocations

AbstractEdge dislocations were created on a surface of a small copper single crystal. Very sharp yield stress was observed when a partial dislocation was created. Edge dislocations in copper were split into Heidenreich–Shockley partial dislocations connected with the stacking fault.

Creation and Motion of Edge Dislocations in Copper Single Crystals

1997 ◽  
Vol 505 ◽  
Author(s):  
Masaodoyama ◽  
Yoshiaki Kogure ◽  
Tadatoshi Nozaki
Keyword(s):  
Molecular Dynamics ◽  
Single Crystals ◽  
Partial Dislocation ◽  
Stacking Fault ◽  
Shockley Partial Dislocation ◽  
Shockley Partial ◽  
Small Crystals ◽  
The Creation ◽  
Copper Single Crystals ◽  
Edge Dislocations

ABSTRACTDislocations were created near the center of the surface (110) of copper small crystals whose surfaces are (111), (111), (110), (110), (112), and (112) by use of n-body atom potentials and molecular dynamics. At first, a Heidenreich-Shockley partial dislocation was created. As the partial dislocation proceeds, the partial dislocation and the surface was connected with a stacking fault until the next Heidenreich-Shockley partial dislocation was created at the surface.Just before the creation of a partial dislocation the stress was the highest. For larger crystals, forming a step on (110) plane was not enough and a shear was necessary to move dislocations.

Sign in / Sign up

Export Citation Format

Share Document