Atomic Core Structures Associated to the Threading Dislocation with Burgers Vector and [0001] Line Direction in GaN

2013 ◽  
Vol 52 (11S) ◽  
pp. 11NG06
Author(s):  
Antoine Béré ◽  
Pierre Ruterana ◽  
Marie-Pierre Chauvat ◽  
Jean Koulidiati
Keyword(s):  
Threading Dislocation ◽  
Burgers Vector ◽  
Atomic Core ◽  
Line Direction

Investigation of Defect Formation in 4H-SiC(0001) and (000-1) Epitaxy

2008 ◽  
Vol 600-603 ◽  
pp. 267-272 ◽  
Author(s):  
Hidekazu Tsuchida ◽  
Isaho Kamata ◽  
Masahiro Nagano
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Defect Formation ◽  
Grazing Incidence ◽  
Microscopic Structure ◽  
Threading Dislocation ◽  
Simultaneous Generation ◽  
Burgers Vector ◽  
X Ray ◽  
Transmission Electron

Defect formation in 4H-SiC(0001) and (000-1) epitaxy is investigated by grazing incidence synchrotron reflection X-ray topography and transmission electron microscopy. Frank-type faults, which are terminated by four Frank partials with a 1/4[0001] type Burgers vector with the same sign on four different basal planes, are confirmed to be formed by conversion of a 1c threading edge dislocation (TSD) in the substrate as well as simultaneous generation of a 1c TSD during epitaxy. The collation between the topography appearance and the microscopic structure and the variety of Frank faults are shown. Formation of carrot defects and threading dislocation clusters are also investigated.

scholarly journals Direct Observations Of Atomic Structures Of Defects In Gan By High Resolution Z-Contrast Stem

1997 ◽  
Vol 482 ◽  
Author(s):  
Y. Xin ◽  
S.J. Pennycook ◽  
N.D. Browning ◽  
P. D. Nellist ◽  
S. Sivananthan ◽  
...  
Keyword(s):  
High Resolution ◽  
Direct Observation ◽  
Stacking Fault ◽  
Threading Dislocation ◽  
Contrast Imaging ◽  
Atomic Core ◽  
Atomic Structures ◽  
Direct Observations ◽  
Z Contrast ◽  
Contrast Image

AbstractGaN/(0001)Sapphire grown by low pressure MOVPE is studied by high resolution Z-contrast imaging using STEM. First direct observation of the threading dislocation with edge character shows the atomic core structure, which appears to have a similar configuration to the {10–10} surface. The surfaces of the nanopipe walls are on {10–10} with the terminating layer between the atoms with one bond per pair. In addition, the high resolution Z-contrast image of the prismatic stacking fault confirms the results by conventional HRTEM.

LACBED Analysis of Threading Dislocation with c+a Burgers Vector in 4H-SiC

2012 ◽  
Author(s):  
Y. Sugawara ◽  
M. Nakamori ◽  
Y. Yao ◽  
Y. Ishikawa ◽  
K. Danno ◽  
...  
Keyword(s):  
Threading Dislocation ◽  
Burgers Vector

On the determination of stacking-fault energy from dislocation nodes observed by TEM

1994 ◽  
Vol 52 ◽  
pp. 686-687
Author(s):  
Paulo J. Ferreira
Keyword(s):  
Stacking Fault ◽  
Stacking Fault Energy ◽  
Radius Of Curvature ◽  
Bright Field ◽  
Burgers Vector ◽  
Partial Dislocations ◽  
Transmission Electron ◽  
Fundamental Understanding ◽  
Line Direction

A fundamental understanding of the mechanical and physical behaviour of metals requires a knowledge of the stacking-fault energy (SFE). This aspect is important because the possibility of cross-slip and thus plastic deformation is a function of the SFE of the material. Impurities may segregate to the faults and change the SFE, which may affect the mechanical behaviour. For low SFE’s materials, the SFE can be determined rather accurately from transmission electron microscopy evaluation of the radius of curvature of dislocation nodes formed by the attractive interaction of dislocations (Fig. 1).This work is directed towards applying the T.E.M. technique to determine the SFE of a 310S stable austenitic stainless steel. The specimens were observed in a JEOL 4000 microscope operated at an accelerating voltage of 200 kV, and equipped with a double tilt stage. Conventional two beam bright field images were used to determine the Burgers vector and line direction of the partial dislocations.

Measurement of Critical Thickness for the Formation of Interfacial Dislocations and Half Loop Arrays in 4H-SiC Epilayer via X-Ray Topography

2014 ◽  
Vol 778-780 ◽  
pp. 328-331 ◽  
Author(s):  
Huan Huan Wang ◽  
Fang Zhen Wu ◽  
Michael Dudley ◽  
Balaji Raghothamachar ◽  
Gil Y. Chung ◽  
...  
Keyword(s):  
Basal Plane ◽  
Critical Thickness ◽  
Opposite Sign ◽  
Substrate Surface ◽  
Dislocation Line ◽  
Threading Dislocation ◽  
X Ray ◽  
Half Loop ◽  
Interfacial Dislocations ◽  
Line Direction

Synchrotron X-ray Beam Topography (SWBXT) and KOH etching observations are presented of interfacial dislocations (IDs) and half-loop arrays (HLAs) which can form under certain growth conditions during homoepitaxy of 4H-SiC on off-cut substrates. The HLAs and IDs are observed to form from pairs of opposite sign basal plane dislocations in the substrate which intersect the substrate surface in screw orientation. These dislocations glide in opposite direction in the epilayer once critical thickness has been exceeded. Half-loop arrays are formed at the same time as the screw-type basal plane dislocations (BPDs) side-glide inside the epilayer. From knowledge of the formation mechanism of the HLAs [, if the line of the HLA is extended to intersect the original threading dislocation line direction, then the distance between this intersection point and the ID along the line direction of the original BPD provides a measure of the critical thickness. It is also calculated that the critical thickness in this case is largely determined by the mutual attractive force between the pairs of opposite sign threading BPDs in the substrate. In addition we observed both interfacial dislocations and HLAs generated from: (a) surface sources of BPDs; (b) micropipes; (c) 3C inclusions; and (d) substrate/epilayer interface scratches.

Investigation of Mechanical Stress-Induced Double Stacking Faults in (11-20) Highly N-Doped 4H-SiC Combining Optical Microscopy, TEM, Contrast Simulation and Dislocation Core Reconstruction

2006 ◽  
Vol 527-529 ◽  
pp. 379-382 ◽  
Author(s):  
Maryse Lancin ◽  
G. Regula ◽  
Joël Douin ◽  
Hosni Idrissi ◽  
Laurent Ottaviani ◽  
...  
Keyword(s):  
Optical Microscopy ◽  
Mechanical Stress ◽  
Compressive Stress ◽  
Stacking Faults ◽  
Dislocation Core ◽  
Burgers Vector ◽  
Partial Dislocations ◽  
Core Composition ◽  
Line Direction

Defects are introduced into (11-20) highly N-doped 4H-SiC by one surface scratch followed by annealing at 550°C or 700°C with or without an additional compressive stress. The defects are planar and always consist of double stacking faults dragged by a pair of partial dislocations. In a pair, the partial dislocations have the same line direction, Burgers vector and core composition. All the identified gliding dislocations have a silicon core. An analysis of their expansion during annealing proves that C(g) partial segments can be created but that C(g) partial dislocations are immobile.

Properties of the Deformation Microstructure in Al-Rich γ-TiAl Deformed by Ordinary Dislocations

1999 ◽  
Vol 578 ◽  
Author(s):  
Fabienne Grjégori ◽  
Patrick VeyssiÈRe
Keyword(s):  
Flow Stress ◽  
Single Crystals ◽  
Peak Temperature ◽  
Clear Correlation ◽  
Microstructural Investigation ◽  
Screw Dislocations ◽  
Burgers Vector ◽  
Dislocation Pinning ◽  
The Relationship ◽  
Line Direction

AbstractIn the near vicinity of the [021] load orientation, γ-TiAl deforms via ordinary dislocations (Burgers vector b = 1/2<110]). As for deformation by <110] dislocations, the flow stress shows a peak at about 600°C. Results of an extensive microstructural investigation aimed at identifying the origin of this mechanical anomaly are presented. The analysis was conducted on single crystals oriented for single slip. It confirmed that ordinary dislocations tend to align themselves along the screw direction. This preferential line direction becomes gradually accentuated as the deformation temperature is raised up to the peak temperature. This effect is accompanied by a strong tendency towards forming cusps, but there is indication that the immobilisation along the screw direction takes place prior to dislocation pinning. In the vicinity of the peak temperature, screw dislocations gather in the form of bundles. No clear correlation is found between the temperature dependence of the flow stress and that of the density of pinning points. The relationship between these microstructural findings and the occurrence of a flow stress anomaly is discussed.

Dislocations in alumina deformed by prismatic slip

1978 ◽  
Vol 36 (1) ◽  
pp. 606-607
Author(s):  
J. Cadoz ◽  
J. Castaing ◽  
J. Philibert
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Basal Slip ◽  
Prismatic Slip ◽  
Compression Tests ◽  
Thin Sections ◽  
Burgers Vector ◽  
Maximum Deformation ◽  
Transmission Electron ◽  
Mechanical Thinning

Plastic deformation of alumina has been much studied; basal slip occurs and dislocation structures have been investigated by transmission electron microscopy (T.E.M.) (1). Non basal slip has been observed (2); the prismatic glide system <1010> {1210} has been obtained by compression tests between 1400°C and 1800°C (3). Dislocations with <0110> burgers vector were identified using a 100 kV microscope(4).We describe the dislocation structures after prismatic slip, using high voltage T.E.M. which gives much information.Compression tests were performed at constant strainrate (∿10-4s-1); the maximum deformation reached was 0.03. Thin sections were cut from specimens deformed at 1450°C, either parallel to the glide plane or perpendicular to the glide direction. After mechanical thinning, foils were produced by ion bombardment. Details on experimental techniques can be obtained through reference (3).

Defects in ion implanted silicon

1978 ◽  
Vol 36 (1) ◽  
pp. 386-387
Author(s):  
J.A. Lambert ◽  
P.S. Dobson
Keyword(s):  
Defect Structure ◽  
Dislocation Loops ◽  
Frank Loop ◽  
Burgers Vector ◽  
Temperature Range ◽  
Perfect Dislocation ◽  
Contrast Analysis ◽  
Image Position ◽  
Ion Implanted

The defect structure of ion-implanted silicon, which has been annealed in the temperature range 800°C-1100°C, consists of extrinsic Frank faulted loops and perfect dislocation loops, together with‘rod like’ defects elongated along <110> directions. Various structures have been suggested for the elongated defects and it was argued that an extrinsically faulted Frank loop could undergo partial shear to yield an intrinsically faulted defect having a Burgers vector of 1/6 <411>.This defect has been observed in boron implanted silicon (1015 B+ cm-2 40KeV) and a detailed contrast analysis has confirmed the proposed structure.

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