Computer Simulation of Defect Images from Transmission Electron Microscopy

1977 ◽  
Vol 35 ◽  
pp. 54-55
Author(s):  
W. D. Cooper
Keyword(s):  
Electron Microscopy ◽  
Simple Procedure ◽  
Defect Structures ◽  
Dislocation Loops ◽  
Burgers Vector ◽  
Plane Normal ◽  
Unambiguous Determination ◽  
Transmission Electron ◽  
Shear Component

During recent years, defect structures resulting from radiation damage have been successfully studied by a large number of investigators. Early studies were based primarily on the analysis of the characteristic black-white lobe contrast from small dislocation loops. Contrast calculations indicated that the sense of the black-white contrast, relative to the diffracting vector at a given depth in the foil, could be used to determine the nature (vacancy or interstitial) of the loop. These calculations have also been used to formulate rules for the determination of the loop Burgers vector and habit plane normal [1]. For pure edge loops this simple procedure is quite satisfactory, but for loops with a shear component of the Burgers vector it becomes very involved and, in certain geometries, may lead to erroneous conclusions. Carpenter has demonstrated that “unsafe” orientations exist which do not permit the unambiguous determination of the Burgers vector relative to the loop plane [2].

Direction of Black-White Contrast from Small Dislocation Loops

1977 ◽  
Vol 35 ◽  
pp. 56-57
Author(s):  
W. D. Cooper ◽  
C. S. Hartley ◽  
J. J. Hren
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Image Plane ◽  
Dislocation Loops ◽  
Burgers Vector ◽  
Simple Concept ◽  
Transmission Electron ◽  
Vector Projection ◽  
Shear Component

Dislocation loops observed in the transmission electron microscope exhibit a characteristic black-white strain contrast under two-beam dynamical diffracting conditions. A simple concept of the nature of this contrast indicates that the black-white direction should lie parallel to the projection of the Burgers vector onto the image plane. Using the results of several contrast calculations for small loops, Wilkens and Riihle (1972) recognized that the black-white direction did not always lie parallel to the Burgers vector projection. For loops with an appreciable shear component, they concluded that a determination of the black-white direction would not be sufficient for analysis of the loop crystallography. However, for pure edge loops they predicted that the black-white direction would correspond (within a few degrees) to the projection of the Burgers vector. Numerous investigators have used this erroneous assumption to analyze the crystallography of loops.

Black-white contrast of dislocation loops

1978 ◽  
Vol 36 (1) ◽  
pp. 328-329
Author(s):  
J. J. Hren ◽  
W. D. Cooper ◽  
L. J. Sykes
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Dislocation Loops ◽  
Major Premise ◽  
Burgers Vector ◽  
Transmission Electron ◽  
Primary Means ◽  
Contrast Analysis ◽  
Dot Product ◽  
Imaging Conditions

Small dislocation loops observed by transmission electron microscopy exhibit a characteristic black-white strain contrast when observed under dynamical imaging conditions. In many cases, the topography and orientation of the image may be used to determine the nature of the loop crystallography. Two distinct but somewhat overlapping procedures have been developed for the contrast analysis and identification of small dislocation loops. One group of investigators has emphasized the use of the topography of the image as the principle tool for analysis. The major premise of this method is that the characteristic details of the image topography are dependent only on the magnitude of the dot product between the loop Burgers vector and the diffracting vector. This technique is commonly referred to as the (g•b) analysis. A second group of investigators has emphasized the use of the orientation of the direction of black-white contrast as the primary means of analysis.

Determination of surface crystallography of faceted nanoparticles using transmission electron microscopy imaging and diffraction modes

2009 ◽  
Vol 42 (3) ◽  
pp. 519-524 ◽  
Author(s):  
Song Li ◽  
Yudong Zhang ◽  
Claude Esling ◽  
Jacques Muller ◽  
Jean-Sébastien Lecomte ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Coordinate System ◽  
Calculation Method ◽  
Microscopy Imaging ◽  
Plane Normal ◽  
Transmission Electron ◽  
Structure Of Nanoparticles ◽  
Normal Vectors

A general calculation method is proposed to characterize the crystalline planes and directions of a faceted nanoparticle using transmission electron microscopy (TEM) imaging and diffraction modes. With the determination of the edge vectors and then the plane normal vectors in the screen coordinate system of TEM, their Miller indices in the crystal coordinate system can be calculated through coordinate transformation. The method is helpful for related studies of the determination of the surface structure of nanoparticles.

Structure Determination of Clusters Formed in Ultra-Low Energy High-Dose Implanted Silicon

2005 ◽  
Vol 108-109 ◽  
pp. 303-308 ◽  
Author(s):  
N. Cherkashin ◽  
Martin J. Hÿtch ◽  
Fuccio Cristiano ◽  
A. Claverie
Keyword(s):  
Electron Microscopy ◽  
Geometric Phase ◽  
Low Energy ◽  
High Dose ◽  
Dislocation Loops ◽  
Weak Beam ◽  
Transmission Electron ◽  
Geometric Phase Analysis

In this work, we present a detailed structural characterization of the defects formed after 0.5 keV B+ implantation into Si to a dose of 1x1015 ions/cm2 and annealed at 650°C and 750°C during different times up to 160 s. The clusters were characterized by making use of Weak Beam and High Resolution Transmission Electron Microscopy (HRTEM) imaging. They are found to be platelets of several nanometer size with (001) habit plane. Conventional TEM procedure based on defect contrast behavior was applied to determine the directions of their Burger’s vectors. Geometric Phase Analysis of HRTEM images was used to measure the displacement field around these objects and, thus, to unambiguously determine their Burger’s vectors. Finally five types of dislocation loops lying on (001) plane are marked out: with ] 001 [1/3 ≅ b and b ∝ [1 0 1], [-1 0 1], [0 1 1], [0 -1 1].

a Dislocation Loops in MgO

1977 ◽  
Vol 35 ◽  
pp. 306-307
Author(s):  
J. Narayan ◽  
S. M. Ohr
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Thermal Breakdown ◽  
Dislocation Loops ◽  
Electron Micrograph ◽  
Burgers Vector ◽  
Electron Microscope Investigation ◽  
Long Period ◽  
The Past ◽  
Transmission Electron

Dislocation loops having a/2 <110> Burgers vectors on {110} planes introduced by plastic deformation and subsequent annealing of MgO have been studied extensively in the past using transmission electron microscopy.1 Recently it was reported that high temperature electrical conduction for a long period of time (> 100 hours) induced a thermal breakdown2 in MgO crystals. Transmission electron microscope investigation of these samples just before the thermal breakdown, revealed the presence of a type of loop not previously observed in this material with a<100> Burgers vector lying in {100} planes.Figure la-d shows electron micrograph of two of these a<100> type loops for diffraction vectors (ḡ) [200], [020], [220] and [220], These micrographs were taken under kinematical diffraction conditions with the deviation parameter w ∽ 1.0. From stereo microscopy it was determined that the loops labeled α and β lie on (001) and (100) planes respectively.

Defect and Microstructural Analyses in Ferromagnetic Material

1985 ◽  
Vol 62 ◽  
Author(s):  
L. L. Horton
Keyword(s):  
Electron Microscopy ◽  
Magnetic Domain ◽  
Ferromagnetic Material ◽  
Ferromagnetic Materials ◽  
Dislocation Loops ◽  
Cavity Shape ◽  
Transmission Electron ◽  
Shape Analyses

ABSTRACTTransmission electron microscopy (TEM) of ferromagnetic materials requires special and often time-consuming procedures to obtain good images. Tilting and high resolution experiments are particularly difficult. A survey of several investigations of microstructures in ferromagnetic materials ranging from pure iron to commercial magnet materials is presented. The topics of these investigations include determination of Burgers vectors and interstitial/vacancy character for dislocation loops, cavity shape analyses, magnetic domain/microstructure correlations, and characterization of structures resulting from isotropic spinodal decomposition. Problems encountered during these studies as they relate to magnetic materials and the modifications to standard microscope operating procedures required to overcome these problems are presented. This discussion includes specimen requirements, specimen loading and insertion, and alignment corrections required during specimen tilting.

Molecular Modeling of Defect Structures in Pentacene

2002 ◽  
Vol 734 ◽  
Author(s):  
Paul K. Miska ◽  
Lawrence F. Drummy ◽  
David C. Martin
Keyword(s):  
Electron Microscopy ◽  
The Other ◽  
Defect Structures ◽  
Burgers Vector ◽  
Surface Energies ◽  
Transmission Electron ◽  
Molecular Semiconductor ◽  
Molecular Deformation ◽  
Scanning Electron ◽  
Dipole Length

ABSTRACTWe have studied defect structures in the crystalline organic molecular semiconductor pentacene. Our investigations included the calculation of free surface energies on low index planes. It was found that that the (001) surface had the lowest energy ∼50 mJ/m2, roughly half that of the other low index planes, (100) and (010) ∼120 mJ/m2 and ∼140 mJ/m2 respectively. These calculations were then compared to experimental data from vapor grown crystals using optical microscopy, Scanning Electron Microscopy (SEM) and High Resolution Transmission Electron Microscopy (HRTEM). We also modeled dislocations dipoles of varying Burgers vector and dipole length. It was found that dislocations were accommodated by extensive molecular deformation near the defect core, as well as a well defined stacking fault that occurred down the length of the dipole. Finally, we investigated low angle tilt grain boundaries. It was seen that low angle boundaries relaxed through molecular deformation in the first layer of molecules at the boundary as well as bending of the (001) planes.

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