Continuous Wavelet Decompositions, Multiresolution, and Contrast Analysis

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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Black-white contrast of dislocation loops

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100108787 ◽

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.

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Strain analysis in composite ceramics

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100144012 ◽

1986 ◽

Vol 44 ◽

pp. 494-497

Author(s):

W. M. Kriven

Keyword(s):

Strain Field ◽

Strain Analysis ◽

Processing Temperature ◽

Transformation Toughening ◽

Zirconia Ceramics ◽

Volume Increase ◽

Analysis Technique ◽

Fundamental Understanding ◽

Contrast Analysis ◽

Elastic Strain Field

Significant progress towards a fundamental understanding of transformation toughening in composite zirconia ceramics was made possible by the application of a TEM contrast analysis technique for imaging elastic strains. Spherical zirconia particles dispersed in a large-grained alumina matrix were examined by 1 MeV HVEM to simulate bulk conditions. A thermal contraction mismatch arose on cooling from the processing temperature of 1500°C to RT. Tetragonal ZrO2 contracted amisotropically with α(ct) = 16 X 10-6/°C and α(at) = 11 X 10-6/°C and faster than Al2O3 which contracted relatively isotropically at α = 8 X 10-6/°C. A volume increase of +4.9% accompanied the transformation to monoclinic symmetry at room temperature. The elastic strain field surrounding a particle before transformation was 3-dimensionally correlated with the internal crystallographic orientation of the particle and with the strain field after transformation. The aim of this paper is to theoretically and experimentally describe this technique using the ZrO2 as an example and thereby to illustrate the experimental requirements Tor such an analysis in other systems.

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Structure of stacking faults in pyrite using TEM techniques

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100122198 ◽

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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Construction of plastic contact deformation maps on ceramics: a case study on aluminum nitride

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100165641 ◽

1996 ◽

Vol 54 ◽

pp. 636-637

Author(s):

D. L. Callahan

Keyword(s):

Plastic Deformation ◽

Aluminum Nitride ◽

Mechanical Response ◽

Three Dimensional ◽

Bright Field Image ◽

Perfectly Plastic ◽

Contrast Analysis ◽

Deformation Patterns

Modern polishing, precision machining and microindentation techniques allow the processing and mechanical characterization of ceramics at nanometric scales and within entirely plastic deformation regimes. The mechanical response of most ceramics to such highly constrained contact is not predictable from macroscopic properties and the microstructural deformation patterns have proven difficult to characterize by the application of any individual technique. In this study, TEM techniques of contrast analysis and CBED are combined with stereographic analysis to construct a three-dimensional microstructure deformation map of the surface of a perfectly plastic microindentation on macroscopically brittle aluminum nitride.The bright field image in Figure 1 shows a lg Vickers microindentation contained within a single AlN grain far from any boundaries. High densities of dislocations are evident, particularly near facet edges but are not individually resolvable. The prominent bend contours also indicate the severity of plastic deformation. Figure 2 is a selected area diffraction pattern covering the entire indentation area.

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Using crystallographic symmetry in diffraction and contrast analysis

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100154494 ◽

1989 ◽

Vol 47 ◽

pp. 504-505

Author(s):

U. Dahmen ◽

K.H. Westmacott

Keyword(s):

Electron Microscopy ◽

High Symmetry ◽

Two Phase ◽

Tem Analysis ◽

Crystallographic Symmetry ◽

The Matrix ◽

Contrast Analysis ◽

Practical Tool ◽

Convergent Beam ◽

Beam Diffraction

Despite the increased use of convergent beam diffraction, symmetry concepts in their more general form are not commonly applied as a practical tool in electron microscopy. Crystal symmetry provides an abundance of information that can be used to facilitate and improve the TEM analysis of crystalline solids. This paper draws attention to some aspects of symmetry that can be put to practical use in the analysis of structures and morphologies of two-phase materials.It has been shown that the symmetry of the matrix that relates different variants of a precipitate can be used to determine the axis of needle- or lath-shaped precipitates or the habit plane of plate-shaped precipitates. By tilting to a special high symmetry orientation of the matrix and by measuring angles between symmetry-related variants of the precipitate it is possible to find their habit from a single micrograph.

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