scholarly journals Modeling Dislocation Contrasts Obtained by Accurate-Electron Channeling Contrast Imaging for Characterizing Deformation Mechanisms in Bulk Materials

2019 ◽  
Author(s):  
Hana Kriaa ◽  
Antoine Guitton ◽  
Nabila Maloufi
Keyword(s):  
Materials Science ◽  
Incident Beam ◽  
Sample Surface ◽  
Diffraction Theory ◽  
Contrast Imaging ◽  
Black Line ◽  
Electron Channeling ◽  
Theoretical Predictions ◽  
Deformation Defects ◽  
First Time

Electron Channeling Contrast Imaging (ECCI) is becoming a powerful tool in Materials Science for characterizing deformation defects. Dislocations observed by ECCI in Scanning Electron Microscope, exhibit several features depending on the crystal orientation relative to the incident beam (white/black line on a dark/bright background). In order to bring new insights concerning these contrasts, we report an original theoretical approach based on the dynamical diffraction theory. Our calculations led, for the first time, to an explicit formulation of the backscattered intensity as a function of various physical and practical parameters governing the experiment. Intensity profiles are modeled for dislocations parallel to the sample surface for different channeling conditions. All theoretical predictions are consistent with experimental results.

scholarly journals Modeling Dislocation Contrasts Obtained by Accurate-Electron Channeling Contrast Imaging for Characterizing Deformation Mechanisms in Bulk Materials

Materials ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1587 ◽  
Author(s):  
Hana KRIAA ◽  
Antoine GUITTON ◽  
Nabila MALOUFI
Keyword(s):  
Materials Science ◽  
Incident Beam ◽  
Sample Surface ◽  
Diffraction Theory ◽  
Contrast Imaging ◽  
Black Line ◽  
Electron Channeling ◽  
Theoretical Predictions ◽  
Deformation Defects ◽  
First Time

Electron Channeling Contrast Imaging (ECCI) is becoming a powerful tool in materials science for characterizing deformation defects. Dislocations observed by ECCI in scanning electron microscope exhibit several features depending on the crystal orientation relative to the incident beam (white/black line on a dark/bright background). In order to bring new insights concerning these contrasts, we report an original theoretical approach based on the dynamical diffraction theory. Our calculations led, for the first time, to an explicit formulation of the back-scattered intensity as a function of various physical and practical parameters governing the experiment. Intensity profiles are modeled for dislocations parallel to the sample surface for different channeling conditions. All theoretical predictions are consistent with experimental results.

scholarly journals Modeling Dislocation Contrasts Obtained by Accurate-Electron Channeling Contrast Imaging for Characterizing Deformation Mechanisms in Bulk Materials

2019 ◽  
Author(s):  
Hana Kriaa ◽  
Antoine Guitton ◽  
Nabila Maloufi
Keyword(s):  
Materials Science ◽  
Incident Beam ◽  
Sample Surface ◽  
Diffraction Theory ◽  
Contrast Imaging ◽  
Black Line ◽  
Electron Channeling ◽  
Theoretical Predictions ◽  
Deformation Defects ◽  
First Time

Electron Channeling Contrast Imaging (ECCI) is becoming a powerful tool in Materials Science such as for characterizing deformation defects. Dislocations observed by ECCI in Scanning Electron Microscope, exhibit several features depending on the crystal orientation relative to the incident beam (white/black line on a dark/bright background). In order to bring new insights concerning these contrasts, we report an original theoretical approach based on the dynamical diffraction theory. Our calculations led, for the first time, to an explicit formulation of the backscattered intensity as function of various physical and practical parameters governing the experiment. Intensity profiles are modeled for dislocations parallel to the sample surface for different channeling conditions. All theoretical predictions are consistent with experimental results.

Analysis of Electron Channeling Contrast Imaging in Scanning Electron Microscopes

2018 ◽  
Vol 768 ◽  
pp. 52-58
Author(s):  
Zi Wei Liu ◽  
Chu Сheng Lin ◽  
Cai Fen Jiang ◽  
Jia Jie Hua ◽  
Ji Mei Zhang ◽  
...  
Keyword(s):  
Influence Factors ◽  
Sample Surface ◽  
Contrast Imaging ◽  
Material Microstructure ◽  
Electron Channeling ◽  
Channel Effect ◽  
The Difference ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes ◽  
Scanning Electron

In the paper, the influence factors of electron channeling contrast imaging (ECCI) on crystalline material microstructure characterization by scanning electron microscopes (SEMs) were analyzed, such as electric current, accelerating voltage and sample material’s surface conditions. It was found that high current, appropriate accelerating voltage and smooth sample surface were more beneficial to obtaining an ideal channel effect pattern. In addition, the difference between the channel effect contrast and the EBSD technology was also investigated. And the results showed that the channel effect contrast image could qualitatively characterize grains with different orientations. However, it was far less sensitive than EBSD in characterizing small angle grain boundaries.

Microscale Characterization of Deformation Defects in Bulk Intermetallics Alloys Using Electron Channeling Contrast Imaging

2003 ◽  
Vol 426-432 ◽  
pp. 1885-1890
Author(s):  
M.A. Crimp ◽  
B.A. Simkin ◽  
B.-C. Ng ◽  
D.E. Mason ◽  
Thomas R. Bieler
Keyword(s):  
Contrast Imaging ◽  
Electron Channeling ◽  
Deformation Defects

Imaging Dislocations in Duplex Tial Using Electron Channeling Contrast

1999 ◽  
Vol 5 (S2) ◽  
pp. 882-883
Author(s):  
B.C. Ng ◽  
T.R. Bieler ◽  
M.A. Crimp
Keyword(s):  
Solid Angle ◽  
Incident Beam ◽  
Beam Current ◽  
Contrast Imaging ◽  
Scattered Electron ◽  
Electron Channeling ◽  
Diode Detector ◽  
Beam Orientation ◽  
Working Distance ◽  
Four Quadrant

Electron channeling contrast imaging (ECCI), performed using a scanning electron microscope, has been used to observe dislocations in bulk TiAl with a duplex microstructure. The ECCI technique is based on the dependence of the back-scattered electron (BSE) yield (of the incident beam orientation) on the crystal lattice and defect orientation near the specimen surface. This allows nearsurface defects to be imaged in bulk specimens [1, 2]. ECCI was carried out in a Camscan 44FE FEG-SEM operated at 25 kV using a beam divergence of ∽8 mrad and a beam current of ∽ 2nA. Specimens were observed at a working distance of approximately 11 mm. To record the BSE signal, the microscope was fitted with an annular (four quadrant) silicon diode detector array attached to the final lens pole-piece, resulting in a solid angle collection of approximately ∽0.6 π str. Images were recorded as 32 frame averages using ∽1.1 frames/sec.

Diffraction Channeling and the Production of Secondary Excitation

1999 ◽  
Vol 5 (S2) ◽  
pp. 688-689
Author(s):  
S.J. Pennycook
Keyword(s):  
Quantitative Description ◽  
Incident Beam ◽  
Diffraction Theory ◽  
Orientation Dependence ◽  
Contrast Imaging ◽  
Dynamical Diffraction ◽  
Efficient Detection ◽  
Annular Detector ◽  
Resolution Imaging ◽  
Z Contrast

The pivotal role played by Archie Howie in the development of many areas of electron microscopy is universary acknowledged.Here I would like to highlight his contribution to the quantitative description of secondary excitations, which was an important influence on the development of Z-contrast imaging in zone-axis crystals. Secondary excitations are those such as x-ray emission which occur following a primary scattering event, in this case excitation of inner shell electrons. The first important concept to be realized by Archie was that dynamical diffraction and channeling are different manifestations of the same physical effect, namely, the multiple scattering of electrons within a crystal. Second was the realization that processes which are localized within the unit cell will show a dependence on diffraction conditions, such as incident beam orientation, and could therefore be described quantitatively using dynamical diffraction theory. Precisely the same theory was used to describe the orientation dependence of cathodoluminescenceThe development of the STEM for high resolution imaging was of course due primarily to Crewe and coworkers, with an annular detector to allow efficient detection of elastic scattering over a wide angular range.

Electron spectroscopic imaging and diffraction

1991 ◽  
Vol 49 ◽  
pp. 706-707
Author(s):  
M. Rühle ◽  
J. Mayer ◽  
J.C.H. Spence ◽  
J. Bihr ◽  
W. Probst ◽  
...  
Keyword(s):  
Materials Science ◽  
Electron Spectroscopic Imaging ◽  
Magnetic Filter ◽  
Magnetic Imaging ◽  
Illumination System ◽  
Probe Size ◽  
Diffraction Patterns ◽  
Fritz Haber ◽  
Koehler Illumination ◽  
First Time

A new Zeiss TEM with an imaging Omega filter is a fully digitized, side-entry, 120 kV TEM/STEM instrument for materials science. The machine possesses an Omega magnetic imaging energy filter (see Fig. 1) placed between the third and fourth projector lens. Lanio designed the filter and a prototype was built at the Fritz-Haber-Institut in Berlin, Germany. The imaging magnetic filter allows energy-filtered images or diffraction patterns to be recorded without scanning using efficient area detection. The energy dispersion at the exit slit (Fig. 1) results in ∼ 1.5 μm/eV which allows imaging with energy windows of ≤ 10 eV. The smallest probe size of the microscope is 1.6 nm and the Koehler illumination system is used for the first time in a TEM. Serial recording of EELS spectra with a resolution < 1 eV is possible. The digital control allows X,Y,Z coordinates and tilt settings to be stored and later recalled.

Rapid misfit dislocation characterization in heteroepitaxial III-V/Si thin films by electron channeling contrast imaging

2014 ◽  
Vol 104 (23) ◽  
pp. 232111 ◽  
Author(s):  
Santino D. Carnevale ◽  
Julia I. Deitz ◽  
John A. Carlin ◽  
Yoosuf N. Picard ◽  
Marc De Graef ◽  
...  
Keyword(s):  
Thin Films ◽  
Misfit Dislocation ◽  
Contrast Imaging ◽  
Electron Channeling

scholarly journals Quantitative misfit dislocation characterization with electron channeling contrast imaging

2021 ◽  
Vol 27 (S1) ◽  
pp. 912-914
Author(s):  
Ari Blumer ◽  
Marzieh Baan ◽  
Zak Blumer ◽  
Jacob Boyer ◽  
Tyler J. Grassman
Keyword(s):  
Misfit Dislocation ◽  
Contrast Imaging ◽  
Electron Channeling

Algorithms for determining the phase of RHEED oscillations

2015 ◽  
Vol 48 (6) ◽  
pp. 1927-1934 ◽  
Author(s):  
Zbigniew Mitura ◽  
Sergei L. Dudarev
Keyword(s):  
Experimental Data ◽  
Direct Method ◽  
Incident Beam ◽  
Diffraction Theory ◽  
High Energy ◽  
Angle Of Incidence ◽  
High Energy Electron ◽  
Dynamical Diffraction ◽  
Glancing Angle ◽  
Low Symmetry

Oscillations of reflection high-energy electron diffraction (RHEED) intensities are computed using dynamical diffraction theory. The phase of the oscillations is determined using two different approaches. In the first, direct, approach, the phase is determined by identifying the time needed to reach the second oscillation minimum. In the second approach, the phase is found using harmonic analysis. The two approaches are tested by applying them to oscillations simulated using dynamical diffraction theory. The phase of RHEED oscillations observed experimentally is also analysed. Experimental data on the variation of the phase as a function of the glancing angle of incidence, derived using the direct method, are compared with the values computed using both the direct and harmonic methods. For incident-beam azimuths corresponding to low-symmetry directions, both approaches produce similar results.

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