Foil thickness measurements from convergent-beam diffraction patterns An experimental assessment of errors

1982 ◽  
Vol 46 (2) ◽  
pp. 243-253 ◽  
Author(s):  
Samuel M. Allen ◽  
Ernest L. Hall
Keyword(s):  
Foil Thickness ◽  
Experimental Assessment ◽  
Diffraction Patterns ◽  
Convergent Beam ◽  
Thickness Measurements ◽  
Beam Diffraction ◽  
Convergent Beam Diffraction

Experimental Assessment of the Accuracy of Foil Thickness Measurements from Convergent-Beam Diffraction Patterns

1980 ◽  
Vol 38 ◽  
pp. 192-193
Author(s):  
Samuel M. Allen ◽  
Ernest L. Hall
Keyword(s):  
Measurement Errors ◽  
Diffraction Theory ◽  
Foil Thickness ◽  
Graphical Technique ◽  
Beam Approximation ◽  
Diffraction Patterns ◽  
Geometrical Factors ◽  
Convergent Beam ◽  
Thickness Measurements ◽  
Beam Diffraction

Convergent-beam electron diffraction (CBED) patterns can be analyzed to determine foil thickness by a simple graphical technique based on the two-beam approximation to dynamical diffraction theory. Errors incurred in such measurements are due to several causes, including: the effect of the two-beam approximation itself, measurement errors in analyzing the fringe positions in the patterns, and geometrical factors relating the thickness in the beam direction to the true foil thickness. This study was undertaken to determine typical errors that might be encountered in experimental applications of the technique.

On the role of the second-order derivative term in the calculation of convergent beam diffraction patterns

2017 ◽  
Vol 179 ◽  
pp. 73-80 ◽  
Author(s):  
S.C. Hillier ◽  
E.T. Robertson ◽  
G.D. Reid ◽  
R.D. Haynes ◽  
M.D. Robertson
Keyword(s):  
Second Order ◽  
Order Derivative ◽  
Derivative Term ◽  
Diffraction Patterns ◽  
Convergent Beam ◽  
Beam Diffraction ◽  
Convergent Beam Diffraction

Use of Stem Convergent Beam Electron Diffraction Patterns for Foil Thickness Determination

1976 ◽  
Vol 34 ◽  
pp. 546-547
Author(s):  
Prakash Rao
Keyword(s):  
Particle Number ◽  
Particle Number Density ◽  
Foil Thickness ◽  
Number Density ◽  
Foil Surface ◽  
Cluster Number ◽  
The Past ◽  
Diffraction Patterns ◽  
Convergent Beam ◽  
Beam Diffraction

A knowledge of the specimen foil thickness to a considerable degree of accuracy is vital to any quantitative microstructural measurement such as dislocation density, precipitate particle number density, or defect cluster number density in irradiated materials. Several techniques have been used in the past with varying degrees of accuracy and success. These include the use of the trace method (with a slip trace, stacking fault or grain boundary), counting extinction contours in a wedge shaped crystal, or stereomicroscopy when there are defects intersecting the foil surface or identifiable material on these surfaces. All of these techniques are seldom accurate to within ±10%. More recently, intensity oscillations observed in convergent beam diffraction patterns have been used to determine foil thicknesses with a considerably greater degree of accuracy.

Improving the accuracy of convergent-beam thickness measurements

1988 ◽  
Vol 46 ◽  
pp. 520-521
Author(s):  
K. K. Christenson
Keyword(s):  
Objective Lens ◽  
Fringe Spacing ◽  
Underlying Assumption ◽  
Angular Scale ◽  
Beam Thickness ◽  
Extinction Length ◽  
Diffraction Patterns ◽  
Convergent Beam ◽  
Thickness Measurements ◽  
Beam Diffraction

Convergent-beam diffraction patterns taken at appropriate “two-beam” conditions allow simple, rapid determinations of a specimen's thickness, extinction length and even its anomalous absorption coefficient (1,2). We here note three points to consider when obtaining the pattern.First, in thickness measurements the ratio of the fringe spacing to the spacing between the disks is utilized; there is an underlying assumption that the two distances are on the same angular scale. This assumption is incorrect if the illumination crossover is not in the plane of the specimen and simultaneously, the diffraction lens is focused incorrectly. If the crossover is at the specimen (Fig. 1a), varying the focus of the diffraction lens (changing w) varies the distance between the disks and the sizes of features within the disks in the same way, only the magnification of the pattern is changed. Likewise, if the diffraction lens is focused correctly, on the back focal plane of the objective lens, the angular scale within the disks matches that between the disks and neither scale is affected by variations in the illumination.

One of my Failures: Diffraction in the TEM

2011 ◽  
Vol 19 (1) ◽  
pp. 72-72 ◽  
Author(s):  
Alwyn Eades
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Standard Method ◽  
Transmission Electron ◽  
Diffraction Patterns ◽  
Convergent Beam ◽  
Beam Diffraction ◽  
Convergent Beam Diffraction

There are two principal techniques for obtaining diffraction patterns in the transmission electron microscope (TEM). They are selected-area diffraction (SAD) and convergent-beam diffraction (CBED). CBED is quicker and easier to use, and it provides a much richer characterization of the sample. Thus, it is clear that CBED should be used in the vast majority of cases. It should be the diffraction technique that students learn first, and students should be taught to consider it the standard method of doing diffraction in the TEM.

Synthesis of BaAl2Si2O8 from solid Ba–Al–Al2O3–SiO2 precursors: Part III. The structure of BaAl2Si2O8 formed by annealing at ≤650 °C and at 1650 °C

1998 ◽  
Vol 13 (11) ◽  
pp. 3122-3134 ◽  
Author(s):  
Xiao-Dong Zhang ◽  
Kenneth H. Sandhage ◽  
Hamish L. Fraser
Keyword(s):  
Heat Treatment ◽  
Stacking Faults ◽  
Antiphase Boundaries ◽  
Analytical Tem ◽  
Diffraction Patterns ◽  
Convergent Beam ◽  
Beam Diffraction ◽  
Convergent Beam Diffraction

Analytical TEM and HREM have been used to examine the structure of BaAl2Si2O8 crystals produced within oxidized Ba–Al–Al2O3–SiO2 precursors upon annealing: (i) at ≤650 °C and (ii) up to 1650 °C. A BaAl2Si2O8 polymorph with a c-axis parameter of 15.6 Å was detected after annealing at ≤650 °C. Stacking faults and antiphase boundaries were detected within this polymorph after the 650 °C treatment. After a 15 h heat treatment at 1650 °C, convergent beam diffraction patterns and HREM confirmed that the predominant phase was β–hexacelsian. Although antiphase boundaries were absent in the β–hexacelsian crystals, dislocations and stacking faults were detected after the 1650 °C anneal. The generation of defects in BaAl2Si2O8 crystals within specimens annealed at ≤650 °C and at 1650 °C is discussed in light of prior structural analyses.

Using the TEM Condenser Lens to Switch between Image and Diffraction Modes

2013 ◽  
Vol 21 (2) ◽  
pp. 40-40
Author(s):  
Lydia Rivaud
Keyword(s):  
Electron Microscope ◽  
Diffraction Pattern ◽  
Transmission Electron Microscope ◽  
Condenser Lens ◽  
Selected Area Diffraction Pattern ◽  
Transmission Electron ◽  
Set Up ◽  
Convergent Beam ◽  
Beam Diffraction ◽  
Convergent Beam Diffraction

Central to the operation of the transmission electron microscope (TEM) (when used with crystalline samples) is the ability to go back and forth between an image and a diffraction pattern. Although it is quite simple to go from the image to a convergent-beam diffraction pattern or from an image to a selected-area diffraction pattern (and back), I have found it useful to be able to go between image and diffraction pattern even more quickly. In the method described, once the microscope is set up, it is possible to go from image to diffraction pattern and back by turning just one knob. This makes many operations on the microscope much more convenient. It should be made clear that, in this method, neither the image nor the diffraction pattern is “ideal” (details below), but both are good enough for many necessary procedures.

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