Index
All the CBED patterns have been calculated using many-beams dynamical
electron diffraction theory (Blochwave approach). They are shown to give
worked examples of using this technique for measuring specimen thickness.
Example 7 shows how to measure both thickness and CBED defocus. It might be
not possible to reproduce experimentally due to the large coherence required
to realize it. Furthermore, only calculations based on large artificial
super-cells are able to reproduce the fringes observed when the probe size
is smaller than the unit-cell size.
Examples
- Al, 2-beams dynamical situation.
- Si, 2-beams dynamical situation.
- Si, [111] axial.
- BeO, [120] axial, many beams.
- ZnTe, [001] axial, many beams.
- Ge, [031], (400) at Bragg condition, many beams.
- CaCO3, [110], (003) at Bragg condition, 100kV, many beams.
- Si, [011], systematic row, (11-1) at Bragg condition, many beams
- GaN [001] axial, many beams.
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Al [031], (200) at Bragg condition. Note the large anomalous absorption effect.
Figure 1 Al [031], intensity profile.
Figure 2 Al [031] many beams fit.
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Si [021], (400) near Bragg condition.
Figure 3 Si [021] near Bragg condition.
Figure 4 Si [021] intensity profile (note
the large number of fine details).
Figure 5 Si [021] many beams fit.
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Si [111], axial, many beams.
Figure 6 Si [111].
Figure 7 Si [111], intensity profile.
Figure 8 Si [111], many beams fit.
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BeO [120], axial, many beams, 10 nm thick, incoherent illumination.
Figure 9 BeO [120], note the overlapping disks (incoherent illumination).
Figure 10 BeO [120], intensity profile, the
colored sections show in blue the transmitted disk and in red the diffracted
disks. The program creates a data structure that contains information about
the overlapping disks.
Figure 11 BeO [120] many beams fit. For
overlapping disks sections the intensity of the related reflections are
added (under coherent illumination condition). The best fit is obtained for 10 nm thick BeO crystal.
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ZnTe [001] axial, typical thickness under high resolution conditions.
Figure 12 ZnTe [001] axial.
Figure 13 ZnTe [001]. 3 nm thick, intensity profile.
Figure 14< ZnTe [001] many beams fit.
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Ge [031], Bragg condition for (400).
Figure 15 Ge [031], (400) at Bragg condition.
Figure 16 Ge [031], intensity profile.
Figure 17 Ge [031] many beams fit.
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CaCO3, [110], (003) at Bragg condition, 100kV.
Figure 18 CaCO3 [110], (003) at Bragg condition.
Figure 19 CaCO3 [110], intensity profile.
Figure 20 CaCO3 many beams fit.
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This example shows overlapping Si [011], (000) and (11-1) disks under coherent
illumination. The fringes system depends on the probe defocus (above the specimen).
Figure 21 (000) and (11-1) CBED disks.
Figure 22 Si, intensity profile across coherent disks.
Figure 23 Si, many beams fit.
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GaN [001] axial, many beams.
Figure 24 GaN [001].
Figure 25 GaN [001], intensity profile.
Figure 26 GaN [001] many beams fit.