Comparisons of Techniques - Sample Preparation Topic for Transmission Electron Microscopy - page 209

3.2 Comparison Between Mechanical Preparations
and Ionic Preparations
3.2.1 Comparison of “Cleaved Wedge” and “Ionic Thinning” Techniques
Wedge Cleavage Technique (“Techniques” Chapter 4, Section 2) and Ion
Milling Technique (“Techniques” Chapter 3, Section 5)
Multilayer material: Cross section of an AlGaAs/GaAs multilayer sample on a
GaAs substrate
Comparison discussion : The cleaved wedge helps to highlight the variation in
chemical composition (indicated by the arrows) near the AlGaAs quantum wells,
visible by means of a change in thickness between the different fringes of equal
thickness near the well. This variation is not visible on the image resulting from
the ion milling preparation, due to the inhomogeneity of the sample thickness
(Fig. 8.17) .
Fig. 8.17 Comparison of
wedge cleavage (at 90 ◦ )and
ion milling techniques for a
sample of AlGaAs/GaAs on a
GaAS substrate. Observation
along the [100] direction.
Bright-field TEM image.
( J-D. Ganière, EPFL - IPEQ,
Lausanne, P.A. Buffat,
EPFL-CIME, Lausanne )