Selection of Preparation Techniques Based on Material Problems and TEM Analyses - Sample Preparation Topic for Transmission Electron Microscopy - page 189

In the case of a textured or multilayer material, it is possible to observe the
microstructure in a thin slice in the direction parallel to the texture (longitudinal
plane) or in the perpendicular direction (cross section).
In the case of fine particles of various shapes, it will be possible to observe all
orientations due to their random deposition. Figure 7.4 shows some 2D projections
of particles based on their shapes and orientation on the slice.

Particular Cut
[110], [111], etc.
2D Projection

Longitudinal
Plane Cut
2D Projection

Cross Section
2D Projection

3D View

Fig. 7.4 Fine isolated particles of varying form in 3D view and 2D projections: ( a ) longitudinal
plane cut; ( b ) cross-sectional cut; and ( c ) a cut specific to a crystallographic orientation

9.2 Defect Geometry

The characterization of crystal defects requires a particular orientation based on
their dimensions. The analytical techniques and their limitations are relatively easy
to use based on the thickness of the samples, the geometry of the defect in the
sample, and the size and density of the defects. In all cases, the problems of pro-
jection and superimposition must be taken into account based on the selected TEM
technique.
Techniques for preparing thin slices by electrolytic, chemical, mechanical, or
ionic thinning do not systematically result in directly observable thin slices for all
of the analytical techniques. For example, the observation conditions for the same
dislocation in weak-beam and high-resolution modes are hardly compatible. The
same goes for combining CBED-LACBED diffraction and HREM imaging modes,
which do not require the same sample thickness. Table 7.6 shows the slice thickness
required, depending on the observation mode and the analysis to be performed.