EFED - Energy filtered electron diffraction
When using the diffraction mode of the transmission electron microscope the sample is generally illuminated with a parallel electron beam. If the sample (gray slab) is oriented appropriately with respect to the electron beam, its lattice planes diffract part of the incoming electrons into specific directions. The objective lens (blue) collects all electrons and focusses each set of parallel rays into a diffraction spot. The illuminated area is typically of the size of a few tens of a micron and smaller. Therefore polycrystalline materials can be studied as if there were single crystals. By use of diffraction methods a number of properties can be accessed quantitatively:
- Lattice spacings
- Crystal symmetries
- Lattice distortions due to stresses (with extreme accuracy)
- Relative orientations of crystals
- Short and long range ordering
In our LIBRA 200 TEM we can combine imaging plates with energy filtering, which allows us to obtain diffraction data with highest contrast both with respect to the background as well as regarding the intensity ratio between individual features of the pattern.