7. Conclusion

In this article, we have attempted to demonstrate the wealth of information about the crystal obtained by electron diffraction techniques. We have limited ourselves to cases where the incident electrons form a parallel beam, and are therefore described by a plane wave. A major advantage of these techniques is the very local nature of the information. It is indeed possible to obtain probe sizes on the entrance side of the specimen, with diameters in the nanometer range. However, care must be taken to ensure that the beam is spread as it passes through the specimen, so that the information comes from a volume of material larger than that of the cylinder whose cross-section is the size of the probe.

Other fast electron diffraction techniques are available for electron microscopy. The incident beam is conical, made up of all plane waves whose incident vector is included...