Electron Diffraction
Electron diffraction is one of major electron mciroscopy techniques. Traditionally, It has been used for phase identification, structure and symmetry determination, foil thickness measurement, lattice parameter measurement, disorder and defect identification . Recent development has significantly improved the quantitative analysis of electron diffraction intensities and has brought new types of highly accuracte electron diffraction techniques for structure refinement and structure factor measurement. The recent development in the new generation of field-emission electron microscopes and energy-filter promise further development in single atomic column scattering and diffraction from nanometer-sized molecules, clusters, wires and other low-dimensional objects.
There are three types of electron diffraction: Low Energy Electron Diffraction (LEED), Transmission High Energy Electron Diffraction (THEED) and Reflection High Energy Electron Diffraction (RHEED). Both LEED and RHEED are major surface characterization techniques. THEED is commonly associated with transmission electron microscopy and molecular scattering. Treatment of LEED is very different from THEED and RHEED, where surface reflection and the quantum mechanical effect of exchange and correlation are dominant. For high energy electrons, diffraction can be described based on individual atomic scattering in the same way as neutron and x-ray diffraction.
Electron diffraction differs from X-ray and neutron scattering from its ability to form images and small probes (angstroms). Equally important, electrons interact with matter through the strong Coulomb potential. As results, electrons interact very strongly and are very sensitive to matter's valence electrons or bonding electrons. The figure below shows a comparison between electron, X-ray and neutron scattering factors:
Click on SOFTWARE button on the left to see a list of electron diffraction simulation programs used in our group's research and for teaching. For further details about electron diffraction, see the books by J.M. Cowley on Diffraction Physics and J.C.H. Spence and J.M. Zuo on Electron Microdiffraction. For a quick reading, below are several lecture notes related to electron diffraction, which JMZ used for teaching graduate electron microscopy class :