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Electron diffraction provides similar structural information as neutron diffraction. Electron beams strongly interact with nuclei and electron diffraction is more useful than X-ray diffraction for determining proton positions. The strong interaction of electrons with matter results in a low penetration depth, and electron diffraction is done in a reflection geometry to study surfaces or thin films or in a transmission mode for films or particles that are sufficiently thin. Electron beams are easy to manipulate, detect, and focus to small spots to provide high spatial resolution, which is a major advantage compared to X-ray diffraction. Using the spatial resolution is referred to as selected-area electron diffraction (SAD).
Electrons scatter from gases and electron diffraction must be performed under vacuum, usually in an electron microscope. For sufficiently thin samples, electron diffraction is performed in a transmission electron microscope (TEM) and the diffraction pattern can be viewed on a phosphor screen or recorded on film. For more experimental details see the electron microscope document.
Electron diffraction can be surface selective by using a grazing incidence geometry or by using low-energy electrons at normal incidence. These two methods are called reflection high-energy electron diffraction (RHEED) and low-energy electron diffraction (LEED). Diffraction experiments can be made with electron energies between these two cases, and these experiments are called medium-energy electron diffraction (MEED). The energies of the incident electron for these experiments are given below.
|LEED||10 - 500 eV|
|MEED||500 eV - 10 keV|
|RHEED||10 - 100 keV|
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