Low energy electron diffraction

The basic ideas and possibilities of application of Low Energy Electron Diffraction (L.E.E.D.) are briefly reviewed. The geometry of the diffraction pattern is due to conservation rules together with the periodicity of the crystal surface. The intensity of the diffracted beams is governed by the electron-solid interaction and the multiple scattering effects. The muffin-tin model allows us to split the problem into four parts: scattering by ion-cores; propagation in a constant potential medium, accounting for the many body interactions of the electron with the electron gas; scattering by the surface potential barrier; self-consistent calculation of the effective wave fields. Possibilities of application are large. L.E.E.D. is a powerful method for surface characterization, sensitive to long range order. It is a necessary complement to the methods suited for the chemical determination of the atoms on a surface, such as Auger electron spectroscopy of X-ray photoelectron spectroscopy. Applications to surface crystallography are still limited to simple superstructures. The analyses are far too much expensive. A suitable choice of the experimental basis should probably reduce their cost to a level manageable for many laboratories