Structural Analysis Of Crystal Surfaces By Reflection High Energy Electron Diffraction

For surface structure determinations by reflection high energy electron diffraction (RHEED), intensity rocking curves are analyzed through RHEED dynamical calculations. Since fast electrons are scattered dominantly in the forward direction by atoms, dynamic diffraction mainly occurs in the forward direction. By the use of this feature, it is possible to choose a diffraction condition under which electrons are diffracted mainly by lattice planes parallel to the surface, when the incident direction is chosen at a certain azimuthal angle with respect to a crystal zone axis. This diffraction condition is called the one-beam condition. Under this condition, the RHEED intensity is a function of interlayer distances and atomic densities of the surface layers. Therefore the surface normal components of the atomic positions are determined by analysis of the one-beam rocking curve using a RHEED dynamical calculation. Then, using the result of the surface normal components of atomic positions, lateral positions of the surface atoms are determined from analysis of the rocking curves at many-beam conditions, where the direction of the incident beam is chosen along a certain crystal zone axis. An example of the surface structure determination of a Si(111) surface at high temperatures is reported. We discuss effects of terraces and antiphase domains of surfaces in structure determinations by RHEED.