Reflection high-energy electron diffraction

RHEED ( reflection high energy electron diffraction English, German, reflection high- energy electron reflection ') is a physical method for the analysis of smooth material surfaces by means of electron diffraction. The electrons in this case have an energy in kilo-electron- volt range (usually about 10-50 keV). The angle between the surface and the electron beam is very small (typically about 2 °), so that the electrons are reflected from the surface. Make the reflected electrons to a phosphor screen, where the diffraction pattern is visible. The type of the crystal lattice and the lattice parameters may be determined from the diffraction pattern.

Since electrons are slowed down very rapidly by air, this process is operated in an ultrahigh vacuum.

The advantage of the process over the RHEED LEED method is that along the surface normals are not in the way of equipment, so that the growth of thin films can be observed on surfaces in the molecular beam epitaxy. This is the main application of RHEED.

From the shape of the intensity of the diffraction peaks ( in the molecular beam epitaxy as a function of time ) and their focus can be concluded as the layer growth takes place (English growth mode). If layerwise growth occurs on a atomically smooth substrate, the diffraction peaks reach maximum intensity and focus upon posting of the last atomic layer is complete. This means that the individual applied atomic layers can be counted.