Reflection high-energy electron diffraction

RHEED

RHEED stands for Reflection High Energy Electron diffraction. RHEED is quite similar to LEED.

RHEED uses an electron gun and a phosphor screen for creating pictures showing the structure and/or morphology of a crystal surface. RHEED uses much higher electron energy (5-100keV) and lower impact angles (<5°) then LEED. The higher energy sharpens the picture, while the lower angle makes the electrons just pass a few atomic layers into the crystal. This makes Rheed pictures represent the stucture of the surface, not the whole crystal.

In case of RHEED, the reziprokal lattice is 2-dimensional, which makes it appear as lines instead of dots in 3-dimensional case. This way the reziprokal lattice lines touch the Ewald-sphere more often than normal and the Laue-diffraction-condition is fullfilled wuite often in the forward direction of the electron beam, where the fluorescent screen is mounted.

RHEED-Analysis to be added soon...

Pro's of RHEED: Real-Time Analysis: RHEED is often used for monitoring crystal growth, as it doesn't block the direction vertical to the surface of the crystal, which is observed.