An Introduction to Reflection High Energy Electron Diffraction

Abstract

Reflection high energy electron diffraction (RHEED) uses electrons of energy from a few keV to ∼100 keV directed at low angles of incidence (0.01 to 0.1 rad) with respect to a surface. RHEED is a fairly old technique. There are several examples1,2 of its use in the 1930’s and it was extensively employed for corrosion studies and epitaxial growth in the 1950’s and 1960’s3–6. However the enthusiasm which existed around 1970 for performing a complete surface structure determination using the low energy electron diffraction technique deflected interest away from RHEED. One of the reasons for this was the sensitivity of RHEED to topography, which the surface scientist took to be a serious disadvantage! The recent revival of interest in RHEED stems from its wide use in monitoring the films and layers grown by molecular beam epitaxy (MBE) particularly of the III–V semiconductors7–9. The technology which has developed for MBE of the III–Vs has now been applied to the growth of II–VIs, group IV, various metals and even oxides. It now seems very likely that the molecule-by-molecule or atom-by-atom approach which is central to the MBE concept can be applied to grow any natural occuring material and to grow completely new “artificial” crystal structures. This has already been achieved for atomic layer superlattices of the III–V systems and the group IV system.