Interpretation of reflection high-energy electron diffraction oscillation phase

The use of reflection high energy electron diffraction (RHEED) became very popular after the discovery of reflected electron beam intensity oscillations in the early 1980s. Although a number of theoretical explanations of the effect have already been given, many aspects of the question as to why RHEED oscillations appear still remains open. We propose a new mechanism which may lead to the appearance of RHEED oscillations. This mechanism can be briefly described as the periodic variation of diffraction peak positions due to changes in the average scattering potential near the crystal surface during the deposition of a new layer. We conclude that in a general case one can explain qualitatively the origin of RHEED oscillations as the superposition of effects due to: (1) periodic variations in surface roughness, (2) changes in interference conditions for waves scattered from different surface terraces and (3) periodic variations in the average potential in the topmost layer. (C) 1999 Elsevier Science B.V. All rights reserved.