On the Phase Shift of Reflection High Energy Electron Diffraction Intensity Oscillations during Ge(001) Homoepitaxy by Molecular Beam Epitaxy

We have conducted a systematic investigation of the phase shift of the Reflection High Energy Electron Diffraction (RHEED) intensity oscillations during homoepitaxy of Ge(001) by molecular beam epitaxy for a wide range of diffraction conditions. Our results show that for small incidence angles with a beam azimuth several degrees away from the <110> crystallographic symmetry direction, the phase is independent of incidence angle; however, it starts to shift once the incidence angle is high enough that the (004) Kikuchi line appears in the RHEED pattern. Moreover, under some conditions we observe the oscillations from only the Kikuchi feature and not from the specular spot, and the oscillatory behavior of the Kikuchi feature is almost out of phase with that of the specular spot. We conclude that the phase shift is caused by the overlap of the specular spot and the Kikuchi features, in contrast to models involving dynamical scattering theory for the phase shift. We discuss necessary conditions for avoiding interference. On the phase shift of RHEED oscillations... June 5, 2006 p.2