Abstract
The authors 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. Their 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 they 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. They 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. They discuss necessary conditions for avoiding interference.
Highlights
Due to its high surface sensitivity and its compatibility with systems for UHV thin film growth by methods such as Molecular Beam Epitaxy (MBE), Reflection High Energy Electron Diffraction (RHEED) has been widely used in monitoring the surface structure and the quality of a film during epitaxial growth.[1]
The kinematic approximation[4] and the phenomenological step-density model[5] are the earliest ones and are still commonly applied to interpreting RHEED results. Both models assume that the RHEED intensity is determined by a single parameter of the evolving morphology such as layer coverage or step density. These models fail to explain the dependence of the RHEED intensity oscillations on diffraction conditions, presumably due to the lack of consideration of multiple scattering, which is believed to be important during RHEED
We have conducted a systematic investigation of the phase shift of the RHEED intensity p.3 oscillations under a wide range of diffraction conditions during homoepitaxial MBE growth of Ge(001), our prototypical system
Summary
Due to its high surface sensitivity and its compatibility with systems for UHV thin film growth by methods such as Molecular Beam Epitaxy (MBE), Reflection High Energy Electron Diffraction (RHEED) has been widely used in monitoring the surface structure and the quality of a film during epitaxial growth.[1]. Fundamental questions about the origin of the oscillation remain.[3] Among the proposed models, the kinematic approximation[4] and the phenomenological step-density model[5] are the earliest ones and are still commonly applied to interpreting RHEED results Both models assume that the RHEED intensity is determined by a single parameter of the evolving morphology such as layer coverage or step density. Our results convincingly demonstrate the importance of the Kikuchi features in influencing the RHEED oscillations, an effect that has not attracted much attention in interpreting RHEED results until now
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