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Modeling RHEED intensity oscillations in multilayer epitaxy: Determination of the Ehrlich-Schwoebel barrier in Ge(001) homoepitaxy
 

Summary: Modeling RHEED intensity oscillations in multilayer epitaxy:
Determination of the Ehrlich-Schwoebel barrier in Ge(001) homoepitaxy
Byungha Shin and Michael J. Aziz
Harvard School of Engineering and Applied Sciences, Cambridge, Massachusetts 02138, USA
Received 9 February 2007; revised manuscript received 19 June 2007; published 8 October 2007
We report the study of submonolayer growth of Ge 001 homoepitaxy by molecular beam epitaxy at low
temperatures, 100150 C, using reflection high energy electron diffraction RHEED intensity oscillations
obtained for a range of low incidence angles, where the influence of the dynamical nature of electron scattering
such as the Kikuchi features is minimized. We develop a model for the RHEED specular intensity in multilayer
growth that includes the diffuse scattering off surface steps and the layer interference between terraces of
different heights using the kinematic approximation. The model describes the measured RHEED intensity
oscillations very well for the entire range of incidence angles studied. We show that the first intensity minimum
occurs well above 0.5 ML monolayer of the total deposited coverage, which contradicts the common practice
of assigning the intensity minimum to 0.5 ML. By using the model to interpret the measured RHEED intensity,
we find the evolution of the coverage of the first 12 ML. We find that second-layer nucleation takes place at
low coverage, 0.3 ML, implying a substantial Ehrlich-Schwoebel ES barrier. The value inferred for the ES
barrier height, 0.0840.019 eV, includes an analysis of the beam steering effect by step edges. Comparison is
made with the value of the barrier height inferred from other measurements. The model for RHEED intensity
and the method of inferring the ES barrier height can be applied to any system for which RHEED measure-
ments can be obtained without interference from Kikuchi features.

  

Source: Aziz, Michael J.- School of Engineering and Applied Sciences, Harvard University

 

Collections: Physics; Materials Science