Epitaxial Growth of Eute on Pbte (111) Influenced by Strain-Induced Coherent 3D Islanding

Abstract

ABSTRACTEuTe on PbTe is an example of a strained layer heteroepitaxial system with a moderate lattice-Mismatch of 2%. Using reflection high-energy electron diffraction (RHEED), the phase diagram of heteroepitaxial growth of EuTe on PbTe (111) by molecular beam epitaxy was established, indicating that only in a narrow regime of growth conditions does two dimensional layer-by-layer growth occur. Using in situ RHEED, combined with ex situ atomic force Microscopy, the evolution of the surface morphology during heteroepitaxial growth was investigated. It is found that at the critical layer thickness an abrupt surface roughening occurs. Studying the dependence of this surface roughening transition on substrate temperature and on the Eu-to-Te2 beam flux ratio used for growth, the critical layer thickness is found to decrease strongly as the surface kinetics are enhanced, even if the substrate temperature is kept constant. These results indicate that the surface roughening is driven only by the surface kinetics, which strongly supports the model of strain relaxation by coherent three dimensional islanding.