A scanning tunnelling microscopy study of local surface modifications induced by misfit dislocation formation in strained-layer heteroepitaxy

The surface modifications caused by misfit dislocation formation in strained-layer heteroepitaxy of 2.1% lattice-mismatched EuTe on PbTe (111) are studied using ultra-high vacuum scanning tunnelling microscopy (STM). It is shown that at the critical layer thickness straight monolayer step lines appear on the surface due to the glide of threading dislocations grown-in from the PbTe buffer layer, in agreement with the classical Matthews-Blakeslee mechanism for strain relaxation. Due to the local lattice distortions around the misfit dislocation segments at the layer/substrate interface, local wave-like deformations with an amplitude equal to the normal component of the Burgers vector are induced on the surface above the misfit dislocations. However, the exact form of the surface deformation depends on the orientation of the Burgers vector. Since the local surface deformations are a direct signature of the dislocations at the interface, the formation of a network of misfit dislocation becomes directly visible even by STM.