Initial stage of the 2D-3D transition of a strained SiGe layer on a pit-patterned Si(001) template

摘要

We investigate the initial stage of the 2D-3D transition of strained Gelayers deposited on pit-patterned Si(001) templates. Within the pits, whichassume the shape of inverted, truncated pyramids after optimized growth of a Sibuffer layer, the Ge wetting layer develops a complex morphology consistingexclusively of {105} and (001) facets. These results are attributed to astrain-driven step-meandering instability on the facetted side-walls of thepits, and a step-bunching instability at the sharp concave intersections ofthese facets. Although both instabilities are strain-driven, their coexistencebecomes mainly possible by the geometrical restrictions in the pits. It isshown that the morphological transformation of the pit surface into low-energyfacets has strong influence on the preferential nucleation of Ge islands at theflat bottom of the pits.