Extended shape evolution of low mismatch Si1−xGex alloy islands on Si(100)

Abstract

The sequence of shape transitions in low mismatch, dilute coherent Si1−xGex (x<0.2) alloy islands was documented by scanning tunneling microscopy and cross-sectional transmission electron microscopy. In dilute Si1−xGex islands we observe an extended shape evolution involving a new “barn” shape formed by introduction of steep {111} facets not observed at higher mismatch strain. This extended shape evolution implies a delayed onset of plastic deformation as a result of an altered competition between strain relaxation via coherent islands and the introduction of dislocations in this regime.