Coherent strain and clustering in Ge/Si heteroepitaxy. Discussion

The Ge/Si heteroepitaxial system grows in the Stranski-Krastanov (layer + island) growth mode with an equilibrium intermediate layer thickness of 3 monolayers. Initially, coherent (dislocation free) islands form above the intermediate layer. These coherent islands relieve part of their lattice mismatch by elastic deformation of the layer + island + substrate system. After cluster growth, these islands may reach a critical radius above which it becomes energetically favorable for strain relief through the introduction of dislocation misfit. Particle size distributions generated from digitally acquired secondary electron images of Ge/Si(100) films grown in situ in an ultra-high vacuum scanning transmission electron microscopy (UHV-STEM) have been used to study particle coarsening processes