The stability of faceted SiGe quantum dots capped with a thin Si layer

摘要

Detailed surface morphologies and facets of partially capped Ge/Si(001) quantum dots were investigated by atomic force microscopy for samples capped with different thicknesses and subsequently annealed in a desiccator for a period of 12 months. The pyramid-shaped quantum dots bounded by {103}, {104} and {105} facets were observed in as-capped samples. After annealing, the {104} and {105} facets remained, while the {103} facets changed their structural profile to {104} facets. Extensive atomic force microscopy and transmission electron microscopy observations confirmed this finding. It is believed that the high surface free energy of the {103} facets and pre-existing Ge atoms in the wetting layer are responsible for this surface evolution.