Influences of the Si(1 1 3) anisotropy on Ge nanowire formation and related island shape transition

Based on the scanning tunneling microscopy observations of Ge coherent growth on Si(1 1 3), we demonstrate that the anisotropy of substrate stiffness is responsible for the anisotropic relaxation of islands, which leads to island elongation perpendicular to the softer direction of the substrate surface. The transition from wire-like islands to dot-like islands indicates that relaxation of islands tends to become isotropic as the size of the islands increase. Island volume measurements reveal that the material grown on the substrate, including the wetting layer, is continuously rebuilt during island formation and transition.