THE INFLUENCE OF DIMERIZATION ON THE STABILITY OF GE-HUTCLUSTERS ON SI(001)

The epitaxial growth of Ge on Si(001) initially proceeds two-dimension al. After a few monolayers, a large number of three-dimensional Ge nan ocrystals are formed with well defined, highly anisotropic shapes and bounded by {105} facets. These facets are unstable in the morphology o f macroscopic crystals. Apparently a different set of parameters gover ns the crystal stability, size, shape and orientation of nanocrystals. By applying elastic continuum theory we calculate the stability of Ge nanocrystals on Si(001), bounded by different facets. We show that {1 05}-faceted nanocrystals are indeed the most stable. The model identif ies some of the principal parameters which control the stability of na nocrystals: the strain due to the lattice mismatch between substrate a nd nanocrystal, the size of the nanocrystal, and the surface energy (o r the reconstruction) of the substrate and of the facets of the nanocr ystal.