Influence of Surface Structure on Epitaxial Growth of Sion Si(111)-(7 × 7) Substrate

To make clear the influence of surface structure on epitaxial growth, we have studied the growth of Si on a Si(111)-(7 × 7) superlattice surface by using scanning tunneling microscopy and reflection high energy electron diffraction. In the initial growth stage on the 7 × 7 superlattice, multilayer islands are formed because lateral growth of the first layer is prevented by the stable 7 × 7 structure and some migrating atoms climb up the first layer and nucleate on it. However, lateral growth of the second layer on the first one is not prevented and the layer-by-layer growth starts, because the structure of the first layer is composed of small domains with some metastable surface structures, which is rather easier to rearrange than the 7 × 7 structure. The starting point of the layer-by-layer growth depends on the substrate temperature, because the surface structure formed on a growing layer is influenced by the temperature. We obtained the result that the nucleation of a two-dimensional island on the 7 × 7 superlattice is also influenced by the surface structure. The island, whose size is less than the half-unit of the 7 × 7 structure, is unstable. The result suggests that, for the nucleation on the stable surface structure, the activation energy of rearrangement of the surfue structure should be taken into the consideration of the formation energy of the nucleus.