Regensburg 2007 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 24: Semiconductor Substrates: Epitaxy and Growth

O 24.3: Vortrag

Dienstag, 27. März 2007, 11:45–12:00, H39

Symmetry breaking in the growth of 2D Ge islands on Bi/Si(111) — •Konstantin Romanyuk and Bert Voigtländer — Institute of Bio and Nanosystems (IBN 3), and cni - Center of Nanoelectronic Systems for Information Technology, Research Centre Jülich, 52425 Jülich, Germany

The threefold rotational symmetry of the Si(111) surface usually leads to the formation of threefold symmetric islands (triangular or hexagonal) in the initial stages of epitaxial growth. However, for Ge growth on the Bi(√3×√3)R30^∘ terminated Si(111) surface we find islands with a reduced symmetry. The Ge islands have a rhomb shape with only one mirror plane and are terminated by <110> steps. We demonstrate that not only the bulk lattice symmetry but the symmetry of the combined substrate/island system is important to define the shape of the islands. It will be shown that the symmetry of the two level system is reduced due to the surface reconstruction to only one σ mirror reflection symmetry. The mirror plane run along small diagonal of the rhomb islands. The triangular symmetry of the Si(111) surface which includes 3 mirror planes leads to three different orientations of the rhomb shaped islands on the surface, as observed in the experiments.