title: Symmetry breaking in the growth of two-dimensional islands on Si(111).
abstract: We find that the shape of two-dimensional (2D) Si or Ge islands has a lower symmetry than the threefold symmetry of the underlying Si(111) substrate if Bi is used as a surfactant during growth. Arrow-shaped or rhomb-shaped 2D islands are observed by scanning tunneling microscopy. This symmetry breaking is explained by a mutual shift between the surface reconstructions present on the substrate and on the islands. Using the kinematic Wulff construction the growth velocities of the steps could be determined from the island shape if the nucleation center has been located by a marker technique.
authors.affiliation: Institute of Bio- and Nanosystems (IBN 3), and cni-Center of Nanoelectronic Systems for Information Technology, Research Center Jülich, 52425 Jülich, Germany.
authors.forename: Konstantin
authors.initials: K
authors.lastname: Romanyuk
authors.forename: Vasily
authors.initials: V
authors.lastname: Cherepanov
authors.forename: Bert
authors.initials: B
authors.lastname: Voigtländer