Hamburg 2001 – wissenschaftliches Programm

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O: Oberflächenphysik

O 25: Postersitzung (Grenzfl
äche fest-flüssig, Methodisches, Nanostrukturen, Organische Dünnschichten, Rastersondentechniken, reine Oberfl
ächen, Teilchen und Cluster, Zeitaufgelöste Spektroskopie, Sonstiges)

O 25.64: Poster

Mittwoch, 28. März 2001, 15:00–18:00, Foyer zu B

A(-)symmetric Wulff construction — •S.B. van Albada, M.J. Rost, and J.W.M. Frenken — Kamerlingh Onnes Laboratory, Universiteit Leiden, P.O.Box 9504 2300 RA Leiden, Netherlands

The equilibrium shape of a 2-dimensional island on a flat crystal surface can be determined from a polar plot of the free energy of steps as a function of step direction by use of the well-known Wulff construction. The origin of the polar plot is called the Wulff point. The equilibrium shape of islands is usually symmetric, because it reflects the symmetry of the crystal. Then the Wulff point and the center of the island coincide. We show that this is not always the case. As an example we consider vacancy islands on the missing-row reconstructed Au(110) surface. Parallel to the missing rows, the steps on both sides of such islands differ in structure and in energy. Hence, the polar plot is asymmetric and one expects asymmetric islands. However, the equilibrium shape of islands observed on Au(110) with scanning tunneling microscopy is twofold mirror symmetric. We derive the condition under which one obtains a symmetric equilibrium shape from an asymmetric polar plot. Finally, we calculate the equilibrium shape of islands on Au(110) analytically.