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O: Oberflächenphysik
O 12: Struktur und Dynamik reiner Oberfl
ächen
O 12.3: Vortrag
Montag, 11. März 2002, 15:45–16:00, H45
Determination of step and kink energies: STM studies of Pt islands on Pt(111) — •Julian Ikonomov1, Kirilka Starbova2, Harald Ibach1, and Margret Giesen1 — 1Forschungszentrum Juelich, ISG 3, 52425 Juelich — 2Central Lab of Photoprocesses, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
As was recently demonstrated for Cu and Ag surfaces [1-3], one may obtain step free energies and kink energies from studies of the equilibrium shape and of the shape fluctuations of islands. The equilibrium shape is determined by the angle dependence of the step free energy. For Cu(111) and Ag(111) the step free energies of A- and B-steps (which form (100)- and (111)-microfacets with the underlying terrace, respectively) are about equal and the islands assume a near-hexagonal shape. For Pt(111), A- and B-steps differ substantially in energy and the islands assume the shape of truncated triangles. We have performed STM investigations of the equilibrium island shape and the corresponding shape fluctuations on Pt(111) as a function of temperature. Using an inverse Wulff-construction, the angle dependence of the step free energy is obtained. Between 500K and 700K, the aspect ratio of the Pt islands varies from 1.20 to 1.12. Using detailed (temperature variable) investigations of the curvature of the island perimeter parallel to <110> and <100> as well as studies of the island shape fluctuations, we determined the step free energies of A- and B-steps and the energies of kinks in A- and B-steps. The experimental results will be discussed. [1] Surf. Sci. 471 (2001) 80. [2] Phys. Rev. Lett. 82 (1999) 3843. [3] Phys. Rev. B 64 (2001) 085416.