Dresden 2006 – wissenschaftliches Programm
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O: Oberflächenphysik
O 14: Poster session I (Adsorption, Epitaxy and growth, Phase transitions, Surface reactions, Organic films, Electronic structure, Methods) (sponsored by Omicron Nanotechnology GmbH)
O 14.15: Poster
Montag, 27. März 2006, 18:00–21:00, P2
Conductance and atomic structure of Pb wires on Si(557) — •Marcin Czubanowski, Herbert Pfnür, Ziad Kallassy, and Christoph Tegenkamp — Institut für Festkörperphysik, Abteilung*Oberflächen, Appelstrasse 2, 30167 Hannover, Germany
The adsorption of Pb on Si(557) substrates leads to the formation of anisotropic metallic structures as revealed by conductivity measurements and STM. In particular, the annealing of at least 1ML Pb to 640K forms an atomic chain structures, which show below Tc=78K a metallic 1/T conductance behavior in the direction along the wires [110], whereas in the [1 12] direction an insulating behavior is found. As seen by STM, this transition in conductance is associated with an order-disorder transition in form of a tenfold periodicity below Tc [1].
Recent LEED experiments support the model, that the superperiodicity along the atomic wires is induced by domain walls. For annealing temperatures of 620K a Pb induced √3 × √3 is found,which is characteristic for Pb on Si(111) and can be explained by the well-known honeycomb structure of triplets of Pb atoms on T4 positions. The coverage of 1ML is in consistency with Auger and conductivity measurements. The LEED pattern changes dramatically for an annealing temperature of 640K, i.e. where 1D conductance is found and the atomic wire structure is formed. A detailed LEED analysis has shown, that a √31 × √3 domain structure along the [110] has formed. Similar results have been obtained for annealing close to the desorption threshold of Pb/Si(111)[2].
[1] C. Tegenkamp et.al. PRL 95, 176804 (2005).
[2] A. Petkova Dissertation Universität Hannover 2003