Berlin 2005 – wissenschaftliches Programm
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O: Oberflächenphysik
O 36: Postersitzung (Elektronische Struktur, Grenzfl
äche fest-flüssig, Halbleiteroberfl
ächen und -grenzfl
ächen, Nanostrukturen, Oberfl
ächenreaktionen, Teilchen und Cluster, Struktur und Dynamik reiner Oberfl
ächen)
O 36.50: Poster
Montag, 7. März 2005, 15:00–18:00, Poster TU F
Electronic transport in anisotropic Pb structures grown on Si(557) — •M. Czubanowski, Z. Kallasy, C. Tegenkamp, and H. Pfnür — Institut für Festkörperphysik,Abteilung Oberflächen ,Appelstr. 2, 30167 Hannover, Germany
Transport measurements between 3K and 300K of epitaxially grown Pb–film on Si(557) have been performed. Using the van der Pauw geometry, both the conductivity parallel and perpendicular to the steps of the uniaxial Si(557) surface have been measured and correlated with Pb-structures obtained by LEED and STM.
Different transport mechanisms have been identified: Above the percoloation limit of 0.6ML the electronic transport in annealed Pb films up to 3ML is activated. With respect to the Si(557) step structure the conductance parallel to the steps is higher (50–100%) than in the perpendicular direction. For higher coverages a metallic behavior is seen, i.e. the conductance decreases with increasing temperature. In contrast to this anisotropic 2-D conductivity, a 1-D conduction channel is formed parallel to the steps, after annealing of Pb–multilayers to 640K. The remaining coverage is close to 1ML. As revealed by STM, atomic wires, separated by 14Å, are formed on the Si(557) substrate.
For TC≤78K, the conductivity shows a (1/T + const.) dependency for the parallel direction. This 1D-transport switches back to 2D for temperatures higher than TC. At this temperature also an insulator-metal transition is seen for the perpendicular direction. This transition at TC can be correlated with an order–disorder phase transition in form of a 10–fold periodicity along the atomic wires.