Regensburg 2007 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 17: Poster Session I (Nanostructures at Surfaces; Metal Substrates: Epitaxy and Growth; Methods: Scanning Probe Techniques; Phase Transitions)
O 17.6: Poster
Montag, 26. März 2007, 17:30–20:30, Poster C
Fermi-nesting in ordered Pb-chains grown on vicinal Si(557) — C. Tegenkamp1, •T. Block1, H. Pfnür1, T. Ohta2, J.L. McChesney2, and K. Horn3 — 1Institut für Festkörperphysik, Leibniz-Universität Hannover, 30167 Hannover, Germany — 2ALS, Lawrence Berkley National Laboratory, Berkley, CA. 94720, USA — 3FHI der Max-Planck Gesellschaft, 14195 Berlin, Germany
The adsorption of 1ML Pb at low temperatures on Si(557) followed by annealing to 640K leads to the formation of Pb-chains with an interachain spacing of d=1.5nm as seen by LEED and STM. The closely packed Pb film on the micro-Si(111) facets forms locally a √3 × √3 structure, which shows in addition a 10-fold periodicity along the [1 10] direction. Conductivity measurements below 78K have shown that electronic transport occurs only along the chain direction, whereas insulating behavior is found in the perpendicular direction. Above 78K, the sytsem switches into a 2d-regime, i.e. activated transport is found in both directions. Using angle resolved photoemission (ARPES), we explored the origins of the quasi one-dimensional (1d) conductance found below 78K. The interchain distance is reflected directly by Umklapp structures in the [11 2] direction close to EF. As ARPES reveals further, ordering into the chain structure below 78K results in complete Fermi nesting in the [11 2] direction and in energy reduction by band filling. The domain structure along the chains forms split-off valence bands with mesoscopic λF, responsible for the 1d conductance.