Regensburg 2010 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 54: Electronic structure II
O 54.7: Vortrag
Mittwoch, 24. März 2010, 16:30–16:45, H33
The Interplay of Conductance, Force, and Structure Change in Metallic Point Contacts — •Markus Ternes1,2, César González Pascual3, Chris P. Lutz1, Franz J. Giessibl4, Pavel Jelńek5, and Andreas J. Heinrich1 — 1IBM Research Division, Almaden Research Center, San Jose, California — 2Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany — 3Instituto Ciencia de Materiales de Madrid, Spain — 4Institute of Experimental and Applied Physics, University of Regensburg, Germany — 5Institute of Physics, Academy of Sciences of the Czech Republic, Prague
A combined scanning tunneling and atomic force microscope was used to measure simultaneously the conductance and the short-range force between an atomically sharp tip and a single metal adsorbate on a metal surface. We found that in the tunneling regime the conductance as well as the attractive short-range force increased exponentially as the tip approached the adsorbate. In the transition regime between tunneling and point-contact a stronger than exponential increase in the conductance was found for a Cu atom on a Cu(111) surface probed with a Cu tip but not for a Pt atom on a Pt(111) surface. To explain the subtle details of the experimental findings, extensive density functional calculations where performed showing that both studied systems show a profound structural change when the transition between tunneling and point-contact occurs. The structural change strongly influences the conductance and forces between tip and sample. The experimental and numerical results are in excellent agreement and give new detailed inside into the transition and formation of metallic point-contacts.