AVS 53rd International Symposium
    Nanometer-scale Science and Technology Monday Sessions
       Session NS-MoM

Paper NS-MoM9
Mapping Atomic-Scale Interaction Potentials

Monday, November 13, 2006, 10:40 am, Room 2016

Session: Nanoscale Imaging Techniques
Presenter: A. Schirmeisen, University of Muenster, Germany
Authors: A. Schirmeisen, University of Muenster, Germany
D. Weiner, University of Muenster, Germany
H. Fuchs, University of Muenster, Germany
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On the atomic level even a perfectly flat surface is not structureless but reflects the electronic structure of the underlying molecular lattice. This potential energy landscape governs molecule adsorption and diffusion,@footnote 1@ which is responsible for a multitude of dynamic surface processes like crystal growth, vicinal to faceting transitions and catalytic action. However, direct experimental access to the spatial variation of the interaction potential energy at the atomic level is difficult. We use an ultrahigh vacuum atomic force microscope in non-contact mode to scan the three-dimensional force field@footnote 2@ of a NaCl (100) surface at room temperature. The interaction forces are systematically probed over a wide range of tip-sample distances, from attractive to strongly repulsive forces. The surface was imaged before and after the 3D spectroscopy experiments with atomic resolution, including single atom defects, thus ensuring an unmodified single atom terminated tip apex. From the force spectroscopy measurements on a predefined grid on the surface we obtain a quantitative characterization of the atomic scale potential energy landscape.@footnote 3@ The energy diagram allows us to identify distinct energy minima at the site of one ion species and extract the effective energy barrier between two adjacent minima. This barrier is directly linked to the dynamics of adsorbed surface atoms and atomic scale friction processes. Furthermore we calculate from the energy landscape the vertical as well as lateral tip-sample forces of the single atom contact. We observe the emergence of a mechanical relaxation process of the investigated single atom contact, which shows a reversible yet hysteretic characteristic. @FootnoteText@ @footnote 1@ R. Gomer, Rep. Prog. Phys. 53, 917 (1990)@footnote 2@ H. Hoelscher et al., Appl. Phys. Lett. 81, 4428 (2002)@footnote 3@ A. Schirmeisen, D. Weiner, H. Fuchs, submitted (2006) .