AVS 47th International Symposium
    Material Characterization Tuesday Sessions
       Session MC-TuP

Paper MC-TuP27
Conservative and Dissipative Tip-sample Interaction Forces Reconstructed from Dynamic Atomic Force Microscopy Data

Tuesday, October 3, 2000, 5:30 pm, Room Exhibit Hall C & D

Session: Poster Session
Presenter: B. Gotsmann, University of Muenster, Germany
Authors: B. Gotsmann, University of Muenster, Germany
H. Fuchs, University of Muenster, Germany
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The conservative and dissipative forces between a tip and a surface are characteristic for the materials involved and contain information on several material parameters. In order to determine these forces quantitatively at all tip-sample distances dynamic atomic force microscopy (AFM) can be used. We based our analysis on a combination of computer simulations and experimental AFM data obtained by the frequency modulation technique. In this way it became possible to reconstruct complete force versus distance curves and damping coefficient versus distance curves from experimental data (frequency shift and energy dissipation) without using free parameters and without using a predefined model for the interaction.@footnote 1@ As an example the interaction between an Al-tip and a Au(111)-sample under UHV conditions was analyzed. It turned out that the parts of the force curves that correspond to long range van-der-Waals-forces as well as strong repulsive contacts can be described well with known contact models. However in the transition regime between attractive and repulsive contact an additional short range force can be found. Similarly, the friction coefficient can be determined quantitatively up to a distance of several nanometers exhibiting an inverse power law. At closer contact both velocity dependent friction and adhesion hysteresis lead to energy dissipation. A strategy to distinguish between the two in AFM experiments will be discussed briefly. @FootnoteText@ @footnote 1@ B. Gotsmann, C. Seidel, B. Anczykowski, H. Fuchs, Phys. Rev. B 60 (1999) p.11051.