AVS 52nd International Symposium
    Nanometer-Scale Science and Technology Monday Sessions
       Session NS1-MoA

Paper NS1-MoA5
On the Influence of Structure on Friction: The Amorphous-Crystalline Transition in Antimony Nanoparticles

Monday, October 31, 2005, 3:20 pm, Room 204

Session: Nanotribology
Presenter: C. Ritter, Humboldt University Berlin, Germany
Authors: C. Ritter, Humboldt University Berlin, Germany
M. Heyde, Fritz-Haber Institute of the Max-Planck Society, Germany
K. Rademann, Humboldt University Berlin, Germany
U.D. Schwarz, Yale University
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This work addresses two of the crucial points in nanotribology, namely the dependence of friction on effective contact area and interface structure. As model system, antimony nanoparticles grown on graphite are used. Such particles can be easily prepared with different sizes, and the effective particle/substrate contact area can be deduced from scanning force microscopy images. Moreover, the particles are undergoing a structural transition from amorphous to polycrystalline during the growth process at about 10000-15000 nm@super 2@ in size. This feature can be used to establish a correlation between structure and friction. Antimony islands have been pushed over atomically flat substrate areas using the tip of a dynamic force microscope while the power dissipation necessary to move the islands was measured. To fully cover the amorphous-crystalline transition, to check on reproducibility, and to obtain sufficient statistics, 95 measurements including 57 islands (areas between 1370 nm@super 2@ and 112000 nm@super 2@) and four different cantilevers were performed. The threshold value of the power dissipation needed for translation of the crystalline islands depends linearly on the contact area between the islands and the substrate. With the assumption of a linear relationship between dissipated power and frictional forces, this implies a direct proportionality between friction and contact area. The amorphous islands, however, also fit with a linear law, but the slope is a factor of three lower than the one found for the larger particles, leading to significantly lower energy dissipation. This change and their tentative relation to the structural transition within the particles will be discussed.