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V. Bus:
"DFT Simulations of nc-AFM: Interaction of Tip and Surface Atoms";
Vortrag: Seminar Institut für Allgemeine Physik (IAP), TU Wien; 21.06.2005.

Non-contact, frequency modulated, Atomic Force Microscopy is able to scan insulating and semiconducting surfaces with atomic resolution.
Our DFT simulations deal with the on-set of covalent bonding between a cantilever tip oscillating above the surface and the surface atoms. This on-set stands behind the contrast formation in an atomically resolved AFM image. Van der Waals interactions, presently beyond the capabilities of our DFT approach, as well as electrostatic interactions are neglected.
A Si-cluster of different size, passivated with hydrogen atoms to leave only one dangling bond to interact with the surface, is used to model the scanning tip. Data obtained from approaching and withdrawing moves of the tip show a hysteresis in the interaction energy and abrupt changes mainly in the lateral force, caused by induced mutual surface reconstruction and tip deformation.