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O: Oberflächenphysik

O 47: Rastersondentechniken III

O 47.6: Talk

Tuesday, March 8, 2005, 17:00–17:15, TU EB202

Tip Models and Surface Atoms in DFT Simulations of AFM Scans — •Vladan Buš and Josef Redinger — Center for Computational Materials Science, Institut f. Allgemeine Physik, Vienna University of Technology, Getreidemarkt 9/134, 1060 Vienna, Austria

Non-contact Atomic Force Microscope operated under ultra-high vacuum conditions is able to display atomic features of insulating or semiconductor surfaces. Oscillations of the cantilever are influenced by forces acting between the surface atoms and the probe tip. In the close-to-contact operation region and for small amplitudes, forces describing the on-set of chemical bonding stand behind the contrast formation in this experiment.

We employ the DFT VASP code, using PAW and PW91 GGA, to simulate probing of surface atoms of GaAs(110) and Si(100) surfaces with a Si tip. Changes in structure during the approaching and withdrawing move lead to abrupt changes in normal and lateral forces and cause a hysteresis in the interaction energy.