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O: Oberflächenphysik

O 47: Rastersondentechniken III

O 47.5: Talk

Tuesday, March 8, 2005, 16:45–17:00, TU EB202

First-priciples simulations of NC-AFM image contrast on InAs(110) surface — •Vasile Caciuc¹, Hendrik Hölscher¹, Stefan Blügel², and Harald Fuchs¹ — ¹Physikalisches Institut der Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster — ²Institut für Festkörperforschung, Forschungszentrum Jülich, 52425 Jülich

In the present contribution we report ab initio pseudopotential calculations based on density functional theory to investigate the non-contact atomic force microscopy (NC-AFM) image contrast on InAs(110) surface. The foremost tip structure is modeled by a SiH₃ tip. The influence of long-range van der Waals forces on the simulated AFM images due to the macroscopic part of the tip was taken into account by an empirical model. The effect of the tip-induced surface relaxations on the calculated forces was investigated for the tip above As and In atoms. The displacement curves corresponding to these vertical scans exhibit an hysteretic behaviour. At the tip-surface separations where the instability induced by this hysteresis is not present, the force curves obtained for relaxed (due to tip-sample interaction) and unrelaxed InAs(110) surface exhibit the same qualitative behaviour. From the calculated forces on a large number of grid points in real space (≈ 1300) we obtained maps of constant frequency shifts. The overall structure and the corrugation of the simulated NC-AFM images are in good agreement with the experimental results and allow us to explain the experimentally observed features of the image contrast mechanism on the basis of the calculated short-range chemical tip-sample interaction forces.