Chemical interactions in noncontact AFM on semiconductor surfaces: Si 111/, Si 100/ and GaAs 110/

Total-energy pseudopotential calculations are used to study the imaging process in noncontact atomic force microscopy AFM.on Si 111., Si 100.and GaAs 110.surfaces. The chemical bonding interaction between a localised dangling bond on the atom at the apex of the tip and the dangling bonds on the adatoms in the surface is shown to dominate the forces and the force gradients and, hence, to provide atomic resolution. The lateral resolution capabilities are tested in both the Si 100.and the GaAs 110.surfaces. In the first case, the two atoms in a dimer can be resolved due to the dimer flip induced by the interaction with the tip during the scan, while in the GaAs 110., we identify the anion sublattice as the one observed in the experimental images. q1999 Elsevier Science B.V. All rights reserved.