We provide new insight into atomic contrast obtained using Kelvin Probe Force Microscopy based on both experimental and theoretical analysis. We approved, that the atomic contrast is not an artefact, but it has a physical background. In particular, we peform a set of complex computer simulations of tip-sample interaction between a scanning probe and surface. The simulations showed a change of the charge density redistribution and consequently the surface dipole due to the formation of the chemical bond between a probe and surface atoms. This local change round surface atoms is the origin of the atomic contrast observed in the experiment. This work opens new posibilities in characterization of materials at atomic scale.

S. Sadewasser et al. Phys. Rev. Lett. 103, 266103 (2009).

 link.aps.org/doi/10.1103/PhysRevLett.103.266103

Fig.

Upper: individual silicon atoms on surface imaged by a traditional nc-AFM topography mode (left) and a new atomic scale image obtained using Kelvin Atomic Force Micorscopy (right). Lower: computer simulations results showing a change in electron density around silicon adatom on surface due to its interaction with scanning probe at different distances, 6,0 Å a 3,5 Å respectivelly.