New Insight on Atomic-Resolution Frequency Modulation Kelvin Porbe Force Microscopy Imaging of Semiconductors

We provide new insight into atomic contrast obtained using Kelvin Probe Force Microscopy based on both experimental and theoretical analysis. We proved that the atomic contrast is not an artefact, but it is based on underlying physics. In particular, we performed a set of complex computer simulations of tip-sample interaction between the scanning probe and the 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 change around surface atoms is the origin of the atomic contrast observed in the experiment. The work opens new posibilities in characterization of materials at atomic scale.
S. Sadewasser et al. Phys. Rev. Lett. 103, 266103 (2009)

Upper: individual silicon atoms on surface imagined by a traditional nc-AFM topography mode (left) and a new atomic scale image obtained using Kelvin Atomic Force Microscopy (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