The effect of sample resistivity on Kelvin probe force microscopy

Kelvin probe force microscopy (KPFM) is a powerful technique to probe the local electronic structure of materials with atomic force microscopy. One assumption often made is that the applied bias drops fully in the tip-sample junction. We have recently identified an effect, the Phantom force, which can be explained by an ohmic voltage drop near the tip-sample junction causing a reduction of the electrostatic attraction when a tunneling current is present. Here, we demonstrate the strong effect of the Phantom force upon KPFM that can even produce Kelvin parabolae of opposite curvature. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4766185]