Electrostatic tip-sample interaction in immersion force microscopy of semiconductors

We evaluate the electrostatic force between the tip of a scanning force microscope and the surface of a depleted semiconductor, when probe and sample are surrounded by a medium with high dielectric permittivity. If this permittivity is larger than that of the semiconductor, the electrostatic image force is repulsive and much weaker than in vacuo and can be compensated by the attractive force due to the semiconductor space charge. By representing the tip as a point charge, force-distance curves are calculated for different semiconductor doping, the location of the zero-force point is determined, and the lateral resolution of the method is estimated. The model may find application to the local determination of dopant density by force microscopy.