Virtual charge method for electrostatic calculations in metallic tip and semiconducting sample systems

We calculate the electrostatic field between a metallic tip and a semiconductor surface by replacing the electrodes by a set of virtual charges, adjusted to fit the boundary conditions on the surfaces. The boundary conditions on the semiconductor side of the surface are obtained by using the result of a direct integration of the Poisson equation. The results of the method are compared to those given by a one-dimensional model. It is then applied to get some information which is useful in the theory of near field microscopy: Curvature of the energy bands at the semiconductor surface, influence of the tip shape, range of the electric field, effect of a dielectric insulating layer. (C) 1997 American Institute of Physics.