3-DIMENSIONAL IMAGE INTERACTION FOR NONSMOOTH EMITTERS

We present a generalized image-charge method to calculate the interact ion energies of a charge placed between a metallic tip of arbitrary sh ape and a sample surface. The basic idea is to replace the electrodes by a set of image charges. These charges are adjusted in order to fit the boundary conditions on the surfaces. As an application of the tech nique, we have calculated the three-dimensional potential barrier (inc luding image interaction) for electron field emission from sharp tips having different geometries. The influence of the presence of a little hemispherical bump on the apex is also discussed. (C) 1996 American I nstitute of Physics.