The interpretation of field ion images

Abstract

Previous work on the simulation of. field ion images by computation of the positions of atoms lying on a spherical crystal has been extended to a range of sizes. Comparison of computed patterns with experimental images has shown that the thickness of the shell of atoms contributing to the image increases for smaller crystal radii. It is shown that the prominence of the planes is determined by the interplanar distances even if interference between planes is allowed for. The planes to be expected on selected zones of spheres of various radii are listed. With ordered structures such as CoPt it is assumed that one atomic species is invisible in experimental images and thus the pattern is considered in terms of the interplanar distances of planes in the array made up of the visible species. The relative number of planes to be expected in a pattern of CoPt is compared with one of a pure Pt crystal.