Modeling of surfaces of constant force above a lattice of close-packed atoms in the repulsive mode

Surfaces of constant force (force contours) are calculated for the scanning of an AFM tip over a lattice of close-packed atoms in the repulsive mode. It is shown that discontinuities are observed on the force contours in the regions between the atoms of the surface lattice for sufficiently small initial scanning heights of a tip with a single atom at its end. A cluster model of the tip end, which ensures continuity of the scanning at arbitrary initial heights, is constructed. The dependence of the AFM images on the orientation of the cluster on the tip end relative to the crystallographic axes of the surface is investigated for both an unperturbed lattice of close-packed atoms and a lattice containing point defects. The diagnostic possibilities of the findings are discussed. Zh. Tekh. Fiz. 67, 77–85 (June 1997)