Tip-structure effects on atomic force microscopy images

Abstract

The authors study the effects of tip structure on images in atomic force microscopy by using a periodic force field fitted to ab-initio force calculations. 'Ideal' images resolving the sample atoms can be obtained with stable and atomically sharp tips in the repulsive range. In the weakly attractive range protrusions may occur at locations different from the atomic positions. Multiatom tips usually yield distorted images in which only the size and the shape of the sample unit cell is conserved. Rotation of a blunt tip or a finite flake lattice-matched to the sample causes stripes to form. Similar patterns can also appear for incommensurate sample-tip (or flake) systems.