Multiple-tip interpretation of anomalous scanning-tunneling-microscopy images of layered materials

Abstract

Graphite and other layered materials have been the substrates for numerous studies with the scanning tunneling microscope (STM) and, more recently, the atomic-force microscope. We argue in this paper that the experimental images for this class of materials are dominated by only three independent Fourier components. A nonideal tip can change the relative amplitudes and shift the relative phases of these components. This changes the shape and amplitude of the protrusions in the image which are interpreted as atoms. The effect of the STM tip on the images can be quantified with the assumption of multiple atomic tips. The multiple-tip model can explain many of the anomalous images that have been obtained, and can aid in their interpretation.