Interpretations of atomic-resolution images in atomic-force microscopy

Abstract
The force curves obtained from atomic-force-microscopy measurements (AFM) over different sites of highly oriented pyrolytic graphite (HOPG) are calculated. With the help of the curves, phenomena in AFM images with atomic resolution are interpreted. It is found that the inverted contrast (positions where atoms in the surface are lower than any other area) may appear in the HOPG images under some imaging forces. The true atomic resolution is defined and the conditions to obtain these kinds of images are also discussed.