Theoretical atomic-force-microscopy study of adsorbed fullerene molecules

The capability of atomic-force microscopy (AFM) to localize both individual adsorbates and aggregates of adsorbed molecules was demonstrated a few years ago. More recently submonolayers of fullerene molecules deposited on a gold substrate have been imaged using such devices. In this paper, simulations of the atomic force between a thin probe tip and a set of adsorbed molecules is presented. The long-range part of the interaction is determined from a whole self-consistent procedure in which many-body effects are accounted for at all orders. In this description the probe tip interacts with the molecules and the surface through many-body dispersion forces. Short-range interactions are then included by using an atom-atom semiempirical pairwise potential. Simulations of AFM images of ${\mathrm{C}}_{60}$ adsorbed molecules are presented in two different modes of imaging: the constant-tip-height mode and the constant-force mode.