Limits of Resolution in Atomic Force Microscopy Images of Graphite

Abstract

We calculate the limits of atomic resolution of an atomic force microscope (AFM) tip probing the elastic surface of graphite. Interaction energies between a "sharp" Pd tip with one apex atom and graphite are obtained from ab initio total energy calculations within the density functional formalism. The effect of long-range Van der Waals forces on the tip-substrate interaction is considered explicitly. We find that in the constant-force mode, atomic resolution is marginally possible for AFM loads (per atom) close to 5 10^-9 N. The optimum operating range is limited by unobservably small height corrugations for smaller lods and by irreversible substrate deformations for larger loads.