Imaging of subatomic electron cloud interactions: Effect of higher harmonics processing in noncontact atomic force microscopy

Abstract

In a previous study of higher harmonics atomic force microscopy imaging of graphite using a tungsten tip [Hembacher et al., Science 305, 380 (2004)], the authors interpreted the observed subatomic features as the signature of tip apex electron bonding lobes. We explore here their higher harmonics processing and filtering methods. We do not find any imaging artifacts inherent to the filtering process, but we find that the harmonics averaging approach used is not appropriate due to non-uniform harmonics ratios across the surface. A promising alternative may be the individual mapping of the first two harmonics.