Adsorption of Benzene on Si(001) from Noncontact Atomic Force Microscopy Simulation

We have simulated noncontact atomic force microscopy on benzene-molecule-adsorbed Si(001) surfaces using the density-functional based tight-binding calculation. We show that three adsorption structures, namely, the standard butterfly, the tight bridge, and the twisted bridge, can be distinguished from topographic line profiles along directions perpendicular and parallel to the Si dimer row. The atomic configuration does not change markedly during the noncontact atomic force microscopy line scan even when the tip almost contacts the surface, which suggests that a stable adsorbed structure hardly changes to another stable structure at zero temperature.