| Popis: |
T hree-dimensional force spectroscopy measurements on 3,4,9,10-perylene-tetracarboxylic dianhydride adsorbed on Ag(111) are combined with fi rst-principles calculations to characterize the dissipative tip‐molecule interactions with submolecular resolution. The experiments reveal systematic differences between the energy dissipation at the end groups and the center of the molecules that change with the tip‐sample distance. Guided by the strength of the experimental conservative forces, an Ag-contaminated Si tip is identifi ed as the likely tip termination in the experiments. Based on this tip confi guration, the energy dissipation in the tip‐sample contact is determined from the approach and retraction force curves calculated as a function of distance for different molecule sites. These calculations provide an explanation for the experimental trends in terms of the competition between localized dissipation mechanisms involving the quite mobile oxygen atoms on the sides of the molecule, and global molecular deformations involving the more rigid perylene core. The results confi rm that the observed dissipation can be explained in terms of adhesion hysteresis and show the power of combined experimental‐theoretical spectroscopy studies in the characterization of the underlying microscopic mechanisms. |
