Understanding Dissipative Tip–Molecule Interactions with Submolecular Resolution on an Organic Adsorbate

Abstract

Three-dimensional force spectroscopy measurements on 3,4,9,10-perylene-tetra-carboxylic dianhydride adsorbed on Ag(111) are combined with first-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 identified as the likely tip termination in the experiments. Based on this tip configuration, 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 confirm 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.

Influence of the adsorption geometry of PTCDA on Ag(111) on the tip–molecule forces in non-contact atomic force microscopy

“…Additionally we find an asymmetry of the forces above the two ends on the molecules, for molecule A as well as for molecule B. Previous ab-initio simulations of PTCDA on Ag(111) predict a slight asymmetry of the end groups in the dissipation channel at small distances [17], but only for one molecular orientation. Therefore we speculate that this effect is related to an asymmetry of the tip apex in this experiment [18].…”

Identifying the absolute orientation of a low-symmetry surface in real space

“…(1) in Ref. [53]. In our dataset, the dissipative contribution raises to a maximum of around 180 meV/cycle at very close tip-sample distances.…”

Force and conductance spectroscopy of second‐layer tin‐phthalocyanine on Ag(111)

“…Then, a decrease of Δf is observed. 1 Furthermore, the simultaneously measured dissipated energy per cycle E d (Fig. 2b, circles) increases at the position marked by the dotted line.…”