Forces during the controlled displacement of organic molecules.

In the ongoing effort to miniaturize the functional elements in electronic devices, molecular dimensions are currently approached. Scanning probe microscopy has demonstrated fascinating capabilities for bottom-up fabrication of atomically defined prototype structures. However, little is known about the underlying interactions during the manipulation of functional organic molecules with a scanning probe tip. Here, we demonstrate the use of noncontact atomic force microscopy at cryogenic temperatures for the lateral displacement of the organic prototype molecule 3,4,9,10-perylene-tetracarboxylicacid-dianhydride on the Ag(111) surface. During repeated manipulation cycles, we measure the precise lateral and vertical tip-molecule force profiles as well as the energy dissipation before and during the manipulation process. The jump of the molecule to an adjacent equivalent substrate lattice site occurs in the regime of repulsive lateral forces, thus constituting a "pushing" mechanism.

Temperature dependence of energy dissipation on NaCl(001) in non-contact atomic force microscopy.

The dissipative tip-sample interactions are measured by dynamic force spectroscopy for silicon tips on NaCl(001) in ultrahigh vacuum in the attractive and repulsive force regimes. Force and dissipation versus distance curves were obtained for different sample temperatures ranging from 35 to 285 K. Detailed comparison in different distance regimes shows that neither the force nor energy dissipation exhibits a systematic variation with sample temperature.