Berlin 2015 – scientific programme
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O: Fachverband Oberflächenphysik
O 89: Inorganic/Organic Interfaces: Molecular Switches
O 89.8: Talk
Thursday, March 19, 2015, 16:45–17:00, MA 043
Measuring forces on a single molecule in an STM junction — •Lukas Gerhard1, Kevin Edelmann1, Jan Homberg1, Marcin Lindner1, Michal Valasek1, Marcel Mayor1,2, Wulf Wulfhekel1,3, and Maya Lukas1 — 1Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), D-76344 Eggenstein-Leopoldshafen — 2Department of Chemistry, University of Basel, CH-4056 Basel — 3Physikalisches Institut, Karlsruhe Institute of Technology (KIT), D-76131 Karlsruhe
The possibility to incorporate molecular groups into carrier platforms allows to isolate functional units from a metallic substrate. Here we present a low-temperature STM study of spirobifluorene platforms with a benzonitrile head group deposited on a Au(111) surface [1]. We show by systematic variation of the tunneling parameters that the dipole moment of the benzonitrile allows us to exert forces on the molecule by applying electric fields in the STM junction. In this way we are able to form and brake a well defined contact between tip and molecule depending on the applied bias voltage. This switching between ON and OFF states of the conductance is highly reproducible and deterministic. Tuning the electrically applied force such that ON and OFF state are close in energy we observe thermally induced random switching which allows to deduce the energy difference between the two states. We measure this energy difference as a function of the distance between tip and sample and hence derive the force that is needed to pull apart the molecular junction. [1] M. Valášek et al., JOC 2014 79 (16), 7342-7357