Dresden 2011 – scientific programme

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O: Fachverband Oberflächenphysik

O 23: Scanning probe methods II

O 23.1: Talk

Monday, March 14, 2011, 17:15–17:30, WIL C307

Simulation of a single molecule stretched within an nc-AFM junction — •Christian Wagner, Norman Fournier, Christian Weiss, Ruslan Temirov, and Frank Stefan Tautz — Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany and JARA-Fundamentals of Future Information Technology

The binding of organic molecules to metal surfaces is extensively studied both in experiment and theory. While techniques such as TDS are valuable tools to determine the binding energy of adsorbed molecules, it does not allow measuring the specific binding properties of individual functional groups or atoms. We approach this question by peeling single PTCDA molecules from a Ag(111) surface using a qPlus sensor. While previous studies already revealed that the molecule can be fully lifted when contacted by a STM tip [1], here, we go one step further and measure the potential energy profile during this pulling process. Due to its complexity, this experiment is very demanding concerning a modeling approach. On the one side, there is the (chemical) interaction between molecule and substrate. On the other side, the measured signal is a frequency shift obtained for an oscillation with a finite amplitude. We present a modeling approach that combines less demanding force-field calculations for the description of the molecule, and of its interaction with the substrate, while fully modeling the tip oscillation process. It shows that some of the key features found in the experiment can only be understood in the context of a finite amplitude.

[1] R. Temirov, A. Lassise, F. B. Anders, and F. S. Tautz,
Nanotechnology 19 065401 (2008)