Regensburg 2010 – scientific programme

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O: Fachverband Oberflächenphysik

O 11: Methods: Scanning probe techniques II

O 11.10: Talk

Monday, March 22, 2010, 17:15–17:30, H32

Imaging short-range forces with a scanning tunnelling microscope — •Temirov Ruslan, Weiss Christian, Wagner Christian, Kleimann Christoph, and Tautz Stefan — Institut für Bio- und Nanosysteme 3, Forschungszentrum Jülich, JARA Fundamentals of Future Information Technology, Germany

One of the unresolved issues in the field of scanning tunnelling microscopy (STM) is the lack of chemical sensitivity. The STM probes the density of states (DOS) close to the Fermi level while the details of the chemical structure are mostly encoded by lower lying orbitals. Thus it is desirable to measure the total electron density (TED) rather than the DOS. Since the TED defines Pauli repulsion, imaging of short-range forces should directly reveal the chemical structure. Indeed, it was demonstrated recently that non-contact atomic force microscopy (AFM) resolves the structure of a complex organic molecule by probing short-range repulsive interactions [1]. In our contribution we show that STM can also be used to map short-range forces and resolve chemical structures. The key to the new functionality is a single hydrogen molecule confined in the STM junction [2]. The molecule acts as a force-sensor/signal transducer, which probes the repulsive branch of the surface adsorption potential and transforms the force signal into variations of the junction conductance [3].

[1] L. Gross et al. Science 325, 1110 (2009). [2] R. Temirov et al. New J. Phys. 10, 053012 (2008) [3] C. Weiss et al. arXiv:cond-mat/0910.5825