Investigating the inside of individual molecules by means of Kelvin Probe and Atomic Force Microscopy

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Recently, AFM imaging of individual molecules with functionalized tips provided an unprecedented resolution of the structure of individual molecules. In addition to providing higher spatial resolution, functionalized tips have the advantage that the short-range interaction between tip and sample is well-defined. This enables an unprecedented control over the imaging process and allows for a much better theoretical description of the underlying physical processes. This does not only apply to imaging, but also to different spectroscopy modes, ranging from 3D-force mapping to Kelvin probe force spectroscopy. The aim of this project is make use of these novel possibilities by studying (i) molecular interactions with intra-molecular spatial resolution and (ii) the polarity of bonds and their response to local fields. Three-dimensional force field mapping and Kelvin probe force spectroscopy shall provide this information at ultimate resolution, for which the frequency shift, local contact potential difference, and the curvature of the Kelvin parabola carry complementary information. To establish the relationship between experimental results and the underlying physical and chemical mechanisms, the experiments will be complemented by simulations from our collaboration partner.