Mechanismus of vibrational assisted electronic transport through single paraphenyl molecules investigated by electron and light sprectroscopy

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This project aims at bridging the research on single molecule tunnelling spectroscopy with research on electron transport through single-molecule junctions by using a low temperature scanning tunnelling microscope (STM) tip to approach to contact a single molecule, investigating the steps leading to the formation of a leadmolecule- lead junction. We will investigate stable molecule-electrode contacts formed by dative bonds between lone-pair electrons of amino, pyridine and nitrile molecular end-groups with oxygen functionalised copper surfaces and with atomic dangling bonds of silicon surfaces. We study i) the tunnel regime, using tunnel spectroscopy (elastic and inelastic) to reveal structure, electronic configuration and phonon structure, ii) the high conductance regime, to follow the transition to contact and the evolution of molecular resonances toward conducting bands, and iii) the contact regime, to identify transport mechanisms (elastic vs. inelastic, coherent vs. sequential) and their relation with molecular and contact structure. The goal is to provide reproducible transport (conductance-voltage) characteristics of well characterised systems, which can be then analysed in collaboration with theoretical partners in the SPP 1243 to answer the following questions: Which is the role of the leads electronic configuration in the charge transport? How do molecular orbitals evolve from local resonances and vibrations to transport bands and phonons? Can we see an electronic blockade effect in molecular junctions? How is energy dissipated in the molecule?