Visualization of charge transport through single molecules

I propose to investigate the conductance properties of single molecules in a radically new way, by utilizing LEEM (low-energy electron microscopy) and PEEM (photo-electron emission microscopy). Up to now, molecular electronics has suffered from the problem that it is impossible to see if a molecule is actually present. Using LEEM/PEEM, I shall change that situation. I will both visualize and fundamentally study electron transport through single molecules. If I succeed, I will open a powerful new research field, as this technique will enable accurate transport studies in a broad set of fascinating systems. Simultaneously, my work will imply the breakthrough of LEEM and PEEM, which are rooted in surface science, to a much broader physics community. My approach is to exploit the sensitivity of LEEM and PEEM to the local sample potential, to visualize charge transport in two-dimensional systems under a voltage bias. To specifically study transport through molecules, I shall therefore spread out a set of molecular junctions in a two-dimensional structure. PEEM will also be used in a complementary way, i.e. to determine the energy levels of molecules coupled to gold. By combining molecular transport data, energy level information and additional optical spectroscopy (UV-Vis, infrared and Raman) a comprehensive data set is constructed that is exceptional in the field of molecular transport. Taking advantage of this opportunity, I will systematically investigate the influence of molecular conjugation and metal-molecule coupling on charge transport through molecules. My fundamental studies therefore relate to the technologically relevant question if we can manipulate molecular conductance properties by the proximity of other molecules or by external stimuli such as light.