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O: Fachverband Oberflächenphysik

O 83: Organic Molecules on Inorganic Substrates VI: Chirality, Charge Transfer, Self-Assembly

O 83.3: Hauptvortrag

Donnerstag, 4. April 2019, 15:30–16:00, H9

Control of charge transfer into large organic molecules on ultrathin MgO(001) films — •Martin Sterrer — University of Graz, Graz, Austria

Charge transfer processes on ultrathin, supported oxide films have received increasing attention in recent years because of the possibility to control the charge state of adsorbates or the direction of catalytic reactions. The main driving forces for the occurence of charge transfer in these systems is the reduction of the substrate work function induced by deposition of the oxide film in combination with an adsorbate with high electron affinity. While previous studies have focused on the charging of metal atoms (e.g. Au) or small molecules (e.g. O_{2}, NO_{2}), we have recently extended these investigations to charge transfer processes into large organic molecules. In this contribution, we present results on the adsorption and charging of pentacene (5A) and tetraphenylporphyrin (2H-TPP) on ultrathin MgO(001) films supported on Ag(001). By combing scanning tunneling microscopy and photoemission spectroscopy and tomography, we are able to identify and quantify charge transfer into the organic monolayer film. In addition, we show that by variation of the work function and the MgO thickness it is possible to drive the system into a state where no charge transfer occurs. In the case of 2H-TPP charge transfer also appears to strongly influence the self metalation of 2H-TPP to Mg-TPP. Thus, our investigations lay the basis for the ultimate control of charge transfer, and the related chemistry, on ultrathin oxide film systems.