Chemisorption aromatischer Moleküle auf Übergangsmetalloberflächen: Bildung molekularer Hybridmagnete

The goal of molecular spintronics is to use molecules for the realization of smallest switchable magnetic units. The molecules serve as building blocks of future electronic devices to increase their integration density and energy effciency. The interaction of individual molecules and molecular monolayers with metal surfaces is one of the key properties and needs to be investigated and controlled. To this end, well-defined and controlled adsorption of molecules with sub-monolayer coverage onto clean single-crystalline surfaces of (transition) metals under ultra-high vacuum conditions is required. In this PhD thesis, the chemisorption of three aromatic molecules on different transition metal surfaces and the associated formation of molecular hybrid magnets was investigated. This research was inspired by the experimental evidence of a molecule-based spin filter effect in mesoscopic junctions given by Raman et al. This thesis focuses on the basics with regard to the experimental realization of the spin-filter effect in a single double-decker molecule. The theoretically proposed spin-filter mechanism is based on the adsorption of intrinsically non-magnetic flat aromatic molecules on ferromagnetic surfaces, whereby strong hybridization of molecular -orbitals with spin-split -orbitals of the substrate occurs. The resulting imbalance of spin-resolved states of the adsorbed molecule induces magnetic properties in the molecule such as a spin-dependent band gap, a stable magnetic moment, or spin polarization at the Fermi energy. The induced magnetic properties as well as the atomic and electronic structure of the molecule-substrate hybrid systems are investigated by (spin-polarized) scanning tunneling microscopy and spectroscopy in ultra-high vacuum and at low temperatures (4 K). [...