Spin-polarized electron transport through selected molecules by means of spin-polarized scanning tunneling microscopy

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Our aim is to determine the spin transport properties of films of organic molecules and single molecules by means of spin-polarized scanning tunneling microscopy and spectroscopy at low temperatures (4K) under ultra high vacuum conditions. Metal-organic molecular films will be prepared in ultra-high vacuum on single crystal surfaces. Two classes of organic molecules will be used as model systems. In a first step, non-magnetic Al-pentanedionate will be grown on ferromagnetic substrates. By using ferromagnetic tips we will study the spin-resolved electronic structure of the molecule-substrate system and the spin-dependent transport of electrons from the tip through the molecule to the substrate. These measurements can be performed on scales from thin molecular films down to the single molecule level. From this, insight in the spin diffusion in metal-organic molecules will be gained. As a second step, identical molecules containing transition metal elements instead of Al will be used. We will investigate the impact of the local spin of the metallic atom in the molecule on the spin transport properties. Effects like enhanced spin scattering, selective spin channel transport or modification of the spin state due to the spin-polarized currents may occur. The knowledge gained by the experiments on the metal-organic model systems can be used for applications in organic spintronics.