Berlin 2012 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 44: Joint Session "Spins in Organic Materials" (jointly with DS)

MA 44.2: Vortrag

Donnerstag, 29. März 2012, 17:00–17:15, H 1012

Spin properties of the Alq₃-cobalt oxide (CoO) interface — •Norman Haag, Sabine Steil, Nicolas Großmann, Mirko Cinchetti, and Martin Aeschlimann — Department of Physics and Research Center OPTIMAS, TU Kaiserslautern, Erwin-Schrödinger-Stra. 46, D-67663 Kaiserslautern

The effect of cobalt oxidation is crucial for the understanding of the performance of organic spin valves with Co electrodes [1], as it is expected that cobalt will partly oxidize during sample production. For this reason, we analyzed the spin properties of the interface formed between tris(8-hydroxyquinoline)aluminium (III) (Alq₃) and cobalt oxide. We deposited 30 ML of Co(100) and exposed the sample to an oxygen atmosphere with varying pressure. The degree of oxidation is extracted by evaluating the changes in the work function according to Wang et al [2]. Subsequently, Alq₃ was grown on the oxidized cobalt. The resulting interface was characterized by means of spin-resolved ultraviolet photoemission spectroscopy. We detected the energy level alignment and the spin polarization in the region of a few eV below E_F, both as a function of degree of oxidation. The most striking result is the shift of the Alq3 molecular orbitals of up to 1 eV (for strong oxidation) away from the Fermi level. This behavior could change the character of spin and carrier conduction (from holes to electrons) in spintronics devices.
Dediu et al., Nature Materials 8, 707 (2009)
Wang et al., Surface Science 124, 51 (1983)