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DS: Fachverband Dünne Schichten

DS 31: Spins in Organic Materials II (Focused Session, jointly with MA -- Organisers: Salvan, Hess, Timm)

DS 31.3: Talk

Wednesday, March 16, 2011, 16:30–16:45, GER 37

Cobalt-Meq₃ (Me=Al, In, Ga) interface formation studied by spin- and time-resolved photoemission spectroscopy — •Nicolas Großmann, Sabine Steil, Martin Laux, Andreas Ruffing, Indranil Sarkar, Mirko Cinchetti, and Martin Aeschlimann — Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, 67663 Kaiserslautern, Germany

We have studied the formation of the interface between an epitaxially grown Co(001) thin film and the organic semiconductors tris(8-hydroxyquinoline)aluminium(III) (Alq₃), tris(8-hydroxyquinoline)gallium(III)(Gaq₃) and tris(8-hydroxyquinoline) indium(III)(Inq₃). The organic semiconductors were progressively grown on the cobalt substrate up to a coverage of 5 monolayers. The grown interfaces have been characterized by means of spin-resolved ultraviolet photoemission spectroscopy and spin- and time-resolved two-photon photoemission spectroscopy. For every growth step we have monitored the changes in the work function, the energetic position of the occupied and unoccupied molecular orbitals and interface states, and the changes in the cobalt spin polarization induced by interface formation. In addition, we have measured the spin-resolved lifetime of unoccupied hybrid interface states. The results will be discussed with focus on the relevance of spin-polarized hybrid interface states on the sign of the magnetoresistance observed in organic spin valves based on Alq₃ [1].

V. A. Dediu, et al., Nature Mater. 8, 707 (2009);