Dresden 2006 – scientific programme
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MA: Magnetismus
MA 25: Spin-Electronics I
MA 25.8: Talk
Thursday, March 30, 2006, 12:00–12:15, HSZ 103
Loss-Free Spin Injection From Co Into Organic Semiconductor CuPc — •Oleksiy Andreyev1, Yongli Gao2, Marina Sánchez-Albaneda1, Mirko Cinchetti1, Huanjun Ding2, Jan-Peter Wüstenberg1, Michael Bauer1, and Martin Aeschlimann1 — 1Department of Physics, University of Kaiserslautern, 67663 Kaiserslautern, Germany — 2Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627-0171, USA
We present experimental evidence for loss-free spin injection of hot electrons from ferromagnetic Co(001) surface into organic semiconductor copper phthalocyanine (CuPc). We used spin-resolved two-photon photoemission (SR-2PPE) spectroscopy, which allows us to study the dynamics of both electron and spin relaxation in solids and interfaces with femtosecond time resolution. With SR-2PPE, we investigated the energy distribution and spin polarization of hot electrons originally excited in Co and injected in CuPc, and observed an almost unchanged spin polarization in comparison to that of the initial Co surface. This demonstrates that interface spin scattering is insignificant. The loss-free spin injection into CuPc suggests that it can be a promising material for spin-based electronic devices. Moreover, we observed a surprising enhanced spin polarization induced by a submonolayer CuPc coverage on the Co surface. This phenomenon is attributed to spin-dependent charge transfer responsible for the bonding between CuPc admolecule and the Co surface. We further investigated CuPc/Co junctions with intentionally enhanced interface roughness, and we found that the junction quality did not affect the efficiency of the spin injection.