Article abstract
Nature Materials
Published online: 23 November 2008 | doi:10.1038/nmat2334
Determination of spin injection and transport in a ferromagnet/organic semiconductor heterojunction by two-photon photoemission
Mirko Cinchetti1, Kathrin Heimer1, Jan-Peter Wüstenberg1, Oleksiy Andreyev2, Michael Bauer2, Stefan Lach1, Christiane Ziegler1, Yongli Gao3,4 & Martin Aeschlimann1
Abstract
A fundamental prerequisite for the implementation of organic semiconductors (OSCs) in spintronics devices is the still missing basic knowledge about spin injection and transport in OSCs. Here, we consider a model system consisting of a high-quality interface between the ferromagnet cobalt and the OSC copper phthalocyanine (CuPc). We focus on interfacial effects on spin injection and on the spin transport properties of CuPc. Using spin-resolved two-photon photoemission, we have measured directly and in situ the efficiency of spin injection at the cobalt–CuPc interface. We report a spin injection efficiency of 85–90% for injection into unoccupied molecular orbitals of CuPc. Moreover, we estimate an electron inelastic mean free path in CuPc in the range of 1 nm and a 10–30 times higher quasi-elastic spin-flip length. We demonstrate that quasi-elastic spin-flip processes with energy loss 
200 meV are the dominant microscopic mechanism limiting the spin diffusion length in CuPc.
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, 67663 Kaiserslautern, Germany
- Institut für Experimentelle und Angewandte Physik, Universität Kiel, 24118 Kiel, Germany
- Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627-0171, USA
- Department of Physics, Central-South University, Changsha 410083, People's Republic of China
Correspondence to: Mirko Cinchetti1 e-mail: cinchett@rhrk.uni-kl.de
