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Determination of spin injection and transport inaferromagnet/organic semiconductor heterojunction by two-photon photoemission

Determination of spin injection and transport inaferromagnet/organic semiconductor heterojunction... 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. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Nature Materials Springer Journals

Determination of spin injection and transport inaferromagnet/organic semiconductor heterojunction by two-photon photoemission

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References (15)

Publisher
Springer Journals
Copyright
Copyright © 2009 by Nature Publishing Group
Subject
Materials Science; Materials Science, general; Optical and Electronic Materials; Biomaterials; Nanotechnology; Condensed Matter Physics
ISSN
1476-1122
eISSN
1476-4660
DOI
10.1038/nmat2334
Publisher site
See Article on Publisher Site

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.

Journal

Nature Materials – Springer Journals

Published: Nov 23, 2008

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