| AVS 59th Annual International Symposium and Exhibition | |
| Graphene and Related Materials Focus Topic | Thursday Sessions |
| Session GR-ThP |
| Session: | Graphene and Related Materials Poster Session |
| Presenter: | D.B. Dougherty, North Carolina State University |
| Authors: | D.B. Dougherty, North Carolina State University A.A. Sandin, North Carolina State University A. Calzolari, CNR-NANO, Istituto Nanoscienze, Italy M. Buongiorno-Nardelli, North Carolina State University A. Al-Mahboob, Brookhaven National Laboratory J.T. Sadowski, Brookhaven National Laboratory J.E. Rowe, North Carolina State University |
| Correspondent: | Click to Email |
Graphene is an ideal material for long-range spin transport due to its very high carrier mobilities and long spin lifetimes due to minimal spin-orbit scattering effects [1]. Direct spin injection into graphene has been demonstrated, but is inefficient due to the well-known bulk conductivity mismatch between graphene and a magnetic metal electrode. The standard approach to overcome this effect is to engineer a tunneling barrier at the interface to provide an effectively large spin-dependent interface resistance. However, for insulating tunnel barrier growth on graphene, great care must be taken to avoid 3D islanding due to the typically weak interactions between the substrate and deposited species [1].
An alternate approach is to consider the use of planar organic materials as interfacial layers to enhance spin injection into graphene. Since weak intermolecular interactions can be comparable in size to molecule-substrate interactions for planar aromatics on graphene, high quality film growth is more likely. We have studied the growth of iron phthalocyanine (FePc), a chemically-robust paramagnet, on epitaxial graphene on SiC(0001) by a combination of STM, STS, LEED, UPS, and density functional theory calculations. Our calculations predict an energetically weak interaction between graphene and FePc that nevertheless leads to a unique spin-dependent electronic mixing. A non-dispersive hybrid interface state is created along with a small gap in one spin sub-band while the graphene band structure is essentially unchanged in the other sub-band. STM and LEED indicate a highly-ordered, flat-lying monolayer film of FePc on epitaxial graphene and UPS measurements compare favorable with the calculated occupied density of states. STS studies of the ordered monolayer show an unoccupied state for FePc on graphene that is not present for FePc on graphite. We interpret this unique state as evidence for the predicted spin-polarized interface state.
*This work was funded by the NSF Phase I Center for Chemical Innovation: Center for Molecular Spintronics (CHE-0943975).
[1] Han et al., J. Magn. Mag. Mat. 324, 369 (2012).