The nature of the Fe-graphene interface at the nanometer level
The emerging fields of graphene-based magnetic and spintronic devices require a deep understanding of the interface between graphene and ferromagnetic metals.
M. Cattelan et al. Nanoscale (2015), DOI: 10.1039/C4NR04956J; M. Cattelan et al. Phys. Chem. Chem. Phys. (2016) DOI: 10.1039/C6CP05368H
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The study of the interface between Graphene (G) and metals is gaining more and more interest thanks to the growing industrial application of G in flexible electronics and its integration in spintronic devices. Nevertheless, in order to implement G in spintronic devices, a careful study of G/ferromagnetic metal interface must be undertaken. We studied how Fe interacts with the G/Pt(111) system either after in-situ UHV deposition at room temperature (RT) or at T=600 K. In this way two complementary systems can be investigated: supported Fe nanoparticles (i.e. Fe/G/Pt(111)) and intercalated Fe layers (i.e. G/Fe/Pt(111)). Moreover, the oxidation of these systems was investigated by dosing oxygen at RT. To understand the electronic properties of G in contact with Pt(111) and Fe, photoemission spectroscopy from core-levels was carried out at CNR-BACH beamline and angle resolved photoelectron spectroscopy (ARPES) on single G grain was performed at Spectromicroscopy beamline. We also obtained a precise view of G lattice morphology at the atomic scale using scanning tunneling microscopy (STM). G was grown on Pt (111) by dosing of C2H4 at 1100 K obtaining a quasi free-standing layer; Fe was deposited on G/Pt(111) by physical vapor deposition at RT. Three different components can be clearly identified in C 1s: the peak at 284.16 eV is due to the unperturbed G atoms (as for G/Pt(111)), whereas the two components at 284.40 eV and 285 eV are associated to the sp2 atoms in contact with Fe and to a partial rehybridization of G to sp3 driven by the strong Fe-C interaction, respectively. The intercalated system, G/Fe/Pt(111), was prepared by depositing Fe at 600 K or heating the Fe/G/Pt(111) system at this temperature. This extraordinary continuity suggests that the combination of these two metals can be one of the best choices for future spintronic studies and devices. The flatness of the Fe layer intercalated below G was confirmed also by photoemission : the peak at 284.16 eV, which is the fingerprint of G in contact with Pt(111) is completely suppressed. |
The magnetic properties of the Fe-G interface have been investigated by x-ray magnetic circular dichroism.
We have compared two systems: an iron layer deposited directly on top of the Pt(111) surface, and an intercalated Fe film sandwiched between graphene and Pt(111). The system composed of a submonolayer Fe deposited directly on Pt(111) maintains an out-of-plane easy magnetization axis, even if it has been covered by graphene that quenches effectively the magnetic orbital moment of Fe. However, when the Fe coverage is increased above 1 ML the easy magnetization axis flips in the in-plane direction.
Cattelan M, Peng GW, Cavaliere E, Artiglia L, Barinov A, Roling LT, Favaro M, Píš I, Nappini S, Magnano E, Bondino F, Gavioli L, Agnoli S, Mavrikakis M, Granozzi G |
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