Nucleation of Graphene Layers on Magnetic Oxides: Co3O4(111) and Cr2O3(0001) from Theory and Experiment.

We report directly grown strongly adherent graphene on Co3O4(111) by carbon molecular beam epitaxy (C MBE) at 850 K and density functional theory (DFT) findings that the first graphene layer is reconstructed to fit the Co3O4 surface, while subsequent layers retain normal graphene structure. This adherence to the Co3O4 structure results from partial bonding of half the carbons to top oxygens of the substrate. This structure is validated by X-ray photoelectron spectroscopy and low-energy electron diffraction studies, showing layer-by-layer graphene growth with ∼0.08 electrons/carbon atom transferred to the oxide from the first graphene layer, in agreement with DFT. In contrast, for Cr2O3 DFT finds no strong bonding to the surface and C MBE on Cr2O3(0001) yields only graphite formation at 700 K, with C desorption above 800 K. Thus strong graphene-to-oxide charge transfer aids nucleation of graphene on incommensurate oxide substrates and may have implications for spintronics.