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.