Nucleation of Graphene Layers On Magnetic Oxides: Co_3O_4(111) and Cr_2O_3(0001) from Theory and Experiment

Abstract

We report direct grown strongly adherent graphene on Co_3O_4(111) by Carbon molecular beam epitaxy (MBE) at 850 K and DFT findings that the first graphene layer is reconstructed to fit the Co_3O_4 surface, while subsequent layers retain normal graphene structure. This adherence to the Co_3O_4 structure results from partial bonding of half the carbons to top oxygen 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, C MBE on Cr_2O_3(0001) yields only graphite formation at 700 K, with C desorption above 800 K. For Cr_2O_3 DFT finds no strong bonding to the surface, with charge transfer is away from the oxide. Thus strong graphene-to-oxide charge transfer aids nucleation of graphene on incommensurate oxide substrates.

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