Direct graphene growth on Co ₃O ₄(111) by molecular beam epitaxy

Direct growth of graphene on Co ₃O ₄(111) at 1000K was achieved by molecular beam epitaxy from a graphite source. Auger spectroscopy shows a characteristic sp ²carbon lineshape, at average carbon coverages from 0.4 to 3ML. Low energy electron diffraction (LEED) indicates (111) ordering of the sp ²carbon film with a lattice constant of 2.5(0.1) characteristic of graphene. Sixfold symmetry of the graphene diffraction spots is observed at 0.4, 1 and 3ML. The LEED data also indicate an average domain size of 1800, and show an incommensurate interface with the Co ₃O ₄(111) substrate, where the latter exhibits a lattice constant of 2.8(0.1). Core level photoemission shows a characteristically asymmetric C(1s) feature, with the expected to * satellite feature, but with a binding energy for the 3ML film of 284.9(0.1)eV, indicative of substantial graphene-to-oxide charge transfer. Spectroscopic ellipsometry data demonstrate broad similarity with graphene samples physically transferred to SiO ₂ or grown on SiC substrates, but with the to * absorption blue-shifted, consistent with charge transfer to the substrate. The ability to grow graphene directly on magnetically and electrically polarizable substrates opens new opportunities for industrial scale development of charge-and spin-based devices.