Raman spectroscopy of lattice-matched graphene on strongly interacting metal surfaces

Regardless of the widely accepted opinion that there is no Raman signal from single-layer graphene when it is strongly bonded to a metal surface, we present Raman spectra of a graphene monolayer on Ni(111) and Co(0001) substrates. The high binding energy of carbon to these surfaces allows formation of lattice-matched (1 × 1) structures where graphene is significantly stretched. This is reflected in a record-breaking shift of the Raman G band by more than 100 cm–1 relative to the case of freestanding graphene. Using electron diffraction and photoemission spectroscopy, we explore the aforementioned systems together with polycrystalline graphene on Co and analyze possible intercalation of oxygen at ambient conditions. The results obtained are fully supported by Raman spectroscopy. Performing a theoretical investigation of the phonon dispersions of freestanding graphene and stretched graphene on the strongly interacting Co surface, we explain the main features of the Raman spectra. Our results create a reliable platform for application of Raman spectroscopy in diagnostics of chemisorbed graphene and related materials.L.V.Ya., D.Yu.U., O.Yu.V., and V.O.S. acknowledge RSF (Grant No. 16-42-01093). E.V.Ch. and I.Yu.S. acknowledge support by the Spanish Ministry of Science and Innovation (Grant No. FIS2016-75862-P). C.L. acknowledges DFG (Grant Nos. LA655-17/1 and LA655-19/1). E.V.Ch., D.Yu.U., D.V.V., V.O.S., and B.V.S. acknowledge Saint Petersburg State University (SPbU) for research Grant Nos. 11.65.42.2017 and 15.61.202.2015 and RFBR (Grant No. 17-02-00427). We thank Helmholtz-Zentrum Berlin für Materialien und Energie for support within the bilateral Russian−German Laboratory program.Peer Reviewe

Raman Spectroscopy of Lattice-Matched Graphene on Strongly Interacting Metal Surfaces

Regardless of the widely accepted opinion that there is no Raman signal from single-layer graphene when it is strongly bonded to a metal surface, we present Raman spectra of a graphene monolayer on Ni(111) and Co(0001) substrates. The high binding energy of carbon to these surfaces allows formation of lattice-matched (1 X 1) structures where graphene is significantly stretched. This is reflected in a record-breaking shift of the Raman G band by more than 100 cm(-1) relative to the case of freestanding graphene. Using electron diffraction and photoemission spectroscopy, we explore the aforementioned systems together with polycrystalline graphene on Co and analyze possible intercalation of oxygen at ambient conditions. The results obtained are fully supported by Raman spectroscopy. Performing a theoretical investigation of the phonon dispersions of freestanding graphene and stretched graphene on the strongly interacting Co surface, we explain the main features of the Raman spectra. Our results create a reliable platform for application of Raman spectroscopy in diagnostics of chemisorbed graphene and related materials