Ordered three-fold symmetric graphene oxide/buckled graphene/graphene heterostructures on MgO(111) by carbon molecular beam epitaxy

Abstract

KEYWORDSphotoemission, electron energy loss, low energy electron diffraction, density functional theory ABSTRACT Theory and experiment demonstrate the direct growth of a graphene oxide/buckled graphene/graphene heterostructure on an incommensurate MgO(111) substrate. X-ray photoelectron spectroscopy, electron energy loss, Auger electron spectroscopy, low energy electron diffraction, Raman spectroscopy and first-principles density functional theory (DFT) calculations all demonstrate that carbon molecular beam epitaxy on either a hydroxylated MgO(111) single crystal or a heavily twinned thin film surface at 850 K yields an initial C layer of highly ordered graphene oxide with C 3v symmetry. A 5x5 unit cell of carbon, with one missing atom, forms on a 4x4 unit cell of MgO, with the three C atoms surrounding the C vacancy surface forming covalent C-O bonds to substrate oxide sites. This leads to a bowed graphene-oxide with slightly modified D and G Raman lines and a calculated band gap of 0.36 eV. Continued C growth results in the second layer of graphene that is stacked AB with respect to the first layer and buckled conformably with the first layer while maintaining C 3v symmetry, lattice spacing and azimuthal orientation with the first layer. Carbon growth beyond the second layer yields graphene in azimuthal registry with the first two C layers, but with graphene-characteristic lattice spacing and πàπ* loss feature. This 3 rd layer is also p-type, as indicated by the 5.6 eV energy loss feature. The significant sp 3 character and C 3v symmetry of such heterostructures suggest that spin-orbit coupling is enabled, with implications for spintronics and other device applications.2

N‐Doped and P‐Doped Graphene on MgO (111): A First‐Principles Study

“…The best solution is to grow graphene films directly on the target substrate material, which not only avoids the transfer process of graphene but also expands the properties of graphene through the interaction between graphene and the substrate material. [10] Currently, complementary metal-oxide semiconductor (CMOS) technology is commonly used to fabricate transistors, and the oxide layer is selected as the dielectric material. [11,12] Among many oxides, MgO, as a high-kappa dielectric material, has attracted the attention of scholars both in theory and experiment.…”