title: Direct graphene growth on MgO: origin of the band gap.
abstract: A 2.5 monolayer (ML) thick graphene film grown by chemical vapor deposition of thermally dissociated C(2)H(4) on MgO(111), displays a significant band gap. The apparent six-fold low energy electron diffraction (LEED) pattern actually consists of two three-fold patterns with different 'A' and 'B' site diffraction intensities. Similar effects are observed for the LEED patterns of a 1 ML carbon film derived from annealing adventitious carbon on MgO(111), and for a 1.5 ML thick graphene film grown by sputter deposition on the 1 ML film. The LEED data indicate different electron densities at the A and B sites of the graphene lattice, suggesting that the observed band gap results from lifting the graphene HOMO/LUMO degeneracy at the Dirac point. The data also indicate that disparities in A site/B site LEED intensities decrease with increasing carbon overlayer thickness, suggesting that the graphene band gap size decreases with increasing number of graphene layers on MgO(111).
authors.affiliation: Department of Chemistry and Center for Electronic Materials Processing and Integration, University of North Texas, Denton, TX 76203-5017, USA.
authors.forename: Sneha
authors.initials: S
authors.lastname: Gaddam
authors.forename: Cameron
authors.initials: C
authors.lastname: Bjelkevig
authors.forename: Siping
authors.initials: S
authors.lastname: Ge
authors.forename: Keisuke
authors.initials: K
authors.lastname: Fukutani
authors.forename: Peter A
authors.initials: PA
authors.lastname: Dowben
authors.forename: Jeffry A
authors.initials: JA
authors.lastname: Kelber
mesh_terms: D004735:Energy Transfer; D006108:Graphite / Q000737:chemistry*; D008277:Magnesium Oxide / Q000737:chemistry*; D008422:Materials Testing; D008567:Membranes, Artificial; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*
chemical_list: D008567:Membranes, Artificial; D008277:Magnesium Oxide; D006108:Graphite