title: Role of hydrogen in chemical vapor deposition growth of large single-crystal graphene.
abstract: We show that graphene chemical vapor deposition growth on copper foil using methane as a carbon source is strongly affected by hydrogen, which appears to serve a dual role: an activator of the surface bound carbon that is necessary for monolayer growth and an etching reagent that controls the size and morphology of the graphene domains. The resulting growth rate for a fixed methane partial pressure has a maximum at hydrogen partial pressures 200-400 times that of methane. The morphology and size of the graphene domains, as well as the number of layers, change with hydrogen pressure from irregularly shaped incomplete bilayers to well-defined perfect single layer hexagons. Raman spectra suggest the zigzag termination in the hexagons as more stable than the armchair edges.
authors.affiliation: Measurement Science & System Engineering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA. vlassioukiv@ornl.gov
authors.forename: Ivan
authors.initials: I
authors.lastname: Vlassiouk
authors.forename: Murari
authors.initials: M
authors.lastname: Regmi
authors.forename: Pasquale
authors.initials: P
authors.lastname: Fulvio
authors.forename: Sheng
authors.initials: S
authors.lastname: Dai
authors.forename: Panos
authors.initials: P
authors.lastname: Datskos
authors.forename: Gyula
authors.initials: G
authors.lastname: Eres
authors.forename: Sergei
authors.initials: S
authors.lastname: Smirnov
mesh_terms: D006108:Graphite / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry*; D011312:Pressure; D013059:Spectrum Analysis, Raman; D014835:Volatilization
chemical_list: D006108:Graphite; D006859:Hydrogen