title: Symmetry-Driven Band Gap Engineering in Hydrogen Functionalized Graphene.
abstract: Band gap engineering in hydrogen functionalized graphene is demonstrated by changing the symmetry of the functionalization structures. Small differences in hydrogen adsorbate binding energies on graphene on Ir(111) allow tailoring of highly periodic functionalization structures favoring one distinct region of the moiré supercell. Scanning tunneling microscopy and X-ray photoelectron spectroscopy measurements show that a highly periodic hydrogen functionalized graphene sheet can thus be prepared by controlling the sample temperature (Ts) during hydrogen functionalization. At deposition temperatures of Ts= 645 K and above, hydrogen adsorbs exclusively on the HCP regions of the graphene/Ir(111) moiré structure. This finding is rationalized in terms of a slight preference for hydrogen clusters in the HCP regions over the FCC regions, as found by density functional theory calculations. Angle-resolved photoemission spectroscopy measurements demonstrate that the preferential functionalization of just one region of the moiré supercell results in a band gap opening with very limited associated band broadening. Thus, hydrogenation at elevated sample temperatures provides a pathway to efficient band gap engineering in graphene via the selective functionalization of specific regions of the moiré structure.
authors.affiliation: Department of Physics and Astronomy and Interdisciplinary Nanoscience Center iNANO, Aarhus University , Aarhus C DK-8000, Denmark.
authors.forename: Jakob Holm
authors.initials: JH
authors.lastname: Jørgensen
authors.affiliation: Department of Physics and Astronomy and Interdisciplinary Nanoscience Center iNANO, Aarhus University , Aarhus C DK-8000, Denmark.
authors.forename: Antonija Grubišić
authors.initials: AG
authors.lastname: Čabo
authors.affiliation: Department of Physics and Astronomy and Interdisciplinary Nanoscience Center iNANO, Aarhus University , Aarhus C DK-8000, Denmark.|CIC nanoGUNE and Ikerbasque, Basque Foundation of Science , Donostia-San Sebastian 20018, Spain.
authors.forename: Richard
authors.initials: R
authors.lastname: Balog
authors.affiliation: Department of Physics and Astronomy and Interdisciplinary Nanoscience Center iNANO, Aarhus University , Aarhus C DK-8000, Denmark.
authors.forename: Line
authors.initials: L
authors.lastname: Kyhl
authors.affiliation: Department of Physics and Astronomy and Interdisciplinary Nanoscience Center iNANO, Aarhus University , Aarhus C DK-8000, Denmark.
authors.forename: Michael N
authors.initials: MN
authors.lastname: Groves
authors.affiliation: Department of Physics and Astronomy and Interdisciplinary Nanoscience Center iNANO, Aarhus University , Aarhus C DK-8000, Denmark.
authors.forename: Andrew Martin
authors.identifier: 0000-0001-8352-8721
authors.initials: AM
authors.lastname: Cassidy
authors.affiliation: Department of Physics and Astronomy and Interdisciplinary Nanoscience Center iNANO, Aarhus University , Aarhus C DK-8000, Denmark.
authors.forename: Albert
authors.initials: A
authors.lastname: Bruix
authors.affiliation: Department of Physics and Astronomy and Interdisciplinary Nanoscience Center iNANO, Aarhus University , Aarhus C DK-8000, Denmark.
authors.forename: Marco
authors.initials: M
authors.lastname: Bianchi
authors.affiliation: Department of Physics and Astronomy and Interdisciplinary Nanoscience Center iNANO, Aarhus University , Aarhus C DK-8000, Denmark.
authors.forename: Maciej
authors.initials: M
authors.lastname: Dendzik
authors.forename: Mohammad Alif
authors.initials: MA
authors.lastname: Arman
authors.affiliation: Department of Physics and Astronomy and Interdisciplinary Nanoscience Center iNANO, Aarhus University , Aarhus C DK-8000, Denmark.
authors.forename: Lutz
authors.initials: L
authors.lastname: Lammich
authors.affiliation: CIC nanoGUNE and Ikerbasque, Basque Foundation of Science , Donostia-San Sebastian 20018, Spain.
authors.forename: José Ignacio
authors.initials: JI
authors.lastname: Pascual
authors.forename: Jan
authors.identifier: 0000-0002-8280-7638
authors.initials: J
authors.lastname: Knudsen
authors.affiliation: Department of Physics and Astronomy and Interdisciplinary Nanoscience Center iNANO, Aarhus University , Aarhus C DK-8000, Denmark.
authors.forename: Bjørk
authors.initials: B
authors.lastname: Hammer
authors.affiliation: Department of Physics and Astronomy and Interdisciplinary Nanoscience Center iNANO, Aarhus University , Aarhus C DK-8000, Denmark.
authors.forename: Philip
authors.initials: P
authors.lastname: Hofmann
authors.affiliation: Department of Physics and Astronomy and Interdisciplinary Nanoscience Center iNANO, Aarhus University , Aarhus C DK-8000, Denmark.
authors.forename: Liv
authors.identifier: 0000-0003-0828-3642
authors.initials: L
authors.lastname: Hornekaer
keywords: Ir(111); STM; band gap engineering; functionalization; graphene; hydrogen; photoemission spectroscopy