Open AccessSymmetry-Driven Band Gap Engineering in Hydrogen Functionalized Graphene
Author(s) -
Jakob Holm Jørgensen,
Antonija Grubišić Čabo,
Richard Balog,
Line Kyhl,
Michael N. Groves,
Andrew Cassidy,
Albert Bruix,
Marco Bianchi,
Maciej Dendzik,
Mohammad A. Arman,
Lutz Lammich,
José Pascual,
Jan Knudsen,
Bjørk Hammer,
Philip Hofmann,
Liv Hornekær
Publication year - 2016
Publication title -
acs nano
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.554
H-Index - 382
eISSN - 1936-086X
pISSN - 1936-0851
DOI - 10.1021/acsnano.6b04671
Subject(s) - graphene , surface modification , materials science , scanning tunneling microscope , band gap , hydrogen , x ray photoelectron spectroscopy , supercell , scanning tunneling spectroscopy , hydrogen atom , density functional theory , chemical physics , nanotechnology , chemistry , computational chemistry , chemical engineering , optoelectronics , organic chemistry , physics , thunderstorm , alkyl , meteorology , engineering
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 (T s ) during hydrogen functionalization. At deposition temperatures of T s = 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.