title: Band Gap Opening Induced by the Structural Periodicity in Epitaxial Graphene Buffer Layer.
abstract: The epitaxial graphene buffer layer on the Si face of hexagonal SiC shows a promising band gap, of which the precise origin remains to be understood. In this work, we correlate the electronic to the atomic structure of the buffer layer by combining angle resolved photoemission spectroscopy (ARPES), scanning tunneling microscopy (STM), and high-resolution scanning transmission electron microscopy (HR-STEM). We show that the band structure in the buffer has an electronic periodicity related to the structural periodicity observed in STM images and published X-ray diffraction. Our HR-STEM measurements show the bonding of the buffer layer to the SiC at specific locations separated by 1.5 nm. This is consistent with the quasi 6 × 6 periodic corrugation observed in the STM images. The distance between buffer C and SiC is 1.9 Å in the bonded regions and up to 2.8 Å in the decoupled regions, corresponding to a 0.9 Å corrugation of the buffer layer. The decoupled regions are sp2hybridized. Density functional tight binding (DFTB) calculations demonstrate the presence of a gap at the Dirac point everywhere in the buffer layer, even in the decoupled regions where the buffer layer has an atomic structure close to that of graphene. The surface periodicity also promotes band in the superperiodic Brillouin zone edges as seen by photoemission and confirmed by our calculations.
authors.affiliation: UR1 CNRS/Synchrotron SOLEIL, Saint-Aubin, 91192 Gif sur Yvette, France.|Laboratoire de Physique des Solides, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Bât. 510 , F-91405 Orsay Cedex, France.
authors.forename: Maya
authors.initials: M
authors.lastname: N Nair
authors.affiliation: UR1 CNRS/Synchrotron SOLEIL, Saint-Aubin, 91192 Gif sur Yvette, France.
authors.forename: Irene
authors.initials: I
authors.lastname: Palacio
authors.affiliation: Laboratoire de Physique des Solides, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Bât. 510 , F-91405 Orsay Cedex, France.|Synchrotron SOLEIL, L'Orme des Merisiers , Saint-Aubin, 91192 Gif sur Yvette, France.
authors.forename: Arlensiú
authors.initials: A
authors.lastname: Celis
authors.affiliation: Laboratoire de Physique des Solides, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Bât. 510 , F-91405 Orsay Cedex, France.
authors.forename: Alberto
authors.identifier: 0000-0001-6581-4353
authors.initials: A
authors.lastname: Zobelli
authors.affiliation: Laboratoire de Physique des Solides, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Bât. 510 , F-91405 Orsay Cedex, France.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Gloter
authors.affiliation: Synchrotron SOLEIL, L'Orme des Merisiers , Saint-Aubin, 91192 Gif sur Yvette, France.
authors.forename: Stefan
authors.initials: S
authors.lastname: Kubsky
authors.affiliation: School of Physics, The Georgia Institute of Technology , Atlanta, Georgia 30332-0430, United States.
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Turmaud
authors.affiliation: School of Physics, The Georgia Institute of Technology , Atlanta, Georgia 30332-0430, United States.
authors.forename: Matthew
authors.initials: M
authors.lastname: Conrad
authors.affiliation: School of Physics, The Georgia Institute of Technology , Atlanta, Georgia 30332-0430, United States.|CNRS/Institut Neél, BP166 , 38042 Grenoble, France.
authors.forename: Claire
authors.initials: C
authors.lastname: Berger
authors.affiliation: School of Physics, The Georgia Institute of Technology , Atlanta, Georgia 30332-0430, United States.
authors.forename: Walter
authors.initials: W
authors.lastname: de Heer
authors.affiliation: School of Physics, The Georgia Institute of Technology , Atlanta, Georgia 30332-0430, United States.
authors.forename: Edward H
authors.initials: EH
authors.lastname: Conrad
authors.affiliation: UR1 CNRS/Synchrotron SOLEIL, Saint-Aubin, 91192 Gif sur Yvette, France.
authors.forename: Amina
authors.initials: A
authors.lastname: Taleb-Ibrahimi
authors.affiliation: Laboratoire de Physique des Solides, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Bât. 510 , F-91405 Orsay Cedex, France.|Synchrotron SOLEIL, L'Orme des Merisiers , Saint-Aubin, 91192 Gif sur Yvette, France.
authors.forename: Antonio
authors.identifier: 0000-0003-0125-4603
authors.initials: A
authors.lastname: Tejeda
keywords: ARPES; Band gap; graphene buffer layer; nanostructuration