title: Electron beam controlled covalent attachment of small organic molecules to graphene.
abstract: The electron beam induced functionalization of graphene through the formation of covalent bonds between free radicals of polyaromatic molecules and C=C bonds of pristine graphene surface has been explored using first principles calculations and high-resolution transmission electron microscopy. We show that the energetically strongest attachment of the radicals occurs along the armchair direction in graphene to carbon atoms residing in different graphene sub-lattices. The radicals tend to assume vertical position on graphene substrate irrespective of direction of the bonding and the initial configuration. The "standing up" molecules, covalently anchored to graphene, exhibit two types of oscillatory motion--bending and twisting--caused by the presence of acoustic phonons in graphene and dispersion attraction to the substrate. The theoretically derived mechanisms are confirmed by near atomic resolution imaging of individual perchlorocoronene (C24Cl12) molecules on graphene. Our results facilitate the understanding of controlled functionalization of graphene employing electron irradiation as well as mechanisms of attachment of impurities via the processing of graphene nanoelectronic devices by electron beam lithography.
authors.affiliation: School of Chemistry, University of Nottingham, NG7 2RD Nottingham, UK. elena.besley@nottingham.ac.uk.
authors.forename: Alexander
authors.initials: A
authors.lastname: Markevich
authors.affiliation: Electron Microscopy Department of Material Sciences, University of Ulm, 89081 Ulm, Germany.
authors.forename: Simon
authors.initials: S
authors.lastname: Kurasch
authors.affiliation: Electron Microscopy Department of Material Sciences, University of Ulm, 89081 Ulm, Germany.
authors.forename: Ossi
authors.initials: O
authors.lastname: Lehtinen
authors.affiliation: Faculty of Physics, University of Bielefeld, 33615 Bielefeld, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Reimer
authors.affiliation: Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
authors.forename: Xinliang
authors.initials: X
authors.lastname: Feng
authors.affiliation: Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Müllen
authors.affiliation: Institute of Physical Chemistry, Friedrich Schiller University Jena, Lessingstraße 10, D-07743 Jena, Germany.
authors.forename: Andrey
authors.initials: A
authors.lastname: Turchanin
authors.affiliation: School of Chemistry, University of Nottingham, NG7 2RD Nottingham, UK. elena.besley@nottingham.ac.uk.
authors.forename: Andrei N
authors.initials: AN
authors.lastname: Khlobystov
authors.affiliation: Electron Microscopy Department of Material Sciences, University of Ulm, 89081 Ulm, Germany.
authors.forename: Ute
authors.initials: U
authors.lastname: Kaiser
authors.affiliation: School of Chemistry, University of Nottingham, NG7 2RD Nottingham, UK. elena.besley@nottingham.ac.uk.
authors.forename: Elena
authors.initials: E
authors.lastname: Besley