title: Luminescence, patterned metallic regions, and photon-mediated electronic changes in single-sided fluorinated graphene sheets.
abstract: Single-sided fluorination has been predicted to open an electronic band gap in graphene and to exhibit unique electronic and magnetic properties; however, this has not been substantiated by experimental reports. Our comprehensive experimental and theoretical study of this material on a SiC(0001) substrate shows that single-sided fluorographene exhibits two phases, a stable one with a band gap of ∼6 eV and a metastable one, induced by UV irradiation, with a band gap of ∼2.5 eV. The metastable structure, which reverts to the stable "ground-state" phase upon annealing under emission of blue light, in our view is induced by defect states, based on the observation of a nondispersive electronic state at the top of the valence band, not unlike that found in organic molecular layers. Our structural data show that the stable C2F ground state has a "boat" structure, in agreement with our X-ray magnetic circular dichroism data, which show the absence of an ordered magnetic phase. A high flux of UV or X-ray photons removes the fluorine atoms, demonstrating the possibility of lithographically patterning conducting regions into an otherwise semiconducting 2D material.
authors.affiliation: Advanced Light Source (ALS), E. O. Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Andrew Leigh
authors.initials: AL
authors.lastname: Walter
authors.forename: Hasan
authors.initials: H
authors.lastname: Sahin
authors.forename: Ki-Joon
authors.initials: KJ
authors.lastname: Jeon
authors.forename: Aaron
authors.initials: A
authors.lastname: Bostwick
authors.forename: Seyda
authors.initials: S
authors.lastname: Horzum
authors.forename: Roland
authors.initials: R
authors.lastname: Koch
authors.forename: Florian
authors.initials: F
authors.lastname: Speck
authors.forename: Markus
authors.initials: M
authors.lastname: Ostler
authors.forename: Peter
authors.initials: P
authors.lastname: Nagel
authors.forename: Michael
authors.initials: M
authors.lastname: Merz
authors.forename: Stefan
authors.initials: S
authors.lastname: Schupler
authors.forename: Luca
authors.initials: L
authors.lastname: Moreschini
authors.forename: Young Jun
authors.initials: YJ
authors.lastname: Chang
authors.forename: Thomas
authors.initials: T
authors.lastname: Seyller
authors.forename: Francois M
authors.initials: FM
authors.lastname: Peeters
authors.forename: Karsten
authors.initials: K
authors.lastname: Horn
authors.forename: Eli
authors.initials: E
authors.lastname: Rotenberg