title: Emergence of photoswitchable states in a graphene-azobenzene-Au platform.
abstract: The perfect transmission of charge carriers through potential barriers in graphene (Klein tunneling) is a direct consequence of the Dirac equation that governs the low-energy carrier dynamics. As a result, localized states do not exist in unpatterned graphene, but quasibound states can occur for potentials with closed integrable dynamics. Here, we report the observation of resonance states in photoswitchable self-assembled molecular(SAM)-graphene hybrid. Conductive AFM measurements performed at room temperature reveal strong current resonances, the strength of which can be reversibly gated on- and off- by optically switching the molecular conformation of the mSAM. Comparisons of the voltage separation between current resonances (∼ 70-120 mV) with solutions of the Dirac equation indicate that the radius of the gating potential is ∼ 7 ± 2 nm with a strength ≥ 0.5 eV. Our results and methods might provide a route toward optically programmable carrier dynamics and transport in graphene nanomaterials.
authors.affiliation: Walter Schottky Institute - ZNN, Physik Department and NIM, Technische Universität München , Am Coulombwall 4, 80333 Garching, Germany.
authors.forename: Emanuela
authors.initials: E
authors.lastname: Margapoti
authors.forename: Philipp
authors.initials: P
authors.lastname: Strobel
authors.forename: Mahmoud M
authors.initials: MM
authors.lastname: Asmar
authors.forename: Max
authors.initials: M
authors.lastname: Seifert
authors.forename: Juan
authors.initials: J
authors.lastname: Li
authors.forename: Matthias
authors.initials: M
authors.lastname: Sachsenhauser
authors.forename: Ozlem
authors.initials: O
authors.lastname: Ceylan
authors.forename: Carlos-Andres
authors.initials: CA
authors.lastname: Palma
authors.forename: Johannes V
authors.initials: JV
authors.lastname: Barth
authors.forename: Jose A
authors.initials: JA
authors.lastname: Garrido
authors.forename: Anna
authors.initials: A
authors.lastname: Cattani-Scholz
authors.forename: Sergio E
authors.initials: SE
authors.lastname: Ulloa
authors.forename: Jonathan J
authors.initials: JJ
authors.lastname: Finley
keywords: atomic microscopy; doping; graphene; photochromatic molecules