title: Bipolar Conductance Switching of Single Anthradithiophene Molecules.
abstract: Single molecular switches are basic device elements in organic electronics. The pentacene analogue anthradithiophene (ADT) shows a fully reversible binary switching between different adsorption conformations on a metallic surface accompanied by a charge transfer. These transitions are activated locally in single molecules in a low-temperature scanning tunneling microscope . The switching induces changes between bistable orbital structures and energy level alignment at the interface. The most stable geometry, the "off" state, which all molecules adopt upon evaporation, corresponds to a short adsorption distance at which the electronic interactions of the acene rings bend the central part of the molecule toward the surface accompanied by a significant charge transfer from the metallic surface to the ADT molecules. This leads to a shift of the lowest unoccupied molecular orbital down to the Fermi level (EF). In the "on" state the molecule has a flat geometry at a larger distance from the surface; consequently the interaction is weaker, resulting in a negligible charge transfer with an orbital structure resembling the highest occupied molecular orbital when imaged close to EF. The potential barrier between these two states can be overcome reversibly by injecting charge carriers locally into individual molecules. Voltage-controlled current traces show a hysteresis characteristic of a bipolar switching behavior. The interpretation is supported by first-principles calculations.
authors.affiliation: Max-Planck-Institute for Solid State Research , 70569 Stuttgart, Germany.
authors.forename: Bogdana
authors.initials: B
authors.lastname: Borca
authors.affiliation: Max-Planck-Institute for Solid State Research , 70569 Stuttgart, Germany.
authors.forename: Verena
authors.initials: V
authors.lastname: Schendel
authors.affiliation: Donostia International Physics Centre , E-20018 Donostia - San Sebastián, Spain.
authors.forename: Rémi
authors.initials: R
authors.lastname: Pétuya
authors.affiliation: Max-Planck-Institute for Solid State Research , 70569 Stuttgart, Germany.
authors.forename: Ivan
authors.initials: I
authors.lastname: Pentegov
authors.affiliation: Max-Planck-Institute for Solid State Research , 70569 Stuttgart, Germany.
authors.forename: Tomasz
authors.initials: T
authors.lastname: Michnowicz
authors.affiliation: Max-Planck-Institute for Solid State Research , 70569 Stuttgart, Germany.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Kraft
authors.affiliation: Max-Planck-Institute for Solid State Research , 70569 Stuttgart, Germany.
authors.forename: Hagen
authors.initials: H
authors.lastname: Klauk
authors.affiliation: Donostia International Physics Centre , E-20018 Donostia - San Sebastián, Spain.|Departamento de Fisica de Materiales UPV/EHU and Material Physics Center (MPC), Centro Mixto CSIC-UPV/EHU , E-20018 Donostia - San Sebastián, Spain.
authors.forename: Andrés
authors.initials: A
authors.lastname: Arnau
authors.affiliation: Max-Planck-Institute for Solid State Research , 70569 Stuttgart, Germany.|SUPA, School of Physics and Astronomy, University of St Andrews , North Haugh, St Andrews, KY16 9SS, United Kingdom.
authors.forename: Peter
authors.initials: P
authors.lastname: Wahl
authors.affiliation: Max-Planck-Institute for Solid State Research , 70569 Stuttgart, Germany.
authors.forename: Uta
authors.initials: U
authors.lastname: Schlickum
authors.affiliation: Max-Planck-Institute for Solid State Research , 70569 Stuttgart, Germany.|Institut de Physique de la Matière Condensée, École Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne, Switzerland.
authors.forename: Klaus
authors.initials: K
authors.lastname: Kern
keywords: Cu(111); DFT; STM; cis/trans ADT isomers; conformational and electronic switching