Bipolar conductance switching of single anthradithiophene molecules

Bogdana Borca, Verena Schendel, Remi Petuya, Ivan Pentegov, Tomasz Michnowicz, Ulrike Kraft, Hagen Klauk, Andres Arnau, Peter Wahl, Uta Schlickum, Klaus Kern

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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.
Original languageEnglish
Pages (from-to)12506-12512
JournalACS Nano
Issue number12
Early online date18 Nov 2015
Publication statusPublished - 22 Dec 2015


  • cis/trans ADT isomers
  • Cu(111)
  • STM
  • DFT
  • Conformational and electronic switching


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