title: A surface-anchored molecular four-level conductance switch based on single proton transfer.
abstract: The development of a variety of nanoscale applications requires the fabrication and control of atomic or molecular switches that can be reversibly operated by light, a short-range force, electric current or other external stimuli. For such molecules to be used as electronic components, they should be directly coupled to a metallic support and the switching unit should be easily connected to other molecular species without suppressing switching performance. Here, we show that a free-base tetraphenyl-porphyrin molecule, which is anchored to a silver surface, can function as a molecular conductance switch. The saddle-shaped molecule has two hydrogen atoms in its inner cavity that can be flipped between two states with different local conductance levels using the electron current through the tip of a scanning tunnelling microscope. Moreover, by deliberately removing one of the hydrogens, a four-level conductance switch can be created. The resulting device, which could be controllably integrated into the surrounding nanoscale environment, relies on the transfer of a single proton and therefore contains the smallest possible atomistic switching unit.
authors.affiliation: Physik Department E20, Technische Universität München, D-85748 Garching, Germany. wau@tum.de
authors.forename: Willi
authors.initials: W
authors.lastname: Auwärter
authors.forename: Knud
authors.initials: K
authors.lastname: Seufert
authors.forename: Felix
authors.initials: F
authors.lastname: Bischoff
authors.forename: David
authors.initials: D
authors.lastname: Ecija
authors.forename: Saranyan
authors.initials: S
authors.lastname: Vijayaraghavan
authors.forename: Sushobhan
authors.initials: S
authors.lastname: Joshi
authors.forename: Florian
authors.initials: F
authors.lastname: Klappenberger
authors.forename: Niveditha
authors.initials: N
authors.lastname: Samudrala
authors.forename: Johannes V
authors.initials: JV
authors.lastname: Barth