title: Measurement of the conductance of single conjugated molecules.
abstract: Electrical conduction through molecules depends critically on the delocalization of the molecular electronic orbitals and their connection to the metallic contacts. Thiolated (- SH) conjugated organic molecules are therefore considered good candidates for molecular conductors: in such molecules, the orbitals are delocalized throughout the molecular backbone, with substantial weight on the sulphur-metal bonds. However, their relatively small size, typically approximately 1 nm, calls for innovative approaches to realize a functioning single-molecule device. Here we report an approach for contacting a single molecule, and use it to study the effect of localizing groups within a conjugated molecule on the electrical conduction. Our method is based on synthesizing a dimer structure, consisting of two colloidal gold particles connected by a dithiolated short organic molecule, and electrostatically trapping it between two metal electrodes. We study the electrical conduction through three short organic molecules: 4,4'-biphenyldithiol (BPD), a fully conjugated molecule; bis-(4-mercaptophenyl)-ether (BPE), in which the conjugation is broken at the centre by an oxygen atom; and 1,4-benzenedimethanethiol (BDMT), in which the conjugation is broken near the contacts by a methylene group. We find that the oxygen in BPE and the methylene groups in BDMT both suppress the electrical conduction relative to that in BPD.
authors.affiliation: Department of Condensed Matter Physics, Weizmann Institute of Science, 76100 Rehovot, Israel.
authors.forename: Tali
authors.initials: T
authors.lastname: Dadosh
authors.forename: Yoav
authors.initials: Y
authors.lastname: Gordin
authors.forename: Roman
authors.initials: R
authors.lastname: Krahne
authors.forename: Ilya
authors.initials: I
authors.lastname: Khivrich
authors.forename: Diana
authors.initials: D
authors.lastname: Mahalu
authors.forename: Veronica
authors.initials: V
authors.lastname: Frydman
authors.forename: Joseph
authors.initials: J
authors.lastname: Sperling
authors.forename: Amir
authors.initials: A
authors.lastname: Yacoby
authors.forename: Israel
authors.initials: I
authors.lastname: Bar-Joseph