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.

Single-molecule transport in three-terminal devices

“…Another three-terminal approach was recently reported by Dadosh et al [23]. Their method is based on synthesizing in solution a dimer structure consisting of two colloidal gold particles connected by a dithiolated molecule.…”

Electron transport through correlated molecules computed using the time-independent Wigner function: Two critical tests

“…1,2,3 No consensus has been reached so far whether the discrepancies are to be attributed to uncontrollable experimental factors (compare measurements on same systems in Refs. 4,5,6,7) or inadequate theoretical frameworks.…”

Amine-linked single-molecule circuits: systematic trends across molecular families

“…This may be attributable to intrinsic changes in electronic coupling through the thiol link for different local link configurations [3]. Experiments are performed using diverse platforms to probe either the conductance of one or a few molecules forming a circuit [4][5][6][7][8][9][10][11][12][13][14] or to probe a small patch of molecules forming an interface in an ensemble measurement [15][16][17]. While progress has been made in comparing different approaches [18], significant puzzles remain, for instance the substantial differences that have been observed between ensemble and single molecule measurements for the same species [19].…”