Measurement of the conductance of single conjugated molecules

An Erratum to this article was published on 25 August 2005

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 conductors1,2: in such molecules, the orbitals are delocalized throughout the molecular backbone, with substantial weight on the sulphur–metal bonds1,2,3,4. However, their relatively small size, typically 1 nm, calls for innovative approaches to realize a functioning single-molecule device5,6,7,8,9,10,11. 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 molecule12,13, 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)14, 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.

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Figure 1: The molecules and colloidal structures under study.
Figure 2: Image and low-temperature differential conductance spectra of dimers.
Figure 3: Temporal fluctuations and temperature dependence of the dimer conductance.
Figure 4: The reproducibility of the conductance spectra measurements of different BPD dimers.

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Acknowledgements

This work was supported by the Minerva foundation. We thank R. Popovitz for assistance in obtaining the TEM image (Fig. 1f).

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Correspondence to Israel Bar-Joseph.

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Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.

Supplementary information

Supplementary Figure S1

Measurements of the conductance of single colloids shown in the Vds-Vg plane. (PDF 4836 kb)

Supplementary Figure S2

A comparison between the conductance spectra of a single colloid and a dimer. (PDF 1516 kb)

Supplementary Figures Legends

Text to accompany the above Supplementary Figures. (DOC 19 kb)

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Dadosh, T., Gordin, Y., Krahne, R. et al. Measurement of the conductance of single conjugated molecules. Nature 436, 677–680 (2005). https://doi.org/10.1038/nature03898

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