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Volume 131, 2006
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Thermal gating of the single molecule conductance of alkanedithiols

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The temperature dependence of the single molecule conductance (SMC) of α,ω-alkanedithiols has been investigated using a scanning tunnelling microscopy (STM) method. This is based on trapping molecules between a gold STM tip and a gold substrate and measuring directly the current across the molecule under different applied potentials. A pronounced temperature dependence of the conductance, which scales logarithmically with T−1, is observed in the temperature range between 293 and 353 K. It is proposed that the origin of this dependence is the change in distribution between molecular conformers rather than changes in either the conduction mechanism or the electronic structure of the molecule. For alkanedithiols the time averaged conformer distribution shifts to less elongated conformers at higher temperatures thus giving rise to higher conductance across the molecular bridges. This is analysed by first calculating energy differences between different conformers and then calculating their partition distribution. A simple tunnelling model is then used to calculate the temperature dependent conductance based on the conformer distribution. These findings demonstrate that charge transport through single organic molecules at ambient temperatures is a subtle and highly dynamic process that cannot be described by analysing only one molecular conformation corresponding to the lowest energy geometry of the molecule.

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Article information

26 May 2005
13 Jun 2005
First published
04 Oct 2005

Faraday Discuss., 2006,131, 253-264
Article type

Thermal gating of the single molecule conductance of alkanedithiols

W. Haiss, H. van Zalinge, D. Bethell, J. Ulstrup, D. J. Schiffrin and R. J. Nichols, Faraday Discuss., 2006, 131, 253
DOI: 10.1039/B507520N

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