Chain length and temperature dependence of alkanedithiol molecular conductance under ultra high vacuum

Pires, Ellis, MacDonald, John Emyr ORCID: https://orcid.org/0000-0001-5504-1692 and Elliott, Martin ORCID: https://orcid.org/0000-0002-9254-9898 2013. Chain length and temperature dependence of alkanedithiol molecular conductance under ultra high vacuum. Nanoscale 5 (19) , pp. 9397-9403. 10.1039/c3nr03682k

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Abstract

We report scanning tunnelling microscope (STM) measurements of the single molecule conductance of α,ω-alkanedithiols for a large range of molecular chain lengths (N = 3–10) and temperatures (180–390 K) under ultra high vacuum. Two STM-based measurement techniques were employed on molecules trapped between tip and substrate: (i) the well established current-distance or I(z) technique and (ii) a new I(V,z) technique in which the current–voltage characteristics are determined as the tip-substrate distance z is varied. Low, medium, and high conductance groups were observed for each molecular length, which were temperature independent over the range examined, consistent with off-resonance tunnelling. For N > 4 the current–voltage characteristics and conductance trend with chain length is well described using a simple rectangular tunnel barrier model with parameters in excellent agreement with previously reported values. However, both 1,3-propanedithiol (N = 3) and 1,4-butanedithiol (N = 4) show an anomalous behaviour which is qualitatively similar to, but much less pronounced than, that reported by Haiss et al. (Phys. Chem. Chem. Phys., 2009, 11, 10831) for measurements performed under air and nitrogen gas.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Physics and Astronomy
Subjects:	Q Science > QC Physics T Technology > TK Electrical engineering. Electronics Nuclear engineering
Publisher:	RSC Publishing
ISSN:	2040-3364
Last Modified:	12 Dec 2022 08:43
URI:	https://orca.cardiff.ac.uk/id/eprint/57448

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