Physics – Condensed Matter – Mesoscale and Nanoscale Physics
Scientific paper
2008-02-05
New J. Phys. 10 (2008) 065008
Physics
Condensed Matter
Mesoscale and Nanoscale Physics
19 pages, 6 figures; v2: changed wrongly given HDA peak position in abstract to correct value, removed typing mistakes; v3: ad
Scientific paper
10.1088/1367-2630/10/6/065008
We have investigated electrical transport through the molecular model systems benzenedithiol, benzenediamine, hexanedithiol and hexanediamine. Conductance histograms under different experimental conditions indicate that measurements using mechanically controllable break junctions in vacuum are limited by the surface density of molecules at the contact. Hexanedithiol histograms typically exhibit a broad peak around 7 * 10^{-4} G_0. In contrast to recent results on STM-based break junctions in solution we find that the spread in single-molecule conductance is not reduced by amino anchoring groups. Histograms of hexanediamine exhibit a very wide peak around 4 * 10^{-4} G_0. For both benzenedithiol and benzenediamine we observe a large variability in low-bias conductance. We attribute these features to the slow breaking of the lithographic mechanically controllable break junctions and the absence of a solvent that may enable molecular readsorption after bond breaking. Nevertheless, we have been able to acquire reproducible current-voltage characteristics of benzenediamine and benzenedithiol using a statistical measurement approach. Benzenedithiol measurements yield a conductance gap of about 0.9 V at room temperature and 0.6 V at 77 K. In contrast, the current-voltage characteristics of benzenediamine-junctions typically display conductance gaps of about 0.9 V at both temperatures.
der Zant Herre S. J. van
Ding Dongsheng
Martin Carol A.
van Ruitenbeek Jan M.
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