Charge Transport through Polyene Self-Assembled Monolayers from Multiscale Computer Simulations

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We combine first-principles density-functional theory with matrix Green's function calculations to predict the structures and charge transport characteristics of self-assembled monolayers (SAMs) of four classes of systems in contact with Au(111) electrodes: conjugated polyene chains (n = 4, 8, 12, 16, and 30) thiolated at one or both ends and saturated alkane chains (n = 4, 8, 12, and 16) thiolated at one or both ends. For the polyene SAMs, we find no decay in the current as a function of chain length and conclude that these 1-3 nm long polyene SAMs act as metallic wires. We also find that the polyene-monothiolate leads to a contact resistance only 2.8 times higher than that for the polyene-dithiolate chains, indicating that the device conductance is dominated by the properties of the molecular connector with less importance in having a second molecule-electrode contact. For the alkane SAMs, we observe the normal exponential decay in the current as a function of the chain length with a decay constant of beta(n) = 0.82 for the alkane-monothiolate and 0.88 for the alkane-dithiolate. We find that the contact resistance for the alkane-monothiolate is 12.5 times higher than that for the alkane-dithiolate chains, reflecting the extra resistance due to the weak contact on the nonthiolated end. These contrasting charge transport characteristics of alkane and polyene SAMs and their contact dependence are explained in terms of the atomic projected density of states.
Publisher
AMER CHEMICAL SOC
Issue Date
2008-11
Language
English
Article Type
Article
Keywords

MOLECULAR-DYNAMICS SIMULATIONS; DENSITY-FUNCTIONAL THEORY; AU(111) SURFACES; NOBEL LECTURE; ALKANETHIOL MONOLAYERS; POLYACETYLENE; POLYMERS; SUPERLATTICE; ADSORPTION; RESISTANCE

Citation

JOURNAL OF PHYSICAL CHEMISTRY B, v.112, no.47, pp.14888 - 14897

ISSN
1520-6106
DOI
10.1021/jp061759l
URI
http://hdl.handle.net/10203/90643
Appears in Collection
EEW-Journal Papers(저널논문)
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