George, Christopher and Yoshida, Hidehiro and Goddard, William A., III and Jang, Seung Soon and Kim, Yong-Hoon (2008) Charge Transport through Polyene Self-Assembled Monolayers from Multiscale Computer Simulations. Journal of Physical Chemistry B, 112 (47). pp. 14888-14897. ISSN 1520-6106 http://resolver.caltech.edu/CaltechAUTHORS:GEOjpcb08
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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 βn = 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.
|Additional Information:||Copyright © 2008 American Chemical Society. Received: March 21, 2006; Revised Manuscript Received: July 9, 2008. Publication Date (Web): October 23, 2008. C.G. was supported primarily by the MRSEC Program of the National Science Foundation under Award No. DMR-0080065 (Caltech). S.S.J. and W.A.G. were supported by NSF CCF-0524490, MARCO FENA, and Intel Component Research. The computational facilities of the MSC were also supported by ONR-DURIP and ARO-DURIP. Y.-H.K. was supported by the Korea Research Foundation (Grant No. KRF-2007-331-C00077) and the Korea Science and Engineering Foundation (Grant No. 2008-02807). Most calculations were performed by using the supercomputing resource of the Korea Institute of Science and Technology (KISTI).|
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|Deposited On:||23 Dec 2008 00:26|
|Last Modified:||26 Dec 2012 10:40|
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