Binary self-assembled monolayers: Apparent exponential dependence of resistance on average molecular length
article
We investigate the electrical transport through mixed self-assembled monolayers of alkanemonothiols and alkanedithiols in large-area molecular junctions. To disentangle the role of the molecular length and the interfacial composition, monothiol-monothiol, dithiol-dithiol, and monothiol-dithiol binary combinations are studied. In all cases, we find that the resistance of these mixed SAMs appears to depend exponentially on the average number of carbon atoms, thus resembling monocomponent SAMs, whose resistance is known to depend exponentially on molecular length. However, in monocomponent SAMs this behavior has a single-molecule tunneling origin, which is not directly relevant for mixtures. Furthermore, in certain mixed SAMs the resistance decreases with increasing average layer thickness (the case of monothiol-dithiol systems). We suggest an explanation for the observed dependence of the resistance in the mixed SAMs on their composition within an equivalent circuit model based on a simple assumption concerning their microdomain structure. The simulated dependence is non-exponential but leads to a good agreement between calculated and measured resistances with only two fit parameters. © 2011 Elsevier B.V. All rights reserved.
Topics
AlkanethiolsElectrical transportMixed monolayersMolecular junctionSelf-assemblyAlkanethiolsAverage molecularAverage numbersBinary combinationsBinary self-assembled monolayerCarbon atomsDithiolsElectrical transportEquivalent circuit modelExponential dependenceFit parametersInterfacial compositionLayer thicknessMicro-domain structuresMixed monolayersMixed SAMMixed self assembled monolayersMolecular junctionMolecular lengthMono-componentMonothiolSamsSingle-moleculeSelf assemblySelf assembled monolayers
TNO Identifier
461469
ISSN
15661199
Source
Organic Electronics: physics, materials, applications, 12(5), pp. 857-864.
Pages
857-864
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