title: Cooperative Molecular Behavior Enhances the Thermal Conductance of Binary Self-Assembled Monolayer Junctions.
abstract: The effect of the local molecular environment on thermal transport through organic-inorganic heterojunctions is investigated using binary self-assembled monolayer (SAM) junctions built from a mixture of alkanethiol and alkanedithiol species sandwiched between gold leads. Thermoreflectance measurements and molecular dynamics simulations demonstrate that the thermal conductances of the binary SAM junctions vary with molecular composition and are greater than predictions of a parallel resistance model. The enhancement results from increased thermal transport through the alkanethiols, whose terminal methyl groups are confined by the anchored alkanedithiols. This confinement effect extends over length scales that are more than twice the range of the van der Waals interactions between molecules and are commensurate to the sizes of experimentally observed molecular domains. Conversely, for a partially packed (i.e., submonolayer) alkanedithiol unary SAM, increasing the molecular packing density decreases the per molecule thermal conductance. This finding indicates that thermal transport measurements of SAMs cannot be used to predict the thermal transport properties of single molecules.
authors.affiliation: Department of Mechanical Engineering, Carnegie Mellon University , 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213, United States.
authors.forename: Shubhaditya
authors.identifier: 0000-0001-9342-7975
authors.initials: S
authors.lastname: Majumdar
authors.affiliation: Department of Mechanical Engineering, Carnegie Mellon University , 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213, United States.|Department of Materials Science and Engineering, Carnegie Mellon University , 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213, United States.
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Malen
authors.affiliation: Department of Mechanical Engineering, Carnegie Mellon University , 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213, United States.|Department of Materials Science and Engineering, Carnegie Mellon University , 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213, United States.
authors.forename: Alan J H
authors.initials: AJ
authors.lastname: McGaughey
keywords: Nanoscale; binary monolayers; molecular dynamics; molecular junctions; thermal transport; thermoreflectance