title: C60 chain phases on ZnPc/Ag(111) surfaces: Supramolecular organization driven by competing interactions.
abstract: Serpentine chain C60 phases were observed in scanning tunneling microscopy (STM) images of C60 layers on zinc phthalocyanine (ZnPc) or pentacene covered Ag(111) and Au(111) surfaces. This low-density, quasi-one-dimensional organization contrasts starkly with the close-packed hexagonal phases observed for C60 layers on bare metal substrates. STM was employed to perform a detailed investigation of these chain structures for C60/ZnPc/Ag(111) heterolayers. Motivated by the similarity of these chain phases, and the chain and stripe organization occurring in dipole-fluid systems, we investigated a model based on competing van der Waals attractions and electrostatic repulsions between C60 molecules as an explanation for the driving force behind these monolayer phases. Density functional theory (DFT) calculations revealed significant charge transfer to C60 from the Ag(111) substrate, through the intervening ZnPc layer, inducing electrostatic interactions between C60 molecules. Molecular dynamics simulations performed with attractive van der Waals interactions plus repulsive dipole-dipole interactions reproduced the C60 chain phases with dipole magnitudes consistent with DFT calculations.
authors.affiliation: Department of Chemistry and Biochemistry, University of Maryland at College Park, College Park, Maryland 20742, USA.
authors.forename: W
authors.initials: W
authors.lastname: Jin
authors.affiliation: Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA.
authors.forename: Q
authors.initials: Q
authors.lastname: Liu
authors.affiliation: Department of Physics, North Carolina State University, Raleigh, North Carolina 27695, USA.
authors.forename: D B
authors.initials: DB
authors.lastname: Dougherty
authors.affiliation: Department of Physics, University of Maryland at College Park, College Park, Maryland 20742, USA.
authors.forename: W G
authors.initials: WG
authors.lastname: Cullen
authors.affiliation: Department of Chemistry and Biochemistry, University of Maryland at College Park, College Park, Maryland 20742, USA.
authors.forename: J E
authors.initials: JE
authors.lastname: Reutt-Robey
authors.affiliation: Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA.
authors.forename: J
authors.initials: J
authors.lastname: Weeks
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, Maryland 20878-8372, USA.
authors.forename: S W
authors.initials: SW
authors.lastname: Robey