title: Observation of long-range orientational order in monolayers of polydisperse colloids.
abstract: Polydisperse amorphous-silicon colloidal particles ranging from approximately 10 to 140 nm in diameter were evaporated onto carbon substrates. The particles formed close-packed monolayers in which each particle had 6-fold nearest-neighbor coordination characteristic of a hexagonal lattice yet completely lacked positional order. Orientational correlation functions were calculated for the particles and found to be constant throughout the aggregate, indicating the occurrence of long-range orientational order. Computer simulations revealed that the structural organization in this system resulted from capillary immersion forces that lead to a size separation as the particles deposit from the evaporating solvent onto the substrate.
authors.affiliation: Department of Chemical Engineering, Texas Materials Institute, Center for Nano- and Molecular Science and Technology, 1 University Station C0400, The University of Texas, Austin, TX 78712-1062, USA.
authors.forename: Brooks D
authors.initials: BD
authors.lastname: Rabideau
authors.forename: Lindsay E
authors.initials: LE
authors.lastname: Pell
authors.forename: Roger T
authors.initials: RT
authors.lastname: Bonnecaze
authors.forename: Brian A
authors.initials: BA
authors.lastname: Korgel