Tuesday, 24 May 2005 - 4:10 PM

This presentation is part of: Surface and Interface Science II

Self-Organizing Aromate Films: Architecture and Domain Evolution

Janice Reutt-Robey, Bo Xu, Hui Li, Diane Evans, Chenggang Tao, and Ellen Williams. University of Maryland, College Park, MD

Nanophase structure impacts the charge- and energy-transfer processes that underlie all practical applications of ultrathin organic materials. We report the molecular architecture and domain mosaic of ultrathin aromate films, produced by physical vapor deposition on Ag(111). Adlayer structures for pure films of the N-heteroaromatic acids isonicotinic acid (INA) and 9-acridine-carboxylic-acid (ACA)) have common structural elements and notable differences. At coverages up to one monolayer, both ACA and INA form large 2-D islands based upon a head-to-tail H-bonding aromate network. At room temperature, these islands coexist with a molecular lattice gas, which is thermally quenched and imaged at 40 K. Orientational differences produce distinctive domain boundary structures: INA orientational domains are stabilized by tail-tail H-Bond fusion. Multilayer (1-5 ML) ACA films show a thickness-dependent reduction in domain size (from 100's nm to ~30 nm) in a mosaic pattern. The binary system, ACA+C60, was investigated as a model "donor-acceptor" organic film. These binary films show a complex multi-domain structure that is process dependent. At a particular compositional mixture, ACA and C60 spontaneously organize into a novel chiral phase, consisting of a net of widely spaced (2.6 nm) C60 and a net of chiral ACA trimers.

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