Morphologies of discontinuous gold films on amorphous polymer substrates

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Abstract
Transmission electron microscopy was used to analyze the effects of annealing treatments on the morphologies of discontinuous gold films evaporated onto polystyrene or poly(2-vinylpyridine) substrates. For polystyrene substrates the average size of discrete gold particles increases significantly during a long-term annealing treatment at 179 °C. The size distribution is well approximated by a log normal distribution function, consistent with a coalescence mechanism for particle growth. The fluid character of the polymer substrates at the annealing temperature of interest allows us to control this coalescence rate, thereby providing a unique method for controlling the microstructure of discontinuous metal films. Cross-sectional transmission electron microscopy showed that the coalescence rate for gold particles in a poly(2-vinylpyridine) matrix is much less than the coalescence rate for gold particles in a polystyrene matrix, indicating that polymer/metal interactions play an important role in the determination of the coalescence rate.