Combinatorial materials science for polymer thin-film dewetting

Combinatorial methods involving data collection in multiparameter space all ow a rapid identification of measured property trends as a function of syst em parameters. The technique has been applied with success to pharmaceutica l, inorganic and organic materials synthesis, but not significantly to meas urements of polymeric films and coatings. We demonstrate the use of 2-D com binatorial libraries to investigate thin-film dewetting. We have prepared l ibraries of thin films of polystyrene on silicon substrates containing orth ogonal, continuous variations of thickness (h), and temperature (T) that re present about 1200 practical state points per library. The libraries were s creened for dewetting behavior using automated optical microscopy. Dewettin g trends were visibly apparent on the libraries, and a comprehensive map of the T, h, and time (t) dependence was generated in a few hours. The combin atorial libraries, spanning a large T, h, and t range, not only reproduced known dewetting structures and phenomena but also enabled a novel T, h supe rposition of the heterogeneous nucleated hole dewetting kinetics. We observ ed three hole nucleation regimes as a function of thickness: heterogeneousl y nucleated holes (h > 55 nm), a crossover regime where both heterogeneous and capillary instability nucleation compete (33 nm < h < 55 nm), and a reg ime of holes nucleated by capillary instability (16 nm < h < 33 nm).