Guided phase separation of polymer blend thin films on ion beam-induced pre-patterned substrates

A technique for fabricating pre-pattern induced phase-separated polymer blend films is presented. The gold layer coated silicon substrates were bombarded with focused ion beams (FIB) to sputter away Au grains in the irradiated regions and expose silicon oxide surface underneath, thereby creating pre-patterns of relatively hydrophobic (Au)/hydrophilic (silicon oxide) regions. In the pre-patterned regions, the spin-coated films consisting of immiscible PS (polystyrene) and PtBA (poly-tert-butyl acrylate) blend exhibited phase separation induced by the underlying pre-patterns and formed two distinct ordered morphologies with periodicities much smaller than that of the pre-patterns. The influence of varying periodicities of the pre-patterned structures, blending ratios and spin-coating paramet ers on the resulting morphologies are presented.