Perpendicular domains in poly(styrene-b-methyl methacrylate) block copolymer films on preferential surfaces

The morphology of poly(styrene-block-methyl methacrylate) films was studied as a function of film thickness by atomic force microscopy and field emission scanning electron microscopy. The obtained morphologies were strongly dependent on the film thickness. Five different thickness regimes could be identified. Perpendicular polymethyl methacrylate cylindrical domains were obtained on Si/native oxide substrates without applying external electric field or surface treatments (hydrogen passivation, functionalized random copolymers, or self-assembled monolayers). The orientation of the domains formed by microphase separation was verified by pattern-transfer using reactive ion etching.