Adsorbed block copolymer nanolayers on solids

Directed self-assembly of block copolymers (BCP) has been used as an advanced lithography method. In this study, we aim to shed light onto the structures of BCP at the polymer melt-solid interface. Polystyrene-block-poly (4-vinylpyridine) (PS-b-P4VP) block copolymer was used. Spun-cast 32 nm PS-b-P4VP thick films on silicon substrates were (i) thermally annealed at high temperature above Tg of the polymers or (ii) solvent vapor annealing with chloroform (non-selective solvent) and subsequent 1-4, dioxane (selective solvent). Using atomic force microscopy (AFM), we found perpendicular hexagonally packed cylinders at the topmost surface of the resultant PS-b-P4VP films regardless of the annealing processing. In addition, to study the adsorbed layer structure, we rinsed the annealed films with toluene and characterized the morphologies and film structures using grazing incidence small-angle X-ray scattering, x-ray reflectivity and AFM. The details will be discussed.