Nanopatterns Produced by Directed Self-Assembly in Block Copolymer Thin Films

Abstract

Block copolymers have fascinating capacities to spontaneously produce organized nanostructures, and, when shaped as thin films, chemically and topographically patterned surfaces. Once morphology is defined by the thermodynamics of the chosen block copolymer macromolecules, the type, extent, and orientation of the nanopattern obtained at the free surface of a thin film will depend on many parameters, which are now very well described in the abundant literature of the field: nanostructure period, film thickness, surface energies, type of substrate, deposition and annealing processes, to name a few. Thin films with hexagonally packed cylinders in perpendicular orientation presenting high degree of order and uniaxial symmetry are now produced with many systems, down to characteristic sizes below 20 nm, and are promising for several applications. Recent progress in copolymer synthesis, as well as in new processes, like gradient and zone processes, or addressable substrates, open many new opportunities for the design of ordered, complex and tunable patterns.