Solvent dependence of the evolution of the surface morphology of thin asymmetric diblock copolymer films

The evolution of surface morphology of thin films of asymmetric diblock copolymers with spherical microdomains was studied using atomic force microscopy (AFM). The investigated polymer was poly(styrene-block-2-ferrocenylethyl methacrylate) (PS-b-FEMA), and the molecular weight ratio of PS and FEMA blocks was 7:1. Different solvents were used for film preparation to investigate the solvent influence to surface topography and evolution of the islands. It was found that the effects of solvent used persist after annealing and that the films prepared from different solvents show markedly different surface topographies. Furthermore, the solvent used influences the mechanical adhesion of the film to the substrate, and thusly affects the annealing temperature, which would cause delamination of the film from the substrate. Finally, some recommendations are given on solvent choice and film preparation in order to improve surface quality of the films, which is necessary for successful pattern transfer over a large area. (C) 2004 Elsevier B.V. All rights reserved.