Ordering of diblock PS-PBMA thin films: An X-ray reflectivity study

Abstract

X-ray specular reflectivity studies of symmetric PS/PBMA (polystyrene/polybutylmethacrylate) diblock copolymer thin-films deposited on silicon substrates are presented. Films of different thickness in the disordered state are annealed for times ranging from a few seconds to several hours. The annealing process produces a lamellar ordering throughout the film which in turn, leads to the formation of holes or islands at the surface of the film. By measuring the specular reflectivity of such films, it is possible to access the bottom (from the interface silicon–thin film to the lowest part of the film) and the top (from the interface silicon–thin film to the highest part of the film) thickness of the films. These two thicknesses which are very accurately measured give us information about the kinetics of ordering and the results are analyzed in terms of spinodal decomposition versus nucleation of the domains.