Experimental study of the surface structure of diblock copolymer films using microscopy and x-ray scattering

Abstract

The surface structure of a model system was measured in real space by atomic force and optical microscopies, and compared with that obtained from measurements in reciprocal space by x‐ray reflectivity and off‐specular scattering at grazing incidence. Experiments were performed on films of symmetric diblock copolymers of polystyrene and polymethylmethacrylate, whose surfaces were covered by micrometer‐size islands or holes (domains) of uniform height. The correlation functions extracted from the images of the film surfaces show weak peaks in the real‐space domain distribution. The corresponding structures were also found in reciprocal space. The height of the domains obtained from the scattering measurements was found to be in excellent agreement with that obtained by atomic force microscopy. We developed a formalism using the kinematical approximation for the analysis of the x‐ray‐scattering measurements. We used a multilayer film model with roughness at each interface and relief domains at the surface. We extracted the domain–domain correlation functions for the x‐ray‐scattering analysis from the atomic force and optical microscopy images.