Large area ordered lateral patterns in confined polymer thin films

The thermal stability of a model system consisting of a polymer film on a Si substrate capped by a thin metal layer has been investigated. When the model system is heated to a sufficiently high temperature characteristic surface wrinkling structures are formed with well defined periodicity over large areas. It is suggested that this wave-like surface morphology is driven by the thermal expansion coefficient mismatch of the different layers. A mechanism based on bending of a thin stiff surface on a thin elastic medium has been adopted to predict the pattern periodicity which gives satisfactory results with the experimental values.