• Wernecke, J.; Okuda, H.; Ogawa, H.; Siewert, F.; Krumrey, M.: Depth-Dependent Structural Changes in PS-b-P2VP Thin Films Induced by Annealing. Macromolecules 47 (2014), p. 5719-5727

10.1021/ma500642d

Abstract:
GISAXS measurements with scattering contrast matching at the silicon K-edge were performed to obtain depthresolved information on structural changes in as-spun and annealed PS-b-P2VP thin films on silicon substrate. Depthsensitive GISAXS measurements of the as-spun film revealed a vertically oriented fingerprint-like lamellar structure with a microphase separation distance of 59 nm throughout the entire film. The annealed film showed a significantly reduced ordering at the surface to a depth of about 30 nm, while the order is preserved toward the substrate interface. At the same time, no significant transition to horizontal ordering was observed after 2 h of annealing at 105 °C. We conclude that the transition process from vertical to horizontal ordering is incomplete after the annealing time and remains in a frozen state at room temperature. Moreover, the transition starts as a disorder increase at the top of the film, which indicates a higher mobility of the coalescing microdomains at the surface.