(614a)  Quantitative Study of Temperature-Dependent Order in Thin Films of Cylindrical Morphology Block Copolymer

Mishra, V., University of California Santa Barbara
Kramer, E. J., Materials Research Lab

While equilibrium behavior of bulk block copolymer melts is relatively well understood, many new technological applications, especially templates for nanopatterning, require the block copolymer in the form of a thin film. Techniques such as graphoepitaxy have been successfully used to direct order in the arrangement of the microdomains, however the resultant structures are still not defect free. Disordering and defect generation in block copolymer systems at high temperatures is of significance to get a better understanding of the physics governing these systems, which can also direct efforts to minimize them. We have studied the smectic-nematic-isotropic transition in graphoepitaxially confined monolayers and bilayers of cylindrical morphology poly (styrene-b-2vinyl pyridine) diblock copolymer. Previous studies of melting phenomena in block copolymer thin films have relied on quantitative AFM studies alone. We have supplemented AFM studies with grazing incidence small angle X-ray diffraction which is a powerful tool to obtain sample information characteristic of large areas and is not limited to the surface, like most microscopy techniques. We find that the monolayer disorders at much lower temperatures than the bilayer, and we have also carried out diffraction peak lineshape analysis to quantify the decay of translational and orientational order with increasing temperature. The results have been interpreted in the context of the Toner?Nelson theory of melting for layered systems.