POLYMER THIN-FILMS ON PATTERNED SI SURFACES

The propagation of roughness from a patterned silicon surface by polym er thin films was measured as a function of film thickness, time, and surface interaction using atomic force microscopy and synchrotron X-ra y reflection. In the presence of an interacting surface, the decay len gth of the surface modulation was much longer than that observed in si mple liquids. By measuring the time dependence of the surface corrugat ion amplitude, we were able to extract a surface diffusion coefficient by applying a modified version of the Mullins theory for surface diff usion in crystalline solids. The measured diffusion coefficients were an order of magnitude smaller than in the bulk, and scaled as 1/M-3/2, in agreement with previous SIMS results. The results are interpreted in terms of surface interactions confining polymer chains over distanc es larger than the radii of gyration.