In situ characterization of block copolymer ordering on chemically nanopatterned surfaces by time-resolved small angle x-ray scattering
Schematic of the directed assembly process on chemically nanopatterned substrates. A PS brush layer is grafted to the substrate, which is then coated with a photoresist. The photoresist is patterned using advanced lithography and etched, thereby transferring the pattern to the PS brush. A block copolymer film is spin coated onto the chemically patterned substrate and annealed, resulting in the assembled block copolymer.
Top-down SEM images of block copolymer films on chemically patterned surfaces with their magnified Fourier transforms. The numbers denote annealing times in minutes. The scale bar is in length.
(a) SAXS intensity vs for various annealing times. Intensity is given in arbitrary units. (b) Fourier intensity vs for the SEM images shown in Fig. 2. T max is the highest temperature the sample reached at the time the measurement was taken.
Schematic of block copolymer film cross section during annealing based on the results of Edwards et al. The PS and PMMA domains are dark gray (red online) and black (blue online), respectively, and the chemical surface pattern is light gray (light blue online) and medium gray (orange online). (a) Initial state of block copolymer film after spin coating. (b) After a short annealing time each block copolymer block wets the patterned region with a similar surface energy and the opposite block is forced to be directly above that region. (c) Substrate pattern order propagates through the film, leaving bridge structures near the free surface. (d) Final equilibrium morphology of lamellae assembled on the striped chemical pattern.
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