Fabrication of nanopatterns using block copolymer and controlling surface morphology

This paper reports an approach for patterning substrates on the nanoscale using a block copolymer, polystyrene-b-polymethylmethacrylate (PS-b-PMMA), which forms cylindrical microdomains. The morphology of the polymer surface was strongly dependent on the thickness of the polymer layer. Spin coating the polymer solution onto the substrate followed by baking resulted in the self-assembly of the components of the polymer. Exposure to ultraviolet radiation degraded the PMMA chain, which could be removed by rinsing in acetic acid to give patterned holes. However, the small size of the hole limits the applications of the template. This problem was solved by sonicating the sample in different solutions in a series of steps to produce a fingerprint pattern or patterns containing PS cylindrical domains having large interstitial spaces with an average of >30 nm. The morphology of the polymer film surface was examined by atomic force microscopy (AFM) and scanning electron microscopy (SEM).