Perpendicular Domain Orientation of Poly(styrene-block-methylmethacrylate (PS-b-PMMA) Thin Films Produced on Zinc Oxide Nanoparticle Layer

Perpendicular di-block copolymer domains are produced when poly(styrene-block-methylmethacrylate (PS-b-PMMA) is spun onto a disordered layer of zinc oxide nanoparticles, followed by thermal annealing in vacuum. The ZnO layer creates a rough surface on the silicon substrate, inducing vertical cylinders of PMMA. The subsequent development of a PS template is illustrated. The wet etching process removed the vertically oriented PMMA nanodomains in the PS matrix. The morphology of the PS mask showed ordered nanopores with diameters around 20 nm. The effect of surface roughness and di-block film thickness on forming perpendicular cylindrical domains of PS-b-PMMA is analyzed. For a typical thickness of PS-b-PMMA film around 33 nm, a specific surface roughness parameter of 0.07 is obtained. These results are compared with other reports on this topic.