2014 Volume 27 Issue 4 Pages 435-440
A photochemical process for transfer printing patterns formed by block copolymer thin films is described here. An unpatterned, transparent substrate coated in liquid conformal layer is pressed to an epitaxially aligned block copolymer thin film. Irradiation through the sample stack by UV light drives a benzophenone-mediated grafting reaction which covalently bonds the top surface of the block copolymer film to the photopolymerized conformal layer. Separation of the sample stack recovers the original guiding pattern as well a new chemically patterned substrate replicated from the original pattern. Using a single lithographically directed chemical pattern, 10 replicas are generated, each possessing 28 nm periodicity, perpendicularly oriented microdomains, and long-range epitaxial alignment.