Mixed-morphology and mixed-orientation block copolymer bilayers
Block copolymers have attracted considerable attention due to their ability to self-assemble into highly regular structures, spanning length scales from several nanometers to over 100 nm. Block copolymers confined in thin films have been extensively utilized as soft templates for nanofabrication, but most applications have been restricted to single-layer templates with smectic and hexagonal symmetries. Here we show that a multi-step approach that includes shear alignment, thin film lift-off, and stacking can access novel three-dimensional block copolymer structures with long-range order and mixed symmetries. This technique allows control over the long-range order and also expands the range of nanolithographic templates accessible through guided self-assembly.