ACS Nano http://doi.org/wf3 (2014)
Block copolymers that have the tendency to self-assemble into nanostructures with a spatial resolution of less than 10 nm are of potential value in the semiconductor industry. To induce self-assembly, thin films of these block copolymers need to be exposed to solvent vapours that promote their swelling and formation into nanostructures. However, this step is incompatible with the established fabrication procedures of the semiconductor industry and researchers are working to find a more viable approach. Yeon Sik Jung and co-workers now report a protocol to create controlled morphologies of block copolymers in the sub-20-nm regime without the need to expose the polymers to vapours.
The researchers — who are based at KAIST and the R&D Center for Hybrid Interface Materials in Korea — simply immerse a block copolymer film into a mixture of two liquids, one of which promotes swelling and nanostructuring. By changing the relative proportions of the two solvents, the temperature and the exposure time, the researchers can controllably induce the formation of spheres, cylinders or lamellae. Furthermore, on immersing in a third solvent, the team could form unusual core–shell nanostructures by direct self-assembly.