Nanofabricated concentric ring structures by templated self-assembly of a diblock copolymer.

The formation of well-controlled circular patterns on the nanoscale is important for the fabrication of a range of devices such as sensors, memories, lasers, transistors, and quantum devices. Concentric, smooth ring patterns with tunable dimensions have been formed from a cylinder-forming poly(styrene- b-dimethylsiloxane) (PS-PDMS) diblock copolymer under confinement in shallow circular trenches. The high etch selectivity between PS and PDMS facilitates pattern transfer, illustrated by the fabrication of arrays of ferromagnetic cobalt rings with a density of 1.1 x 10 (9)/cm (2). The effects of confinement diameter and commensurability on the diameter and period of the concentric rings are analyzed using a free energy model that includes interfacial, strain, and bending energies. This work provides a simple process for the fabrication of nanoscale circular patterns with very narrow line width using a much coarser-scale template, and may facilitate the miniaturization of a variety of microelectronic devices.