Decoupling of diameter and pitch in nanostructure arrays made by colloidal self-assembly

This paper reports the fabrication of ordered nanostructure array using colloidal self-assembly. Colloidal lithography, also known as nanosphere lithography (NSL), has been extensively and exhaustively utilized to create various nanostructures with the limitation in the resulting morphology and array spacing. Especially, independent control over the individual nanostructure size and array pitch remains a challenge and is the subject of this paper. Here, we show three different methods that expand the type of the nanostructure array produced from NSL. First, the combined technique of NSL and metal-assisted chemical etching (MACE) is shown to generate vertically-aligned Si nanowire (SiNW) array with the unprecedented dimensional control. Second, a stretchable elastomer with transfer printing is utilized to control the pitch of the original NS arrays, and with a custom-designed radial stretcher, a hexagonal symmetry of the resulting nanostructures is conserved. An array of sparsely ordered silicon or quartz nanopillars is obtained along with metallic nanostructures on NSs as etch masks. Finally, a double lift-off method is introduced to create an array of metallic nanodots that are not conventionally realized using the NSL template.