Hemispherical arrays of colloidal crystals fabricated by transfer printing

The self-assembly of colloidal spheres is an effective strategy for producing nanopatterns. To use colloidal crystals in lithographic applications, the key challenge is to fabricate a monolayer of colloidal crystals uniformly over a large area. A simple and effective method for fabricating a colloidal crystals monolayer from a 3D colloidal crystal is described. The top layer of a surface-etched 3D colloidal crystal is picked up on a PDMS stamp, and by simply heating the receiving substrate, the polymeric colloidal crystal can be easily transferred to many types of substrates, including curved or flexible materials, without utilizing a glue layer. Moreover, the colloidal spheres are deformed to hemispheres during the transfer process, which is a suitable form of a lithographic mask for both dry and wet etching processes. An array of silicon nanocones and gold dots is demonstrated by pattern transfer from an array of hemispherical polymeric particles. In addition, it is also shown that the transferred hemispherical array has good antireflective properties.