Monolayer colloidal mask with tunable interstice size for nanosphere lithography

Nanosphere lithography (NSL), which utilizes self-assembled monolayer colloidal crystal (MCC) as a mask to fabricate ordered nanostructures over large areas, is a high through-put and low-cost method. In this work, polystyrene (PS) MCC with tunable interstice size is prepared by a combination of self-assembly of PS nanospheres at the air-water interface and chemical vapor deposition (CVD) of siloxane polymers. Water vapor around the MCC reacts with the silicon tetrachloride (SiCl4) steam introduced by nitrogen carrier gas to form siloxane polymers. Consequently, it induces the formation of a siloxane polymers layer coating on the surface of each PS sphere, which results in the shrinkage of the interstice between neighboring PS spheres. In this way, the deformation of colloidal spheres during thermal annealing could be avoided. Accordingly, extra cracks arising from the constraint of spheres deformation on a rigid substrate are eliminated. Furthermore, the interstice size of the colloidal mask can be precisely controlled by manipulating the CVD conditions. In addition, the colloidal mask could be transferred onto any kind of substrates including rigid, flexible, flat, or curved solid substrates after CVD coating. The method provides a facile approach to the fabrication of interstice-size-tunable, high-quality colloidal masks for NSL application.