Nanosphere lithography

Nanosphere lithography (NSL) is an economical technique for generating single-layer hexagonally close packed or similar patterns of nanoscale features.

[3] Spin Coating and solvent evaporation methods are capable of producing large areas of particles, but with limited control over the layer homogeneity or thickness.

A lithographic mask can be promptly achieved via particle self-assembly, as previously described, whose pattern resolution is entirely dependent on the colloidal size that can be deposited in high-quality monolayer arrays.

[12] Moreover, the fabricated structures can be produced with a high accuracy on a large scale, as the method is not limited in terms of the deposition area, meaning that it offers the possibility to be adapted to mass production techniques such as roll-to-roll.

[13] The NSL method generally starts by the preparation of the patterning mask, comprising a self-assembled monolayer array of colloidal nano/micro-particles, followed by the nano/micro-structure production.

The variety of techniques that can be used for the colloidal array formation, as well as for the subsequent structure production, shows the high versatility of this method for implementation in various applications.

Polystyrene nanoparticle coating done with the Langmuir-Blodgett method
Polystyrene nanoparticle coating done with the Langmuir-Blodgett method
Illustration of the four main steps of a NSL process, depicting the sequence of: (a) the deposition of colloidal nano/micro-particles on a surface, which will act as mask; (b) reactive ion etching (RIE) for particle shaping, producing a non-close packed array; (c) material infiltration via physical deposition; (d) lift-off of the colloids leaving only the nano/micro-patterned material in between the particles. [ 11 ]