Direct etching at the nanoscale through nanoparticle-directed capillary condensation.
We report on a method to locally deliver at the nanoscale a chemical etchant in vapor phase by capillary condensation in a meniscus at a nanoparticle/substrate interface. The process is simple, scalable and does not require functionalization of the nanoparticles. Furthermore, it does not rely on any specific chemical properties of the materials other than the solution being aqueous and the wettability properties of the surfaces involved, which should enable its application to other materials and chemicals combinations. In particular, in this work we demonstrate the proposed process by periodically pattering a SiO2 layer using a self-assembled monolayer of polystyrene particles exposed to HF vapor. The patterned SiO2 layer is then used as a mask to etch a pattern of inverted nanopyramids in Si. The silicon nanopatterning has been demonstrated for particles sizes from 800 nm down to 100 nm, achieving pyramids with a size down to 50 nm for 100 nm nanoparticles.