A combined top-down and bottom-up approach for precise placement of metal nanoparticles on silicon

A combined top-down and bottom-up approach was used for precise placement of metal nanoparticles on silicon substrates. The study used laser interference lithography (LIL) technique, to open windows on a silicon wafer with a silicon oxide mask. Inverted pyramids were obtained at the window region, by etching the silicon wafer in KOH under the top-down approach. The bottom-up approach involved the evaporation of a gold (Au) layer on the whole silicon wafer and annealing at elevated temperature. The Au inside the inverted pyramids was coarsened and formed Au dots inside them. The results show that the diameter of the metal nanoparticles can be tuned more effectively, by changing the Au layer thickness, along with the annealing temperature.