Surface plasmon resonance tuning of silver nanoparticle array produced by nanosphere lithography through ion etching and thermal annealing.

It was demonstrated that size of the Ag nanoparticles array fabricated by nanosphere lithography (NSL) can be changed as needed by reactive ion etching (RIE) of the self-assembled polystyrene (PS) nanosphere template and post-annealing of the Ag particle array. A macroscopic 2D array of ordered Ag nanoparticles stretching over an area greater than 1 cm2 was achieved using a modified nanosphere lithography method. The wavelength corresponding to the extinction maximum of the surface plasmon resonance (SPR) from the Ag nanoparticle array was systematically tuned by RIE of the PS template. Additional tuning of SPR was achieved by post-annealing the Ag nanoparticles which induced shape-changes in the Ag nanoparticles. We demonstrated that SPR can be tuned over the entire visible spectrum by RIE of the PS mask and thermal annealing, which can be potentially used to display localized SPR spectrum (hence, different color) throughout the visible range.