Tailoring a periodic metal nanoantenna array using low cost template-assisted lithography

Recently, great effort has been invested into nanofabrication approaches that allow fast, reproducible and parallel surface patterning over a large area at the nanoscale. Here, a simple and reproducible approach for the fabrication of a large area highly ordered array of metal nanostructures by nanosphere lithography (NSL) is presented. Based on the self-assembly of close-packed polystyrene (PS) particles, at the air/water interface, this cost-effective approach enables the fabrication of a large-area and transferrable colloidal mask with a high quality crystal-like structure. An interesting tool based on optical diffraction for non-invasive inspection of the monolayer quality to perform in situ monitoring of the colloid packing at the air/water interface before deposition onto solid substrates was developed. Exploiting the interstitial geometry of the colloidal mask, a periodic array of plasmonic nanostructures was easily prepared. Tailoring the optical response of metal nanoparticle assemblies by controlling their morphology to route and manipulate light at the nanoscale is a key topic in the field of nano-optics; to this aim, exploitation of a low-cost nanofabrication technique, allowing a dynamic tunability either in morphology and periodicity arrangement, can be of remarkable added value in a cost-effectiveness evaluation. Here, the versatility of the NSL technique, coupled to a proper annealing post-processing is demonstrated to meet the above needs, allowing parallel surface patterning of large area metal assemblies in a hexagonal periodic configuration and morphology tuning from three dimensional nanoprisms to zero dimensional nanodot profiles. Related optical properties were monitored by UV-vis spectroscopy investigations and compared with proper theoretical analysis and numerical simulation.