Tailoring periodic metal nanoantennas array by template-assisted low cost lithography
Recently, a very large effort has been invested into nanofabrication approaches allowing fast, reproducible and parallel surface patterning at the large area nanoscale. Here, a simple and reproducible approach for the fabrication of large area highly ordered array of metal nanostructures by nano-sphere lithography (NSL) is presented. Based on the self-assembling of close-packed polystyrene (PS) particles, at air/water interface, this cost-effective approach enables the fabrication of large–area and transferrable colloidal mask with a high quality crystal-like structure. An interesting tool based on optical diffraction for non-invasive inspections of the monolayer quality to perform an in-situ monitoring of colloid packing at the air/water interface before the deposition onto solid substrates was developed. Exploiting the interstitial geometry of the colloidal mask, periodic array of plasmonic nanostructures can be 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 purpose, exploitation of a low-cost nanofabrication technique, allowing a dynamic tunability either in morphology and periodicity arrangement, can be a remarkable added value in a cost-effectiveness evaluation. Here, the versatility of NSL technique, coupled to a proper annealing post-processing is demonstrated to meet the above needs, allowing parallel surface patterning of large areas metal assemblies in hexagonal periodic configuration and a morphology tuning from three dimensional nano-prisms to zero dimensional nano-dots profiles. Related optical properties are monitored by UV-Vis spectroscopy investigations and compared with proper theoretical analysis and numerical simulation.