Novel high-throughput and maskless photolithography to fabricate plasmonic molecules

Fabrication of nanostructures for applications such as plasmonics and metamaterials is typically low throughput, due to the required submicron feature sizes. Therefore, rapid production of optically engineered structures with low cost and large area is an enabling technology for many applications, such as light harvesting, solid state lighting, disposable biosensing, and metamaterials. Here, the authors propose a simple technique, based on microsphere nanolithography, to fabricate arrays of optical elements, or so-called plasmonic molecules, at about one third of exposure wavelength. This method is capable of producing many symmetric/asymmetric array of submicron arrangement of circles and is compatible with high-throughput nanomanufacturing schemes such as roll-to-roll production. The gap size between disks is precisely controllable by the angle of exposure. Here, the authors demonstrate the capabilities of this method in producing an array of complex plasmonic molecules over a large area. The periodicity of array and element's diameter can be tuned by microsphere size and exposure/develop time, respectively. Finite-difference time domain simulation agrees well with our experimental results and suggests that much smaller feature sizes can be achieved at shorter wavelengths.