Microellipsometric investigation of ordered plasmonic nanostructures

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This project is devoted to the investigation of ordered plasmonic nanostructures by angle-resolved extinction spectroscopy and imaging spectro-ellipsometry with high spatial resolution. Structures for these investigations are prepared by electron beam lithography. Cylindrical nanoparticles are arranged in ordered lattices on a spacer separating those particles from an additional metallic layer (so-called metal-insulator-metal (MIM) structures). Such a system has a variety of electromagnetic resonances, spectral and geometrical position of which may be tuned besides the used materials by the geometrical parameters of the constituting nanoparticles, the lattice parameters, and the thickness of the spacer. In contrast to random distributions of nanoparticles, the lattice form-factor should provide an additional channel to manage the response of such systems with the same filling fraction of nanoparticles but different kinds of lattices. The use of extinction and imaging ellipsometry at different angles of incidence will allow both longitudinal and transverse resonances of the system to be excited and separated, revealing individual, lattice, and cooperative resonances as well as providing not only amplitude but phase information. The latter will help to reveal different interactions in such systems. Raman spectra will be taken to reveal the local plasmonic near-field enhancement of the investigated structures, while subsequent etching of the spacer will help to evaluate the role of the gap modes. The additional options of the ellipsometer system to be used enable the combination with atomic force microscopy (AFM) to determine the real arrangement of nanoparticles in the lattice and its orientation. Such additional information can be very valuable in the analysis of plasmonic properties of these structures.