Effect Of Ga Implantation And Hole Geometry On Light Transmission Through Nanohole Arrays In Al And Mg

The study of plasmonic nanostructures in the ultraviolet (UV) is a relatively uncharted field because of the challenges in both engineering and materials science. In this work, two-dimensional periodic nanohole arrays in aluminium (Al) and magnesium (Mg) films were fabricated using gallium (Ga) focused ion beam. Optical transmission through the arrays was obtained in the UV-visible range for varying array periodicity. Transmission results show strong resonance transmission enhancement and suppression with corresponding red shift as the period increases and the presence of stationary waveguide modes. Comparing Al and Mg, Al hole arrays enable greater transmission than those of Mg. Numerical analysis was carried out through the finite-difference time-domain method, which showed far-field transmission consistent with experiments. The simulation model was constructed based on transmission electron microscopy of cross-sectioned samples to take into account tapered sidewall geometry and undercut into the substrate. Energy-dispersive X-ray spectroscopy was used to assess elemental composition, including oxidation and alloying. The effect of Ga implantation was qualitatively studied, which indicates that Ga implants inside the hole, with greater implantation concentration within Mg than within Al, and affects the transmission through both Al and Mg arrays.