From disk to ring: Aspect ratio control of the magnetoplasmonic response in Au/Co/Au nanostructures fabricated by hole-mask colloidal lithography

Morphology tuning of a series of Au/Co/Au nanostructures which gradually evolve from disk to ring allows controlling their optical and magneto-optical spectral responses in the visible and near infrared ranges. This is achieved by the combined use of hole mask colloidal lithography with off-normal deposition and substrate rotation. The morphological parameters responsible for this control, the disk/ring outer diameter and height, are determined by the off-normal deposition angle and the amount of deposited material, respectively. The single dipolar symmetric resonance mode in nanodisk splits into two characteristics, low (symmetric) and high energy (antisymmetric) ring modes. The ring's high energy mode, determined by the rings' section, is basically independent of the deposition angle, while the low energy symmetric mode is basically controlled by the outer diameter/height aspect ratio for both disk-like and ring structures, and therefore allowing a fine tuning of the wavelength position of this resonance. (C) 2015 AIP Publishing LLC.