Readily tunable surface plasmon resonances in gold nanoring arrays fabricated using lateral electrodeposition

Generation and fine-tuning of surface plasmon resonances is a prerequstite for several established and emerging applications such as photovoltaics, photocatalysis, photothermal therapy, surface-enhanced spectroscopy, sensing, superlensing and lasing. We present a low-cost and scalable lateral electrodeposition method for fabrication of high aspect ratio gold nanoring arrays that exhibit multiple surface plasmon resonances in the visible to near-infrared region. Nickel disc arrays of 2 µm size were initially fabricated using maskless lithography and e-beam evaporation. Selective electrodeposition of gold on the lateral surfaces of nickel disc arrays was achieved using a 50 nm SiO₂ film as an insulating mask. Growing from miniscule 100 nm wide lateral surfaces of nickel discs, nanorings with height up to 1084 nm could be obtained with their thickness and aspect ratio governed by the duration of electrodeposition. Facile tuning of the number of plasmon resonances, their resonant wavelength and relative intensity is demonstrated with applications in plasmon mediated photocatalysis and surface-enhanced Raman scattering.