Investigation of Broadband Surface Plasmon Resonance of Dewetted Au Structures on TiO₂ by Aperture-Probe SNOM and FDTD Simulations

The surface plasmon resonance of dewetted Au structures on TiO₂ substrate using physical vapor deposition and post-annealing is investigated. In this work, we employ an aperture-probe scanning near-field optical microscope (SNOM) to study the plasmonic properties of dewetted Au structures and the influence of the size, shape, and interdistance of the dewetted structures on their plasmonic behavior. This investigation is corroborated by numerical calculations performed using finite-difference time-domain (FDTD) and atomic force microscopy (AFM) to provide a realistic and direct comparison with SNOM experiments. The near-field images obtained by both experiments and simulations reveal surface plasmon resonance around Au structures which are correlated to the broadband activity in the visible light region observed by UV-Vis spectrophotometry and photoluminescence. In addition, near-field enhancement is associated with the external quantum efficiency (EQE), which shows a multi-peak response after 570 nm due higher-order modes of plasmon resonance. This broadband improvement in the visible region obtained by controlled dewetting has potential use in large-scale solar energy applications. [Figure not available: see fulltext.]