Effect of Postdeposition Heat Treatment on the Nanoplasmonic Behavior of Glancing Angle-Deposited Silver Nanostructures

Postdeposition heat treatment-induced modifications of nanoplasmonic response in glancing angle-deposited (GLAD) Ag nanostructures are systematically investigated. The as-deposited GLAD Ag thin films are annealed at various temperatures namely 200, 250, 300, and 350 & DEG;C in air atmosphere. The reduction in localized surface plasmon resonance (LSPR) absorption peak width is detected with annealing. Morphological characterization of the as-deposited and annealed films reveals reduction in grain size and shape distributions responsible for narrowing of the LSPR peak width. The refractive index sensitivities of the as-deposited and annealed films are measured using an in-house-developed optical setup and figure of merit (FOM) of the sensors is also estimated. An increase in FOM of the sensors is observed upon annealing while sensitivity is found to be reduced. E-field profile surrounding the Ag nanoparticles is also simulated to explain the experimental observations on refractive index sensitivity of the films. The figure of merit (FOM) of plasmonic refractive index sensors is always limited by the width of extinction peak. Herein, postdeposition annealing of glancing angle-deposited silver nanostructures is utilized to improve FOM of the sensors. Although an increase in FOM is achieved, sensitivity is reduced with the annealing temperature.image & COPY; 2023 WILEY-VCH GmbH