Tuneability and optimum functionality of plasmonic transparent conducting oxide-Ag core-shell nanostructures

Abstract

Tunning localized surface plasmon resonance (LSPR) in transparent conducting oxides (TCO) has a great impact on various LSPR-based technologies. In addition to the commonly reported mechanisms used for tunning LSPR in TCOs (e.g., size, shape, carrier density modifications via intrinsic and extrinsic doping), integrating them in core-shell structures provides an additional degree of freedom to expand its tunability, enhance its functionality, and widen its versatility through application-oriented core-shell geometrical optimization. In this work, we explore the tuneability and functionality of two TCO nanostructures; indium doped tin oxide (ITO) and gallium doped zinc oxide (GZO) encapsulated with silver shell within the extended theoretical Mie theory formalism. The effect of core and shell sizes on LSPR peak position and line width as well as absorption and scattering coefficients is numerically investigated. Simulations showed that LSPRs of ITO-Ag and GZO-Ag core-shell nanostructures have great tunning capabilities, spanning from VIS to IR spectral range including therapeutic window of human tissue and essential solar energy spectrum. Potential functionality as refractive index sensor (RIS) and solar energy absorber (SEA) are examined using appropriate figure of merits $\left(\mathrm{FoM}\right)$. Simulations indicate that a geometrically optimized core-shell architecture with exceptional $\mathrm{FoMs}$ for RIS and SEA can be realized. Contrary to carrier density manipulation, integrating TCO cores to metallic shells proves to be an effective approach to enhance tunability and optimize functionality for high performance TCO-based plasmonic devices, with minimum impact on the inherited physical and chemical properties of the used TCO-core materials.