Fano Resonances in Nanoshell Clusters Deposited on a Multilayer Substrate of -SiC/SiO2/Si to Design High-Quality Plasmonic Sensors

We numerically demonstrate high quality excitation, localization, and hybridization of plasmon resonant modes in an antisymmetric eight-member nanoshell oligomer (octamer) consisting of gold (Au) nanoshells deposited on a multilayer substrate composed of β-SiC/SiO₂/Si layers. Using the geometrical tunability of nanoshells, we analyze excitation and interference of sub- and superradiant plasmon modes and present scattering cross-sectional spectra. It is shown that multilayer substrate plays a fundamental role in confinement of optical power in the nanoshell octamer, and results in the formation of a pronounced Fano minimum. A maximum value of ~0.992 for the confinement factor is achieved in the proposed structure by optimizing the substrate thickness. To demonstrate the possibility of practical applications, we immerse the structure in liquids with different refractive indices, and observe how the Fano dip shifts. This method allows the calculation of figure of merit (FoM) which is plasmon resonance variations (ΔE eV) over the refractive perturbations (n) as 22.25 for the proposed nanocomplex. This study would make the utilization of compact multilayer configurations composed of nanoparticle aggregates possible to design high-precision, high-sensitivity (bio) chemical sensors.