Surface plasmon resonances and plasmon hybridization in compositional Al/Al2O3/SiO2 nanorings at the UV spectrum to the near infrared region (NIR)

In this study, we have investigated the optical properties and spectral response of an isolated aluminum nanoring in pure and compositional regimes. The effects of geometrical and chemical modifications regarding examined Al nanoparticle have been studied theoretically and numerically using a finite-difference time-domain (FDTD) method. Changing the structural sizes of the pure Al nanoring, modifications in the thickness of covering oxide layer, and utilizing various substrates with different permittivities (epsilon) have been considered as the key factors which have dramatic influences on the scattering efficiency of the structure. Considering nanoring strategic structural versatility, the peak of scattering intensity can be adjusted and shifted to the desired spectrum, and this opportunity allows us to red-shift the dipolar plasmon resonance extreme from the UV to the visible and near infrared region (NIR) efficiently. Utilizing Al nanoring with appropriate geometrical sizes and the oxide layer thickness of 48% and glass substrate to design a plasmonic dimer nanostructure, we investigated the quality of plasmon resonance peak shifting along the wavelength variations (from UV to NIR). Considering studied nanoparticles in dimer regime (composed of Al/Al2O3/SiO2), we measured the LSPR sensitivity of the structure while the configuration is immersed in dielectric liquid substances. Using different materials with different refractive indices as a surrounding medium, we plotted a linear figure of merit (FoM=5.9) for the configuration to quantify the LSPR sensitivity. It is shown that proposed nanostructure has a strong potential to exploit in designing CMOS-compatible plasmonic devices, localized surface plasmon resonance (LSPR) sensing and biochemical sensing nanostructures, and SERS applications. (C) 2014 Elsevier Ltd. All rights reserved.