Field Enhancement Around Al Nanostructures in the DUV–Visible Region

Abstract

Aluminium supports strong and tunable surface plasmon resonances in the deep ultraviolet (DUV)–visible–near infrared (NIR) region. We have used theoretical modelling based on finite difference time domain (FDTD) to study localized surface plasmon resonance (LSPR) and local field enhancement in isolated, dimer and multimer Al nanostructures. The spherical shape nanostructure shows a larger field enhancement in the DUV–UV region, whereas the anisotropic shape nanostructure shows a larger field enhancement with tunability in the peak wavelength towards the visible region. The extinction spectra and the electric field distribution profiles of interacting nanoparticles are compared with those of corresponding monomers to reveal the extent of plasmon coupling. The dimer configuration shows polarization-dependent higher field enhancement ~108 at 196 nm, whereas a multimer forming a rhombus shape nanostructure shows field enhancement ~107 at 411 nm. By optimizing size, interparticle separation and shape of the aluminium nanostructure, a larger field enhancement factor in the DUV–visible region can be achieved for sensitive surface-enhanced Raman scattering (SERS) detection of biomolecules.