Background: A relatively narrow LSPR peak and a strong inter band transition ranging around 800 nm makes Al
strongly plasmonic active material. Usually, Al nanoparticles are preferred for UV-plasmonic as the SPR of small size Al
nanoparticles locates in deep UV-UV region of the optical spectrum. This paper focused on tuning the LSPR of Al
nanostructure towards infrared region by coating Au layer. The proposed structure has Au as outer layer which prevent the
further oxidation of Al nanostructure.
Methods: The Finite Difference Time Domain (FDTD) and Plasmon Hybridization Theory has been used to evaluated the
LSPR and field enhancement of single and dimer Al-Al2O3-Au MDM nanostructure.
Results: It is observed that the resonance mode show dependence on the thickness of Al2O3 layer and also on the
composition of nanostructure. The Au layered MDM nanostructure shows two peak of equal intensities simultaneously in
UV and visible region tuned to NIR region. The extinction spectra and electric field distribution profiles of dimer
nanoparticles are compared with monomer to reveal the extent of coupling. The dimer configuration shows higher field
enhancement ~107 at 1049 nm. By optimizing the thickness of dielectric layer the MDM nanostructure can be used over
Conclusion: The LSPR peak shows dependence on the thickness of dielectric layer and also on the composition of
nanostructure. It has been observed that optimization of size and thickness of dielectric layer can provide two peaks of equal
intensities in UV and Visible region which is advantageous for many applications. The electric field distribution profiles of
dimer MDM nanostructure enhanced the field by ~107 in visible and NIR region shows its potential towards SERS substrate.
The results of this study will provide valuable information for the optimization of LSPR of Al-Al2O3-Au MDM
nanostructure to have high field enhancement.