Tailoring Plasmon Resonances in Aluminium Nanoparticle Arrays Fabricated Using Anodic Aluminium Oxide

Aluminium (Al) nanoparticles (NPs) over a 1.2-cm2-size area are fabricated using nanoporous anodic aluminium oxide as shadow masks. With this technique, plasmon response of Al NP arrays with different out-of-plane height is investigated. The dipolar-localized surface plasmon resonances (LSPRs) peak of Al NP arrays is blueshifted and then redshifted slightly with an increase in particle height because of interparticle interactions. Moreover, a novel method is demonstrated to reduce the size of Al particle via removing the oxide shell by wet chemical etching and taking advantage of the rapid oxidization of the metal core upon exposure to atmosphere. Three kinds of acid solutions (mixture of H3PO4 and H2CrO4, H3PO4, and H2SO4) are demonstrated as effective etchants. By adjusting the etching conditions, the blueshift of LSPRs can be controlled precisely. Dipolar LSPR is obtained at wavelength down to 234 nm (5.3 eV), among the shortest ones ever observed in patterned Al NP arrays.