The proper exploitation of the plasmon resonance typical of metallic nanoparticles can allow for the confinement of the electromagnetic field in nanometric volumes, thus creating the so called "hot spots". These nanometric volumes are characterized by high field, remarkably useful characteristic for a huge variety of applications in photonics and optics.
The most commonly employed plasmonic metals, Au and Ag, yield resonances only reaching up to the near-UV electromagnetic range, in fact stretching upwards the energy of plasmon resonances requires the use of different materials.
Deep-ultraviolet plasmon resonances were indeed predicted exploiting one of the cheapest and most abundant materials available on earth. Aluminium holds the promise of a broadly-tuneable plasmonic response, theoretically extending far into the deep-ultraviolet (DUV). Complex fabrication issues, including the strong Al reactivity, have however stood in the way of achieving this ultimate DUV response.
We report the successful realization of 2-dimensional arrays of ultrafine aluminium nanoparticles that exhibit a remarkable plasmonic response up to the DUV electromagnetic range. Careful nanofabrication allowed to maintain the mean NP size below 20 nm, preserving a purely-metallic core. These systems exhibit a striking high-energy plasmon resonance up to 6.8 eV photon energy, and preserve their DUV plasmon response when exposed to atmosphere [1,2]. These observations pave the way to the full exploitation of aluminium plasmonic tunability, hence extending the numerous applications of plasmonics to the high-energy side of the spectral range.