Hybridization of Electronic Bands for Extending Plasmonic Band by Alloyed Nanostructures

AbstractPlasmonic nanostructures have extensive applications in sensors and optoelectronic devices. Noble metals are the most suitable candidates for the construction of plasmons due to their high electrical conductivity and high plasmonic activities. However, silver is easy to get oxidized and is thus not suitable for plasmonic nanostructures with long-term stability. In contrast, gold is a most stable metal and more extensive employed in plasmon photonic structures. Nevertheless, plasmon band for gold starts from 2.38 eV to lower photon energies, ruling out the possible designs of plasmonic device in the blue spectrum. We solve this challenge by alloying gold and silver, which not only overcomes the oxidization problem of silver, but also extends largely the plasmonic band of gold to the blue spectrum. Using a volume ratio between gold and silver of 1:1, we achieved a blue shift of the plasmonic band edge to 3.1 eV, allowing construction of plasmons in the blue spectral band. This is found to be based on the realignment of the Fermi level between gold and silver in the alloyed nanoparticles. Furthermore, a practically applicable method is proposed here for the fabrication of alloyed plasmonic nanostructures of gold and silver, where the thermally evaporated bilayers of them are simply annealed into alloyed nanoparticles. The alloy ratio is controlled by the thickness of the metals, and the quality of the alloyed nanostructures may be optimized through adjusting the depositi...
Source: Plasmonics - Category: Biomedical Science Source Type: research