UV plasmonic-based sensing properties of aluminum nanoconcave arrays

For several decades the plasmonic behavior of materials has been almost exclusively studied in visible region. Emerging applications require, however, the development of efficient materials operating in UV range. In UV nanoplasmonics aluminum (Al) can play a leading role due to its advantageous electronic properties. Yet, there is still lack of reproducible method to obtain Al nanostructures with desired parameters. Al nanoconcaves can provide a way to overcome these limitations. Here, two different periodicities of the Al nanoconcaves arrays were analyzed. It was observed that the Al concaves can dramatically reduce the optical reflectivity as compared to flat, unstructured Al. At the same time pronounced reflectivity dips were discernible, which were ascribed to (0,1) plasmonic mode. The positions of the dips were at around 250 nm and 350 nm for Al concaves with interpores distance (D_c) of 246.3 nm and 456.7 nm, respectively. The refractive index sensitivity (RIS) was: ∼191 nm/RIU for the Al concaves with D_c = 246.3 nm, and ∼291 nm/RIU for the Al nanoconcaves arrays with D_c = 456.7 nm.