UV plasmonic-based sensing properties of aluminum nanoconcave arrays

• Ultraviolet plasmonic properties of Al concaves arrays were studied.
• Al concaves with two different periodicities were analyzed.
• Reflectivity spectra were acquired at normal incidence.
• Refractive index sensitivities of the Al concaves arrays were determined.
• The obtained data were correlated with structural features of the material.

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 (Dc) of 246.3 nm and 456.7 nm, respectively. The refractive index sensitivity (RIS) was: ∼191 nm/RIU for the Al concaves with Dc = 246.3 nm, and ∼291 nm/RIU for the Al nanoconcaves arrays with Dc = 456.7 nm.

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