Surface Plasmon Resonance Dispersion Relation of Gold-Aluminum Thin Films Using the Kretschmann Configuration

The prevalence of gold (Au) in the excitation of surface plasmon resonance (SPR) has been widely explored, due to these elements’ pronounced dip in reflected intensity in the visible and near-IR spectrum, and their integrity in sensors owing to their resistance to oxidization. Other metals such as aluminum also exhibit SPR, but it remains a challenge to work with because of its propensity to form a surface oxide layer which can inhibit the response. Our research explores SPR in gold-aluminum (AuAl) alloyed thin films. We fabricate the thin films using the co-sputtering technique, with some concentrations (Au_0.85Al_0.15) showing a higher SPR quality factor than pure gold. The mixture of these elements should reduce the possibility of oxidization of Al, and therefore exhibit a better response. Numerous works have explored SPR using AuAl thin films, but few have done so with such high angular and spectral resolution, over such a wide range, using this many alloys. This is a result of the precision, equipment, and time necessary to take such measurements. We were able to produce high-resolution, homogenous images of SPR for various concentrations of AuAl alloys, that strongly agree with calculations.