Tailoring Ag-Pt nanoalloys through solid-state dewetting: structural and optical insights

In this work, a cost-effective method for fabricating silver-platinum nanoalloys through thermally activated dewetting of thin metallic films is demonstrated. Ag and Pt bilayers with a total thickness of 8 nm were deposited using DC magnetron sputtering, followed by annealing at 650 °C under an argon atmosphere. The process induced the transformation of continuous bilayers into isolated nanoislands through solid-state dewetting. Scanning electron microscopy and transmission electron microscopy analyses revealed the formation of well-defined, nearly spherical nanoislands with a homogeneous elemental distribution, as measured by energy dispersive spectroscopy. Additionally, X-ray photoelectron spectroscopy measurements confirmed the coexistence of both metals in metallic states, with a slight Ag deficiency attributed to its higher instability and desorption during the annealing process. Optical measurements revealed the presence of a single resonance peak. The composition-dependent plasmonic resonance band was observed for low Pt contents, while progressively blue-shifting and decreasing in intensity with increasing Pt concentration. This behavior is consistent with the strong d-electron contribution of platinum, which suppresses plasmonic oscillations. The obtained results demonstrate that thermally activated dewetting enables the synthesis of homogeneous Ag-Pt nanoalloys at the nanoscale, both in volume and on the surface of nanostructures, overcoming miscibility limitations of the bulk Ag-Pt system, and provide insight into their structure-property relationships relevant for catalytic and plasmonic applications.