Thickness Thresholds for Generating Plasmonic Surfaces via Solid-State Dewetting of Ultrathin Silver Films on Soft...

This study demonstrates a dewetting process on polymeric polydimethylsiloxane (PDMS) substrates, enabling the fabrication of soft plasmonic masks based on silver thin films of varying thicknesses, applied to both planar and structured surfaces. The adaptation and suitability of thermal dewetting processes, typically employed on rigid substrates, for the creation of plasmonic applications are investigated. A distinct threshold behavior was observed: ultrathin films with thicknesses between 1 and 9 nm exhibited pronounced plasmonic resonance, whereas thicker layers of 13-19 nm showed no measurable response. These results indicate that both the initial thin-film thickness and the resulting nanoparticle geometry critically influence the collective plasmonic properties. Thinner layers produced higher Q factors and sharper resonance dips, with the maximum Q factor of 4.58 observed at an initial film thickness of 3 nm, indicating that this thickness is most suitable for plasmonic sensing. In contrast, an initial thickness of 9 nm produced the strongest overall plasmonic response, making it preferable for applications where resonance strength is the primary factor, such as plasmonic lithography or surface-enhanced Raman spectroscopy. The long-term stability of the fabricated samples was additionally examined over six months, revealing that the plasmonic response remains detectable, albeit with a significant decrease in intensity. Structural and optical analyses confirm the process's compatibility with structured substrates, enabling precise nanostructuring while preserving underlying surface features. The simplicity of the proposed method makes it a practical alternative to the typically more complex techniques used in plasmonic system fabrication.