Scalable laser fabrication of disordered dual-purpose silver nanostructures towards secure plasmonic devices

Plasmonic nanoparticles (NPs) are widely utilized in various applications including sensing and imaging due to their strong localized surface plasmon resonances (LSPRs). Recently, plasmonic NP assemblies and configurations have also been explored as physical unclonable functions (PUFs) for security applications, however, many existing PUF designs face challenges such as complex fabrication processes and high costs, which complicate their implementation. This study introduces a scalable and practical approach to fabricate disordered self-assembled silver NPs for use as dual-purpose features in plasmonic devices. These nanostructures could offer multifunctionality by simultaneously serving as a functional plasmonic feature and as a potential PUF, providing an extra security layer in the device configuration. The proposed nanostructuring method could support the large-scale production of plasmonic nanostructures with desirable LSPR characteristics, essential for diverse plasmonic applications, while their structural uniqueness enables their potential exploitation as unclonable PUF fingerprints. In this work, disordered silver NPs were grown via laser annealing of silver ultrathin films with thicknesses ranging from 12.5 to 15 nm. Ultraviolet-visible spectroscopy and atomic force microscopy revealed high-intensity LSPRs and unique nanopatterns, demonstrating their potential multifunctionality.