Plasmonically Tuned Ag@Cu Core–Satellite Nanoparticles Synthesized Via Magnetic-Field-Driven Laser Ablation for Enhanced UV Photodetection

Ag@Cu core–satellite bimetallic nanoparticles (BNPs) were synthesized in ethanol via magnetic-field-assisted pulsed laser ablation in liquid (PLAL) using a sequential ablation strategy. A preformed silver (Ag) colloid served as nucleation seeds and the liquid medium for subsequent copper (Cu) ablation, producing Cu-rich spherical cores decorated with Ag satellites. The applied magnetic field (250 mT) enhanced plasma confinement and nanoparticle production, generating hybrid nanostructures with distinct Ag and Cu localized surface plasmon resonance (LSPR) features. Although n-type (111) porous silicon is attractive for UV sensing, its low hole population and high surface recombination often limit the improvements expected from plasmonic nanoparticle decoration. To address these constraints, we explored whether a bimetallic Ag–Cu architecture could introduce stronger plasmonic fields and more effective charge-transfer pathways. Integrated onto n-type (111) PSi to form Ag–Cu/PSi metal–semiconductor photodetectors (PDs), the BNPs exhibited enhanced optoelectronic performance through plasmonic–electronic coupling. The net photocurrent density increased from 1.80 × 10⁻² to 3.02 × 10⁻¹ mA cm⁻² (≈ 1578% enhancement) after BNP decoration, while the optimized device achieved a responsivity of 48.65 mA W⁻¹, external quantum efficiency (EQE) of 16.53%, and detectivity of 3.66 × 10⁹ Jones at 5 V, along with stable photo-switching. In comparison, the undecorated porous n-type (111) PSi exhibited a responsivity of only 2.90 mA W⁻¹ and EQE of ~ 1%, confirming the strong plasmonic contribution of the BNPs in enhancing n-type porous silicon. These results demonstrate a clean, surfactant-free, and controllable platform for engineering Ag–Cu plasmonic nanostructures, enabling scalable fabrication of enhanced UV photodetector devices.