Plasmon Mode-Selective Gold Nanodimers with a Metal-Semiconductor Hybrid Junction

Plasmonic dimers are versatile platforms for manipulating light-matter interactions at the nanoscale, supporting hybridized modes such as capacitive plasmons (CPs) and charge transfer plasmons (CTPs), which are highly sensitive to the nature of the interparticle junction. However, these junctions have largely been restricted to noble metals, limiting fundamental understanding and design flexibility. Here, we report gold nanosphere dimers interconnected by a metal-semiconductor hybrid junction that enables selective regulation of plasmonic modes. Single-particle scattering measurements show that the hybrid junction, comprising metallic Ag pathways embedded within a high-permittivity AgI matrix, produces enhanced CPs and suppressed CTPs. Supported by electromagnetic simulations, we reveal that interfacial field localization driven by induced dipoles in AgI governs the mode selectivity by trapping oscillating surface plasmons and impeding long-range electronic conduction. This hybrid junction offers a tunable plasmonic platform, expanding opportunities in surface-enhanced Raman spectroscopy, optothermal therapeutics, nanophotonics, and optoelectronics that benefit from enhanced CP modes.