Local-field enhancement and plasmon tuning in bimetallic nanoplanets

A full-interaction electromagnetic approach is applied to interpret the local- and far-field properties of AuAg alloy nanoplanets (i.e. a central cluster surrounded by small "satellite" clusters very close to its surface) fabricated in silica by ion implantation and ion irradiation techniques. Optical extinction spectroscopy reveals a large plasmon redshift which is dependent on the irradiation conditions. Simulations strongly suggest that the peculiar topological arrangement of the satellite clusters is responsible for the observed plasmonic features. Theoretical results also indicate that strong local-field enhancement is obtained between coupled clusters. Calculations for Ag models show that enhancement factors as high as ~100 are readily achievable.