Plasmonic nanoparticle heterodimers in a semiembedded geometry fabricated by stepwise upright assembly.

We report the experimental realization of plasmonic heterodimers, pairs of directly adjacent, interacting metallic nanoparticles. A novel fabrication and positioning approach is utilized for the stepwise assembly of upright nanoparticle pairs, where the first nanoparticle is almost entirely embedded in an elastomeric dielectric medium prior to attachment of the second nanoparticle. The plasmon energies of the embedded nanoparticles are red-shifted, and the strongly anisotropic dielectric environment of the semiembedded nanoparticle pairs effectively transforms the structures into plasmonic heterodimers. The asymmetric hybridization of the plasmon modes of differing energies on the constituent nanoparticles of the heterodimer is clearly observed.