Broadband Dielectric–Metal Hybrid Nanoantenna: Silicon Nanoparticle on a Mirror

Abstract

We developed a broadband dielectric–metal hybrid nanogap resonator composed of a silicon nanoparticle (Si NP) and gold (Au) flat surface. We fabricate the nanogap resonator by depositing a monolayer of colloidal quantum dots (QDs) (∼2.8 nm in diameter) on a Au surface followed by dropping a diluted colloidal solution of Si NPs (∼150 nm in diameter). The QD monolayer acts as a precisely length-controlled nanogap as well as a light emitter to monitor the radiative properties of the nanogap resonator. We investigate the light-scattering properties of single-nanogap resonators experimentally and theoretically and found that the coupling of the Mie resonance of Si NPs with a Au surface effectively confines the electromagnetic field into the nanogap in a wider wavelength range than an all-metal nanogap resonator with a comparable size. Furthermore, we show that the resonance wavelength of the hybrid nanogap resonator is less sensitive to the gap length than that of the all-metal one. We demonstrate that the broadband hybrid nanogap resonator enhances photoluminescence of a QD monolayer integrated in the nanogap by a factor of 786.