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
