Tuning the spontaneous emission of CdTe quantum dots with hybrid silicon-gold nanogaps.

Hybrid dielectric-metal nanogaps offer unique properties such as enhanced local density of optical states (LDOS) and simultaneously high quantum yield and coupling efficiency, with applications in bright single-photon sources, efficient nanoLEDs and imaging spectroscopy. In this work we report on silicon-gold hybrid nanogaps, considering both silicon nanorods on a gold film and gold nanorods on a silicon surface and compare them to their purely metallic and dielectric equivalent. To obtain the necessary nanometer-scale control, a combination of colloidal lithography, metal assisted chemical etching (MACE), and layer-by-layer polyelectrolyte approach were used to construct the nanogaps. Quantum emitters were incorporated in the nanogap in the form of a CdTe quantum dot monolayer. The efficient coupling between the quantum dot monolayer and the nanogap modes results in hybrid nanogaps outperforming their homogeneous counterpart, with the gold nanorod-silicon hybrid nanogap offering the largest emission rate enhancement factor of 51. Specifically, Purcell enhancements were increased by a factor of ∼2 for silicon nanorod-gold film and ∼1.5 for gold nanorod-silicon surface nanogaps compared to purely dielectric and metallic geometries respectively. These results, supported by FDTD simulations, highlight hybrid nanogaps as cornerstones for probing light-matter-interactions under extreme optical confinement with applications such as low cost and low power consumption ultrafast LEDs for short distance on-chip and chip-to-chip communications.