Polarization-Resolved Plasmon-Modulated Emissions of Quantum Dots Coupled to Aluminum Dimers with Sub-20 nm Gaps

An aluminum dimer nanoantenna with nanogaps is an ideal platform for enhancing light matter interaction at the nanoscale for the UV-vis spectrum, but its realization has been hindered by the surface oxidation of aluminum nanostructures, aluminum interband loss, and practical limitations in lithographic patterning. Here, we have overcome these problems and demonstrated the successful fabrication of an aluminum dimer antenna with a similar to 10 nm gap, which to the best of our knowledge marks the smallest features of an AI nanoantenna. We present the first in-depth study of strongly polarization-dependent emissions of colloidal quantum dots coupled with Al dimers and elucidate the individual contributions of the excitation intensity, quantum yield, and extraction efficiency enhancements from numerical and experimental perspectives. We estimate the Purcell effect corresponding to a single Al-dimer antenna as similar to 104 by taking into account the ensemble averaging effect and the distributions in emitter dipole orientations. This finding brings us a step closer toward a cost-effective realization of bright and ultrafast single emitters.