Boosting the Photoluminescence of Monolayer MoS₂ on High-Density Nanodimer Arrays with Sub-10 nm Gap

Patterned plasmonic nanodimers are fabricated exploiting an ultrathin porous anodic aluminum oxide membrane as a mask during angle-resolved shadow deposition. The fabricated nanodimer arrays exhibit consistent sub-10 nm gaps and a high particle density up to 1.0 × 10¹⁰ cm⁻² over a large area. The ultrasmall dimer gaps provide highly confined electromagnetic fields, which strongly enhance the photoluminescence (PL) emission and Raman scattering from the surrounding monolayer molybdenum disulphide (MoS₂). The ensemble PL intensity from MoS₂/dimers is enhanced by up to a factor of ≈160 by resonant excitation of the dimer modes. Anisotropic polarization-dependent characteristics of PL and Raman from the MoS₂/dimers confirm that the dominant enhancement originates from the dimer configuration. These experiments demonstrate a facile approach for the fabrication of low-cost high-performance 2D material-based optoelectronic devices.