Augmenting photoluminescence of monolayer MoS₂ using high order modes in a metal dimer-on-film nanocavity

Abstract

Plasmonic particle-on-film nanocavities, supporting gap modes with ultra-small volume, provide a great solution to boost light–matter interactions at the nanoscale. In this work, we report on the photoluminescence (PL) enhancement of monolayer <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m1"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>MoS</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> using high order modes of an Au nanosphere dimer-on-film nanocavity (DoFN). The high order plasmon modes, consisting of two bonding quadrupoles in the dimer and their images in the Au film, are revealed by combining the polarization-resolved scattering spectra with the numerical simulations. Further integrating the monolayer <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m2"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>MoS</mml:mi> </mml:mrow> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> </mml:math> into the DoFN, these high order modes are used to enhance PL intensity through simultaneously boosting the absorption and emission processes, producing a 1350-fold enhancement factor. It opens an avenue to enhance the light–matter interaction with high order plasmon modes and may find applications in future optoelectronics and nanophotonics devices.