Robust B-exciton emission at room temperature in few-layers of MoS2:Ag nanoheterojunctions embedded into a glass matrix

Abstract

Tailoring the photoluminescence (PL) properties in two-dimensional (2D) molybdenum disulfide (MoS₂) crystals using external factors is critical for its use in valleytronic, nanophotonic and optoelectronic applications. Although significant effort has been devoted towards enhancing or manipulating the excitonic emission in MoS₂ monolayers, the excitonic emission in few-layers MoS₂ has been largely unexplored. Here, we put forward a novel nano-heterojunction system, prepared with a non-lithographic process, to enhance and control such emission. It is based on the incorporation of few-layers MoS₂ into a plasmonic silver metaphosphate glass (AgPO₃) matrix. It is shown that, apart from the enhancement of the emission of both A- and B-excitons, the B-excitonic emission dominates the PL intensity. In particular, we observe an almost six-fold enhancement of the B-exciton emission, compared to control MoS₂ samples. This enhanced PL at room temperature is attributed to an enhanced exciton-plasmon coupling and it is supported by ultrafast time-resolved spectroscopy that reveals plasmon-enhanced electron transfer that takes place in Ag nanoparticles-MoS₂ nanoheterojunctions. Our results provide a great avenue to tailor the emission properties of few-layers MoS₂, which could find application in emerging valleytronic devices working with B excitons.