Structure-property relationships of strain-induced ultrabright nanoscale emitters in a hybrid 2D semiconductor metal system

Nanoscale solid-state light sources with tailorable properties which can be integrated into photonic systems are important for technologies ranging from sensing to the quantum information sciences. Here, we report the multimodal characterization of nanoscale light sources that are embedded in a hybrid system composed of single-layer (1L) WS₂ bound to a pristine gold surface. The emitters are ultrabright and correspond to localized “nanobubbles” of the 1L-WS₂ that have lateral sizes smaller than 100 nm. Structure-property relationships of the nanobubbles are investigated by correlating atomic force microscopy characterization with the corresponding properties of their photoluminescence (PL), including brightness, saturation, and emission spectra. Power-dependent PL spectroscopy shows a blue shift of the emission energy with increasing power, which is attributed to the state-filling of the localized strain regions within the nanobubbles. At low excitation power, excitons concentrate in the higher strain areas and emit photons with lower energies. With increasing power, excitons fill these states and recombine in less-strained areas and emit at higher energies. Spatial imaging of the PL emission of the nanobubbles at different powers confirms this funneling picture as the emission profile gets larger with increasing power. These strain-tailored nanoscale emitters open new possibilities in optoelectronic applications like single-photon emission at cryogenic temperature.