Defect-related photoluminescence from networks of suspended 2D crystal membranes*

Luminescent defects in 2D semiconductors hold promise for applications in photonics and quantum communication. For instance, strain-induced defects in WSe₂ have attracted attention as narrow line-width single photon sources. We present a series of low-temperature photoluminescence (PL) microscopy studies on networks of suspended 2D crystal membranes formed by controlled dewetting and recrystallization of an underlying metal film. For monolayer membranes of WSe₂ and heterojunctions of WSe₂/MoS₂ formed on a porous Au film, we find a strong (1000x) enhancement of PL intensity from the suspended regions, as well as the appearance of relatively sharp (< 1 meV) emission lines. The crystallographic texturing of the metal under-layer may also lend itself to low-loss propagation of surface plasmon polaritons (SPP), offering a means for energy transfer between discrete luminescent centers. We use a split excitation/collection imaging approach to characterize nonlocal luminescence in this unique material system, and discuss the outlook for studying networks of interconnected defects in 2D materials.