Thermal Stability of Near-60° Twisted MoS2 Bilayers with Implications for Twistronic Optoelectronic Devices

Twisted bilayers of transition metal dichalcogenides (TMDs) have attracted significant attention due to nanoscale exciton confinement within moiré superlattices, which opens pathways for twistronic optoelectronic devices, such as tunable light emitters and quantum-light sources. However, the properties of twisted bilayers are intrinsically dependent on the twist angle and on the nanoscale reconstruction of the moiré superlattice. Techniques capable of probing variations in the moiré structure are often impractical, including scanning probe microscopy (SPM) or transport measurements. The rapidly advancing field of twistronics demands versatile and fast tools to probe moiré variations, especially under variable temperature conditions relevant for device processing. Here, we employ Raman and photoluminescence (PL) spectroscopic mapping to probe local variations of the moiré-averaged response of twisted bilayer MoS2 with near-60° twist angle (TBM-n60) under different annealing temperatures. We observe the formation of reconstructed nanoscale domains after annealing at 200 °C, while sample degradation occurs at 400 °C. Our results shed light on the thermal stability of moiré structures, providing a practical and efficient approach to characterize temperature-induced changes in the moiré-averaged response, a prerequisite for reliable twistronic optoelectronic devices.