Substrate-Modulated Effect on the Photoluminescence and Carrier Dynamics of Large-Area Monolayer MoS₂

The monolayer thickness of MoS 2 enables it to exhibit exceptional physical and chemical properties; yet, it also renders it highly susceptible to substrate modulation. Concurrently, its optical and electronic properties might be greatly affected by the intrinsic attributes, structures, and morphologies of the underlying substrates. Hereby, studies on the substrate-modulated effect stemming from interfacial interactions are essential for the applications of monolayer MoS 2 . Herein, large-size monolayer MoS 2 films were successfully grown on sapphire, mica, and TiO 2 substrates with 6 × 6 mm 2 by chemical vapor transfer. The optical properties, carrier dynamics, and interface charge transfer of MoS 2 for three types of substrates are investigated to evaluate the substrate-modulated effect through femtosecond laser transient absorption spectroscopy. The comparative result reveals that the semiconducting TiO 2 substrate exerts significant modulatory effects on the photoluminescence, absorption properties, and exciton dynamics of MoS 2, in contrast to the insulating sapphire and mica substrates. Intriguingly, the exciton dynamics display substrate-dependent variations across the investigated platforms: MoS 2 on the sapphire exhibits the shortest exciton lifetime among the three substrates, while mica-supported MoS 2 demonstrates exceptionally prolonged excitonic lifetimes, highlighting the critical role of substrate interactions in modulating nanoscale exciton behavior. These observed discrepancies could be attributed to three factors: heterogeneity in the dielectric environments, interfacial electron transfer, and variations in crystalline quality of the synthesized MoS 2 films. The insights gained from this study on the substrate-modulating effect on the optical properties of MoS 2 could be extended to other two-dimensional heterostructures, paving the way for innovative applications in optical and optoelectronic devices.