Enhanced Interlayer Excitons in WS ₂ -MoS ₂ Heterostructures via Coupling with the TiO ₂ Support

Interlayer excitons in van der Waals heterostructures of transition metal dichalcogenides (TMDCs) exhibit electrical tunability and long lifetimes, offering unique opportunities for optoelectronic and quantum technologies. However, their stabilization typically requires external gating or chemical treatments, limiting applications. Here, we demonstrate a substrate-mediated strategy for stabilizing interlayer excitons at room temperature without the need for external fields. By introducing TiO2 as a functional oxide substrate, we achieve high-quality MoS2/TiO2 and WS2/TiO2 interfaces via chemical vapor deposition. Stacking these monolayers into WS2/MoS2/TiO2 and MoS2/WS2/TiO2 heterostructures enables control of excitonic behavior through interfacial coupling. The TiO2 substrate modulates charge distribution across the heterostructure, facilitating robust interlayer exciton formation. Furthermore, reversing the stacking sequence significantly alters exciton characteristics due to asymmetric substrate interactions. Our results establish TMDCs-oxides interfaces as a powerful platform for exciton modulation and offer a practical route toward ambient-stable excitonic applications based on TMDCs van der Waals heterostructures.