Mixed-dimensional heterostructures of transition-metal dichalcogenides and metal oxides combine strong light–matter interaction with efficient charge transport, offering a versatile platform for optoelectronic devices. However, the influence of the metal oxide surface structure and chemistry on exciton behavior remains poorly understood. Here, we investigate monolayer WS2 integrated with two ZnO model systems: single-crystalline m-plane (11−00) ZnO and polycrystalline ZnO grown by atmospheric-pressure spatial atomic layer deposition. Multi-modal spectroscopy, microscopy, and density functional theory reveal that single-crystalline ZnO provides a smooth, OH-rich interface that promotes type-II band alignment, efficient dielectric screening, and ultrafast exciton dissociation. In contrast, polycrystalline ZnO exhibits a rough, defect-rich surface that forms a gapped interface, inducing spatially inhomogeneous charge transfer, trap-assisted recombination, and slower, diffusion-limited exciton decay. These findings establish WS2/ZnO as a model system for interface-driven optoelectronic design, highlighting oxide surface engineering as a powerful tool for tailoring exciton dynamics in mixed-dimensional heterostructures.
Kharsah et al. (Tue,) studied this question.