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Ultrathin semiconducting van der Waals (vdW) heterostructures based on transition metal dichalcogenides (TMDs) play a critical role in developing next-generation electronic and optoelectronic devices. The replacement of one component of the heterostructure by transition metal oxides (TMOs) certainly brings in numerous benefits including long-term stability and novel functionalities. However, the single-step chemical-vapor deposition growth of TMOs/TMDs vdW heterostructures, as a highly desired approach for large-scale fabrication and practical implementation, is challenging due to contradictory growth atmospheres of TMOs and TMDs.Here, the single-step growth of an ultrathin WO 3-x /WS 2 vdW heterostructure based on the quantity-driven discrepant interaction between S and the precursor, in which S induces sulfidation to produce WS 2 in the S-rich phase and is changed to the reduction role to obtain sub-stoichiometric WO 3-x in the S-deficient phase is realized. Both WO 3-x and WS 2 exhibit semiconducting properties with a favorable type-II band alignment. A wide response across the entire visible spectrum with a large photoresponsivity of 4375 A W −1 , a detectivity of 5.47 × 10 11 Jones, and sub-ms switching kinetics at 405 nm is achieved without gating bias, which is significantly improved over other reported ultrathin vdW heterostructures. This study demonstrates the possibility of single-step-growing TMOs/ TMDs vdW heterostructures and their strong potential in high-performance optoelectronic devices.

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