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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.

An electrothermal microgripper is an important actuator in microelectromechanical and micro-operating systems, and its temperature field analysis is the core problem in research and design. Because of the small size of an electrothermal microgripper, its microscale heat transfer characteristics are different from those of the macrostate. At present, only a few studies on the heat transfer scale effect in electrothermal microgrippers have been conducted, and the heat transfer analysis method under the macrostate is often used directly. The temperature field analysed and simulated is different from the actual situation. In the present study, the heat transfer mechanism of an electrothermal microgripper in the microscale was analysed. The temperature field of a series of microscale heating devices was measured using microthermal imaging equipment, and the heat transfer parameters of the microscale were fitted. Results show that the natural convective heat transfer coefficient of air on the microscale can reach 60–300 times that on the macroscale, which is an important heat transfer mode affecting the temperature field distribution of the electrothermal microgripper. Combined with the finite element simulation software, the temperature field of the electrothermal microgripper could be accurately simulated using the experimental microscale heat transfer parameters measured. This study provides an important theoretical basis and data support for the optimal design of the temperature controller of the electrothermal microgripper.

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