Strong interfacial coupling in vertical WSe₂/WS₂ heterostructure for high performance photodetection

Two-dimensional van der Waals (vdWs) heterostructures have shown great potential in the field of electronic and optoelectronic applications over the recent decade. However, the controlled preparation of high-quality vdWs heterostructures remains a great challenge ascribing to the incompatibility of different material synthesis processes. Here, we report a two-step chemical vapor deposition method for the growth of high quality WS2 on a WSe2 template with a very low temperature of similar to 550 degrees C, where WO3 nanosheets formed in the first step are further employed as the precursor for synthesis of the top WS2 layer in the second step. Such low growth temperatures in the second step also enable the effective protection of bottom WSe2 during the WS2 growth process and, therefore, result in high-quality WSe2/WS2 heterostructures. Photoluminescence characterizations are further conducted, where significant interlayer exciton emission is observed, indicating strong interlayer coupling in the heterostructure. Based on the obtained WSe2/WS2 heterostructure, dual-channel photosensitive devices were further designed and systematically studied, where high photoresponsivity (3A/W) as well as fast response speed (<1ms) are obtained. The developed WO3-assisted growth technique would provide an effective reference for the controlled synthesis of high quality vdWs heterostructures and promote further applications in high-performance optoelectronic devices.