Selective Chemical Vapor Deposition Growth of WS₂/MoS₂ Vertical and Lateral Heterostructures on Gold Foils

Vertical and lateral heterostructures consisting of atomically layered two-dimensional (2D) materials exhibit intriguing properties, such as efficient charge/energy transfer, high photoresponsivity, and enhanced photocatalytic activities. However, the controlled fabrication of vertical or lateral heterojunctions on metal substrates remains challenging. Herein, we report a facile and controllable method for selective growth of WS₂/MoS₂ vertical or lateral heterojunctions on polycrystalline gold (Au) foil by tuning the gas flow rate of hydrogen (H₂). We find that lateral growth is favored without H₂, whereas vertical growth mode can be switched on by introducing 8-10 sccm H₂. In addition, the areal coverage of the WS₂/MoS₂ vertical heterostructures is tunable in the range of 12-25%. Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) results demonstrate the quality and absence of cross-contamination of the as-grown heterostructures. Furthermore, we investigate the effects of the H₂ flow rate on the morphology of the heterostructures. These pave the way to develop unprecedented 2D heterostructures towards applications in (opto)electronic devices.