Multilayered Vertical Heterostructures Comprised of MoS₂ and WS₂ Nanosheets for Optoelectronics

Vertically stacked two-dimensional (2D) transition-metal dichalcogenide (TMDC) heterostructures (HSs) offer a prospective approach to manipulating their physical characteristics via a transfer strategy. However, the synthesis of 2D multilayered TMDC vertical HSs is still challenging through one-step chemical vapor deposition (CVD). Here, two-, three-, and four-layer 2D TMDC van der Waals (vdW) HSs, including 1L-MoS2/1L-WS2, 1L-WS2/1L-MoS2, 1L-MoS2/2L-WS2, 2L-MoS2/2L-WS2, and 3L-MoS2/1L-WS2, have been achieved under two opposite preparation routes through a one-step CVD approach via alternating utilization of metallic Mo (or W) foil and WO3 (or MoO3) powder as precursors. The structure, phase number, and layer number of these peculiar multilayered HSs are comprehensively evaluated by optical microscopy, atomic force microscopy, and Raman and photoluminescence spectroscopy/mapping. Our results suggest that the growth of these multilayered vdW HSs may be attributed to the characteristic difference between metallic Mo (or W) foil and MoO3 (or WO3) powder and the effect of the growth temperature on the concentration evolution of Mo/W atoms in vapor, and the reaction with S vapor. Moreover, the new growth strategy for the fabrication of multilayered vertical HSs offers a novel and innovative method for the application of multilayered HSs to diverse fields, including photodetectors, catalysts, and solar cells.