Interlayer Coupling in Anisotropic/Isotropic Van der Waals Heterostructures of ReS₂ and WS₂

Van der Waals (vdW) heterostructures are composed of atomically thin layers assembled through weak (vdW) force, which have opened a new era for integrating materials with distinct properties and specific applications. However, few studies have focused on whether and how anisotropic materials affect heterostructure system. The study introduces anisotropic and isotropic materials in a heterojunction system to change the in-plane symmetry, offering a new degree of freedom for modulating its properties. The sample is fabricated by manually stacking ReS2 and WS2 flakes prepared by mechanical exfoliation. Raman spectra and photoluminescence measurements confirm the formation of an effective heterojunction, indicating interlayer coupling of the system. The anisotropy and asymmetry of the WS2-ReS2 heterostructure system can be adjusted by the introduction of isotropic WS2 and anisotropic ReS2, which can be proved by the change of the polarized Raman pattern. In the transient absorption measurement, the transient absorption spectra of WS2-ReS2 heterostructure are red-shifted compared to those of WS2 monolayer, and the charge transfer is observed in the heterostructure. These results show the potential of anisotropic 2D materials in anisotropy modulation of heterostructures, which may promote future electronic or photonic application.