Optical anisotropy induced by ultra-strong interfacial coupling in CVD-grown WSe₂/ReSe₂ vertical heterostructures

Integrating high-mobility isotropic transition metal dichalcogenides (TMDs) with anisotropic layered materials offers an ideal strategy to break through the application bottleneck of a single material. Van der Waals assembly has proven a direct route to realize anisotropic heterostructures for polarization-sensitive electronics and photoelectronics, yet conventional methods typically rely on artificial stacking of TMD materials with varying symmetries. This approach not only limits the efficiency of fabrication but also yields poor interfacial coupling, resulting in weak anisotropy in heterostructures. Here, we directly grow high-quality monolayer WSe₂ on low-symmetry monolayer ReSe₂ to fabricate WSe₂/ReSe₂ vertical heterostructures by NaCl-assisted chemical vapor deposition (CVD). Angle-resolved polarization Raman spectroscopy confirms that the isotropic WSe₂ exhibits pronounced in-plane optical anisotropy upon combining with low-symmetry ReSe₂, which is attributed to the intrinsic symmetry breaking of WSe₂ induced by ultra-strong interlayer coupling between WSe₂ and ReSe₂. Notably, the pronounced photoluminescence (PL) quenching and shortened exciton lifetime of WSe₂ provide direct evidence of ultra-strong interfacial coupling in the CVD-grown WSe₂/ReSe₂ vertical heterostructures. Consequently, this study demonstrates the pivotal role of interfacial coupling in achieving high-degree anisotropy in TMD heterostructures, offering a new design paradigm for polarization-sensitive electronics and optoelectronics.