Symmetry breaking in a WS2/Te heterostructure with enhanced second-harmonic generation and strong anisotropic optical properties

Abstract

Anisotropic van der Waals (vdW) heterostructures are crucial for smart optoelectronic device development. Although transition metal dichalcogenides (TMDCs) like WS₂ hold great potential for high-performance optoelectronic devices, their C₃ rotational symmetry restricts polarization-sensitive applications. Crystal symmetry breaking of TMDCs by forming heterostructures is a powerful approach for achieving anisotropic optoelectronic properties. Considering the promising potential of the WS₂/Te p–n heterostructure in broad photoresponse and enhanced nonlinearity, we successfully fabricated this heterostructure and investigated its anisotropic optical properties. The formation of the heterostructure induces interfacial symmetry breaking, and the interface shows twofold symmetry as confirmed by polarization-dependent second-harmonic generation (SHG) measurements. Moreover, the WS₂/Te heterostructure exhibits enhanced SHG signals across the 850–1064 nm wavelength range. The interlayer anisotropic moiré potential induced by symmetry breaking leads to anisotropic Raman scattering and exciton emission with degrees of polarization (DOP) of 0.268 and 0.310. Furthermore, the heterostructure formation reduces intervalley scattering, enhancing valley polarization in WS₂. In particular, the valley polarization degree of the trion in the heterostructure is 0.495 at 93 K. These results demonstrate the potential of the WS₂/Te heterostructure for strong nonlinear optical responses and anisotropic optoelectronic properties, establishing a foundation for their broad application in next-generation photonic devices.