Bottom-up Fabrication of Bandgap-Tunable Patterned Lateral WS₂-Janus W(S_xSe_1-x)Se Heterostructure Arrays

Two-dimensional (2D) heterostructures have significant application promise in electronics, optoelectronics, and integrated circuits due to their unique structural designs, high-density integration, and transformative physical properties. To establish 2D heterostructures as essential components for next-generation integrated devices, it is crucial to develop approaches for the integration of heterostructure units with varying physical properties. Herein, we demonstrate an atomic substitution method for preparing composition- and bandgap-tunable patterned lateral Janus heterostructure arrays. Patterned WS₂-WSe₂ lateral heterostructure arrays were synthesized through a laser-assisted epitaxial regrowth process. Then, using a hydrogen plasma-assisted sulfur substitution method at room temperature, the top layer atoms of WSe₂ were sulfurized to different degrees to Janus W(S_xSe_1-x)Se (0 ≤ x ≤ 1), successfully fabricating WS₂-Janus W(S_xSe_1-x)Se lateral heterostructure arrays. Notably, the composition and bandgap of W(S_xSe_1-x)Se are tunable with the S content, which is proved by density functional theory calculations, X-ray photoelectron spectroscopy, Raman, and photoluminescence spectra. Comprehensive characterizations prove that the lateral heterostructures remain an atomically clean and sharp interface. The successful introduction of bandgap-tunable Janus structures into monolayer lateral heterostructure arrays provides unprecedented flexibility for constructing 2D lateral heterostructures, which is important for the development of complex 2D lateral devices and integrated circuits.