Bottom‐up Fabrication of Bandgap‐Tunable Patterned Lateral WS ₂ ‐Janus W(S _x Se _1‐x )Se Heterostructure Arrays

ABSTRACT 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 WS ₂ ‐WSe ₂ 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 WSe ₂ were sulfurized to different degrees to Janus W(S _x Se _1‐x )Se (0 ≤ x ≤ 1), successfully fabricating WS ₂ ‐Janus W(S _x Se _1‐x )Se lateral heterostructure arrays. Notably, the composition and bandgap of W(S _x Se _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.