Composition-Modulated Two-Dimensional Semiconductor Lateral Heterostructures via Layer-Selected Atomic Substitution.

Composition-controlled growth of two-dimensional layered semiconductor heterostructures is crucially important for their applications in multifunctional integrated photonics and optoelectronics devices. Here, we report the realization of composition completely modulated layered semiconductor MoS2-MoS2(1-x)Se2x (0 < x < 1) lateral heterostructures via the controlled layer-selected atomic substitution of pregrown stacking MoS2, with a bilayer located at the center of a monolayer. Through controlling the reaction time, S at the monolayer MoS2 at the peripheral area can be selectively substituted by Se atoms at different levels, while the bilayer region at the center retains the original composition. Microstructure characterizations demonstrated the formation of lateral heterostructures with a sharp interface, with the composition at the monolayer area gradually modulated from MoS2 to MoSe2 and having high-quality crystallization at both the monolayer and the bilayer areas. Photoluminescence and Raman mapping studies exhibit the tunable optical properties only at the monolayer region of the as-grown heterostructures, which further demonstrates the realization of high-quality composition/bandgap modulated lateral heterostructures. This work offers an interesting and easy route for the development of high-quality layered semiconductor heterostructures for potential broad applications in integrated nanoelectronic and optoelectronic devices.