Synthesis of 2D MoS2(1−x)Se2x semiconductor alloy by chemical vapor deposition

Abstract

Alloying/doping in two-dimensional (2D) materials is emerging as an increasingly important strategy due to the wide-range bandgap tunability and versatility of these materials. Monolayer 2D transition metal dichalcogenide (TMD) alloy has been investigated both theoretically and experimentally in recent years. Here, we synthesized a bilayer MoS_2(1−x)Se_2x semiconductor alloy via the chemical-vapor deposition technique. The as-grown triangular MoS_2(1−x)Se_2x flakes with size of roughly 10 μm were observed by optical microscope and scanning electron microscope (SEM). The 1.4–1.9 nm thickness of the samples, as measured by AFM, means that bilayer MoS_2(1−x)Se_2x alloys were grown. The characteristic Raman modes related to Mo–S and Mo–Se vibrations were observed in the Raman spectrum. Two emission peaks were respectively found, corresponding to the A and B excitons in the photoluminescence (PL) spectrum. XPS measurements confirmed the Se doping of the alloy. The first-principles calculation results show a contraction of the band gap value with the increase of Se doping in the MoS₂ lattice. Compared with monolayer MoS_2(1−x)Se_2x alloy, the band bending effect is more obvious, and the bilayer MoS_2(1−x)Se_2x alloy still shows the direct band gap luminescence characteristic, which has certain guiding significance for the growth of two-dimensional materials and for device preparation.