Investigation of 1T′ MoxRe(1–x)S2/2H MoS2 Heterojunction Morphology Evolution through Vapor–Liquid–Solid Growth Mechanism by Temperature-Gradient CVD

Abstract

Mo doping optimizes the electronic structure of ReS₂. Mo_xRe_(1–x)S₂/MoS₂ alloy heterojunction exhibits more favorable application prospects in photodetection due to its higher electrical conductivity than ReS₂/MoS₂ heterojunction. However, alloy heterojunctions are difficult to prepare controllably using conventional vapor-phase chemical vapor deposition (CVD), and the heterojunction growth mechanism remains unclear. Here, a vapor–liquid–solid temperature-gradient process is proposed to grow alloy heterojunctions within predeposited molten Mo precursor droplets. The sulfuration reaction between Re diffusing into the droplet and Mo atoms facilitates the formation of alloy structures. The growth temperatures T_Re and T_Mo in the temperature-gradient significantly affect the growth patterns and morphology evolution of the heterojunction. The MoS₂ morphology in vertical alloy heterojunctions becomes triangular as the growth temperature increases. The dimension of the top Mo_xRe_(1–x)S₂ alloy is positively correlated with the Re diffusion concentration. Moreover, lateral alloy heterojunctions and single alloys are formed at lower and higher growth temperature differences between T_Re and T_Mo, respectively. These results provide a controllable strategy for the synthesis of isotropic/anisotropic van der Waals TMDC heterojunctions.