CVD synthesis of Mo(1-x)WxS2 and MoS2(1-x)Se2x alloy monolayers aimed at tuning the bandgap of molybdenum disulfide

As a rising star in two-dimensional (2D) layered materials, transition metal dichalcogenides (TMDs) have attracted tremendous attention for their potential applications in nanoelectronics, optoelectronics and photonics. Driven by the high standards of practical devices, alloying theory has been proposed for modulating the electronic structure of TMDs materials as well as their physical and chemical properties. To date, however, very limited alloy materials can be synthesized by chemical vapor deposition (CVD) and a very limited band gap range can be achieved. Herein, for the first time, we report a one-step CVD strategy for the growth of ternary alloy Mo(1-x)WxS2 monolayers (ML) on SiO2/Si substrates with controllable composition. Both Mo(1-x)WxS2 and MoS2(1-x)Se2x alloy materials with high crystallinity were synthesized in this study. Therefore, the bandgap photoluminescence (PL) can be broaden from 1.97 eV (for ML-WS2) to 1.55 eV (for ML-MoSe2). Furthermore, density functional theory calculations were performed to reveal the important role of alloying in tailoring the electronic structure of 2D materials.