Large-area synthesis of monolayer MoTe_xSe_2-x alloys by chemical vapor deposition

Great achievements have been made in the alloying of two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDs), which can allow tunable bandgaps for practical applications in optoelectronic devices. However, telluride-based TMDs alloys were less studied due to the difficulties of sample synthesis. Here, in this work, we report the large-area synthesis of monolayer MoTe_xSe_2-x alloys with a controllable Te composition by a modified alkali metal halide assisted chemical vapor deposition method. Photoluminescence (PL) spectra demonstrate that the bandgap changes from 1.55 to 1.38 eV with increasing Te concentrations. The behaviors of Raman modes of MoSe₂ are well explained by a phonon confinement model. The density functional theory calculation provides insights into the atomic vibration images and better understanding of the Raman properties of MoTe_xSe_2-x alloys. Our work provides a simple method to synthesize large-scale 2H phase Te-based 2D TMDs alloys for their further applications in near-infrared devices.