Tunable band gap coupling in 2D heterostructures based on ternary alloys of transition metal dichalcogenides

Transition metal dichalcogenides (TMDs) ternary alloys have composition dependent electronic properties. For instance, their bandgap as well as their electrical response (n-type or p-type conductivity) can be continuously tune with the chemical composition. However, these advantages of individual ternary alloys can be greatly expanded if we combine them into a heterostructure, and the number of possible materials combinations is larger than for binary TMDs heterojunctions. In this work we performed a systematic study to explore the production of ternary alloy heterostructures of the type MoS_2(1-x)Se_2x-WS_2(1-x)Se_2x (where x is the composition of the chalcogen atom). We demonstrate the successful and continuous tuning of the band gap for both materials forming the heterostructure. We identified conditions in which in-plane or vertically stacked 2D heterostructures can be in situ fabricated. The alloy-based heterostructures were extensively studied by Raman, PL and Transmission Electron Microscopy.