A Strategy for Transition Metal Chalcogenide Synthesis Using Sequential Selenium Substitution

The direct synthesis of wafer-scale single-crystal transition metal dichalcogenides (TMDs) remains challenging, albeit with enormous potential applications as semiconductors. In this work, we demonstrate the feasibility of using single-crystal 2H-MoTe2 films as templates, followed by a sequential selenium substitution reaction to synthesize a variety of TMDs and their heterostructures. We also demonstrate the synthesis of a MoTe2/MoSe2 lateral heterostructure with various substitution temperatures for Se substitution in 1T' and 2H phase MoTe2. Computational results illustrate that Se substitution is likely to start at Te vacancy sites, where generated strain lowers the energy barrier for further substitution, leading to a chain reaction that propagates until the entire layer is selenized. The obtained MoSe2 shows a high hole mobility of 32 cm2 V-1 s-1, comparable to the 2.8-31.6 range from mechanically exfoliated samples. Consequently, this MoSe2-based photodetector shows a comparable responsivity of 41 mA W-1 under near-infrared (1060 nm) illumination.