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.