Transformation of monolayer MoS 2 into multiphasic MoTe 2 : Chalcogen atom-exchange synthesis route

Molybdenum ditelluride (MoTe 2 ), which is an important transition-metal dichalcogenide, has attracted considerable interest owing to its unique properties, such as its small bandgap and large Seebeck coefficient. However, the batch production of monolayer MoTe 2 has been rarely reported. In this study, we demonstrate the synthesis of large-domain (edge length exceeding 30 μm), monolayer MoTe 2 from chemical vapor deposition-grown monolayer MoS 2 using a chalcogen atom-exchange synthesis route. An in-depth investigation of the tellurization process reveals that the substitution of S atoms by Te is prevalently initiated at the edges and grain boundaries of the monolayer MoS 2 , which differs from the homogeneous selenization of MoS 2 flakes with the formation of alloyed Mo−S−Se hybrids. Moreover, we detect a large compressive strain (approximately −10%) in the transformed MoTe 2 lattice, which possibly drives the phase transition from 2H to 1T’ at the reaction temperature of 500 °C. This phase change is substantiated by experimental facts and first-principles calculations. This work introduces a novel route for the templated synthesis of two-dimensional layered materials through atom substitutional chemistry and provides a new pathway for engineering the strain and thus the intriguing physics and chemistry.