Phase Engineering of Two-Dimensional Transition Metal Dichalcogenides

Transition metal dichalcogenides (TMDs) possess a large number of two-dimensional (2D) materials with novel physical and chemical properties and hold great potential applications in electronic devices, optical devices as well as catalysts. TMDs usually have poly-phases, such as 2H, 3R and 1T. Chemical and physical properties, including electrical conductivity, superconductivity, magnetism and catalytic activity, are different for different phases of TMDs. Therefore, great efforts have been made to obtain a specific pure phase of 2D TMD materials. Here, we review the recent phase engineering research for 2D TMDs, including ion insertion, alloying, temperature, defects, strain and electric field.