Phase-Pure 1T' Molybdenum Disulfide Synthesis and Stabilization.

Metastable-phase transition metal dichalcogenides (TMDs) show distinct structures and properties compared with the well-studied thermodynamically stable phase. The phase impurity and degeneration are two critical challenges for the research and applications of metastable 1T'-phase MoS₂. Here, a self-intercalation method is demonstrated to synthesize and stabilize the phase-pure 1T' MoS₂. The K₂S intercalation and 1T' MoS₂ synthesis are simultaneously done in only one step, leading to uniform intercalation and 1T' phase purity. This engineered intercalation structure achieves stabilization of 1T' MoS₂ without changing its in-plane structure. It keeps 1T' phase structure and 100% phase purity even after 750 °C annealing or 1-year aging exposed to air, while 1T' MoS₂ transforms to 2H phase gradually, or instantly over 97 °C. The theory calculation results show that the K₂S intercalation lowers the formation energy and makes metastable 1T' phase become stable. As a result, this stabilization method prevents gradual degeneration of applications performance that is inevitable in the past. This mass-production-available method has been successfully proved versatile for various 1T' TMDs with numerous alkali metal chalcogenides intercalation. It eliminates a significant disadvantage of 1T' TMDs, which can facilitate the investigation of novel properties and the development of fresh applications.