Phase-pure 1T’ molybdenum disulfide synthesis and stabilization

Abstract

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.