High Intrinsic Phase Stability of Ultrathin 1T′ WS2

Abstract

Metastable 1T′-phase transition metal dichalcogenides (TMDs) attract increasing interests owing to their fascinating physicochemical properties in superconductors, optical materials, and energy storage. However, spontaneous 1T′ to 2H phase transition severely hinders practical application of 1T′ TMD. In this study, through systematic investigation and theoretical simulation of phase change of 1T′ WS2, we demonstrate ultrathin 1T′ WS2 has significantly higher intrinsic thermal and antioxidant stabilities than the bulk counterparts. 1T′ to 2H phase transition temperature increases from 120°C to 350°C and durability increases from 2 days to more than 5 months in the air as thickness of 1T′ WS2 is lessened from bulk to monolayer. The higher stability of thinner 1T′ WS2 is attributed to stiffened intralayer bonds and enhanced thermal conductivity, originated from weakened interlayer Coulombic interactions. The high intrinsic phase stabilities of ultrathin 1T′ TMDs can pave the way for their wide tempting practical applications.