Metastable 1T′-phase group VIB transition metal dichalcogenide crystals

A general method for the synthesis of high-purity crystals of metastable 1T '-phase transition metal dichalcogenides is reported, providing a source of phase-engineered materials that can be used to systematically explore their intrinsic properties. Metastable 1T '-phase transition metal dichalcogenides (1T '-TMDs) with semi-metallic natures have attracted increasing interest owing to their uniquely distorted structures and fascinating phase-dependent physicochemical properties. However, the synthesis of high-quality metastable 1T '-TMD crystals, especially for the group VIB TMDs, remains a challenge. Here, we report a general synthetic method for the large-scale preparation of metastable 1T '-phase group VIB TMDs, including WS2, WSe2, MoS2, MoSe2, WS2xSe2(1-x) and MoS2xSe2(1-x). We solve the crystal structures of 1T '-WS2, -WSe2, -MoS2 and -MoSe2 with single-crystal X-ray diffraction. The as-prepared 1T '-WS2 exhibits thickness-dependent intrinsic superconductivity, showing critical transition temperatures of 8.6 K for the thickness of 90.1 nm and 5.7 K for the single layer, which we attribute to the high intrinsic carrier concentration and the semi-metallic nature of 1T '-WS2. This synthesis method will allow a more systematic investigation of the intrinsic properties of metastable TMDs.

Automated summary

A general synthetic method for large-scale preparation of high-purity metastable 1T'-phase transition metal dichalcogenide crystals, including WS2, WSe2, MoS2, MoSe2, WS2xSe2(1-x) and MoS2xSe2(1-x), has been reported. The crystal structures of 1T'-WS2, -WSe2, -MoS2 and -MoSe2 were solved using single-crystal X-ray diffraction. The as-prepared 1T'-WS2 showed thickness-dependent intrinsic superconductivity, demonstrating critical transition temperatures of 8.6 K for a thickness of 90.1 nm and 5.7 K for a single layer, attributed to its high intrinsic carrier concentration and semi-metallic nature. This synthesis method will facilitate a more systematic investigation of the intrinsic properties of metastable TMDs.