Thickness-Dependent Semiconductor-to-Metal Transition in Molybdenum Tungsten Disulfide Alloy under Hydrostatic Pressure

Abstract

Layered two-dimensional transition-metal dichalcogenide (TMD) alloys with strong intralayer ionic-covalent bonds and weak interlayer van der Waals bonds have been extensively studied in recent years owing to their tunable electronic and optoelectronic properties. However, the relationship among atomic bond identities, band offset, and related semiconductor-to-metal transition in ternary alloys of TMDs with different thicknesses under hydrostatic pressure at the atomic level remains largely unexplored, despite the fact that it plays an important role in the functionality of TMD-based devices. In this work, we investigate the thickness-dependent band offset and semiconductor-to-metal transition in Mo (1-x) W x S 2 with different thicknesses under hydrostatic pressure based on the atomic-bond-relaxation correlation mechanism. It was found that the compression ratio in the out-of-plane direction is significantly higher than that of in-plane, and the band shift and semiconductor-to-metal transition are significantly modulated by the hydrostatic pressure, number of layers, and composition. The theoretical predictions are consistent with the experimental observations and calculations, suggesting that our approach can be suitable for other layered TMDs.