Compositional dependence of the optical and electronic properties of single layer MoS₂-WS₂ alloys

Recent studies on atomically thin lateral heterostructures have demonstrated the formation of complex interfaces that could be exploited for tuning the physical properties of 2D semiconductors for optoelectronic applications. In order to understand the compositional dependence of the optical and electronic properties in these interfaces, tip-enhanced Raman scattering (TERS) imaging and spectroscopy have been used to characterize 2D lateral heterostructures at different sites across the interface, showing a continuous evolution of the Raman active modes when transitioning from one pristine material to the other. Here, we use density functional theory (DFT) for calculating the evolution of vibrational modes, non-resonant Raman spectra, optical absorption and electronic structure of single-layer MoS₂, WS₂ and Mo_xW_1-xS₂ alloys. We further explore the role of S vacancies in the appearance of a defect mode in these systems and its evolution, allowing a direct comparison to recent non-resonant Raman measurements on analogous systems. Lastly, we anticipate that the same computational approach can be useful for predicting the compositional-dependent properties of additional lateral heterostructures, and providing a valuable resource for quantitatively interpreting state-of-the-art characterization measurements.