Monitoring and engineering interface coupling between monolayer WS₂ and substrate through controllably introducing interfacial strain

The interface properties in two-dimensional (2D) layered materials and their van der Waals (vdW) homo-/heterostructures are of importance in both uncovering novel physical phenomena and optimizing device performance. Despite considerable research interest and enthusiasm direct toward the interlayer coupling in 2D homo- and heterostructures, there is limited research on the coupling at the 2D layered material-substrate interface. This limitation is due to the challenges in achieving direct detection. Currently, the coupling mechanisms at the 2D layered material-substrate interface is ambiguous, which needs greater attention. In this study, we have systematically investigated the interface coupling between monolayer WS₂ and its supported substrates using high-temperature and high-vacuum in-situ Raman spectroscopy through monitoring the low-frequency Raman mode of monolayer WS₂. Our findings reveal that both interfacial spacing and strain can significantly affect the coupling strength between the monolayer WS₂ and the supported substrate. More notably, we found that the strategic introduction of appropriate interfacial strain can effectively enhance the interface coupling. Consequently, we have succeeded in achieving effective regulation of the sample-substrate coupling via a convenient way of controlling the cooling process during annealing. Our findings contribute to a deeper understanding of the coupling correlation between 2D layered materials and substrates, which is of great significance for the design and optimization of high-performance devices based on 2D layered semiconductors.