High‐Contrast Photoluminescence Imaging of Imperfections in Large‐Area WS₂ Monolayers via Surface Wave Excitation

Transition metal dichalcogenides (TMDCs) exhibit significant potential in the development of next‐generation optoelectronic devices, owing to their excellent electronic and optical properties. Nonetheless, the defects and strain introduced in the growth and transfer of large‐area TMDCs frequently undermine the performance of these devices. Here, the high‐contrast photoluminescence (PL) imaging of strain‐induced defects in large‐area WS 2 monolayers is investigated by exploiting the surface wave excitation achieved by coupling laser light into a Si 3 N 4 /Ag heterostructure. The electric field enhancement in the surface wave leads to an enhanced PL from the WS 2 monolayer, revealing the defects and imperfections in the WS 2 monolayer. This technique allows a high‐contrast and non‐destructive PL imaging of extensive WS 2 monolayers, which is crucial for comprehensive defect and strain analysis. A comparative assessment of this method against traditional techniques, such as Raman spectroscopy, single‐photon, and two‐photon confocal microscopy, demonstrates the superior resolution of the defects offered by this method. A detailed analysis of PL and Raman spectra indicates strain‐induced alterations in the optical properties of WS 2 monolayers. These findings suggest the potential applications of surface wave excitation in revealing the imperfections in large‐area TMDCs monolayers, which is crucial for the fabrication of TMDCs‐based optoelectronic devices.