Enhanced Second-Order Nonlinearities at Strained Ultrasharp Zigzag Edges in Multilayer MoS2

Transition metal dichalcogenide (TMD) materials attract significant research attention thanks to their exceptional excitonic and optical properties. In this work, we analyze the formation of strained ultrasharp zigzag edges in MoS2 multilayers produced by anisotropic wet etching. The topography of the edges is determined by the relative stability of the different crystallographic directions of the multilayer as well as the interlayer interactions. Furthermore, we study the linear (Raman) and nonlinear (second-harmonic generation) spectroscopic characteristics of such edges and observe enhanced second-order nonlinearity originating from the strained zigzag edges. We also confirm that ultrasharp hexagonal nanoholes in MoS2 grow along the most stable crystallographic directions despite potential stacking faults or instabilities in the crystal quality. Our results open the way to exploit a broad range of phenomena occurring at the edges of MoS2 material, including the unique determination of crystal orientation for moire ' engineering and strongly correlated phenomena in 2D material-based systems, as well as potential applications in TMD-based electrocatalysis and gas sensing.