Utilising buckling modes for the determination of the anisotropic mechanical properties of As ₂ S ₃ nanosheets

The mechanical properties and interfacial behaviour of two-dimensional (2D) materials are crucial for their use in a number of technological applications. In this paper, two buckling modes, wrinkling and buckling delamination, were used to characterize the mechanics of As₂S₃ nanosheets. The plane-strain moduli of As₂S₃ nanosheets along the armchair (AC) and zigzag (ZZ) directions were determined via periodic wrinkles to be 16.7 ± 0.5 GPa and 51.5 ± 1.9 GPa, respectively. This is one of the largest reported anisotropies of in-plane mechanical properties among 2D materials. Using the delaminated buckles, the adhesion energy of few-layer As₂S₃ nanosheets on silicon and polymer (polymethyl methacrylate and polydimethylsiloxane) substrates was determined to be 0.110 ± 0.006 and 0.022 ± 0.002 J m^-2, respectively. A buckling mode map for As₂S₃ nanosheets on different substrates is presented.