Nonlinear mechanical response of rippled MoS2 nanosheets evaluated by in situ transmission electron microscopy

When stretching or shearing a suspended two-dimensional ribbon, the width is reduced due to Poisson's effect. However, in the central region between both fixed sides, a ripple structure is formed transversely due to relaxation, such that the period and amplitude of the ripple structure are related to the Poisson's ratio. In this study, we estimate the mechanical response of the MoS2 nanosheets by investigating their subnanometer-scale ripple structures during the stretching by in situ transmission electron microscopy. We find a nonlinear mechanical response of MoS2 nanosheets such that the Poisson's ratio is 0.27 below 1.1% in tensile strain along the zigzag direction and gradually increases to 0.57 at 1.6% strain. This nonlinear response can be explained by the non-linear mechanical response of the Mo-S bond, suggesting that nanoscale mechanics is sensitive to the nature of atomic bonds.