Determining the interlayer shearing in twisted bilayer MoS2 by nanoindentation

YF Sun and YJ Wang and EZ Wang and BL Wang and HY Zhao and YP Zeng and QH Zhang and YH Wu and L Gu and XY Li and K Liu, NATURE COMMUNICATIONS, 13, 3898 (2022).

DOI: 10.1038/s41467-022-31685-7

The study of the mechanical properties of twisted van der Waals structures can provide important information about their interlayer coupling and electronic behaviour. Here, the authors report a nanoindentation-based technique to determine the interlayer shear stress in bilayer MoS2, showing its independence as a function of the twist angle. The rise of twistronics has increased the attention of the community to the twist-angle-dependent properties of two-dimensional van der Waals integrated architectures. Clarification of the relationship between twist angles and interlayer mechanical interactions is important in benefiting the design of two-dimensional twisted structures. However, current mechanical methods have critical limitations in quantitatively probing the twist-angle dependence of two-dimensional interlayer interactions in monolayer limits. Here we report a nanoindentation-based technique and a shearing-boundary model to determine the interlayer mechanical interactions of twisted bilayer MoS2. Both in-plane elastic moduli and interlayer shear stress are found to be independent of the twist angle, which is attributed to the long-range interaction of intermolecular van der Waals forces that homogenously spread over the interfaces of MoS2. Our work provides a universal approach to determining the interlayer shear stress and deepens the understanding of twist-angle-dependent behaviours of two-dimensional layered materials.

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