Thickness-dependent interfacial mechanical behaviours of the MoS₂ nanoflakes on metal substrates: Insights from in-situ tensile experiments and molecular dynamics simulations

The unique interaction property between molybdenum disulfide (MoS₂) and metals renders MoS₂ nanoflake a good coating or reinforcement phase material for enhancing the mechanical properties of metals. However, the deformation behaviour of the MoS₂/metal interface under mechanical loading remains unexplored. Herein, the interfacial mechanical behaviour of multilayer MoS₂ transferred onto copper (Cu) was investigated through in-situ tensile tests, molecular dynamics (MD) simulations and theoretical analysis. The experimental results show that MoS₂ flakes with different thicknesses exhibit different deformation behaviours when the underlying Cu substrate is under tension. Specifically, the wrinkling with small amplitudes and delamination due to large buckling deformation are found in thin and medium-thick MoS₂ flakes, respectively, while no wrinkling or buckling behaviour is observed in thick flakes. According to MD simulations and shear lag modelling, the different mechanical behaviours of the MoS₂ flakes with varying thickness are attributed to the competition between the load transferred at the MoS₂/Cu interface and the bending rigidity of the MoS₂ layer. This work is expected to expand the existing knowledge on interfacial mechanical behaviours of the MoS₂/Cu nanocomposites and provide important guidance for the design and application of the MoS₂/metal interfaces.