Dependence of shear behavior and interface evolution on modulation period of Cu/Ta nanofilms

Cu/Ta nanofilms are widely used in microelectronics applications due to their excellent physical and mechanical properties. However, the lack of research on size-dependent shear responses limits the structural design of Cu/Ta nanofilms. In this paper, molecular dynamics simulations are conducted to explore shear behaviors and failure mechanisms of Cu/Ta nanofilms with different modulation periods (λ). The findings indicate that the incoherent Cu/Ta interface forms a periodic misfit dislocation network after relaxation. The shear stress–strain curves for the samples display two distinct yield points. The shear modulus remains insensitive to variations in λ. The yield strength and yield strain of the sample at λ = 15 nm are significantly higher than those in the other cases. Defects tend to nucleate at the heterointerface where stress is concentrated. The specimens undergo four deformation stages at different λ: elastic deformation, yield of Cu, yield of Ta, and plastic flow. The shear failure is primarily associated with the Ta layer. The dislocation density in Cu decreases as λ increases, while no clear trend is observed in Ta. The shear bands first propagate from the interface into Cu and then extend into Ta. Moreover, the degree of strain localization in constituent layers becomes more pronounced with increasing λ. This study reveals the atomic-scale shear failure mechanisms of Cu/Ta nanofilms under different λ, which provides important theoretical guidance for their shear-resistant design and practical applications.