Applicability of fracture mechanics on brittle delamination of nanoscale film edge

The stress concentration near the interface edge of a film/substrate, which dominates the delamination, is analyzed by molecular dynamics (MD) analysis. Here, the film thickness is on the nanoscale and the interatomic interaction is simulated by Morse-type model potentials. Three types of load are applied to the film/substrate to examine the effect of the stress-concentrated region on the delamination at the interface edge. At lower applied load, the stress distribution along the interface near the edge in the MD simulation coincides well with that obtained by linear elastic analysis (FEM: Finite Element Method). However, after the stress near the edge reaches the ideal strength of the interface, it deviates from the FEM result. The delamination crack is initiated from the free edge when the stress at y < 1 nm (y: distance from the edge) reaches the ideal interface strength. This signifies the criterion of interface toughness that the delamination is governed by the stress in the region (process zone). This also suggests the limit of applicability of linear elastic fracture mechanics on the nanoscale components.