Applicability of Fracture Mechanics on Brittle Delamination of Nanoscale Film Edge.

Abstract

The stress concentration near the interface edge of film/substrate, which dominates the delamination, is analyzed by the molecular dynamics (MD) analysis. Here, the thickness of film is in the nanoscale, the interatomic interaction is simulated by the Morse type model potentials. Three types of load are applied to the film/substrate in order to examine the effect of 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 the one obtained by a 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 initiates 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 nano-scale components.