Atomistic simulation of nanoindentation into copper multilayers

Atomic-scale simulations are used to examine the plastic behaviour of copper multi-layered thin films during nanoindentation tests. It is found that glide of nucleated dislocation loops and slip in the grain boundaries are the main operating deformation mechanisms in such multi-layered polycrystals. Furthermore, for a very small layer thickness, slip in the grain boundary dominates over the dislocation mediated plasticity. In order to survey the resistance of a multi-layered metal thin film to plastic deformation during nanoindentation, hardness versus penetration depth curves are plotted. Hardness curves reveal softening of multi-layer films, i.e. a reverse Hall-Petch effect is found for layer thicknesses in the nanometre range.