Plasticity at a Cu/α-Al2O3 interface with nanovoids

For the epitaxial (1 1 1)Cu/(0 0 0 1)Al2O3 interface with a periodic array of nanovoids, plasticity, and debonding were simulated at atomic scale using interatomic potentials fitted to ab initio results. Copper atoms are free to move within a certain distance of the interface (plastic zone) between the rigid sapphire and copper half-spaces. The copper in the plastic zone is strained by relative, stepwise separation of the rigid sapphire and copper half-spaces having normal and tangential components. The effects of the plastic zone size are investigated in order to find a characteristic plastic zone thickness. For the orientation relationship studied, it was found that when the tangential component of separation is large compared to the normal component, yielding occurs within a few interfacial (1 1 1) copper monolayers, and the resultant density of dislocations in the bulk copper is small. When the normal component of separation is large, slip occurs not only in the planes parallel to the interface, but also in other slip systems, resulting in dislocation gliding in the bulk copper.