First-principles study of the tensile strength and failure of α-Al2O3(0001)/Ni(111) interfaces

Tensile strength and failure of Al2O3(0001)/Ni(111) interfaces have been examined by the first-principles pseudopotential method, and compared with Al2O3(0001)/Cu(111) interfaces, and effects of the interface stoichiometry, configurations, and metal species have been analyzed. From rigid-type tensile tests, the Ni-O interfaces at the O-terminated interfaces are much stronger than the back Ni-Ni interlayers, while the strength of the Ni-Al interfaces at the Al-terminated ones is less than half of the back Ni-Ni interlayers. Relaxed-type tensile tests have been applied to the most stable configurations (Al-site and O-site models of the O-terminated and Al-terminated interfaces, respectively) to examine the behavior of atoms and electrons at the failure. For the Al-terminated interface, the Ni-Al interface is naturally broken under lower stress, while catastrophic failure occurs within the interface Ni layer for the O-terminated interface because of the irregular configuration of the interface Ni layer of the Al-site model. Tensile strength and interfacial Young's moduli of Al2O3/Ni interfaces are larger than those of the Al2O3/Cu interfaces due to stronger Ni-O and Ni-Al interactions.