A calculation of the structure and energy of the Nb/Al2O3 interface

We have modelled the (111)(Nb)/(0001)(s)Nb/Al2O3 interface using an atomistic, static lattice simulation technique. The interaction between the metal and the oxide combines the short range interaction between the metal atoms and the oxide ions, the Coulomb interaction between the oxide ions and the induced image charge of the metal, and the energy required to immerse the ionic cores in the metal jellium. The short range interaction between the Al3+ ion and the Nb atom was found to be repulsive, but the O2-/Nb interaction was found to be attractive at separations greater than 0.23 nm. As a result the lowest energy interface was found to terminate on an oxygen plane of the Al2O3; crystal, with the Nb atoms placed over the vacant sites in the Al lattice. The interfacial energy of this interface was calculated to be -3.6 J/m(2). As in previous work the results agree well with LDF calculations. The calculated structure is also in good agreement with the interpretation of the HREM images of Nb films grown on the (0001) face of Al2O3 using Molecular Beam Epitaxy. Copyright (C) 1996 Acta Metallurgica Inc.