Characteristic interface point defects at transition metal–oxide interfaces

Abstract

For transition metal–oxide interfaces, the local interface core equilibrium chemistry and the space charge layer defect chemistry in the oxide are deduced from a point defect model. This model considers characteristic equilibrium point defects at the interface, structural vacancies and charge transfer clusters, which are stabilized at the interface by the chemical interaction between the two phases and by the crystal constraints at the interface. Majority type and concentration of the interface defects strongly depend on oxygen activity and interface crystallography. The defect model has been solved for three limiting cases: ideal defect behavior at very small deviations of the local interface stoichiometry from the oxide bulk stoichiometry, non-ideal defect behavior in a bicrystal that respects volume constancy and non-ideal defect behavior in a bicrystal, in which all adsorption stresses are immediately relaxed. Generals trends for the interface chemistry as function of oxygen activity and type of interface are derived. The model is applied to alumina–copper interfaces and compared to experimental results in this system.