Atomistic and electronic structure of Al/MgAl₂O₄ and Ag/MgAl₂O₄ interfaces

Abstract

For the first time, very precise experimental data on the atomistic structure of a metal/oxide interface were obtained by quantitative high-resolution transmission electron microscopy (HRTEM). They are compared with the results of ab initio density-functional theory (DFT) calculations for the same real interface structure, performed without the need for introducing artificial coherency strains. The model system of this study is the coherent (001)-oriented interface between Al and MgAl₂O₄ in parallel orientation. By means of quantitative HRTEM we determined the relative translation of the two crystals with picometre precision, and also within this error limit our ab initio calculations correctly predict the experimental structure. The electron density distribution obtained by the calculations indicates a directional bonding between the metal and the oxide beyond the concept of the image charge model. Furthermore, we have carried out ab initio DFT calculations for the (001) interface between Ag and MgAl₂O₄. Since this interface has the same crystallography as Al/MgAl₂O₄, comparison of the electron density distribution reveals the net effect of the electron configuration in the metal on the nature of the metal oxide adhesion.