Electronic states and adhesion properties at metal/MgO incoherent interfaces: First-principles calculations

We investigate interface structure and adhesion behavior of incoherent metal/oxide interfaces with large misfit, Cu∕MgO(001) and Ni∕MgO(001), based on the density functional theory. We show that the interfacial strain and bonding characteristics are inhomogeneous, depending on local atomic configurations at the incoherent interfaces. In regions where a metal atom is located near an O atom, the interfacial metal layer is stretched to the coherent positions and the metal-O interfacial bond has a covalent and ionic bonding character. On the other hand, in regions where a metal atom is situated near a Mg atom, the metal layer is hardly strained and the atomic geometry remains incoherent. The metal-Mg adhesive interaction is mediated by the image-charge electron accumulation, which is absent in the coherent interface model results. We also find that effects of the interfacial strain as well as the metal-Mg interaction on the adhesive energy are significant for accurate estimation of the stability of incoherent metal/oxide interfaces.