Adhesion of niobium films to differently oriented $\alpha$-Al$_2$O$_3$ surfaces

The atomic and electronic structures of the Nb/$\alpha$-Al$_2$O$_3$ interface are studied by the electron density functional method. The structural and electronic properties of three corundum surfaces, as well as chemical bonds produced by metallic niobium films at variously oriented interfaces, are discussed. Relations between the electronic structure, geometry, and mechanical properties of the interfaces are analyzed. It is shown that the adhesion of niobium films to a great extent depends on the type of oxide surface.