SrTiO3(001) thin films on MgO(100) : a theoretical study

The epitaxy of ultrathin SrTiO3 films on the stoichiometric MgO(001) surface is studied through first-principles calculations. The detailed atomic structure, the elastic properties, and the bonding characteristics of various interfaces are discussed and synthesized in a coherent picture. In particular, we show that (1) only the TiO2/MgO contact is thermodynamically stable and makes possible the growth of thicker strontium titanate layers on magnesia; (2) many characteristics of the thick SrTiO3(001)/MgO(001) epitaxial interface are recovered already when a SrTiO3 bilayer is adsorbed. The evolution of the valence band offset at the interface is also studied as a function of the nature and the thickness of the deposited films. For both epitaxial, TiO2 terminated, adsorbed bilayer and thick SrTiO3(001)/MgO(001) interface, the upper edges of the valence band are almost aligned.