Effectiveness of BaZrO3 buffer layer in SmBa2Cu3Oy epitaxial growth on MgO substrate: A first-principles study

The atomic structure and energies of SmBa2Cu3O6(Sm123)/BaZrO3(BZO) and Sm123/MgO interfaces have been investigated using first-principles calculations. The interfacial energies were evaluated for various atomic configurations under relevant conditions of the chemical potentials. For the Sm123/BZO, an interface composed of a BaO layer is found to be energetically favorable, irrespective of the chemical potentials. This is much lower in energy than the Sm123/MgO interfaces where the preferable configuration even varies with the chemical potential conditions. The stability of the Sm123/BZO interface is attributed to the local atomic arrangement and chemical composition common to Sm123 and BZO, and such an atomic structure is confirmed by high-resolution transmission electron microscopy. The results suggest that the insertion of a BZO buffer layer facilitates the epitaxial growth of Sm123 films on MgO substrates because of the energetically favorable film/buffer layer interface.