Evidence of multiphase nucleation in perovskite film growth on MgO substrate from medium energy ion scattering analysis: Example of YBaCuO and (Ba,Sr)TiO3

Initial stages of perovskite YBa2Cu3O7−x and BaySr1−yTiO3 films growth on MgO substrate were studied by middle energy ion scattering (MEIS) with He+190 keV ions. It was found that at the nucleation of main (YBa2Cu3O7-x or BaySr1−yTiO3) phases the simultaneous formation of additional phases consisting of protoxides Cu2O or TiO takes place. The formation of protoxide nuclei is favoured by well fit of their lattice parameters with substrate MgO ones. With increasing of the substrate coverage and film thickness over about 10 nm the transition from two-phase nucleation to monophase coalescence occurs due to decrease of substrate influence on the film growth process.