Microstructure of epitaxial Ba0.7Sr0.3TiO3∕SrRuO3 bilayer films on SrTiO3 substrates

The thickness evolution of the microstructure of epitaxial Ba0.7Sr0.3TiO3 thin films grown on SrRuO3∕SrTiO3 was investigated by means of transmission electron microscopy. Within the Ba0.7Sr0.3TiO3 layer, a layered structure (three sublayers) is distinguished as for the configuration of lattice strain and defects. The first sublayer extends for 3nm from the lattice-coherent Ba0.7Sr0.3TiO3∕SrRuO3 interface. The second 13-nm-thick sublayer forms a semicoherent interface with the first sublayer due to the creation of a misfit dislocation network. The third sublayer extends beyond the second sublayer exhibiting a structure characterized by compact columnar features. Planar defects are formed at the boundaries between such features. The formation of a layered structure within the Ba0.7Sr0.3TiO3 films is discussed in the light of the growth modes of films on lattice-mismatched substrates.

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