Microstructures and surface step-induced antiphase boundaries in epitaxial ferroelectric Ba0.6Sr0.4TiO3 thin film on MgO

Ba0.6Sr0.4TiO3 thin films were epitaxially grown on (001) MgO substrates using pulsed laser ablation. Cross-sectional and plan-view transmission electron microscopy have been employed to study the microstructures and the interface behavior of the as-grown thin films. The 110-nm-thick Ba0.6Sr0.4TiO3 thin films have a flat surface and sharp interface. The entire thin film has a single-crystal cubic structure with an interface relationship of (001)(Ba 0.6 Sr 0.4 TiO 3)//(001)(MgO) and <100>(Ba 0.6 Sr 0.4 TiO 3)//<100>(MgO) with respect to the substrate. The 6.4% lattice mismatch between Ba0.6Sr0.4TiO3 and MgO was completely released at the interface by forming equally spaced misfit dislocations with a distance of similar to3.2 nm. High-resolution transmission electron microscopy investigation shows that the initial grown layer of the film is the TiO2 monolayer. The growth models of substrate surface-terrace induced defects for perovskite on a rock-salt system have been developed to understand the as-grown features where the conservative and nonconservative antiphase boundaries can be formed. (C) 2002 American Institute of Physics.