The effects of post-annealing on the interface microstructure of Ba0.6Sr0.4TiO3 (BST) thin films prepared by metalorganic chemical vapor deposition have been studied by a transmission electron microscopy (TEM). As-deposited BST film was partially crystallized on (1 1 1) textured Pt/SiO2/Si substrate. After a post-annealing process at 750 degreesC, the BST films were preferably crystallized with (1 1 I) plane. However, the lattice of crystallized BST was distorted at the BST/Pt interface, though Ba0.6Sr0.4TiO3 has a cubic structure. From a high-resolution TEM study we found that the adjacent BST crystallitas with different orientations lead to the lattice distortion. A selected area electron diffraction pattern clearly shows the split-spots from the distorted lattices which has 4-5 degrees distortion angles. (C) 2001 Elsevier Science B.V. All rights reserved.