O.M. ZHIGALINA, V.M. MUKHORTOV, Y.I. GOLOVKO, A.L. CHUVILIN, A.N. KUSKOVA

In the paper the high resolution transmission electron microscopy has been used for investigation and analysis of the defect microstructure in single-crystal nanoscale ferroelectric Ba0.8Sr0.2TiO3 films grown on MgO substrates by magnetron sputtering. All samples were characterized in a Tecnai G2 30ST and a FEI Titan 80-300 at accelerating voltage of 300kV, using imaging, electron diffraction and high-angle-annular dark-field (HAADF) STEM detector. BST thin films revealed a monocrystalline structure with low-angle blocks boundaries (θ < 0,5-1). The main reason of the block structure was a surface geometry (holes and hills) of MgO substrate. TEM observation of the parallel moire arising from superposition of MgO and BST lattices, allows to reveal dislocations with vectors of Burgers <100>and 1/2<110> and borders of blocks defined by them. Digital analysis of cross sections HREM images allowed us to visualize and compare misfit dislocations and displacement fields around their cores at the heterostructure interface for films with different thickness. It has been shown that stress relaxation in the films is realized by misfit dislocations formed at the film-substrate interface.