Effect of internal strain fields on the controllability of nanodimensional ferroelectric films in a plane capacitor

Nanodimensional ferroelectric heteroepitaxial Ba0.8Sr0.2TiO3 films grown by the layer-by-layer mechanism on MgO(100) substrates are examined by the X-ray diffraction and transmission electron microscopy methods. It is established that, when the thickness of the film changes, the stress relaxation proceeds via generation of misfit dislocations at the film-substrate interface. There exists a critical thickness (≈40 nm) of the film below and above which the film possesses tensile and compression stresses, respectively. Examples of how the stresses influence the insulating properties of the films are given.