Influence of thickness on the domain structure of barium-strontium-titanate films on MgO substrates

Ba_0.8Sr_0.2TiO₃/MgO(001) heterostructures are studied using atomic-force spectroscopy in several modes (the contact and semicontact modes and that of piezoelectric response) to obtain information on the relief and the distribution of the electric potential on the surface. Based on data obtained for films with different thicknesses, the correlation between the domain sizes and orientations and the film thickness and the surface relief is established. It is shown that the films with thicknesses less than 36 nm contain only aa domains whose dimensions decrease with increasing film thickness. The films with thicknesses greater than 36 nm contain only c domains whose dimensions increase with increasing film thickness.