Structural characteristics of Sr$_{0.61}$Ba$_{0.39}$Nb$_{2}$O$_{6}$/MgO(001) thin films grown by RF-cathode sputtering

Thin films of the congruent composition of the barium-strontium niobates solid solutions Sr$_{0.61}$Ba$_{0.39}$Nb$_{2}$O$_{6}$ (SBN: 61) with thicknesses from 30 to 630 nm on a MgO (001) substrate were fabricated by RF-cathode sputtering in an oxygen atmosphere. By X-ray diffraction it was found that the films are epitaxial and there are no impurities in them. In the films, there is practically no unit cell deformation in the interface plane and tensile strain is present in the normal to the surface direction, which increases with decreasing film thickness. Dielectric measurements indicate high tunability in the films.