Dielectric parameters of elastically strained heteroepitaxial SrTiO$_3$ films

Three-layer epitaxial Sr$_{0.71}$Al$_{0.65}$Ta$_{0.35}$O$_{3}$ heterostructures with the 900-nm-thick intermediate layer of strontium titanate have been grown on single-crystal (001)La$_{0.29}$Sr$_{0.71}$Al$_{0.65}$Ta$_{0.35}$O$_{3}$ substrates by the laser evaporation method. Plane-parallel film capacitors have been formed on the basis of the grown heterostructures using photolithography and ion etching. Temperature dependences of the dissipation factor have been measured for these capacitors at different bias voltages applied to strontium ruthenate electrodes. Temperature dependences of the permittivity of the intermediate SrTiO$_3$ layer in the formed capacitor structures are visualized with compensation of the internal electric field and without it. The reasons for the sharp increase in the dielectric loss in the formed film capacitors at temperatures below 50 K are analyzed.