Response of the capacitance and dielectric loss of the SrRuO$_{3}$/SrTiO$_{3}$/SrRuO$_{3}$ film heterostructures to variations in temperature and electric field

Three-layer epitaxial heterostructures with a 750-nm-thick intermediate strontium titanate layer between two strontium ruthenate conductive thin-film electrodes have been grown by laser deposition. Photolithography and ion etching have been used to form film parallel-plate capacitors based on the grown heterostructures. The capacitance (C) and dielectric loss tangent $(\tan\delta)$ of the parallel-plate capacitors have been measured in the temperature range $T$ = 4.2–300 K at an applied bias voltage of up to $\pm$ 2.5 V and without it. At $T>$ 100 K, the temperature dependence of the dielectric permittivity $(\varepsilon)$ of the SrTiO$_3$ intermediate layer is well approximated by the Curie–Weiss law taking into account the capacitance induced by the penetration of an electric field into the oxide electrodes. At $T\approx$ 20 K, the dielectric permittivity $\varepsilon$ of the SrTiO$_3$ intermediate layer decreases by approximately 20% in an electric field of 25 kV/cm. The dielectric loss tangent of the film capacitor heterostructures decreases monotonically with a decrease in the temperature in the range from 300 to 80 K and almost does not depend on the electric field strength. However, in the range from 80 to 4.2 K, the dielectric loss tangent increases nonmonotonically (abruptly) with a decrease in the temperature and decreases significantly in an applied electric field.