Effect of Mn-doping on high field energy storage properties of Ag(Nb,Ta)O3 epitaxial films on ⟨100⟩ SrTiO3

Abstract

Single-phase epitaxial thin films of pure and 0.5 mol. % Mn-doped perovskite Ag(Nb0.45Ta0.55)O3 (ANT) were prepared by pulsed laser deposition on ⟨001⟩ oriented SrTiO3 substrates with (La0.5, Sr0.5)CoO3 bottom electrodes. Films of 195–245 nm thickness with smooth surface morphology were obtained. Mn-doping improved high field leakage current both by reducing electrical conductivity and by improving the onset electric field from 125 to 300 kV/cm, where conductivity diverges precipitously. The increase in the onset electric field is attributed to the donor dopant behavior of Mn by substitution on the perovskite A-site, counteracting the native p-type conductivity of ANT due to Ag-deficiency. Oxygen annealing of both films at 1 atm, 500 °C for 1 h drastically decreased the loss tangent while having a modest effect on the permittivity in the Mn-doped films. Hysteresis (PE) loops with applied electric fields up to 1200 kV/cm were obtained in Mn-doped films for which Pmax = 14.8 μC/cm2 and Wrec = 5.6 J/cm3 with η = 80%, which shows great improvement in energy storage properties compared to undoped ANT epitaxial thin films.