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

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 (PLD) on 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 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 {degree sign}C for 1 hour 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 thin films.