Optimized energy storage performance by a depolarization field in BaMn0.01Ti0.99O3/Na0.5Bi0.5TiO3 multilayer thin films

Abstract

Ferroelectric thin film capacitors have attracted increasingly more attention due to their excellent energy storage performance and ability to be miniaturized and meet the requirements of lightweight electronic equipment. In this study, BaMn_xTi_1−xO₃ thin films were grown on Pt/Ti/SiO₂/Si substrates using the sol–gel method. An enhanced breakdown strength was achieved for a BaMn_0.01Ti_0.99O₃ film due to deepened electron trap levels caused by introducing appropriate oxygen vacancies. Decreased remnant polarization and further improved breakdown strength (BDS) were achieved in the aged thin film, resulting from the depolarization field introduced by defect dipoles in the aging process. Besides this, BaMn_0.01Ti_0.99O₃/Na_0.5Bi_0.5TiO₃ multilayer thin films with different NBT layers were constructed to introduce interfaces to enhance polarization and BDS, where a BMT/2NBT multilayer thin film exhibited an outstanding energy density of 53.9 J cm⁻³ and excellent efficiency of 74.3% under 4105 kV cm⁻¹ at room temperature. Furthermore, this capacitor showed excellent temperature stability with minor fluctuations in both the energy storage density (<2%) and energy storage efficiency (<5%) from 15 °C to 115 °C under 20 kHz. These results demonstrate that the BMT/NBT multilayer thin film is a promising candidate for use in energy storage capacitors.