Ultrahigh Energy Density in SrTiO3 Film Capacitors

Abstract

Solid-state dielectric film capacitors with high-energy-storage density will further promote advanced electronic devices and electrical power systems toward miniaturization, lightweight, and integration. In this study, the influence of interface and thickness on energy storage properties of SrTiO₃ (STO) films grown on La_0.67Sr_0.33MnO₃ (LSMO) electrode are systematically studied. The cross-sectional high resolution transmission electron microscopy reveals an ion interdiffusion layer and oxygen vacancies at the STO/LSMO interface. The capacitors show good frequency stability and increased dielectric constant with increasing STO thickness (410-710 nm). The breakdown strength (E_b) increases with decreasing STO thickness and reaches 6.8 MV/cm. Interestingly, the E_b under positive field is enhanced significantly and an ultrahigh energy density up to 307 J/cm³ with a high efficiency of 89% is realized. The enhanced E_b may be related to the modulation of local electric field and redistribution of oxygen vacancies at the STO/LSMO interface. Our results should be helpful for potential strategies to design devices with ultrahigh energy density.

Keywords: breakdown strength; dielectric capacitor; energy storage; ion interdiffusion; oxygen vacancy.