High Energy Performance Ferroelectric (Ba,Sr)(Zr,Ti)O₃ Film Capacitors Integrated on Si at 400 °C

Abstract

BaTiO₃-based ferroelectrics have been extensively studied due to their large dielectric constants and a high saturated polarization, which have the potential to store or supply electricity of very high energy and power densities. In order to further improve the energy efficiency η and the recyclable energy density <i>W</i>_rec, an A, B-site co-doped (Ba_0.95,Sr_0.05)(Zr_0.2,Ti_0.8)O₃ ceramic target was used for sputter deposition of film capacitor structures on Si. This film composition reduces the remnant polarization <i>P</i>_r, while the choice of a low-temperature, templated sputtering process facilitates the formation of high-density arrays of columnar nanograins (average diameter <i>d</i> ∼20 nm) and grain boundary dead layers. This self-assembled nanostructure further delays the saturation of the electric polarization, leading to a high energy density <i>W</i>_rec of ∼148 J/cm³ and a high energy efficiency <i>η</i> of ∼90%. Moreover, the (Ba_0.95,Sr_0.05)(Zr_0.2,Ti_0.8)O₃ film capacitors retain their high energy storage performance in a broad range of working temperature (-175-300 °C) and operating frequency (1 Hz-20 kHz). They are also fatigue-free after up to 2 × 10⁹ switching cycles. Our work provides a new method and a cost-effective processing route for the creation and integration of high-performance dielectric capacitors for energy storage applications.