Enhanced Dielectric Energy Storage in Hf0.5Zr0.5O2-Based Oxides by Structure-Evolution Amorphization

Abstract

The scale-down demands of electronic power devices make high-energy-density dielectric thin-film capacitors highly desirable. Most recently, improved dielectric energy storage properties have been reported in high-k binary materials, particularly the HfO₂-based oxides, showing promising applications. Here, we show a record-high energy storage density of 185 J/cm³ in this community achieved in Ba²⁺-doped Hf_0.5Zr_0.5O₂ (BHZO) thin films by structure-evolution amorphization. Employing molecular dynamics simulations, we reveal the amorphization mechanism of the structure transformation between the fluorite Hf_0.5Zr_0.5O₂ and perovskite Ba(Hf_0.5Zr_0.5)O₃, in which the oxygen instability and diffusion spreading over the Hf/Zr metal sublattices result in the collapse of long-range orderings. Strong disorder is achieved in the Hf_0.5Zr_0.5O₂ matrix, giving rise to an ultrahigh breakdown strength of 13.3 MV/cm in amorphous structure with the Ba²⁺ concentration of 12 at%. In addition, the maintenance of metal frames also allows further modulation of the amorphous BHZO films by substrate clamping and improved dielectric permittivity is achieved when the lattice mismatch is large. As a result, a giant energy storage density is obtained owing to the dielectric properties that are far beyond the trade-off between breakdown strength and permittivity. Our findings give theoretical and experimental insights for creating high-quality amorphous dielectric oxides and shed light on the exploitation of dielectric energy storage for advanced electronic devices.