Robust energy storage density and negative capacitance in antiferroelectric heterostructures grown by atomic layer epitaxy

Abstract

Energy storage devices with high energy storage density (U_ESD), fast operating speed, and high output power are indispensable for modern energy needs. This study presents a wafer-scale epitaxial antiferroelectric ZrO₂/TiN heterostructure with a state-of-the-art high U_ESD of ∼118.6 J cm⁻³. This significant U_ESD originates from the predominant [110] antiferroelectric polar axis of ZrO₂ oriented out-of-plane, which is confirmed by macroscopic and microscopic analyses of the epitaxial relationships. The construction of a coincidence site lattice indicates the low lattice mismatch between ZrO₂(110) and TiN(111). The stacking of ZrO₂ sublayers demonstrates the importance of precise epitaxy in controlling crystal orientation, minimizing leakage current, and improving antiferroelectric characteristics. Furthermore, the epitaxial growth of ZrO₂ enables a clear observation of inductive-like negative capacitance response, providing insights into antiferroelectric dynamics. The high U_ESD highlights the significance of atomic layer epitaxy for high-quality antiferroelectric heterostructures, particularly in epitaxial growth methods and energy storage applications.