Enhancing ferroelectric stability: Wide-range of adaptive control in epitaxial HfO2/ZrO2 superlattices

TL;DR

This paper demonstrates that epitaxial HfO2/ZrO2 superlattices can achieve highly stable ferroelectricity over a wide thickness range, overcoming traditional stability issues and enabling broader application potential.

Contribution

It introduces a novel superlattice design that significantly enhances ferroelectric stability and fatigue resistance in HfO2-based materials, supported by first-principles calculations.

Findings

Stable ferroelectricity up to 100 nm thickness

Fatigue resistance exceeding 10^9 cycles

Low coercive field of ~0.85 MV/cm

Abstract

The metastability of the polar phase in HfO2, despite its excellent compatibility with the complementary metal-oxide-semiconductor process, remains a key obstacle for its industrial applications. Traditional stabilization approaches, such as doping, often induce crystal defects and impose constraints on the thickness of ferroelectric HfO2 thin films. These limitations render the ferroelectric properties vulnerable to degradation, particularly due to phase transitions under operational conditions. Here, we demonstrate robust ferroelectricity in high-quality epitaxial (HfO2)n/(ZrO2)n superlattices, which exhibit significantly enhanced ferroelectric stability across an extended thickness range. Optimized-period superlattices maintain stable ferroelectricity from up to 100 nm, excellent fatigue resistance exceeding 109 switching cycles, and a low coercive field of ~0.85 MV/cm. First-principles calculations reveal that the kinetic energy barrier of phase transition and interfacial formation energy are crucial factors in suppressing the formation of non-polar phases. This work establishes a versatile platform for exploring high-performance fluorite-structured superlattices and advances the integration of HfO2-based ferroelectrics into a broader range of applications.