Epitaxial Ferroelectric La-doped Hf0.5Zr0.5O2 Thin Films

TL;DR

This study investigates La-doped epitaxial Hf0.5Zr0.5O2 ferroelectric films, showing they achieve high endurance and retention with limited wake-up effects, challenging the notion that doping inherently causes retention degradation.

Contribution

It demonstrates that La-doped epitaxial Hf0.5Zr0.5O2 films can overcome the endurance-retention dilemma observed in polycrystalline films, with high endurance and long-term retention.

Findings

Epitaxial La-doped films exhibit high polarization over a wide thickness range.

Endurance exceeds 10^10 cycles with retention over 10 years.

Wake-up effect is limited to a few cycles in epitaxial films.

Abstract

Doping ferroelectric Hf0.5Zr0.5O2 with La is a promising route to improve endurance. However, the beneficial effect of La on the endurance of polycrystalline films may be accompanied by degradation of the retention. We have investigated the endurance - retention dilemma in La-doped epitaxial films. Compared to undoped epitaxial films, large values of polarization are obtained in a wider thickness range, whereas the coercive fields are similar, and the leakage current is substantially reduced. Compared to polycrystalline La-doped films, epitaxial La-doped films show more fatigue but there is not significant wake-up effect and endurance-retention dilemma. The persistent wake-up effect common to polycrystalline La-doped Hf0.5Zr0.5O2 films, is limited to a few cycles in epitaxial films. Despite fatigue, endurance in epitaxial La-doped films is more than 1010 cycles, and this good property is accompanied by excellent retention of more than 10 years. These results demonstrate that wake-up effect and endurance-retention dilemma are not intrinsic in La-doped Hf0.5Zr0.5O2.