Robust Antiferroelectric Response in the Pbca Phase of Hafnium Zirconium Oxide via Aluminum Substitution

Abstract

Hafnium zirconium oxide (HZO) has attracted attention for applications in nonvolatile memory and energy harvesting devices. However, it faces practical challenges such as insufficient endurance. One promising strategy to address this limitation is the utilization of antiferroelectric (AFE) behavior in HZO-based materials. Previous studies have shown that various metal substitutions into HZO can result in AFE-like properties within specific substitution concentration windows. While AFE-like properties have often been attributed to the tetragonal phase of ZrO₂, recent studies suggest that the antipolar orthorhombic phase (space group Pbca) may instead be responsible for the observed AFE behavior. This study investigates how varying aluminum substitution concentration influences the phase and electrical properties of HZO devices to clarify the origin of AFE behavior. The results demonstrate that low aluminum concentrations in HZO, particularly in 8:1 and 6:1 HZO:Al composition ratio HZO devices, lead to pronounced real AFE behavior associated with the formation of the Pbca phase.