Orthorhombic phase stabilization and ferroelectric enhancement in ZrO2 thin films via stress engineering

Abstract

In the present work, the ZrO₂ ferroelectric thin films were prepared by chemical solution deposition (CSD). The effects of crystallization temperature and reduced-pressure annealing on the ferroelectric properties of the ZrO₂ thin films were systematically investigated. Semi-quantitative analysis based on Rietveld refinement showed that, at an annealing temperature of 800 °C, the ferroelectric orthorhombic phase fraction reached 37.2%, with a remanent polarization of 7.59 µC cm⁻². Annealing under reduced pressure (0.06 MPa) further increased the orthorhombic phase fraction to 88.29% and enhanced the remanent polarization to 14.45 µC cm⁻². High-resolution transmission electron microscopy (HRTEM) analysis revealed that reduced-pressure annealing introduced in-plane tensile stress, which expanded the interplanar spacing of the orthorhombic phase and effectively stabilized this metastable ferroelectric phase at room temperature. This work demonstrates a promising strategy for optimizing the performance of fluorite-structured oxide ferroelectric thin films.