Influence of epitaxial stress on temperature-dependent ferroelectric endurance of Hf0.5Zr0.5O₂ from cryogenic to ambient conditions

Herein, we describe a comparative study of the ferroelectric properties of epitaxial Hf 0.5 Zr 0.5 O 2 films grown on La 0.67 Sr 0.33 MnO 3 /SrTiO 3 (100) and La 0.67 Sr 0.33 MnO 3 /DyScO 3 (110) across a temperature range of 32-298 K for the purpose of assessing the influence of epitaxial stress on material behavior. Despite the nearly 300% greater in-plane strain in the LSMO layer on DSO (110) than STO (100), strain in the HZO layer was minimal. The absence of strain propagation into the HZO film via LSMO is the result of domain matching epitaxy, in which the conventional strain induced by differences in the lattice parameters of HZO and LSMO is compensated and minimized by the generation of periodic integer multiples of HZO and LSMO planes matched along the interface of the two materials. However, epitaxial stress present during growth modifies the stability of the orthorhombic and monoclinic phases in the films, and produces differences in observed variable-temperature ferroelectric behavior. The HZO film grown on LSMO-buffered DSO (110) exhibits 20% greater remanent polarization than its LSMO-buffered STO (100) counterpart due to its enhanced orthorhombic phase volume and also experiences a smaller polarization-based wake up effect. The defect migration-mediated variable-temperature wake-up characteristics of both films, which manifest as pinched hysteresis loops at low temperatures, are comparable. Slight differences in the variable-temperature fatigue characteristics of the films suggest subtle electronic dissimilarities between HZO/LSMO/STO (100) and HZO/LSMO/DSO (110), which can also be explained by slight differences in domain pinning behavior due to differences in polar phase volume present in these films. Our findings provide insight into the influence of epitaxial stress on the behavior of HZO, which should prove useful for researchers aiming to utilize mismatch strain-based methods of introducing structural modifications for enhanced functionality and understanding material behavior in epitaxial HZO films.