Influence of epitaxial stress on thermally activated endurance phenomena in Hf_0.5Zr_0.5O₂

Fluorite ferroelectrics exhibit an abundance of thermally activated phenomena that impact their ferroelectric electric field cycling endurance and thus performance during long-term utilization. Some phenomena, such as oxygen vacancy defect migration and phase transformations, possess activation energies that are sensitive to applied stress and resulting crystallographic structural distortions. This sensitivity provides a relatively unexplored opportunity to more closely examine ways in which stress sources like misfit strain impact the endurance of fluorite ferroelectrics. To this end, we will report on the influence of epitaxial stress on thermally activated endurance phenomena in thin epitaxial Hf_0.5Zr_0.5O₂ (HZO) films prepared via pulsed laser deposition. Stress is transmitted via the La_0.67Sr_0.33MnO₃ (LSMO) bottom electrode, whose lattice mismatch with SrTiO₃ (100), DyScO₃ (110), or TbScO₃ (110) substrates induces increasingly tensile strain in the LSMO layer. This tensile strain modifies the resulting misfit strain between LSMO and HZO, imposing a variable epitaxial stress in the ferroelectric layer. Temperature-dependent ferroelectric endurance behavior will then be examined via Arrhenius analysis, and extraction of substrate-dependent wake-up and fatigue activation energies will reveal the role of epitaxial stress on thermally activated endurance phenomena in HZO.