Interface Engineering for Expanded Stable Polarization Regime Upon Cycling in Ferroelectric Hf 0.5 Zr 0.5 O 2

Interfaces have a significant influence on the functional properties of ferroelectric devices, and their optimization is necessary to accelerate the path toward applications. Interface engineering has been extensively investigated in polycrystalline HfO 2 , but research on epitaxial films is scarce. In this work, we use epitaxial La‐doped HfO 2 (LHO) in a Pt/LHO/La 0.67 Sr 0.33 MnO 3 capacitor grown on SrTiO 3 (001) and SrTiO 3 (110) substrates and we investigate the impact of ZrO 2 nanolayers when inserted as top layers, bottom layers, or simultaneously in both positions. It is found that the position of the ZrO 2 nanolayers and the substrate orientation influence the formed phases and functional properties. In the multilayers on SrTiO 3 (110) polarization is larger, but there is pronounced wake‐up. Multilayers on SrTiO 3 (001) with a ZrO 2 nanolayer at the bottom interface exhibit presence of monoclinic phase and low polarization, as well as wake‐up effect. However, inserting ZrO 2 solely as a capping layer on SrTiO 3 (001) results in high polarization, minimal wake‐up effect, long endurance of 10 11 cycles, retention beyond 10 years, leakage current less than 10 −7 A/cm 2 at 1 V and switching time shorter than 90 ns.