Interface Engineering for Expanded Stable Polarization Regime Upon Cycling in Ferroelectric Hf0.5Zr0.5O2.

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 HfO2, but research on epitaxial films is scarce. In this work, we use epitaxial La-doped HfO2 (LHO) in a Pt/LHO/La0.67Sr0.33MnO3 capacitor grown on SrTiO3(001) and SrTiO3(110) substrates and we investigate the impact of ZrO2 nanolayers when inserted as top layers, bottom layers, or simultaneously in both positions. It is found that the position of the ZrO2 nanolayers and the substrate orientation influence the formed phases and functional properties. In the multilayers on SrTiO3(110) polarization is larger, but there is pronounced wake-up. Multilayers on SrTiO3(001) with a ZrO2 nanolayer at the bottom interface exhibit presence of monoclinic phase and low polarization, as well as wake-up effect. However, inserting ZrO2 solely as a capping layer on SrTiO3(001) results in high polarization, minimal wake-up effect, long endurance of 1011 cycles, retention beyond 10 years, leakage current less than 10-7 A/cm2 at 1 V and switching time shorter than 90 ns.