Guidelines for the Optimization of Hafnia-Based Ferroelectrics through Superlattice Engineering

Hafnia-based ferroelectrics are revolutionizing the data storage industry and the field of ferroelectrics, with improved materials and devices being reported monthly. However, full understanding and control have not been reached yet, and the ideal material still needs to be found. Here, we report ferroelectric hafnia-zirconia superlattices made out of zirconium-substituted hafnia (Hf_1-<i>x</i> Zr _<i>x</i> O₂) sublayers of varying stoichiometries alternating with pure ZrO₂ sublayers. It is observed that the ZrO₂ layers in these superlattices act as a booster for total remnant polarization (<i>P</i> _r). By combining the benefits of the ZrO₂ layers and the added interfaces, which help prevent breakdown, we fabricate superlattices with a total 87.5% ZrO₂ content, exhibiting record polarizations with a 2<i>P</i> _r value of 84 μC/cm² that can be cycled 10⁹ times while maintaining a 2<i>P</i> _r > 20 μC/cm². Next to these attractive properties, substitution of HfO₂ by the much more abundant ZrO₂ offers a significant step toward the sustainable application of these devices.