Doping engineering to reduce the coercive field of ferroelectric ZrO2

Abstract

ZrO2 and HfO2 have attracted significant attention in the past decade due to their unexpected ferroelectric properties at the nanoscale, enabling the miniaturization of lead-free ferroelectric devices. Elemental doping is commonly used to further enhance their ferroelectric properties. However, in contrast to HfO2, the role of dopants with varying valences in ZrO2 remains incompletely understood at the atomic level. Herein, through first-principles simulations, we investigated the impact of 21 dopants on ZrO2, revealing a volcano-type relationship between the coercive field and ionic radii of dopants. Our simulations demonstrated that Al and Ga doping in ZrO2 not only enhance the stability of the polar orthorhombic phase but also reduce the coercive field by more than 50% relative to its pristine polar phase. Furthermore, we identified eight other dopants, such as Fe, Ti, Cu, Co, Y, La, Ce, and Sr, with the potential to improve the ferroelectric properties of ZrO2. The phonon analysis further elucidated the origin of the different roles of these dopants in ZrO2. We believe our results hold promise for guiding the design of low-voltage operational ferroelectric devices, thereby advancing the ferroelectric properties of ZrO2-based materials.