Ab Initio Study on 3D Anisotropic Ferroelectric Switching Mechanism and Coercive Field in HfO ₂ and ZrO ₂

Abstract This study proposes a new ferroelectric switching mechanism in HfO 2 ‐based ferroelectric films by using density functional theory calculations. It predicts a theoretical coercive field (E c ) consistent with the experimental value (≈1 MV cm −1 ). To this end, this work considers the anisotropic nucleation and growth of reversed polarization along the three principal axes of the orthorhombic phase of HfO 2 and ZrO 2 . This approach differs from the earlier theoretical study that assumed homogeneous switching and predicted too high E c (≈10 MV cm −1 ), and from the recent theoretical prediction that assumed domain switching but still predicted unrealistically high E c . Along the b‐direction involving the non‐polar spacer sub‐unit cell layer, the switching barriers (E s s) for nucleation and growth of a reversed domain are similar. In contrast, along the a‐direction, which lacks a non‐polar layer and is previously overlooked, nucleation affects neighboring polar layers, significantly reducing the E s for growth. Switching types along the c‐direction (homogeneous or stepwise) has little effect on the overall E s . These distinct E s characteristics along three directions predict an E c of 1–2 MV cm −1 for a 10‐nm‐thick (Hf,Zr)O 2 film, consistent with experimental results.