Dopant-controlled switching polarization mechanisms in Y- and Sc-doped ferroelectric HfO2 from first principles

Ferroelectric HfO₂ is a CMOS-compatible functional oxide whose polarization emerges when the non-centrosymmetric orthorhombic phase is stabilized by dopants. Among common dopants, yttrium (Y) and scandium (Sc) are particularly effective yet exhibit distinct switching behavior that is challenging to quantify from first principles because Berry-phase polarization is defined modulo a polarization quantum. Here we use density functional theory combined with the modern Berry-phase formalism to compute switching polarization in Y- and Sc-doped HfO 2 using symmetry-related ± P endpoint structures in 2 × 2 × 2 supercells (3.125%–9.375% cation doping). By selecting the physically continuous branch of the polarization lattice, the extracted switching polarization quantitatively reproduces the experimentally observed nonmonotonic dependence on dopant concentration, including a maximum near-low-cation doping and a systematic suppression at higher concentrations. Real-space charge-density difference maps, ∆ ρ = ρ + P − ρ − P , further show that Y doping promotes a more collective “soft-mode-like” redistribution, whereas Sc induces a more localized “stiff-mode-like” response consistent with stronger Sc O bonding. These results establish a unified microscopic mechanism linking dopant chemistry, bonding strength, charge redistribution coherence, and switching polarization in doped HfO 2 . Dopant chemistry governs ferroelectric switching in HfO₂ through dopant-dependent charge redistribution and Berry-phase branch selection, leading to a non-monotonic dependence of switching polarization on dopant concentration. Y-doping induces collective soft-mode switching, whereas Sc-doping promotes localized stiff-mode behavior.