Atomic-scale mechanism unlocks thermal-stable high-κ performance in HfO₂ via coherent interfaces

Complementary-metal-oxide-semiconductor-compatible HfO₂-based high-κ dielectrics are pivotal for next-generation electronics in the post-Moore's Law era. However, establishing coherent interfaces via morphotropic phase boundaries across the tetragonal and orthorhombic (ferroelectric or antiferroelectric) phases-a key strategy for enhancing dielectric properties-remains challenging due to unclear atomic-scale mechanisms and inherent thermal instability, which compromises long-term stability and reliability. To address this, we leverage metallurgical quenching principles to stabilize tetragonal/orthorhombic-antiferroelectric morphotropic phase boundaries in HfO₂-based (Lu:Hf_0.6Zr_0.4O₂) bulk crystals. Through precise composition tuning and growth optimization, we stabilize these metastable morphotropic phase boundaries at the tetragonal/orthorhombic-antiferroelectric interface at room temperature, achieving a comparable κ-value (57) to actively studied tetragonal/orthorhombic-ferroelectric counterparts. Microstructural characterization reveals how tensile strain within the t-phase drives dielectric enhancement through softening of the low-frequency E_u phonon mode. Critically, the tetragonal/orthorhombic-antiferroelectric morphotropic phase boundary demonstrates a ~58% reduction in κ variation rate over 30-200 °C relative to tetragonal/orthorhombic-ferroelectric counterparts, signifying superior thermal stability. Our study establishes a generalizable design paradigm for developing high-κ dielectrics in fluorite-structured materials, advancing next-generation complementary-metal-oxide-semiconductor-compatible-integrated functional devices for data storage, energy harvesting, sensing, and integrated photonics.