Fatigue-Resistant Ferroelectric Hafnium Oxides by Modulating Grain Boundaries.

Abstract

Recently, high-endurance ferroelectric HfO₂ is highly desirable since the emerging of in-memory computing requires non-volatile memories not only to store data but also to execute computation, challenging writing/erasure switching reliability. Understanding and exploitation of the polarization fatigue diagram are crucial for improving endurance performances. Here, we show fatigue-resistant Sm:HfO₂ thin films by modulating grain boundaries (GBs) in orientation-controllable orthorhombic phase. On GBs, orientation discontinuity raises energy levels of O 2p orbitals due to lattice distortion, which promote electron accumulation and yield a high-symmetry structural transform at the boundary, facilitating 90° switching of out-of-plane domains because of lowered switching barrier. Then the domains are frozen in plane by the charged GBs and polarization fatigue takes place. By eliminating GBs associated with phase transform, remarkably-improved fatigue resistance is achieved in uniform 180° switching, which exhibits the increase of fatigue-free endurance by 200 times to 2.0 × 10⁹ cycles with, more importantly, a large field-cycling non-volatile polarization of ∼60 µC/cm², showing the state-of-the-art endurance performances in hafnium oxides. Roadmaps of the fatigue scenarios are given based on key roles of GBs in domain configurations and switching pathways. Our findings open a new perspective for fatigue studying and guide the material design of high-reliability hafnium oxide memories.