AFE-like Hysteresis Loops from Doped HfO₂: Field Induced Phase Changes and Depolarization Fields

Interplay between oxygen defects and dopants: effect on structure and performance of HfO2-based ferroelectrics

“…(2) A phase transition from a non-polar tetragonal to a polar o-phase can occur. 71,90 This field induced phase transition can flip back to the non-polar phase when the field is removed, 91 or stay in the po-phase as recently reported. 92 The back-switching to the non-polar phase is expected to be influenced by strain/stress in the layer 91 and would cause the pinched hysteresis loop in pristine films.…”

Electric‐Field‐Induced Ferroelectricity in 5%Y‐doped Hf0.5Zr0.5O2: Transformation from the Paraelectric Tetragonal Phase to the Ferroelectric Orthorhombic Phase

“…[7] Furthermore, a small number of studies on the direct observations of structural phase transformations after applying an electric field have been reported. [19,23,26,27] In this study, we demonstrated a direct observation of a fieldinduced phase transition from the paraelectric tetragonal phase to the ferroelectric orthorhombic phase. A microarea XRD measurement carried out in the synchrotron radiation source suggests a phase transition after applying an electric field because 110 diffraction appeared, which was not observed for the tetragonal phase before applying the electric field.…”

Discovery of Nanoscale Electric Field‐Induced Phase Transitions in ZrO2

“…[33][34][35] The challenge of distinguishing between FE and AFE in fluorite-structured materials, which is critical for advancing technology, stems from not one but several experimental limitations: i) The FE polar orthorhombic (o) Pca2 1 phase is structurally similar to the nonpolar tetragonal (t) P4 2 /nmc phase, obfuscating clear identification of the phases in thin films by grazing incidence x-ray diffraction (GIXRD). [36] ii) AFE behavior is widely attributed to a reversible electric field-induced tetragonal to polar orthorhombic phase transition, but it has been challenging to obtain unambiguous structural identification of the phase transition under applied fields. [36,37] iii) An irreversible electric-field driven tetragonal to orthorhombic phase transition has been observed and may cause "wake-up".…”

“…[36] ii) AFE behavior is widely attributed to a reversible electric field-induced tetragonal to polar orthorhombic phase transition, but it has been challenging to obtain unambiguous structural identification of the phase transition under applied fields. [36,37] iii) An irreversible electric-field driven tetragonal to orthorhombic phase transition has been observed and may cause "wake-up". [38] iv) FE domains cannot be directly observed from electrical device measurements, but must be inferred from behavioral models at the device terminals.…”