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Improving the endurance performance for hafnia-based ferroelectric thin films and devices is of considerable significance from both scientific and technological perspectives. Here, we obtained robust ferroelectricity in Hf0.5Zr0.5O2 (HZO) thin films without the need of the confinement from top electrodes by systematically optimizing the conditions and parameters for the post-deposition annealing (PDA) process. Compared with the post-metallization annealing (PMA) process, PDA is found to markedly improve the ferroelectric endurance performance. In particular, wake-up-free ferroelectric HZO thin films with an exceptional endurance performance (∼3 × 1010 cycles) are obtained by PDA processing conducted under an oxygen atmosphere, which is attributed to the suppression of oxygen deficiency in the HZO thin films and the inhibition of interfacial reaction layer that inevitably forms during annealing treatment for PMA processing. Our work offers insight into improving ferroelectricity and endurance for hafnia-based ferroelectric materials and devices. [ABSTRACT FROM AUTHOR]

Topological quad-domain textures in ferroelectric nanoislands have been considered as enablers for nanoelectric devices. However, the fabrication of ordered arrays of ferroelectric islands exhibiting this domain structure is a challenge. By using substrate patterning to create nucleation sites, highly ordered quad-domain ferroelectric polarization configurations were achieved in BiFeO3 nanoisland arrays. Reversible switching of the quad-domain between the center divergent state with highly conductive domain walls and the center convergent state with insulating domain walls can be realized, resulting in a resistance change with a large on/off ratio. This templated growth strategy enables the controllable fabrication of exotic topological domains and sheds light on their applications for configurable electronic devices. [ABSTRACT FROM AUTHOR]

Self‐assembled two‐phase vertically aligned nanocomposites consisting of ferromagnetic pillars embedded in a ferroelectric matrix provide an attractive geometry for observing magnetoelectric coupling based on the strain‐coupled magnetostrictive and piezoelectric effects at the interfaces. In perovskite‐spinel nanocomposites the ferroelectric phase typically consists of BiFeO3, BaTiO3 or Pb(Zr,Ti)O3. Here, the ferroelectric phase is Y‐rich YFeO3 which exhibits ferroelectricity originating from the local inversion symmetry breaking caused by YFe antisite defects. Coherent interfaces observed between Y‐rich YFeO3 and a magnetic spinel CoFe2O4 in a vertically aligned nanocomposite enable strain‐mediated magnetoelectric coupling at room temperature, confirming the ferroelectricity and piezoelectricity in Y‐rich YFeO3 and extending the range of magnetoelectric nanocomposite compositions. [ABSTRACT FROM AUTHOR]

Single-phase multiferroic materials that allow the coexistence of ferroelectric and magnetic ordering above room temperature are highly desirable, motivating an ongoing search for mechanisms for unconventional ferroelectricity in magnetic oxides. Here, we report an antisite defect mechanism for room temperature ferroelectricity in epitaxial thin films of yttrium orthoferrite, YFeO3, a perovskite-structured canted antiferromagnet. A combination of piezoresponse force microscopy, atomically resolved elemental mapping with aberration corrected scanning transmission electron microscopy and density functional theory calculations reveals that the presence of YFe antisite defects facilitates a non-centrosymmetric distortion promoting ferroelectricity. This mechanism is predicted to work analogously for other rare earth orthoferrites, with a dependence of the polarization on the radius of the rare earth cation. Our work uncovers the distinctive role of antisite defects in providing a mechanism for ferroelectricity in a range of magnetic orthoferrites and further augments the functionality of this family of complex oxides for multiferroic applications. Ferroelectricity in orthoferrite perovskites has stimulated intense research, but the mechanism remains unclear. Here, the authors propose an antisite defect mechanism for introducing ferroelectricity in magnetically ordered YFeO3 and the family of rare earth orthoferrites. [ABSTRACT FROM AUTHOR]