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arXiv · 2406.13382

Flexoelectricity in Amorphous Hafnium Oxide (HfO2)

Daniel Moreno-Garcia·Kaitlin M. Howell·Luis Guillermo Villanueva
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Abstract

Flexoelectricity, inherent in all materials, offers a promising alternative to piezoelectricity for nanoscale actuation and sensing. However, its widespread application faces significant challenges: differentiating flexoelectric effects from those of piezoelectricity and other phenomena, verifying its universality across all material structures and thicknesses, and establishing a comprehensive database of flexoelectric coefficients across different materials. This work introduces a groundbreaking methodology that accurately isolates flexoelectricity from piezoelectric, electrostrictive and electrostatic effects, with a detection threshold extending below 1 fC/m. The robustness of this method is demonstrated through its application to amorphous hafnium oxide (HfO$_2$), successfully measuring a flexoelectric coefficient of 105 $\pm$ 10 pC/m. This measurement signifies the first measurement of flexoelectricity in hafnia, as well as in any amorphous material. Additionally, the study compiles a list of published flexoelectric coefficients, revealing an important insight. The relationship between the flexoelectric coefficient and the material's relative permittivity is better approximated by a quadratic proportionality. This challenges the traditional linear assumption proposed in Kogan's work and opens new avenues for future research in flexoelectric materials.

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Daniel Moreno-Garcia, Kaitlin M. Howell, Luis Guillermo Villanueva. 2024-06-19. Flexoelectricity in Amorphous Hafnium Oxide (HfO2). https://arxiv.org/abs/2406.13382

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