Invited
Oxygen defective metal oxides: boosting non-classical electrostriction at the nanoscale in thin films and heterostructures

Electrostriction is the response of induced strain in insulating materials subjected to an electric field. In classical electrostrictors, the electromechanical properties are generally low as they arise from slight structural electric charge strain in the materials. Thus the electrostriction effect strictly depends on the dielectric properties of the materials [1]. Highly oxygen-defective ionic metal oxides, e.g., fluorites such as ceria and bismuth oxide, are non-classical electrostrictors. These crystalline structures are centrosymmetric with no piezoelectricity and a low dielectric constant. However, these oxygen-defective metal oxides` electrostrictive properties can be superior to any known material.

In this lecture, we describe the genesis of these new functional materials, reporting the recent findings underlying the exceptional electromechanical performances of oxygen-defective electrostrictors from the bulk to the nanoscale [2, 3]. We highlight the effect of dopants, microstructure, and crystallography on their properties, focusing on the exceptional electromechanical effects registered at the nanoscale in thin films and heterostructures. We present the latest developments in the definition of the physical model describing the effect, giving an insight into new possible materials design criteria. We also show how the materials perform in devices and how this novel technology can impact micro/nano-electromechanical system design and related technologies.

References

[1] S. Santucci and V. Esposito, "Electrostrictive Ceramics and Their Applications." In: Pomeroy, M. (ed) Encyclopedia of Materials: Technical Ceramics and Glasses, vol. 3, pp. 369–374. Oxford: Elsevier 82021; http://dx.doi.org/10.1016/B978-0-12-803581-8.12071-5

[2] H. Zang et al., "Atomically engineered interfaces yield extraordinary electrostriction", Nature 609, 696-700 (2022); https://doi.org/10.1038/s41586-022-05073-6

[3] D.-S. Park et al.," Induced giant piezoelectricity in centrosymmetric oxides", Science 375, 653–657 (2022); DOI: 10.1126/science.abm7497