Invited
In-situ TEM studies of ferroelectric domains: The effect of temperature and chemical environment

Ferroelectrics are polar materials characterized for their spontaneous polarization which can be reversible switched upon the application of an external field. The resulting domain structure, and switching dynamics, is driven by boundary conditions to minimize electrostatic, and often elastic energy in the system, as the material is cooled below its Curie temperature (TC).

Transmission electron microscopy (TEM) is one of the routine techniques used to study ferroelectrics, mainly in a static or almost ‘post-mortem’ manner. However, the later advancements in the field have made in-situ TEM experiments more accessible, making the technique an increasingly powerful tool, providing direct observation into the delicate relationship between domain dynamics and the applied external stimuli.

A particularly interesting aspect of ferroelectrics is the effect that surface chemical species have on the screening mechanism, and its resulting domain structure, and vice versa, how domains affect the surface chemistry. The latter could be exploited to tailor surface reactivity for electrochemical, catalytical,[1-6] and other energy harvesting applications.[2, 7-9]

In this work, the thermally induced behavior of ferroelectric-ferroelastic domains in free-standing thin films, under different chemical environments, are studied via in-situ scanning transmission electron microscopy (STEM) techniques. Differences and communalities are discussed, as well as associated challenges.

To our knowledge this is the first time that in-situ TEM heating under a controlled gas environment has been performed to study ferroelectric domains and phase transformation. We offer valuable insight into the delicate link between key ferroelectric characteristics and the chemical environment. Moreover, it showcases in-situ TEM gas as a novel technique to explore the effect that external variables (pressure and temperature) have on polar materials in a dynamic manner, particularly.

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[7] H. Li, C. R. Bowen, Y. Yang, Advanced Functional Materials 2021, 31, 2100905.

[8] M. Xie, S. Dunn, E. L. Boulbar, C. R. Bowen, International Journal of Hydrogen Energy 2017, 42, 23437.

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