Speaker: Christopher T. Nelson
Affiliation: University of California, Berkeley
Abstract Details: Ferroelectric oxides possess a spontaneous polarization which can be oriented with an applied electric field. This can be harnessed directly as a next-generation non-volatile memory or indirectly by coupling across heterojunctions to produce extrinsic electric- field controlled materials properties. The polarization switching process underpinning these applications is poorly understood at device-relevant sub-micrometer length scales. This is primarily due to a high sensitivity to defects, many of which are atomic-scale and inhomogenous. In this talk I will discuss our use of transmission electron microscopy (TEM) to study nanoscale ferroelectric switching of two prominent exemplar materials: PbZr0.2Ti0.8O3 (PZT) and BiFeO3 (BFO). I will provide a brief introduction to the operating principle and capabilities of TEM for in situ and ex situ characterization of transition metal oxides. This includes atomic- scale resolution of chemical and structural information which we use to calculate unit- cell maps of polarization distribution. I will then discuss the ferroelectric switching we observe in-situ, especially as it relates to macroscale switching properties. Of particular interest are preferential sites for domain nucleation and pinning, the presence of inactive regions, and the stability of switched domains.

About The Speaker: Dr. Christopher T. Nelson is affiliated with the University of California at Berkeley and the Singapore-Berkeley Research Initiative for Sustainable Energy (SinBeRISE).

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