Evidence of 90° polarization switching in polycrystalline macro-domains of self-supported BaTiO3 films
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It was shown previously that the self-supported films of nanocrystalline (30–80 nm) BaTiO3 spontaneously split into regions, within which the direction of spontaneous polarization of each grain is aligned as closely as possible to some average direction. These regions, called polycrystalline macro-domains, may be of two types: (1) those with out-of-plane polarization and (2) those with in-plane polarization. In-plane macro-domains exhibit in-plane optical anisotropy which can be monitored using cross-polarized transmitted light. This property was utilized in the current work to study the influence of temperature variation on macro-domains. According to the temperature dependence of the intensity of cross-polarized transmitted light, the films could be divided into three groups: (group 1) those films that did not exhibit strong changes in intensity; (group 2) those that exhibited a strong and abrupt change at a temperature between 20 and 120 °C; and (group 3) those that upon heating exhibited a gradual increase in the intensity of the cross-polarized transmitted light. The observed changes were reversible and consistent with a 90° rotation of the c-axis of some grains, which caused reversible changes in the macro-domain structure.
KeywordsBaTiO3 Zirconium Titanate Optical Anisotropy Lead Zirconium Titanate Polarization Switching
The authors wish to acknowledge the US–Israel Binational Science Foundation, the Nancy and Stephen Grand Research Center for Sensors and Security and the Israel Ministry of Science for funding this research. This research is made possible in part by the historic generosity of the Harold Perlman Family. We are grateful to Drs. Ellen Wachtel and Yshai Feldman of the Weizmann Institute of Science for fruitful discussions and help with XRD measurements.
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