Abstract
We have used energy-filtered photoemission electron microscopy (PEEM) at the photoemission threshold to carry out a microscopic scale characterization of the surface charge and domain structure of the (001) surface in BaTiO3. Signatures of ferroelectric and ferroelastic domains, and tweed, dominate the surface structure of BaTiO3 at room temperature. The surface ferroic signatures are maintained on heating to temperature (~550 K), well above the transition temperature (393 K). This surface proximity effect provides the mechanism for memory of the bulk ferroelectric domain arrangement up to 150 K above TC and thus can be considered as a robust fingerprint of the ferroelectric state near the surface. Self-reversal of polarization is observed for the tweed below TC and for the surface domains above TC. Annealing at higher temperature triggers the dynamic tweed which in turn allows a full reorganization of the ferroic domain configuration.
Highlights
The ferroic surface patterns are expected to transform at much higher temperatures than the bulk phase transitions as electrostatic and elastic boundary conditions significantly alter the thermodynamic stability fields[22]
We demonstrate the persistence of FE-domain patterns at the surface up to 550 K, far above the bulk phase transition as measured by Raman spectroscopy
We have shown that the stepwise bulk phase transition in BaTiO3 does not occur at TC
Summary
The ferroic surface patterns are expected to transform at much higher temperatures than the bulk phase transitions as electrostatic and elastic boundary conditions significantly alter the thermodynamic stability fields[22]. Morozovska et al have shown how surface ionic charge can couple with bulk ferroelectric states to create specific ferroionic domain patterns at the surface of thin films. These patterns may persist well above the www.nature.com/scientificreports/. PEEM images at E-EF = 3.00 and 4.45 eV at 300 K, showing contrast inversion in the intensity of the broad vertical stripes due to the difference in the local photoemission threshold. We use photoemission electron microscopy (PEEM) with in-situ temperature control to investigate the surface polarity of ferroelectric BaTiO3 by probing the local potential modulations at the microscopic scale[33]. The FE domain structure and FE memory is lost when the tweed becomes dynamic after annealing at 975 K while it conserves the fingerprint of the initial state up to 550 K, i.e. up to 150 K above TC
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