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Communication Dans Un Congrès Année : 2018

Cationic ordering in Ga2-xFexO : atomic scale characterisation of the polarisation walls

Résumé

The knowledge and control of the electric polarization in multiferroic thin films is currently the subject of extensive research efforts. This is the key toward a possible transformation into devices of the exciting phenomena such as conductance modification or polarity observed at ferroelectric domain walls. A considerable effort has been dedicated these last years to the exploration of the properties of ferroelectric domain walls, which show locally modified conductance or field effects. The ferroelectric polarisation of the GaxFe2-xO3 structure can be easily observed along the c-axis by HR-STEM (Pna21, isomorphic to -Fe2O3). The thin layers that were studied here are composed of columnar nanocrystals with this axis mainly oriented along the growth direction. Extensive walls on which the polarization of the structure reverses can cross the nanocrystals perpendicularly to the c-axis. These walls separate areas whose polarization directions are oriented either face-to-face or tail-to-tail. HRSTEM images do not reveal clearly a breakdown of order in the inversion zone of the polarization, even if from HAADF imaging the polarisation inversion was identified in this structure on only one plane thick. Spatially resolved STEM-EELS allowed visualizing the ionic ordering of the bulk. A different ionic structuration was identified in the seat of polarization inversions. Some walls also present steps at 45 °. The absence of gallium in these steps, suggests a high ionic mobility. Mechanisms of the polarization inversion of the structure during its stress by an electric field will be discussed.
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Dates et versions

hal-02327125 , version 1 (22-10-2019)

Identifiants

  • HAL Id : hal-02327125 , version 1

Citer

X Devaux, A. Demchenko, Ch Lefevre, F. Roulland, D Preziosi, et al.. Cationic ordering in Ga2-xFexO : atomic scale characterisation of the polarisation walls. C'NANO 2018, Dec 2018, TOULON, France. ⟨hal-02327125⟩
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