Browsing by Author "Rodriguez, Brian J."

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Ferroelectric domain wall pinning at a bicrystal grain boundary in bismuth ferrite
(2008-10-06)
Rodriguez, Brian J.
;
Chu, Y. H.
;
Ramesh, R.
;
Kalinin, Sergei V.
;
材料科學與工程學系
The ferroelectric polarization switching behavior at the 24 degrees (100) tilt grain boundary (GB) in an epitaxial multiferroic BiFeO(3) bicrystal film is studied using piezoresponse force microscopy (PFM). The PFM amplitudes across positively and negatively poled GB regions suggest the presence of a frozen polarization component at the interface. The switching experiments demonstrate that the GB attracts the domain wall and acts as a pinning center. The PFM results are compared with conductive atomic force microscopy and spectroscopy, which suggest domain wall pinning at the GB can be partially attributed to increased conductance at the GB. (C) 2008 American Institute of Physics.
Unraveling Deterministic Mesoscopic Polarization Switching Mechanisms: Spatially Resolved Studies of a Tilt Grain Boundary in Bismuth Ferrite
(2009-07-10)
Rodriguez, Brian J.
;
Choudhury, Samrat
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Chu, Y. H.
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Bhattacharyya, Abhishek
;
Jesse, Stephen
The deterministic mesoscopic mechanism of ferroelectric domain nucleation is probed at a single atomically-defined model defect: an artificially fabricated bicrystal grain boundary (GB) in an epitaxial bismuth ferrite film. Switching spectroscopy piezoresponse force microscopy (SS-PFM) is used to map the variation of local hysteresis loops at the GB and in its immediate vicinity. It is found that the the influence of the GB on nucleation results in a slight shift of the negative nucleation bias to larger voltages. The mesoscopic mechanisms of domain nucleation in the bulk and at the GB are studied in detail using phase-field modeling, elucidating the complex mechanisms governed by the interplay between ferroelectric and ferroelastic wall energies, depolarization fields, and interface charge. The combination of phase-field modeling and SS-PFM allows quantitative analysis of the mesoscopic mechanisms for polarization switching, and hence suggests a route for unraveling the mechanisms of polarization switching at a single defect level and ultimately optimizing materials properties through microstructure engineering.