Real-Time Observations of Long-Range Strains on 180° Ferroelectric
Domain Walls in Lithium Niobate using X-ray Topography
Terrence Jach, Surface and Microanalysis Division, NIST
(in collaboration with Sungwon Kim, Venkatraman Gopalan, Stephen Durbin, and David Bright)
Ferroelectric domains with antiparallel polarization are readily
induced in congruent LiNbO3 with electric fields above 240 kV/cm
at room temperature. Using x-ray topography with synchrotron radiation
while applying electric fields of 0-90 kV/cm, we are able to observe
large-scale reversible domain changes. By employing both Bragg and
Laue topography, we observe the effects of strain as manifest in
surface and bulk displacements, respectively. A detailed strain
analysis of the piezoelectric behavior at the domain walls, as
well as within the domains, indicates that substantial surface
displacement is associated with the high contrast of ferroelectric
domains. Even in the absence of external fields, these 180° walls
exhibit wide regions of shear strain, on the order of 10-5, within
a 10 μm range of the domain walls. We have been able to use reverse
ray tracing and finite element analysis to compare the observed
behavior with strains predicted from the bulk physical constants.
Some discrepancies are observed. We have also observed nucleation
of domains with Bragg topography and some unusual behavior in the
bulk domains with Laue topography.
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