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تسجيل مستخدم جديدDomain wall creep in epitaxial ferroelectric Pb(Zr0.2Ti0.8)O3 thin films
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T. Tybell
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Ferroelectric switching and nanoscale domain dynamics were investigated using atomic force microscopy on monocrystalline Pb(Zr0.2Ti0.8)O3 thin films. Measurements of domain size versus writing time reveal a two-step domain growth mechanism, in which initial nucleation is followed by radial domain wall motion perpendicular to the polarization direction. The electric field dependence of the domain wall velocity demonstrates that domain wall motion in ferroelectric thin films is a creep process, with the critical exponent mu close to 1. The dimensionality of the films suggests that disorder is at the origin of the observed creep behavior.
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The static configuration of ferroelectric domain walls was investigated using atomic force microscopy on epitaxial PbZr0.2Ti0.8O3 thin films. Measurements of domain wall roughness reveal a power law growth of the correlation function of relative disp
lacements B(L) ~ L^(2zeta) with zeta ~ 0.26 at short length scales L, followed by an apparent saturation at large L. In the same films, the dynamic exponent mu was found to be ~ 0.6 from independent measurements of domain wall creep. These results give an effective domain wall dimensionality of d=2.5, in good agreement with theoretical calculations for a two-dimensional elastic interface in the presence of random-bond disorder and long range dipolar interactions.
Atomic force microscopy was used to investigate ferroelectric switching and nanoscale domain dynamics in epitaxial PbZr0.2Ti0.8O3 thin films. Measurements of the writing time dependence of domain size reveal a two-step process in which nucleation is
followed by radial domain growth. During this growth, the domain wall velocity exhibits a v ~ exp[-(1/E)^mu] dependence on the electric field, characteristic of a creep process. The domain wall motion was analyzed both in the context of stochastic nucleation in a periodic potential as well as the canonical creep motion of an elastic manifold in a disorder potential. The dimensionality of the films suggests that disorder is at the origin of the observed domain wall creep. To investigate the effects of changing the disorder in the films, defects were introduced during crystal growth (a-axis inclusions) or by heavy ion irradiation, producing films with planar and columnar defects, respectively. The presence of these defects was found to significantly decrease the creep exponent mu, from 0.62 - 0.69 to 0.38 - 0.5 in the irradiated films and 0.19 - 0.31 in the films containing a-axis inclusions.
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