Domain wall roughness and creep in nanoscale crystalline ferroelectric polymers

Abstract

X., "Domain wall roughness and creep in nanoscale crystalline ferroelectric polymers" (2013). Stephen Ducharme Publications. 85.

Two-Step Polarization Switching in Ferroelectric Polymers

“…A close look to the nearly circular domains reveals that their borders are not smooth but rough. Such moderately rough circular domains are consistent with previous observations on P(VDF-TrFE) [23,24] or inorganic ferroelectric thin films [13]. The application of a voltage pulse to the nanostripes with well-oriented lamellae, however, generates reversal domains having a different shape.…”

“…We note that the two-step polarization switching process can explain very well the recently observed fractal domain patterns in P(VDF-TrFE) thin films [23,24], which should result from domain flow motion within lamellae and pinning of amorphous components at the crystal boundaries. The crossover behavior of frequency-dependent coercivity found in P(VDF-TrFE) [36], can also be interpreted by the two-step model.…”

“…For one-dimensional domain walls μ ¼ 0.25, whereas for two-dimensional ones μ ¼ 0.5 under a pinning potential with a short range [33]. Indeed, μ ≈ 0.25 has been observed in one-dimensional P(VDF-TrFE) monolayers [23,24]. The microscopic origin of μ ¼ 0.5 in our case is that the lamellae are much thicker than the monolayer and the resulting interfaces between lamellae and the surrounding amorphous component provide a twodimensional short range pinning potential.…”

“…Intrinsic switching does not require heterogeneous nucleation, whereas the cold field switching is mediated by defects. At nanoscale, spatially nonuniform velocity of domain growth has been observed and attributed to defects in chain conformation and molecular packing [23,24]. The fact that defects exist at different structural levels makes the unambiguous determination of the polarization switching mechanism rather challenging.…”

Domain Wall Roughness in Stripe PhaseBiFeO3Thin Films

“…For ferroelectric domain walls, dipolar interactions were shown to increase the effective dimensionality, leading to lower values of the roughness exponents [33,34]. Considering dipolar forces as a first approach towards long-range effects, we find that the effective elastic energy term contains two parts: one related to the Ginzburg gradient term, quadratic in the local variation of polarization across the domain wall [14] leading to a standard short-range q 2 elasticity, the second related to the dipolar interactions with a more complex form (see Supplemental Material).…”