Nanoscale domain patterns in ultrathin polymer ferroelectric films

Abstract

High-resolution studies of domain configurations in Langmuir-Blodgett films of ferroelectric polymer poly(vinylidene fluoride-trifluoroethylene), P(VDF-TrFE), have been carried out by means of piezoresponse force microscopy (PFM). Changes in film thickness and morphology cause significant variations in polarization patterns. In continuous films and nanomesas with relatively low thickness/grain aspect ratio (<1/10), the relationship between the average domain size and thickness follows the Kittel law. Nanomesas with high aspect ratio (>1/5) exhibit significant deviations from this law, suggesting additional surface-energy-related mechanisms affecting the domain patterns. Polarization reversal within a single crystallite has been demonstrated and local switching parameters (coercive voltage and remnant piezoresponse) have been measured by monitoring the local hysteresis loops. Reliable control of polarization at the sub-grain level demonstrates a possibility of studying the mechanism of the intrinsic switching behavior down to the molecular scale.

Synthesis and characterization of lead-free 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 ceramic

“…The peak in Figure 5(e) corresponds to the average size of the areas with uniform polarization direction. The behavior of the average auto-correlation function is shown in Figure 5(f), fitted with the formula 44 CðRÞae…”

Orientational imaging in polar polymers by piezoresponse force microscopy

“…Contrast variations in the VPFM phase image are due to the presence of a number of domains in the as-grown nanomesas with an average domain size of approximately 30-40 nm, which is in agreement with previously reported results. 18 Dark and bright contrast in the VPFM-p image indicates an upward and downward polarization, respectively. A saturated signal in the VPFM-a map suggests that polymer chains are lying parallel to the substrate and that there is no or very little variations in the molecular arrangement across the nanomesas thickness.…”

Polarization imaging in ferroelectric polymer thin film capacitors by pyroelectric scanning microscopy

“…2(b), and have both high contrast and a high resolution of order 10 nm, as we have found before with polarization patterns prepared in similar ferroelectric copolymer LB films. [48][49][50][51] The ferroelectric polymer film was then covered with a 20-nm thick, 200-lm wide, aluminum top electrode by thermal evaporation and then installed in the PSM apparatus for imaging [see Fig. 1(a)].…”