ferroelectricity

Ferroelectric polymer thin films crystallize in different phases and microstructures depending on fabrication conditions such as annealing temperature or layer deposition technique.*

In the article “Spherulite-like microstructure observed for spin-cast P(VDF-TrFE) thin films and their ferroelectric characteristics” Davide Disnan, Jonas Hafner, Michael Schneider and Ulrich Schmid demonstrate how the morphology of spin-cast poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) thin films changes as a function of annealing temperature from rice-like to spherulite-like microstructure, whereas the latter morphology is closer to the crystallization characteristic of poly(vinylidene-fluoride) (PVDF).*

Thin films of PVDF and P(VDF-TrFE) were analyzed at the nanometre-scale using atomic force microscopy. *

NanoWorld Pyrex-Nitride PNP-TR AFM probes were used for the ferroelectric characterization of the polymer thin films by atomic force microscopy. *

The displacement of the metal-ferroelectric-metal structure in response to the electric field applied was measured at one single point in the centre of the capacitor. For that purpose, the AFM cantilever (NanoWorld PNP-TR with a spring constant of k = 0.32 N/m made of silicon nitride (non-conductive cantilever for avoiding electrical interference caused by ground loops) was used.*

The deflection during the electrical stimulation was calibrated through the measurement of the inverse optical lever sensitivity of the probe. In order to avoid significant indentation effects, the silicon wafer surface surrounding the capacitor structure was used to land the cantilever for the calibration. *

Fig. 1 from «Spherulite-like microstructure observed for spin-cast P(VDF-TrFE) thin films and their ferroelectric characteristics» by D. Disnan et al: Spherulite-like microstructure of P(VDF-TrFE) and spherulite microstructure of PVDF. a, b Optical micrograph and AFM height image of the spherulite-like microstructure of P(VDF-TrFE). Features like needle-shaped crystals (NSC), nucleation centres (NC) and grain boundaries (GB) are highlighted on the spherulite-like microstructure surface. C ,d Analog for the spherulite microstructure of PVDF. NanoWorld Pyrex-Nitride AFM probes of the PNP-TR type were used for the Ferroelectric characterization of the polymer thin films. — Fig. 1 from «Spherulite-like microstructure observed for spin-cast P(VDF-TrFE) thin films and their ferroelectric characteristics» by D. Disnan et al:
Spherulite-like microstructure of P(VDF-TrFE) and spherulite microstructure of PVDF. a, b Optical micrograph and AFM height image of the spherulite-like microstructure of P(VDF-TrFE). Features like needle-shaped crystals (NSC), nucleation centres (NC) and grain boundaries (GB) are highlighted on the spherulite-like microstructure surface. C ,d Analog for the spherulite microstructure of PVDF.

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*Davide Disnan, Jonas Hafner, Michael Schneider and Ulrich Schmid
Spherulite-like microstructure observed for spin-cast P(VDF-TrFE) thin films and their ferroelectric characteristics
Polymer, Volume 272, 17 April 2023, 125840
DOI: https://doi.org/10.1016/j.polymer.2023.125840

The article “Spherulite-like microstructure observed for spin-cast P(VDF-TrFE) thin films and their ferroelectric characteristics” by Davide Disnan, Jonas Hafner, Michael Schneider and Ulrich Schmid is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/.

In the article “Influence of orientation and ferroelectric domains on the photochemical reactivity of La₂Ti₂O₇” Mingyi Zhang, Paul A. Salvador and Gregory S. Rohrer describe how they measured the effects of crystal orientation and ferroelectric domain structure on the photochemical reactivity of La₂Ti₂O_7.*

The reactivity is greatest on (001) surfaces (this is the orientation of the layers in this (110)p layered perovskite structure) while surfaces perpendicular to this orientation have the least reactivity. Complex domain structures were observed within the grains, but they appeared to have no effect on the photocathodic reduction of silver, in contrast to previous observations on other ferroelectrics. La₂Ti₂O₇ is an example of a ferroelectric oxide in which the crystal orientation has a greater influence on the photochemical reactivity than polarization from the internal domain structure. *

NanoWorld™ conductive Platinum Iridium coated Arrow-EFM AFM probes were used for the Piezo-force microscopy (PFM) that was used to determine the ferroelectric domain structure on the surface. *

The ferroelectric domains on the surface were found to have irregular shapes and there was no correlation between the pattern of silver reduction and the domain shape. The results indicate that the ferroelectric polarization of La2Ti2O7 does not alter the reactivity enough to overcome the influence of the anisotropic crystal structure. *

Fig. 6 a and b from “Influence of orientation and ferroelectric domains on the photochemical reactivity of La2Ti2O7” by Mingyi Zhang et al.
A La2Ti2O7 grain imaged with different modalities. (a) a PFM out-of-plane amplitude image. (b) a PFM out-of-plane phase image. A meandering black line in (a), marked by the arrow, corresponds to a change from light to dark contrast in the phase image. The dark (light) contrast corresponds to regions with -180° (0°) phase shift. NanoWorld conductive Arrow-EFM AFM probes were used for the piezo-force microscopy.

Please have a look at the full article cited below for the full figure — Fig. 6 a and b from “Influence of orientation and ferroelectric domains on the photochemical reactivity of La2Ti2O7” by Mingyi Zhang et al.
A La2Ti2O7 grain imaged with different modalities. (a) a PFM out-of-plane amplitude image. (b) a PFM out-of-plane phase image. A meandering black line in (a), marked by the arrow, corresponds to a change from light to dark contrast in the phase image. The dark (light) contrast corresponds to regions with -180° (0°) phase shift. Please have a look at the full article cited below for the full figure

*Mingyi Zhang, Paul A. Salvador and Gregory S.Rohrer
Influence of orientation and ferroelectric domains on the photochemical reactivity of La₂Ti₂O₇
Journal of the European Ceramic Society (2020)
DOI: https://doi.org/10.1016/j.jeurceramsoc.2020.09.020

Please follow this external link to read the full article https://www.sciencedirect.com/science/article/pii/S0955221920307445

Open Access : The article “Influence of orientation and ferroelectric domains on the photochemical reactivity of La₂Ti₂O₇” by Mingyi Zhang, Paul A. Salvador, Gregory S. Rohrer is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/.