Ferroelectric Switching of Thin Langmuir-Blodgett Films of P(VDF-TrFE) Copolymer: Comparison with Liquid Crystal Switching

Abstract

The switching of polarization in ferroelectric polymer films is traditionally explained in terms of nucleation and motion of domain walls although such walls have never been observed in polymer ferroelectrics. As an alternative, the Landau-Ginzburg theory of the coercive field seems to be appropriate for ultrathin (1–5 monolayer) films. Data on the switching dynamics in the ultrathin films are very scarce. In this work the experiments on the polarization switching in the 20–240 nm thick films prepared by the Langmuir-Blodgett technique had been carried out using triangular voltages of low frequency in order to separate capacitive and polarization components of the current. Then the results have been compared with the data on polarization switching in liquid crystalline, antiferroelectric Langmuir-Blodgett films. There is a striking similarity in the time dependences of repolarization current for two materials. Due to this, we tentatively suggest a switching mechanism based on the field-induced rotation of the polarization vector. The latter allows one to estimate the rotational viscosity coefficient of the ferroelectric polymer responsible for the energy dissipation.

Keywords:

• Ferroelectricity
• thin films
• polymers
• liquid crystals

PACS:

• 77.80 Fm
• 77.55.tf

Acknowledgements

The work is supported in frame of a scientific program of the Physical Department of Russian Academy of Sciences.