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THE PECULIARITIES OF DIELECTRIC RELAXATION OF FERROELECTRIC POLYMER NANOSIZED FILMS

Keywords:

A.A.PLAKSEEV, K.A.VERKHOVSKAYA


In 1995 the first ultrathin ferroelectric Langmuir-Blodgett (LB) films were prepared from copolymer vinylidenefluoride with trifluoroethylene P[VDF/TrFE] [1]. It was shown that ferroelectricity exists even in one monolayer of this copolymer [2]. Dynamic dielectric measurements were carried out for Langmuir-Blodgett films (1-2 monolayes) of copolymer P(VDF/TrFE) 70/30 over the frequency range 10-1-2•107 Hz for temperature interval 25-130°C. The observed dielectric relaxation follows the Debye-type frequency dependence of ε* for ultrathin LB films. The mean relaxation time τ was obtained from the ε'' peak-frequency fm (τ =1/2fm, fm =5•105 Hz, τ =3•10-7s). The new observation for ultrathin LB film 2 nm thick is the appearance of second relaxation maximum ε'' at the frequency f=5 103 Hz in paraelectric phase. These two anomalies ε'' exist during cooling in the region of temperature hysteresis, where the coexistance of ferroelectric and parae-lectric phases takes place. The one maximum appears again in ferroelectric phase. We can assume, that the medium polarization of Maxwell-Wagner type exists at phase transition due to injection of charge carriers from electrodes and accumulation of carriers on the boundaries in inhomogeneous medium, connected with the coexistence of two phases.
References:
May 29, 2020

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