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. 2014 Oct 14;14(10):19115-27.
doi: 10.3390/s141019115.

Hot plate annealing at a low temperature of a thin ferroelectric P(VDF-TrFE) film with an improved crystalline structure for sensors and actuators

Rahman Ismael Mahdi  1 , W C Gan  2 , W H Abd Majid  3
Affiliations

Hot plate annealing at a low temperature of a thin ferroelectric P(VDF-TrFE) film with an improved crystalline structure for sensors and actuators

Rahman Ismael Mahdi et al. Sensors (Basel). .

Abstract

Ferroelectric poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) copolymer 70/30 thin films are prepared by spin coating. The crystalline structure of these films is investigated by varying the annealing temperature from the ferroelectric phase to the paraelectric phase. A hot plate was used to produce a direct and an efficient annealing effect on the thin film. The dielectric, ferroelectric and pyroelectric properties of the P(VDF-TrFE) thin films are measured as a function of different annealing temperatures (80 to 140 °C). It was found that an annealing temperature of 100 °C (slightly above the Curie temperature, Tc) has induced a highly crystalline β phase with a rod-like crystal structure, as examined by X-ray. Such a crystal structure yields a high remanent polarization, Pr = 94 mC/m2, and pyroelectric constant, p = 24 μC/m2K. A higher annealing temperature exhibits an elongated needle-like crystal domain, resulting in a decrease in the crystalline structure and the functional electrical properties. This study revealed that highly crystalline P(VDF-TrFE) thin films could be induced at 100 °C by annealing the thin film with a simple and cheap method.

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Figures

Figure 1.
Figure 1.
(a) XRD result of poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) thin films of different annealing temperatures (80, 90, 100, 110, 120, 140 °C); (b) Deconvolution of the X-ray diagram for P(VDF-TrFE) thin film annealed at 100 °C.
Figure 2.
Figure 2.
Dependence of the degree of the crystalline structure as a function of annealing temperature.
Figure 3.
Figure 3.
FESEM images of P(VDF-TrFE) annealed at (a) 80 °C; (b) 100 °C; (c) 120 °C; (d) 140 °C; (e) An amplified picture of (b); (f) an amplified picture of (d).
Figure 4.
Figure 4.
FTIR spectra of P(VDF-TrFE) thin films treated at different annealing temperatures.
Figure 5.
Figure 5.
D-E hysteresis loops of P(VDF-TrFE) as a function of annealing temperature.
Figure 6.
Figure 6.
Dependence of remnant polarization, Pr, as a function of annealing temperature.
Figure 7.
Figure 7.
Dielectric frequency spectra for the P(VDF-TrFE) thin film annealed at 100 °C and measured at a temperature step size of 10 °C from 30 °C to 140 °C.
Figure 8.
Figure 8.
Room temperature dielectric frequency spectra of P(VDF-TrFE) treated with various annealing temperatures.
Figure 9.
Figure 9.
Pyroelectric coefficient, p, of P(VDF-TrFE) thin films with varying annealing temperature (T).
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References

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