Electrical and optical dielectric constants of /3-phase poly(vinylidene fluoride-trifluoroethylene) ferroelectric films

The /3-phase poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE), 70/30] copolymer ferroelectric films were fabricated by a sol-gel method. The electrical dielectric permittivity in the frequency range of 10 2 - 10 6 Hz was derived from capacitance and dielectric loss of the P(VDF-TrFE)-based capacitor. It was found that the real dielectric permittivity decreases with the frequency due to the relaxation arising from interfacial polarization. Furthermore, optical constants have been extracted by fitting ultraviolet-infrared ellipsometric spectra with a three-layered structure (air/film/Si) and dielectric models. In the transparent region, the refractive index value is about 1.42. In addition, some main first-order infrared-active modes (3A 1 and 3B 2 ) and the corresponding structure vibrations are explained. Particularly, the A 1 mode ( similar to 877.4 cm -1 ) comes from the CF 2 /CC symmetric stretching. The B 2 mode ( similar to 840.4 cm -1 ) arises from CH 2 rocking and CF 2 antisymmetric stretching. The results are helpful for the ferroelectric P(VDF-TrFE)-based flexible photoelectronic biomedical sensor.