Electrical and optical dielectric constants of [formula omitted]-phase poly(vinylidene fluoride-trifluoroethylene) ferroelectric films.

The β -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 1 0 2 - 1 0 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 (∼ 877.4 cm−1) comes from the CF 2 /CC symmetric stretching. The B 2 mode (∼ 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. [Display omitted] • A high quality β -P(VDF-TrFE) ferroelectric film was deposited by a sol–gel method. • Electrical dielectric permittivity of β -P(VDF-TrFE) films is obtained in 102–106 Hz. • Optical constants are extracted in a wide range of 200 nm–15 μ m. [ABSTRACT FROM AUTHOR]