Spherulite-like microstructure observed for spin-cast P(VDF-TrFE) thin films and their ferroelectric characteristics

Ferroelectric polymer thin films crystallize in different phases and microstructures depending on fabrication conditions such as annealing temperature or layer deposition technique. In this work, we demonstrate how the morphology of spin-cast poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) thin films changes as a function of annealing temperature from rice-like to spherulite-like microstructure, whereas the latter morphology is closer to the crystallization characteristic of poly(vinylidene-fluoride) (PVDF). Thin films of PVDF and P(VDF-TrFE) are analyzed at the nanometre-scale using atomic force microscopy. Chain conformation and crystallization characteristics are studied by Fourier transform infrared spectroscopy and X-ray diffraction. Furthermore, the electro-mechanical behavior of P(VDF-TrFE) thin films with a spherulite-like microstructure is measured and compared to other microstructures of PVDF-based polymers reported in literature. Our findings show that ferro- or piezoelectric properties of P(VDF-TrFE) thin films are less sensitive to the microstructure.