Different Surface Morphology of Annealed PVDF-TrFE Thin Films and the Effect on its Ferroelectric Properties

Abstract

The different morphology of 250 nm PVDF-TrFE (70:30 mol%) thin films were observed in relation to its ferroelectricity. The annealing temperatures were varied from solvent evaporation (Ts), Curies transition (Tc), up to melting temperature (Tm). It was found that the annealing process promoted the development of elongated crystallite structure also known as ferroelectric crystal, which significantly improved the ferroelectric properties of PVDF-TrFE (70:30 mol%) thin films. However, the presence of nanoscale separations on the thin film annealed over Tm (AN160) suggested high possibility of defects, and hence a reduction in ferroelectric properties of thin films.

Evolution of morphology, ferroelectric, and mechanical properties in poly(vinylidene fluoride)–poly(vinylidene fluoride‐trifluoroethylene) blends

“…Similar observations were made previously by several other workers . The transformation of smooth surface morphology into fiber‐like rough morphology with increasing annealing temperature has been attributed to the fusion of neighboring grains into rods, resulting in the formation of long extended fiber‐shaped crystals . It was observed that length of these rods increases with increasing annealing temperatures .…”

“…Further, presence of defects such as HH, TT, or ‐TrFE content in the crystalline regions of P(VDF‐TrFE) as also evidenced from Figure (c) causes a reduction in orientation of polymer chains. These defects being detrimental to the ferroelectric properties of P(VDF‐TrFE) films can cause reduction in the values of P r and also increment in coercive field values . From SEM micrographs of Figure (d–f), it can be seen that P(VDF‐TrFE) rich melt‐mixed blends consist of needle and fiber‐like structures.…”