Temperature dependence of piezo- and ferroelectricity in ultrathin P(VDF-TrFE) films

The polymer poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) is highly desirable for piezoelectric and ferroelectric functional applications owing to its considerable electromechanical activity and reliable electrical polarization. However, a clear understanding of the effect of the thermal annealing on the electromechanical behavior and polarization nature of ultrathin crystalline P(VDF-TrFE) films is severely lacking. Here we report the thermally induced structural reorganization, and piezo- and ferroelectric features in the ultrathin P(VDF-TrFE) films. On applying a 40 °C annealing treatment, the polarization-patterned electrostrictive strain reaches the highest value of ∼53.7 pm. Besides, the ultrathin film exhibits a highly ordered antiparallel dipole alignment, the highest local piezoelectric activity, and an improved polarization relaxation time. The optimum film properties are achieved owing to a high degree of polymer chains oriented parallel to the substrate plane. Our results can reveal a promising avenue for nano-electro-mechanical and nano-ferroelectric electronic applications using ultrathin P(VDF-TrFE) films.