Temperature dependence of imprint mechanism in poly(vinylidene fluoride-trifluoroethylene) copolymer ultrathin films

摘要

The temperature dependence of imprint in ferroelectric poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) copolymer thin film capacitors has been investigated. The descriptions of imprint versus different temperatures and annealing process are given. It is found that the temperature-induced shift of the imprint rate is limited for all the investigated temperature conditions, and this low shift is mainly associated with the competition between the trap states increasing and detrapping process induced by the temperature rise. Also, the annealing temperature-dependent imprint rates in the polymer chains hzave been analyzed, and the annealed cell shows low imprint rate after 104 switches at an annealing temperature above 100 ℃. Re-annealing recovery process of "inherent" imprint in the ferroelectric thin film capacitor shows improved imprint behaviors, which may be a wake-up of the polarization and detrapping from imprint traps. The internal electric fields for these processes are well analyzed and it is thought that the effective fields as well as charge trap states in ferroelectric layers are strongly responsible for the switching behaviors. This result may be useful for memory device design if extended to cover the temperature dependence of the polarization reversal based on P(VDF-TrFE) copolymer thin film.