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Zhang X.,Shanghai University of Engineering Science | Zhang X.,East China University of Science and Technology | Du X.,Shanghai University of Engineering Science | Hou Y.,East China University of Science and Technology | And 3 more authors.
Applied Physics Letters | Year: 2014

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 C. 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. © 2014 AIP Publishing LLC. Source


Hou Y.,East China University of Science and Technology | Zhang X.,East China University of Science and Technology | Zhang Y.,East China University of Science and Technology | Xu G.,Kunshan Hisense Electronics Co. | Xu H.,East China University of Science and Technology
Journal of Applied Physics | Year: 2012

A universal model and experiments on the polarization switching for ferroelectric poly(vinylidene fluoride-trifluoroethylene) copolymer ultra-thin films with an interface layer have been studied. It is found that polarization switching could complete if the capacitance of the interface layer is large enough compared with that of the ferroelectric film. Based on this model, a conducting polymer, poly(3,4-ethylene dioxythiophene)-poly(styrene sulfonic) acid, is introduced as an interface layer between metal electrodes and ferroelectric polymer film and the switching property measurements well agree with the simulation results of the model. These findings provide an effective route to enhance the polarization switching for the ferroelectric films, which is promising for potential applications. © 2012 American Institute of Physics. Source


Hou Y.,East China University of Science and Technology | Zhang X.,East China University of Science and Technology | Zhang Y.,East China University of Science and Technology | Xu G.,Kunshan Hisense Electronics Co. | Xu H.,East China University of Science and Technology
Journal of Applied Physics | Year: 2012

The high-temperature ferroelectric behaviors for poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) copolymer ultrathin films with electroactive interlayers have been studied. The different electroactive polymers, commercial poly(3,4-ethylene dioxythiophene)-poly(styrene sulfonic) acid (PEDOT-PSSH), in situ synthesized PEDOT-PSSH with high PEDOT ratio and poly(3,4-ethylene dioxythiophene)-poly(styrene sulfonic) ammonia (PEDOT-PSSNH 4), are used as the interlayer between P(VDF-TrFE) and metal electrodes. It is found that the ferroelectric properties at high temperature are strongly dependent on the interlayer and the faster degradation occurs on the sample with the interlayer which has enough protons as compensating charges. Further analysis on the polarization response behaviors and capacitance shows that the high-temperature ferroelectric properties are more closely associated with the compensating charges in interlayer than the ferroelectric film itself, illustrating the importance of the appropriate interlayer materials. © 2012 American Institute of Physics. Source


Xu H.S.,East China University of Science and Technology | Zhang Y.N.,East China University of Science and Technology | Zhang X.L.,East China University of Science and Technology | Zhang X.L.,Shanghai University of Engineering Science | Ma Y.P.,Kunshan Hisense Electronics Co.
Ferroelectrics | Year: 2011

A functional interlayer, poly(3,4-ethylene dioxythioohene)-poly(styrene sulfonic) acid, is introduced as a buffer layer between the metal electrodes of a capacitor composed of ferroelectric poly(vinylidene fluoridetrifluoroethylene) copolymer ultrathin film. The sandwiched structure shows prominent ferroelectric properties even as the thickness of P(VDF-TrFE) film is reduced to 50 nm and the fatigue property is also improved tremendously. We demonstrate that the proton in the PSSH instead of the electron in the PEDOT plays a significant role to improve the ferroelectric properties of P(VDFTrFE), furthermore, polyvinyl phosphoric acid as well as other polyacid also supplies the proton. © Taylor & Francis Group, LLC. Source


Zhang X.,East China University of Science and Technology | Zhang X.,Shanghai University of Engineering Science | Xu H.,East China University of Science and Technology | Xu H.,Kunshan Hisense Electronics Co. | Zhang Y.,East China University of Science and Technology
Journal of Physics D: Applied Physics | Year: 2011

The experimental intrinsic coercive field of ferroelectric poly(vinylidene fluoride-trifluoethylene) copolymer films, with both bottom and top gold electrodes is measured at a wide temperature range. In the lower temperature region from -20 to 25 °C, the temperature dependence of coercive field shows good agreement with the prediction by the Landau-Ginzburg (LG) mean-field theory. In the higher temperature region from 25 to 80 °C, the coercive field shows a slow decrease with the increased temperature, where the LG theory is not applicable any more. The temperature-dependent changes in the polymer chains have been analysed. A reversible 'inherent fatigue' is observed from the partially recovered remanent polarization after re-annealing a fatigued P(VDF-TrFE) film. FTIR spectra indicate that the interchain spacing does not change from 10 to 107 switching cycles while the degree of all-trans ferroelectric phase decreases gradually with applied switching cycles. After a re-annealing treatment, ferroelectric phase recovers and dipoles at the boundary of crystallites acquire much higher energy. © 2011 IOP Publishing Ltd. Source

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