Effects of silicon Interface and frequency dependence in solution-processed high-K poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) dielectric characteristics (original) (raw)
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Organic Electronics, 2008
Poly(vinylidene fluoride-trifluoroethylene) (70-30 mol%) was used as the functional dielectric layer in organic ferroelectric field effect transistors (FeFET) for non-volatile memory applications. Thin P(VDF-TrFE) film samples spin-coated on metallized plastic substrates were stretch-annealed to attain a topographically flat-grain structure and greatly reduce the surface roughness and current leakage of semi-crystalline copolymer film, while enhancing the preferred b-phase of the ferroelectric films. Resultant ferroelectric properties (P R = |10| lC/cm 2 , E C = |50| MV/m) for samples simultaneously stretched (50-70% strain) and heated below the Curie transition (70 o C) were comparable to those resulting from high temperature annealing (>140 o C). The observed enhancements by heating and stretching were studied by vibration spectroscopy and showed mutual complementary effects of both processes. Organic FeFET fabricated by thermal evaporating pentacene on the smooth P(VDF-TrFE) films showed substantial improvement of semiconductor grain growth and enhanced electrical characteristics with promising non-volatile memory functionality.
Macromolecules, 2003
The dynamic processes in poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) copolymer, lead lanthanum zirconate titanate (PLZT)-P(VDF-TrFE) composite, electron-irradiated P(VDF-TrFE) copolymer, and poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) terpolymer have been studied by measurements of the temperature and frequency-dependent linear (1) and third-order nonlinear (3) dielectric constants. While a paraelectric-to-ferroelectric transition takes place in the crystalline region of the nonirradiated copolymer and composite, electron-irradiated P(VDF-TrFE) copolymer and P(VDF-TrFE-CFE) terpolymer show a significantly different dielectric response: a broad frequency dispersion in 1 and 3, asymmetric temperature evolution of the relaxation spectrum as the longest relaxation time diverges at a finite freezing temperature while the shortest relaxation times remain active down to the lowest temperatures, and a paraelectric-to-glass crossover in the temperature dependence of the dielectric nonlinearity a3) 3/ 0 3 1 4. All these properties, together with the temperature dependence of the static field cooled dielectric constant, are very similar to those observed in the classical relaxor systems and are reminiscent of the dynamic behavior observed in various spin glasses. Thus, additional confirmation that giant electrostrictive response of the electron-irradiated P(VDF-TrFE) copolymer and P(VDF-TrFE-CFE) terpolymer is the consequence of their relaxor-like structure is obtained.
Applied Physics Letters, 2014
Low-voltage-operated top-gate polymer thin-film transistors with high capacitance poly(vinylidene fluoridetrifluoroethylene)/poly(methyl methacrylate) dielectrics Displacement current analysis of carrier behavior in pentacene field effect transistor with poly(vinylidene fluoride and tetrafluoroethylene) gate insulator Interface screening and imprint in poly(vinylidene fluoride/trifluoroethylene) ferroelectric field effect transistors Electric field induced structural change for poly(vinylidene fluoride-co-trifluoroethylene) ultrathin films studied by scanning Maxwell stress microscope
Physical Review B, 2001
The high-energy electron irradiated poly͑vinylidene fluoride-trifluoroethylene͒, P͑VDF-TrFE͒, copolymer exhibits many features resembling the relaxor ferroelectric behavior. In polymer systems, there are local dipolar motions at the monomer or unit cell scale, which manifest themselves as various relaxation processes. In this paper we investigate the relationship between the relaxor ferroelectric behavior, especially, Vogel-Fulcher ͑V-F͒ behavior and these local dipolar relaxation processes in irradiated P͑VDF-TrFE͒ 65/35-mol % copolymer. In order to cover the change in polarization dynamics of the copolymer system, the dielectric behavior of copolymer is measured over a broad frequency ͑0.01 Hz-10 MHz͒ and temperature ͑Ϫ40 to 80°C͒ range. The results indicate that there is an increased coupling among the local dipolar motions with reduced temperature in the crystalline region. On the other hand, the randomness introduced in the irradiation prevents the formation of a polar phase, on both the macroscale and the microscale, in the polymer. The observed relaxor behavior is a consequence of the competition of these two effects. The results further show that the V-F process of the irradiated copolymer system is different from the glass transition, which occurs in the amorphous phase of the copolymer.
Polymer, 2009
A series of P(VDF-TrFE-CTFE)s were synthesized via a well-controlled chemical route including VDF/CTFE copolymerization and dechlorination of P(VDF-CTFE)s to convert CTFE units into TrFE units. The microstructure and properties of the terpolymers were characterized and tested with differential scanning calorimeter (DSC), NMR, dielectric constant and electric displacement-electric field (D-E) hysteresis loop. Thanks to the clean reaction system and ambient reaction condition of VDF/CTFE copolymerization and the hydrogenation of P(VDF-CTFE)s, the terpolymers obtained with high purity and uniformity exhibit a high electric breakdown field of over 500 MV/m, as a result, the highest energy density is obtained as 10.3 J/cm 3. Via comparing the structure and properties of terpolymers with different compositions and from different preparing processes side-by-side, the TrFE content and the method of TrFE introduced are found to strongly affect the microstructure of the materials and consequently the dielectric properties. The advantages including the lower cost of materials, convenience of the materials preparation and relatively lower energy loss make it possible to be employed as capacitor material.
Physics Procedia, 2011
The carrier motion mechanism in capacitors with ferroelectric poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] film was investigated in terms of displacement current analysis. The coercive electric field of the ferroelectric polymer was measured by applying a ramp voltage on an IZO/P(VDF-TrFE)/Au structure (MFM structure) with a value about 0.7 MV/cm. Subsequently, by introducing a pentacene layer to the MFM structure, namely the IZO/P(VDF-TrFE)/Pentacene/Au structure (MFSM structure) we studied carrier injection and accumulation process in the pentacene semiconductor layer under the effect of dipole reversal in the ferroelectric layer. Interestingly, three peaks were found for the MFSM structure and they were understood by taking into account charge motion in pentacene layer. The present study shows displacement current measurement is a useful technique to detect carrier motion in organic devices.
Journal of Polymer Science Part B: Polymer Physics, 2013
Effects of intermolecular interaction on the energy distribution of valance electronic states of a carbazole-based material in amorphous thin films J. Chem. Phys. 136, 204706 (2012) Single molecules probe the polarization dynamics of poly (methyl methacrylate) in external electric field Appl. Phys. Lett. 100, 203118 (2012) Correlation between near infrared-visible absorption, intrinsic local and global sheet resistance of poly(3,4ethylenedioxy-thiophene) poly(styrene sulfonate) thin films APL: Org. Electron. Photonics 5, 88 (2012) Correlation between near infrared-visible absorption, intrinsic local and global sheet resistance of poly(3,4ethylenedioxy-thiophene) poly(styrene sulfonate) thin films Appl. Phys. Lett. 100, 153301 Modification of the electrical properties of poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) upon doping of ZnO nanoparticles of different content Forced assembly microlayer coextrusion was used to produce polycarbonate/poly(vinylidene fluoride-co-hexafluoropropylene) [PC/P(VDF-HFP)] layered films for dielectric capacitor applications. Low field dielectric spectroscopy was systematically carried out on the layered films and controls. A low frequency relaxation was found that shifted to higher frequency and decreased in intensity as the P(VDF-HFP) layer thickness was reduced. The interfacial Maxwell-Wagner polarization, being layer thickness independent, could not account for this reduced low frequency relaxation behavior as the layer thickness decreased. Charge diffusion models by Sawada and Coelho, however, satisfactorily predicted the observed layer thickness effect, indicating that the migration of impurity ions in the P(VDF-HFP) layer caused the low frequency relaxation. A new, convenient fitting procedure was developed for the Sawada model yielding an ion concentration and diffusion coefficient of 2 Â 10 21 ions/m 3 and 2 Â 10 À13 m 2 /s, respectively, for films with layer thicknesses of 430 to 50 nm. Thicker layers of 7000 nm had significantly different diffusion parameters, which were attributed to differing crystal orientations in the P(VDF-HFP) layers. These findings show that low ion concentrations, whether from catalyst residue and processing or intentionally added, significantly affect the dielectric properties and can play a vital role in many applications (i.e., LCD displays, solar cells, light-emitting electrochemical cells, capacitors).
Journal of Applied Polymer Science, 2010
Poly(vinylidene fluoride) (PVDF) and copolymers of vinylidene fluoride and trifluoroethylene [P(VDF/ TrFE)s] were deposited on silicon substrates, and their structure and properties were comparatively investigated. Compared to P(VDF/TrFE), which is the polymer material currently most dominant for ferroelectric thin-film devices applications, our b-phase PVDF homopolymer thin film demonstrated several advantages, such as higher dielectric breakdown strength, improved polarization fatigue endurance, and larger ferroelectric polarization at elevated temperatures with improved thermal stability. The reasons for the observed different characteristics between the PVDF and P(VDF/TrFE) thin films were analyzed on the basis of their different structures and morphologies. The results indicate that the low-cost b-phase PVDF homopolymer thin films have great potential as an alternative to P(VDF/TrFE) for ferroelectric and piezoelectric thin-film-device applications.
Kongunadu Research Journal, 2015
Polyvinylidene fluoride (PVDF) and Trifluoroethylene ((TrFE) are potential polymers which are used in acoustic transducers and electromechanical actuators because of their inherent piezoelectric response, as heat sensors because of their inherent pyroelectric response and as dielectric layer in organic thin filmtransistors. In the present study thin films of copolymer Poly(vinylidene fluoride-trifluoroethylene) were prepared by spin coating method for two different concentrations 2% to 8% and for various spin speeds from 2000 RPM to 5000 RPM. A P-type Si wafer was used as a substrate to deposit P(VDF-TrFE) thin films. 2-butanone was used as a solvent to prepare P(VDF-TrFE) solution. To study the annealing effect, the films were annealed for three different temperatures 50°C, 100° C and 175° C. Ellipsometry was used to measure the thickness of the films. The identification of the films prepared was done by using FTIR spectrophotometer. The structure of the films was studied by using ...