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Ferroelectric switching characteristics during continuous polarization reversal were investigated in thin vinylidene fluoride/trifluoroethylene copolymer films by using a train of bipolar on-off electric field pulses. It was found that polarization reversal is accelerated as the pulse width Δt is decreased whereas it is decelerated as Δt is increased. For a given Δt, the switching time ts depends...
In this paper we present data of protein adsorption on topographically altered active polymeric films, investigated using atomic force microscopy (AFM), fluorescence microscopy, and contact angle measurement. The surface wettability of biocompatible polypyrrole (PPy) films was altered via low applied currents, and we have demonstrated switchable hydrophobic-hydrophilic surfaces, used as protein adhesion...
Copolymers of vinylidene fluoride, VDF, and trifluoroethylene, TrFE, are representative ferroelectric polymers. Their local properties, such as domain structure and domain wall motion, are not well known because of its complex structure. In the isothermally crystallized samples, we can obtain lamellae that grow separately on the substrates. Then in order to discuss the local state of the polarization...
Polarization reversal in a ferroelectric is accompanied by heat generation which causes a temperature rise depending on thermal boundary conditions. An adiabatic condition yields (E: electric field, D: electric displacement, C: heat capacity). The copolymer of vinylidene fluoride (VDF) and trifluoroethylene (TrFE) copolymer is expected to generate a large amount of heat because of its large remanent...
Annealing of thin copolymer films of vinylidene fluoride (VDF) and trifluoroethylene (TrFE) causes a strong increase in grain size as well as in crystallinity. It is known from AFM topographic images that flat-on lamella with diameters of up to 100 mum grow when thin films are annealed at temperatures around 140degC for several hours. To examine the orientation and the polarization state of the lamella,...
The copolymer of vinylidene fluoride (VDF) with trifluoroethylene (TrFE) has attracted much interest due to the potential use in nonvolatile memory devices with easy formability. A repetitive application of electric stress causes a decrease of switchable polarization. This phenomenon, referred to as fatigue, is one of the primary sources of concern in the ferroelectric memory devices. Having realized...
Piezoelectric response force microscopy, PFM, is a kind of SPM technique. It measures the change of the position of surface in accordance with the applied voltage, giving local piezoelectric activity. This method is widely applied to ferroelectric ceramics as well as to ferroelectric polymers. We used this method to study the dynamics of polarization reversal in thin films of VDF/TrFE copolymer.
The copolymer of vinylidene fluoride (VDF) with trifluoroethylene (TrFE) is a ferroelectric polymer undergoing polarization reversal as a result of rotational motions of molecules about their chain axes. It requires a very high electric field of approximately 100 MV/m for polarization reversal. Therefore, the thickness reduction below 50 nm is a technological requirement to achieve low-voltage operations...
Ferroelectric switching characteristics in vinylidene fluoride (VDF)/trifluoroethylene (TrFE) copolymer films have been shown to depend to a variety of factors not only the electric field E and temperature but also film thickness and previous poling conditions. Polarization reversal is believed to progress via nucleation-growth mechanism. However, there remains uncertainty about its microscopic features...
A metal-ferroelectrics-semiconductor (MFS) capacitor with a ferroelectric polymer as a gate dielectric has recently attracted much interest owing to its potential applications in nonvolatile memory. In order to understand switching dynamics, we performed simultaneous measurements of the charge Q and the capacitance C for Au/vinylidene fluoride- trifluoroethylene (VDF-TrFE) /n-Si structure using a...
A novel hydrophilic method of the polyurea film surface at room temperature was developed using vacuum ultraviolet (VUV) light 172 nm in wavelength. The treated film has highly hydrophilic surface for long time (~ 2 months). Hydrophilic surface is stable and is kept even after very hard condition of ultrasonic cleaning in de-ionized water. The polyurea film was applied for PMMA (polymethylmethacrylate)...
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