Electric Properties Of Ferroelectric Polymer And Its Composites

Poly(vinylidene fluoride) (PVDF) and its copolymer with trifluoroethylene P(VDF-TrFE) have been widely used in sensors, transducers as the most promising organic ferroelectric material. In recent years, it is investigated intensively as the functional material in organic memory for many advantages. It exhibits a large spontaneous polarization, excellent polarization stability, low leakage for high resistivity and short switching time. Furthermore, they do not require high-temperature processing, have outstanding chemical stability and low fabrication costs. The ferroelectric layer in ferroelectric memory decides the performance of device, such as life time, reliability, working voltage, read/write speed. As a result, it is important to study how to improve the properties of the ferroelectric polymer.We introduced poly(methyl methacrylate)(PMMA) into P(VDF-TrFE) to fabricate the ferroelectric composite PMMA/P(VDF-TrFE) and then studied their topography, structure, insulation property and ferroelectricity by AFM, XRD and home-made circuit. We found the blending of PMMA can improve the smoothness of surface, the insulating properties and decrease the ferroelectric switching time of the composite. Besides, at certain PMMA composition ratio, the fatigue endurance is improved. In ferroelectric memory, a smooth interface and good insulation can improve the reliability of device, a short switching time can increase memory's reading and writing speed, good fatigue endurance can increase the lift time,. In these aspects, PMMA can improve the properties of ferroelectric polymer. Meanwhile, we found that the retention property of PMMA/P(VDF-TrFE) composites are as good as P(VDF-TrFE). Furthermore, PMMA would not increase the built-in bias in ferroelectric films, thus the stability of coercive voltage keeps the same. However, the blending of PMMA would decrease the polarization and increase the coercive voltage, which are disadvantageous for memory device. As a result, we should choose proper PMMA composition ratio to meet different requirements of different memory devices.In the work, the measurements of fatigue endurance and built-in bias are performed automatically by a self-made program. The function and development of the program is introduced in the appendix.