PDF(Pubmed)
Abstract：
Copolymers based on vinylidene fluoride are potential materials for ferroelectric memory elements. The trend in studies showing that a decrease in the degree of crystallinity can lead to an unexpected increase in the electric breakdown field is noted. An analysis of the literature data reveals that in fluorine-containing ferroelectric polymers, when using a bipolar triangular field, the hysteresis loop has an unclosed shape, with each subsequent loop being accompanied by a decrease in the dielectric response. In this work, the effect of the structure of self-polarized films of copolymers of vinylidene fluoride with tetrafluoroethylene and hexafluoropropylene on breakdown processes was studied. The structure of the polymer films was monitored using infrared spectroscopy (IR) and X-ray diffraction. Kelvin probe force microscopy (KPFM) was applied to characterize the local electrical properties of the polymers. For the films of the first copolymer, which crystallize in the polar β-phase, asymmetry in the dielectric response was observed at fields greater than the coercive field. For the films of the copolymers of vinylidene fluoride with hexafluoropropylene, which crystallize predominantly in the nonpolar α-phase, polarization switching processes have also been observed, but at lower electric fields. The noted phenomena will help to identify the influence of the structure of ferroelectric polymers on their electrical properties.
摘要：
基于偏二氟乙烯的共聚物是用于铁电存储器元件的潜在材料。注意到研究表明结晶度降低可导致击穿电场意外增加的趋势。对文献数据的分析表明，在含氟铁电聚合物中，当使用双极三角场时，磁滞回线具有未闭合的形状，每个随后的循环都伴随着介电响应的降低。在这项工作中,研究了偏氟乙烯与四氟乙烯和六氟丙烯共聚物的自极化薄膜的结构对击穿过程的影响。使用红外光谱(IR)和X射线衍射监测聚合物膜的结构。使用开尔文探针力显微镜（KPFM）来表征聚合物的局部电性能。对于第一共聚物的薄膜，在极性β相结晶，在大于矫顽场的场中观察到介电响应的不对称性。对于偏二氟乙烯与六氟丙烯的共聚物的薄膜，主要在非极性α相结晶，还观察到了极化切换过程，但在较低的电场。注意到的现象将有助于识别铁电聚合物的结构对其电性能的影响。
