Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands.
Nat Mater. 2013 May;12(5):433-8. doi: 10.1038/nmat3577. Epub 2013 Mar 17.
Ferroelectric poly(vinylidene-fluoride) (PVDF) has, in the past, been proposed as an ideal candidate for data storage applications as it exhibits a bistable, remanent, polarization that can repeatedly be switched by an electric field. However, fabrication of smooth ferroelectric PVDF thin films, as required for microelectronic applications, is a long-standing problem. At present, the copolymer of PVDF with trifluoroethylene P(VDF-TrFE) is used, but the stack integrity and the limited thermal stability of its remanent polarization hamper large-scale integration. Here we show that smooth neat PVDF films can be made at elevated substrate temperature. On applying a short electrical pulse the ferroelectric polar δ-phase is formed, an overlooked polymorph of PVDF proposed 30 years ago, but never experimentally verified. The remanent polarization and coercive field are comparable to those of the copolymer. The enhanced thermal stability of the polarization is directly related to the high Curie temperature, whereas the ferroelectric properties are related to the molecular packing as derived from the refined crystal structure. The replacement of P(VDF-TrFE) by the commodity polymer PVDF may boost large-scale industrial applications.
聚偏二氟乙烯（PVDF）过去曾被提议作为数据存储应用的理想候选材料，因为它具有双稳定、剩余、极化的特性，可以通过电场反复切换。然而，制造适用于微电子应用的光滑铁电 PVDF 薄膜是一个长期存在的问题。目前，使用的是聚偏二氟乙烯与三氟乙烯的共聚物 P(VDF-TrFE)，但其剩余极化的堆叠完整性和有限的热稳定性阻碍了大规模集成。在这里，我们表明可以在升高的基底温度下制造出光滑的纯 PVDF 薄膜。施加短电脉冲后，会形成铁电 δ 相，这是 30 年前提出的 PVDF 被忽视的多晶型，但从未得到实验验证。剩余极化和矫顽场与共聚物相当。极化的热稳定性增强与居里温度有关，而铁电性能则与从细化的晶体结构得出的分子堆积有关。用商品聚合物 PVDF 替代 P(VDF-TrFE)可能会推动大规模的工业应用。
