柔性压电薄膜的织构控制及其微结构与电性能关系研究

Piezoelectric polymers, such as PVDF and P(VDF-TrFE), show great potentials in the fields of sensors, transducers and nonvolatile memories. To enhance the piezoelectric and ferroelectric performances, piezoelectric polymer films are usually textured by mechanical stretching, thermal annealing and electrical poling. With the development of microelectronic technologies, in order to integrate piezoelectric films into functionalized devices, it is required to fabricate high-performance piezoelectric polymer thin films with thickness less than 1μm or even in the nanometer scale to meet the requirement of low operation voltage and low power consumption. The traditional texturing processes cannot meet these requirements. The aim of this project is to develop new processes to texture piezoelectric polymer thin films. Two feasible texturing methods are going to be further developed: 1) high throughput epitaxy of piezoelectric polymer films based on ordered poly(tetrafluoroethylene) templates, and 2) mechanical stretching of piezoelectric films deposited on flexible polymer substrates. The structures and electrical performances of these textured piezoelectric films are controlled by mechanical, thermal and electrical parameters. The correlation between the complicated structures and electrical properties in polymer films are determined to finally to optimize the texturing process parameters and obtain piezoelectric polymer thin films with high electrical performances.

以PVDF和P(VDF-TrFE)为代表的压电聚合物材料在传感器、换能器、存储器等领域有着广泛应用前景。为提高压电聚合物薄膜压电、铁电性能，通常需采用拉伸、退火、极化等织构化处理工艺。随着微电子工业的发展，要求制备膜厚小于1μm甚至纳米量级的高性能压电聚合物薄膜，以便与功能器件集成，满足低工作电压、低功耗的要求。目前，传统的织构化处理工艺无法实现这一目标。根据NSAF联合基金指南明确要求，本课题申请旨在开发新的柔性压电聚合物薄膜织构化处理工艺，发展并完善两种织构化方法: 1) 基于有序聚四氟乙烯模板的压电聚合物外延生长法；以及2) 沉积在柔性衬底上的压电薄膜拉伸法。通过热、力、电学等工艺参数调控压电薄膜微结构及电性能，确定织构化薄膜复杂结构与电性能间关系，由此优化薄膜织构化处理工艺，获得高性能压电聚合物薄膜。

以PVDF和P(VDF-TrFE)为代表的压电聚合物材料在传感器、换能器、存储器等领域有着广泛应 用前景。为提高压电聚合物薄膜压电、铁电性能，通常需采用拉伸、退火、极化等织构化处理 工艺。随着微电子工业的发展，要求制备膜厚小于1μm甚至纳米量级的高性能压电聚合物薄膜 ，以便与功能器件集成，满足低工作电压、低功耗的要求。目前，传统的织构化处理工艺无法 实现这一目标。根据NSAF联合基金指南明确要求，本课题申请旨在开发新的柔性压电聚合物薄 膜织构化处理工艺，发展并完善两种织构化方法: 1) 基于有序聚四氟乙烯模板的压电聚合物 外延生长法；以及2) 沉积在柔性衬底上的压电薄膜拉伸法。通过热、力、电学等工艺参数调 控压电薄膜微结构及电性能，确定织构化薄膜复杂结构与电性能间关系，由此优化薄膜织构化 处理工艺，获得高性能压电聚合物薄膜。课题研究严格按照预定研究目标进行。设计并开发了控温、控压及可控摩擦速度制备高度有序PTFE模板的工艺及设备；在该PTFE模板上实现了铁电聚合物的外延生长，其中外延P(VDF-TrFE)薄膜展现明显改善的铁电、压电性及热学稳定性。基于PVA衬底，开发了衬底协同拉伸工艺，获得了电活性的PVDF薄膜。系统探讨了各工艺参数(温度、压强、拉伸比、电场等)对织构薄膜结构和电性能的影响。