Organic Ferroelectric Material P (VDF-TrFE) Nanostructures Preparation And Performance

Organic ferroelectric material, P (VDF-TrFE), finds a wide range of applications, including sensing and actuation, data storage, energy harvest and storage, based on its unique ferroelectric, piezoelectric and pyroelectric properties. With the ever-increasing demand for miniaturization of electronic and photonic devices, there have been tremendous efforts in developing nanostructured ferroelectric patterns with smaller feature size, higher density and improved sensitivity and functionality.The fabrication of one-dimensional 1D and OD nanostructures is based on direct writing using SPM or electron beam, which is very time-consuming, high-cost and thus not suitable for manufacturing. Ink jet printing is also applied to fabricate FeRAM integrated with CMOS under low temperature with low cost, but it is incapable of nanoscale process. To date although nanostructures with less than 100nm can be fabricated with sate-of-the-art optical lithography technique, it is still hard to get nanostructures with less than 40nm. Furthermore, for photo and e-beam lithography, photoresist, electron beam or ultraviolet beam, and etching processes all can easily cause damages in polymer materials and hence degradation of their electrical properties. In order to avoid unnecessary degradation of ferroelectricity of in P (VDF-TrFE) nanostructures, simplify the processing and lower the cost, we have applied Nanoimprint lithography (NIL) to fabricate nanostructures of P (VDF-TrFE) and systematically studied the properties of the nanoimprinted structures.In this paper, we fabricate nanowire, nanodot matrix and electrode structures of P (VDF-TrFE) with thermal NIL, and study the size-effect of P (VDF-TrFE) under OD, 1D and 2D through a series of physical and electrical characterizations. The key parameters of the thermal NIL process of P (VDF-TrFE) have been analyzed in detail, including the relationship among the depth of NIL, temperature and pressure, and hydrophobic treatment of the template. Then the influence of NIL process on the properties of P (VDF-TrFE) has been studied, and the possibility of using NIL technique to fabricate multi-bit memory with ferroelectric polymer has been discussed. This work paves the way for further research on the properties of nanoscale PVDF copolymer, developing new fabrication methods of micro/nano-structure and the downscaling of electrical device based on ferroelectronics. First we use nanoimprint lithography to fabricate high density nanostructures on the P (VDF-TrFE).Through adjusting technical parameters and the components in film control of their shape, size, and crystallographic orientation. High quality and ultrathin films of P (VDF-TrFE) (<200nm) has been prepared by spin-coating method on the lcm x lcm Si substrate. The NIL is applied under the temperature between glass transition and melting temperature of P (VDF-TrFE) on the template prepared with electron beam direct write lithography. The influences of pressure, temperature and conditions before and after baking on the nanoscale structures and their physical properties have been comprehensively studied, and the optimal conditions on different substrates have been found.Then the physical and electrical properties of nanostructures of P (VDF-TrFE) prepared by NIL technique have been systematically characterized using X-ray diffraction, PFM and FTIR. The emphasis is put on the effect of processing and structures on morphology, structure and crystallinity. The ferroelectric leakage, surface charge and other properties at nanostructures has been studied by using PFM.In NIL fabrication of P (VDF-TrFE), both the processing and the structure strongly influence the material and electrical properties, so and thus we investigated the correlation between process/structure and the material/ferroelectric properties. We have found that the morphology, orientation and crystallinity are influenced by NIL, and controlling the NIL condition can improve the crystallinity and change preferred orientation of P (VDF-TrFE). The ferroelectric properties have been studied by PMF, and the results show that the nanostructures ferroelectric polymer film maintains good piezoelectric and ferroelectric properties via thermal NIL. The results offer very useful reference for the application of the thin film in ultra-high density data storage and other ferroelectric and piezoelectric nanodevices.