Nanopatterning of Ferroelectric Polymer and High-resolution Pyroelectric Scanning Microscopy

We have developed a low-pressure reverse nanoimprint lithography method that uses low-cost polycarbonate and polydimethylsiloxane soft molds to fabricate residual-layer-free ferroelectric polymer nanostructures over large areas on flexible substrates. The results of this study showed that the nanostructures were faithful, high-yield replicas of the soft molds with no detectable residual layer. The nanostructures have very stable and switchable piezoelectric, pyroelectric response, typical ferroelectric I-V characteristics and good crystallinity, and are highly promising for use in organic electronics enhanced or complemented by the unique properties of the ferroelectric polymer, such as bistable polarization, piezoelectric response, pyroelectric response, or electrocaloric function. The fabrication of large-area ferroelectric polymer nanostructures with very good ferroelectric properties on flexible substrates using the soft mold based low pressure reverse nanoimprint lithography will be a significant basis for a wide range of research and applications for flexible electronics. We have implemented a high-resolution Pyroelectric Scanning Microscopy (PSM) system that achieves high lateral resolution by means of a tightly focused violet laser beam for localized heating and high modulation frequency to minimize thermal diffusion. The system achieved a lateral resolution of 660±28 nm when imaging the polarization pattern in a thin film of vinylidene fluoride copolymer. The results are in excellent agreement with a four-layer thermal model implemented by finite element analysis. The high-resolution PSM system with submicron resolution is an efficient, non-invasive tool complementary to PFM in studies of thin film ferroelectric materials, and is uniquely valuable for studying nonferroelectric pyroelectric materials, which usually have negligible piezoresponse. Pyroelectric Scanning Microscopy should be useful for testing pyroelectric devices, and in the development and characterization of new ferroelectric and pyroelectric materials. The use of high modulation frequencies also permits studying transient polarization phenomena