Systematic Control of the Nanostructure of Semiconducting-Ferroelectric Polymer Composites in Thin Film Memory Devices.

In polymer-based ferroelectric diodes, films are composed of a semiconducting polymer and a ferroelectric polymer blend sandwiched between two metal electrodes. In these thin films, the ferroelectric phase serves as the memory retention medium while the semiconducting phase serves as the pathway to read-out the memory in a nondestructive manner. As such, having distinct phases for the semiconducting and ferroelectric phases have proven critical to device performance. In order to evaluate this crucial structure-property relationship, we have fabricated ordered ferroelectric devices (OFeDs) through common lithographic techniques to establish systematically the impact of nanoscale structure on the macroscopic performance. In particular, we demonstrate that there is an optimal domain size (∼400 nm) for the interpenetrating networks, and we show that the ordered device, with semiconducting domains that span the entire length of the active layer film, provides a significant increase in the ON/OFF ratio relative to the blended film fabricated using standard solution blending and spin-coating techniques. This improved performance occurs due to a combination of the ordered nanostructure and the nature of the ferroelectric-semiconductor interface. As this is the first demonstration of macroscopic OFeDs, this work helps to elucidate the underlying physics of the device operation and establishes a new archetype in the design of polymer-based, nonvolatile memory devices.