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