Experiments confirm the mechanism behind phase-separated ferroelectric memory diodes

Organic memory devices based on ferroelectricity are a promising approach toward the development of a nonvolatile and rewritable memory technology suitable for a wide range of applications. Ferroelectric capacitors present a major disadvantage because the read-out of the stored information destroys the information state, and the memory must be reprogrammed after every read operation.

A decade ago, researchers introduced the concept of phase-separated blends for ferroelectric memory diodes, which can combine an insulating ferroelectric polymer with a semiconducting polymer, allowing for nondestructive read-out. New work by Dehsari et al. provides an experimental demonstration of the underlying operation mechanism behind these diodes.

Previous work using theoretical two-dimensional simulations has suggested that the phase-separated ferroelectric diode is a true interface device that only requires a fraction of the contact underneath the semiconductor-ferroelectric polymer interface for memory operation. Charge injection into the diode takes place at the corner where three different materials meet — the metal contact, ferroelectric polymer and semiconductor. Modulation of the charge injection barrier at this interfacial point causes resistance switching.

In order to test this theory, the authors employed a variety of experimental techniques along with numerical simulations. They created a modified diode structure where the electrode contacting the semiconductor phase had been intentionally removed and still observed resistance switching. Numerical simulations reproduced the experimentally measured current-voltage characteristics of the diodes and confirmed the memory operation mechanism.

Currently, the authors are studying the mechanism in order to further improve the performance of such resistive switches. In terms of future work, they may include printing of such structures on solid substrates or even foils.

Source: “Interfacial conduction in organic ferroelectric memory diodes,” by Hamed Sharifi Dehsari, Manasvi Kumar, Matteo Ghittorelli, Gunnar Glasser, Thomas Lenz, Dago M. de Leeuw, Fabrizio Torricelli, and Kamal Asadi, Applied Physics Letters (2018). The article can be accessed at https://doi.org/10.1063/1.5043244 .