Unusual Resistance Hysteresis in n-Layer Graphene Field Effect Transistors Fabricated on Ferroelectric Pb(Zr_0.2Ti_0.8)O_3

TL;DR

This study reports an unusual resistance hysteresis in graphene transistors on ferroelectric PZT, caused by water molecule dynamics at the interface, with potential applications in memory devices.

Contribution

It reveals a novel resistance hysteresis mechanism in graphene-PZT devices due to water molecule dynamics, differing from polarization switching effects.

Findings

Resistance hysteresis occurs at high voltages, opposite to polarization switching expectations.

Hysteresis relaxation is thermally activated with a 50-110 meV barrier.

Water molecules at the interface are responsible for the hysteresis.

Abstract

We have fabricated n-layer graphene field effect transistors on epitaxial ferroelectric Pb(Zr_0.2Ti_0.8)O_3 (PZT) thin films. At low gate voltages, PZT behaves as a high-k dielectric with k up to 100. An unusual resistance hysteresis occurs in gate sweeps at high voltages, with its direction opposite to that expected from the polarization switching of PZT. The relaxation of the metastable state is thermally activated, with an activation barrier of 50-110 meV and a time constant of 6 hours at 300 K. We attribute its origin to the slow dissociation/recombination dynamics of water molecules adsorbed at the graphene-PZT interface. This robust hysteresis can potentially be used to construct graphene-ferroelectric hybrid memory devices.