Polarization description of successive ferroelectric switching in hafnia

TL;DR

This paper develops a free-energy and domain model to describe successive ferroelectric switching in HfO2, revealing the interplay of ionic conduction and ferroelectricity with potential applications in oxide-ion conductors and artificial synapses.

Contribution

It introduces a comprehensive theoretical framework combining free-energy modeling and first-principles calculations for ferroelectric switching in HfO2, highlighting ionic conduction mechanisms.

Findings

Nesting-domain pattern with opposite piezoelectric loops during nucleation.

Field-dependent ionic conductivity following Merz's law.

Ionic conductibility is coupled with ferroelectricity in HfO2.

Abstract

Intertwined ionic conduction and ferroelectric (FE) switching in HfO2 lead to extensive focuses. To describe its fundamental phenomena, we present a free-energy model describing the potential of ferroelectrics with successive FE switching paths, and extend the domain model of ionic conduction to ferroelectric domains. Associate theoretical analyses and first-principles calculations suggest a nesting-domain pattern with opposite piezoelectric loops during the nucleation-and-growth process in displacive FE-HfO2. A collective oxygen ion conduction mechanism is also proposed with a field-dependent ionic conductivity following the Merz's law. We conclude that the ionic conductibility is concomitant with the ferroelectricity in HfO2, and it may provide a new venue for pursuing low temperature fast oxide-ion conductors and artificial synapses.