Unraveling ferroelectric polarization and ionic contributions to electroresistance in epitaxial Hf0.5Zr0.5O2 tunnel junctions

TL;DR

This paper investigates how the microstructure of epitaxial Hf0.5Zr0.5O2 films influences ferroelectric polarization and defect-related mechanisms, affecting the electroresistance in tunnel junctions, with implications for data storage technologies.

Contribution

It reveals the fundamental role of grain boundary microstructure and phase coexistence in controlling reversible and irreversible electroresistance in HZO-based tunnel devices.

Findings

Reversible electroresistance up to 450% with orthorhombic phase only.

Irreversible electroresistance up to 100,000% with mixed phases.

Microstructure determines the balance between polarization and defect contributions.

Abstract

Tunnel devices based on ferroelectric Hf0.5Zr0.5O2 (HZO) barriers hold great promises for emerging data storage and computing technologies. The resistance state of the device can be changed by a suitable writing voltage. However, the microscopic mechanisms leading to the resistance change are an intricate interplay between ferroelectric polarization controlled barrier properties and defect-related transport mechanisms. Here is shown the fundamental role of the microstructure of HZO films setting the balance between those contributions. The oxide film presents coherent or incoherent grain boundaries, associated to the existence of monoclinic and orthorhombic phases in HZO films, which are dictated by the mismatch with the substrates for epitaxial growth. These grain boundaries are the toggle that allows to obtain either large (up to 450 %) and fully reversible genuine polarization controlled electroresistance when only the orthorhombic phase is present or an irreversible and extremely large (1000-100000 %) electroresistance when both phases coexist.