Device-area selection of memristive transport regimes in epitaxial $Hf_{0.5}Zr_{0.5}O_{2}$-based ferroelectric devices

TL;DR

This study investigates how device size influences memristive transport regimes in epitaxial HfZrO2-based ferroelectric devices, revealing a size-dependent transition between tunneling and conductive channel mechanisms.

Contribution

It identifies a crossover device area where transport mechanisms switch, linking nucleation, oxygen vacancies, and ferroelectric wake-up in epitaxial hafnia devices.

Findings

Small devices show tunneling transport with resistance inversely proportional to area.

Larger devices exhibit area-independent resistance due to localized conductive channels.

A statistical model captures the crossover area and correlates with ferroelectric wake-up onset.

Abstract

Ferroelectric memristive devices based on hafnia are promising systems for neuromorphic electronics, yet the interplay between polarization-modulated resistive changes and defect-mediated transport often leads to complex and debated switching mechanisms. Here, we investigate this competition in epitaxial Hf$_{0.5}$Zr$_{0.5}$O$_2$/La$_{0.67}$Sr$_{0.33}$MnO$_3$ heterostructures with Pt top electrodes by combining structural, ferroelectric, and memristive characterization with a statistical analysis across a broad range of device areas spanning three orders of magnitude. We identify two distinct memristive regimes with opposite resistance--voltage chiralities. Small devices exhibit a low-resistance state that scales inversely with area, consistent with area-distributed tunneling transport, while larger devices display an area-independent resistance indicative of localized conductive channels. A statistical nucleation model quantitatively captures this behavior and yields a crossover characteristic area $A^* \approx 10^3~\mu\mathrm{m}^2$. This crossover also correlates with the onset of ferroelectric wake-up in larger devices, linking conductive-channel nucleation and oxygen-vacancy redistribution within a unified physical picture. These results establish lateral device size as a key parameter controlling the dominant transport mechanism in epitaxial hafnia-based devices.