Resistive switching in ferroelectric BiFeO3 by 1.7 eV change of the Schottky barrier height

TL;DR

This paper demonstrates that resistive switching in ferroelectric BiFeO3 is driven by a 1.7 eV change in Schottky barrier height, enabling high-speed ferroelectric memory readout through local conductivity measurements.

Contribution

It provides direct evidence linking polarization states to Schottky barrier height changes in BiFeO3, revealing a novel mechanism for resistive switching.

Findings

Schottky barrier height changes by 1.7 eV between polarization states

Resistive switching enables high-speed ferroelectric memory readout

Large charge switching observed in BiFeO3 compared to PZT

Abstract

Using metal-ferroelectric junctions as switchable diodes was proposed several decades ago. This was shown to actually work in PbZr(1-x)TixO3 (PZT) by Blom et al. [P.W. M. Blom et al., Phys. Rev. Lett. 73, 2107 (1994)], who reported switching in the rectification direction and changes of the current of about 2 orders of magnitude upon switching the polarization direction of the ferroelectric layer. This form of resistive switching enables the read out of a ferroelectric memory state at higher speed compared to the capacitive design, without destroying the information in each reading cycle. Recently, Jiang and coworkers have shown that these Schottky barrier effects are enormous in BiFeO3, giving thousand times more switched charge than found by in PZT [A.Q. Jiang. et al., Adv. Mat. 23, 1277 (2011)]. Here, by performing local conductivity measurements, we attribute this to a large change of the Schottky barrier height between the as-grown, down-polarized domains and the up-polarized domains. These measurements allow to estimate the relative effect of polarization charges and screening charges on the conduction through the ferroelectric.