Toward accurate polarization estimation in nanoscopic systems

TL;DR

This paper highlights the challenges in accurately estimating polarization in ferroelectric thin films due to background current subtraction issues and proposes an improved method using asymmetric least squares subtraction for better characterization.

Contribution

It introduces an alternative background subtraction technique that enhances the accuracy of polarization measurements in ferro-resistive ferroelectric samples.

Findings

Standard methods can lead to large errors in polarization estimation.

Asymmetric least squares subtraction improves measurement accuracy.

Ferro-resistive behavior complicates polarization characterization.

Abstract

The nanoscopic characterization of ferroelectric thin films is crucial from their device application point of view. Standard characterization techniques are based on detecting the nanoscopic charge compensation current (switching current) caused by the polarization reversal in the ferroelectric. Owing to various surface and bulk limited mechanisms, leakage currents commonly appear during such measurements, which are frequently subtracted using the device I-V characteristic by employing positive-up-negative-down (PUND) measurement scheme. By performing nanoscopic switching current measurements on a commonly used ferroelectric, BiFeO3, we show that such characterization methods may be prone to large errors in the polarization estimation on ferro-resistive samples, due to current background subtraction issues. Especially, when ferro-resistive behavior is associated with the polarization reversal of the ferroelectric thin film, background current subtraction is not accurate due to the mismatch of the I-V characteristics for the two polarization states. We show instead that removing the background current by an asymmetric least squares subtraction method, though not perfect, gives a much better estimation of the ferroelectric properties of the sample under study.