Limitations to Electrical Probing of Spontaneous Polarization in Ferroelectric-Dielectric Heterostructures

TL;DR

This paper critically examines the limitations of the PUND technique in accurately measuring spontaneous polarization in ferroelectric-dielectric heterostructures, highlighting sources of error and the influence of physical phenomena.

Contribution

It provides analytical and numerical insights into the inaccuracies of PUND measurements in MFDM structures, emphasizing the effects of depolarization, charge trapping, and physical constraints.

Findings

PUND results may significantly differ from actual polarization switching.

Physical quantities involved in measurements are often inaccessible experimentally.

Depolarization and charge trapping critically affect measurement accuracy.

Abstract

An accurate estimate of the ferroelectric polarization in ferroelectric-dielectric stacks is important from a materials science perspective, and it is also crucial for the development of ferroelectric based electron devices. This paper revisits the theory and application of the PUND technique in Metal-Ferroelectric-Dielectric-Metal (MFDM) structures by using analytical derivations and numerical simulations. In an MFDM structure the results of the PUND technique may largely differ from the polarization actually switched in the stack, which in turn is different from the remnant polarization of the underlying ferroelectric. The main hindrances that prevent PUND measurements from providing a good estimate of the polarization switching in MFDM stacks are thus discussed. The inspection of the involved physical quantities, not always accessible in experiments, provides a useful insight about the main sources of the errors in the PUND technique, and clarifies the delicate interplay between the depolarization field and the charge injection and trapping in MFDM stacks with a thin dielectric layer.