Direct Probing of Polarization Charges at the Nanoscale

TL;DR

This paper demonstrates a method to directly measure polarization charges at the nanoscale in ferroelectric materials using conventional CAFM, overcoming previous limitations related to tip size and noise.

Contribution

It introduces a novel approach that enables direct nanoscale probing of polarization charges without additional corrections or specialized circuits.

Findings

Successfully measured polarization charge densities of 73.7 and 119.0 uC/cm2.

Proved the feasibility of evaluating ferroelectricity at the nanoscale.

Provided new guidelines for nanoscale ferroelectric characterization.

Abstract

Ferroelectric materials possess spontaneous polarization that can be used for multiple applications. Owing to a long term development for reducing the sizes of devices, the preparation of ferroelectric materials and devices are entering nanometer-scale regime. Accordingly, to evaluate the ferroelectricity, there is a need to investigate the polarization charge at the nanoscale. Nonetheless, it has been generally accepted that the detection of polarization charges using a conventional conductive atomic force microscopy (CAFM) without a top electrode is not feasible because the nanometer-scale radius of an atomic force microscopy (AFM) tip yields a very low signal-to-noise ratio. However, the detection is unrelated to the radius of an AFM tip, and in fact, a matter of the switched area. In this work, we demonstrate the direct probing of the polarization charge at the nanoscale using the Positive-Up-Negative-Down method based on the conventional CAFM approach without additional corrections or circuits to reduce the parasitic capacitance. We successfully probed the polarization charge densities of 73.7 and 119.0 uC/cm2 in ferroelectric nanocapacitors and thin films, respectively. The obtained results show the feasibility of the evaluation of the polarization charge at the nanoscale and provide a new guideline for evaluating the ferroelectricity at the nanoscale.