Quantification of the Electromechanical Measurements by Piezoresponse Force Microscopy

Abstract

Piezoresponse force microscopy (PFM) is widely used for characterization and exploration of the nanoscale properties of ferroelectrics. However, quantification of the PFM signal is challenging due to the convolution of various extrinsic and intrinsic contributions. Although quantification of the PFM amplitude signal has received considerable attention, quantification of the PFM phase signal has not been addressed. A properly calibrated PFM phase signal can provide valuable information on the sign of the local piezoelectric coefficient—an important and nontrivial issue for emerging ferroelectrics. In this work, two complementary methodologies to calibrate the PFM phase signal are discussed. The first approach is based on using a standard reference sample with well‐known independently measured piezoelectric coefficients, while the second approach exploits the electrostatic sample–cantilever interactions to determine the parasitic phase offset. Application of these methodologies to studies of the piezoelectric behavior in ferroelectric HfO2‐based thin‐film capacitors reveals intriguing variations in the sign of the longitudinal piezoelectric coefficient, d33,eff. It is shown that the piezoelectric properties of the HfO2‐based capacitors are inherently sensitive to their thickness, electrodes, as well as deposition methods, and can exhibit wide variations including a d33,eff sign change within a single device.

Vector piezoelectric response and ferroelectric domain formation in Hf0.5Zr0.5O2 films

“…Note that the particular polarization sign for the bright or dark regions cannot be inferred due to the absence of a reference region. 7 Similar shapes are observed if deflection along the perpendicular axis is probed (Fig. 4(d–f)).…”

“…1–3 Piezoelectric response, on the other hand, has gotten less attention, until very recently when a negative piezoelectric response has been theoretically predicted 4–6 and experimentally probed. 6,7…”

“…[1][2][3] Piezoelectric response, on the other hand, has gotten less attention, until very recently when a negative piezoelectric response has been theoretically predicted [4][5][6] and experimentally probed. 6,7 So far, most of the studies related to the piezoelectric response of ferroelectric doped HfO 2 make use of the Piezoelectric Force Microscopy (PFM) tool. These studies mainly focus on the characterization of PFM loops and/or PFM images after electric lithography to further demonstrate the ferroelectric character of the material.…”

Electromechanics of Domain Walls in Uniaxial Ferroelectrics

“…The PFM phase signal is calibrated following procedures in Ref. [12]. 1b,e,h), the DWs appear in a conventional way: they exhibit a low PFM amplitude signal in comparison to the antiparallel in-plane domains delineated by these walls.…”

“…The PFM phase signal was calibrated following procedures in Ref. [12], i.e., 0° denoted an in‐phase signal, and 180° indicated a signal, which is out‐of‐phase with the ac driving voltage.…”