Piezoresponse Force Spectroscopy of Ferroelectric Materials

TL;DR

This paper analyzes the mechanisms of Piezoresponse Force Spectroscopy (PFS) in ferroelectric materials, linking domain nucleation parameters to the PFM signal and exploring effects of surface screening and Debye length.

Contribution

It provides a theoretical framework for understanding PFS signal formation and the influence of surface screening and Debye length on ferroelectric switching behavior.

Findings

Critical nucleus size is controlled by surface screening.

Tip-induced switching requires surface screening.

PFS can study domain nucleation near defects and in low-dimensional ferroelectrics.

Abstract

Piezoresponse Force Spectroscopy (PFS) has emerged as a powerful technique for probing highly localized switching behavior and the role of microstructure and defects on switching. The application of a dc bias to a scanning probe microscope tip in contact with a ferroelectric surface results in the nucleation and growth of a ferroelectric domain below the tip, resulting in changes in local electromechanical response. Resulting hysteresis loops contains information on local ferroelectric switching behavior. The signal in PFS is the convolution of the volume of the nascent domain and the probing volume of the tip. Here, we analyze the signal formation mechanism in PFS by deriving the main parameters of domain nucleation in a semi-infinite material and establishing the relationships between domain parameters and PFM signal using a linear Greens function theory. The effect of surface screening and finite Debye length on the switching behavior is established. In particular, we predict that the critical nucleus size in PFM is controlled by the surface screening mechanism and in the absence of screening, tip-induced switching is impossible. Future prospects of PFS to study domain nucleation in the vicinity of defects, local switching centers in ferroelectrics, and unusual polarization states in low-dimensional ferroelectrics are discussed.