Nanoelectromechanics of Polarization Switching in Piezoresponse Force Microscopy

TL;DR

This paper analyzes nanoscale polarization switching in ferroelectric materials using Piezoresponse Force Microscopy, proposing a phase transition framework and detailing the electrostatic and electroelastic field effects during domain nucleation and growth.

Contribution

It introduces a comprehensive electrostatic and electroelastic model for polarization switching in ferroelectrics under PFM, linking domain nucleation to phase transition theory and providing exact solutions for tip-surface interactions.

Findings

Switching can be first or second order depending on tip-surface separation.

Domain nucleation occurs only above a critical tip bias.

Large domains can be created with arbitrary size in pure ferroelectric switching.

Abstract

Nanoscale polarization switching in ferroelectric materials by Piezoresponse Force Microscopy (PFM) in weak and strong indentation limits is analyzed using exact solutions for electrostatic and coupled electroelastic fields below the tip. It is proposed that the tip-induced domain switching can be mapped on the Landau theory of phase transitions with the domain size as an order parameter. For a point charge interacting with a ferroelectric surface, switching of both first and second order is possible depending on the charge-surface separation. For a realistic tip shape, the domain nucleation process is first order in charge magnitude and polarization switching occurs only above a critical tip bias. In pure ferroelectric or ferroelastic switching, the late stages of the switching process can be described using point charge/force model and arbitrarily large domains can be created; however, the description of the early stages of nucleation process when domain size is comparable with the tip radius of curvature requires exact field structure to be taken into account.