Local 90° switching in Pb(Zr0.2Ti0.8)O3 thin film: Phase-field modeling

Polarization switching under an applied electrical field is a fundamental property of ferroelectric materials and has been explored for ferroelectric memory and electromechanical sensor applications. Ferroelectric/ferroelastic Pb(Zr0.2Ti0.8)O-3 (PZT) epitaxial thin films have been extensively studied due to their high electromechanical responses. Herein, we study the switching kinetics of PZT thin films under a local applied bias simulating a piezoresponse force microscopy tip via the phase-field approach. Local 90 degrees switching was observed along with 180 degrees switching, in good agreement with previous experimental observations. Different switching patterns are observed at different applied bias for films under different substrate strains. Generally, under low to medium bias, 90 degrees switching is favored due to the huge release of elastic energy. While under a high applied bias, 180 degrees switching dominates with large electrostatic energy decrease. It is worthwhile noting that the less mobile 90 degrees domain wall cannot be fully switched back by a reverse electric field, which could lead to the fatigue behavior. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.