In-situ Polarization Switching of Ferroelectric Pb(Zr,Ti)O3 thin film Capacitor in Transmission Electron Microscopy

Abstract

The ferroelectric domain switching is widely investigated as an enabling phenomenon of non-volatile random access memory, field-effect transistors, and tunneling barriers. In most applications, the functionality is based on capacitor-type structures formed by a ferroelectric embedded between two metallic electrodes. Correspondingly, understanding the fundamental physics of ferroelectric domain switching behavior in capacitor structures is crucial in determining the application limits and performance. Direct imaging of domain evolution in the sufficient resolution is best way to investigate the polarization switching process. Recently, the development in the synthesis, fabrication, and imaging technique of nano-scale ferroelectric structures has been able to establish an understanding of intriguing polarization switching. In-situ transmission electron microscopy (TEM) is a powerful tool that provides micro or even atomic-scale information on depth distribution of polarization switching process. In-situ biasing of ferroelectric thin film in TEM is still quite new technique and just two studies reported by H. Chang et al. [38] and C. T. Nelson et al. [39] in this year, which investigated the polarization switching process in cross-sectional thin film under applied the electric field with the tip-electrode electrical contact in TEM. These studies have the limitation that the whole reversible polarization switching process cannot be observed due to directly contact to the bare surface of ferroelectric thin film without the top electrode.Here, the ferroelectric domain dynamics in the cross-sectional PbZr0.2Ti0.8O3 thin film of capacitor structure with two metallic electrode closed to real ferroelectric capacitors-based electronic devices is observed directly by applied electric field to top electrode in TEM. Studies of the kinetics in domain evolution allow clear visualization of nucleation, forward growth and sideways growth steps of domain formation. We observed the preferential nucleation site dependent on electric field direction, asymmetric domain switching dynamics related to imprint, and effects of 90° ferroelastic domains on polarization switching. These results provide how the interface-induced phenomena affect the polarization switching of capacitor-type ferroelectric thin film structure.