Fatigue and dielectric properties of undoped and Ce doped PZT thin films

Abstract

Ce doping improves the ferroelectric properties of sol-gel derived PZT thin films by facilitating easier domain wall movement. It also decreases the leakage current densities by reducing the concentration of free carriers through a decrease in concentration of Pb and O vacancies. Ce-PZT films retain good dielectric dispersion characteristics since the concentration of defects and defect dipoles are reduced. Ce doping dramatically improves the fatigue resistance of PZT thin films. We have studied the frequency dependence of fatigue behavior and shown that the loss of polarization due to fatigue follows a universal scaling behavior with N/f², where N is the number of the switching cycles and f is the frequency. The origin of the scaling is attributed to the drift of oxygen vacancies, which is the rate limiting process in the growth of the interface layer responsible for fatigue. Empirical fits for both undoped and cerium doped samples show that switchable polarization follows a stretched exponential decay with time or N/f. Cerium doping is believed to improve fatigue resistance by impeding the motion of oxygen vacancies.