A critical study of defect migration and ferroelectric fatigue in lead zirconate titanate thin film capacitors under extreme temperatures

The temperature dependence of the ferroelectric switching behavior was measured for lead zirconate titanate capacitors with the composition Pb(Zr.60Ti.40)O-3. Results indicated that a temperature rise contributes to an increasing rate of logarithmic decay in the polarization during repeated switching reversals. Most current theories dealing with polarization degradation, known as fatigue, are based on the motion of defects. In support of this phenomena, where the decay rate R(T) is proportional to exp(Delta Q/kT), two quantitative models are developed used to measure the thermally activated fatigue process. Fatigue curves of polarization versus number of cycles reveal that extremes in temperature are necessary to distinguish changes in the rate of fatigue, translating to a very small measured activation energy of approximately 0.05 eV. This small value leads one to believe that the mechanism responsible deals with the transport of electrons/holes, not ionic defects. Caution must be taken in this conclusion since the measured value is only the thermal component for the activation energy, and does not account for a work term.