POLARIZATION FATIGUE CHARACTERISTICS OF SOL-GEL FERROELECTRIC PB(ZR0.4TI0.6)O3 THIN-FILM CAPACITORS

Fatigue characteristics of PbZr0.4Ti0.6O3 (PZT) thin-film capacitors made by sol-gel spin coating have been evaluated using hysteresis measurement by bipolar continuous pulses. The following three stages were found according to the cumulative polarization switching cycles: (1) slow fatigue stage at the initial switching cycles, (2) logarithmic fatigue stage at middle switching cycles which is recognized in general, (3) saturated stage at extremely large number of switching cycles. The decays of the nonswitched parts started in the middle of the logarithmic fatigue stage. The switching cycles at half of the initial remanent polarization are exponentially proportional to reverse electric field, and the degradation is explained in terms of an ''electric-field-activating process'' with an accelerating factor of 1.2 x 10(-3) in units of decade kV/cm on our PZT thin-film capacitors. Temperature dependence of fatigue characteristics was unexpectedly small and activation energy was estimated to be 0.051 eV. A plausible fatigue model is proposed in which injected charge initiates the polarization fatigue.