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 m ade by sol-gel spin coating have been evaluated using hysteresis measu rement by bipolar continuous pulses. The following three stages were f ound according to the cumulative polarization switching cycles: (1) sl ow fatigue stage at the initial switching cycles, (2) logarithmic fati gue 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 logarithm ic 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-act ivating process'' with an accelerating factor of 1.2 x 10(-3) in units of decade kV/cm on our PZT thin-film capacitors. Temperature dependen ce of fatigue characteristics was unexpectedly small and activation en ergy was estimated to be 0.051 eV. A plausible fatigue model is propos ed in which injected charge initiates the polarization fatigue.