CHARACTERISTIC CHANGE DUE TO POLARIZATION FATIGUE OF SOL-GEL FERROELECTRIC PB(ZR0.4TI0.6)O-3 THIN-FILM CAPACITORS

We studied the fatigue characteristics of sol-gel ferroelectric Pb(Zr0 .4Ti0.6)O-3(PZT) thin-film capacitors measuring hysteresis loops, time -zero current voltage characteristics and the dielectric constant afte r polarization switching. All evaluations were carried out on samples with certain switching cycles at the slow fatigue stage, logarithmic f atigue stage and saturated stage. Oxygen-deficient regions at the inte rfaces at both the top and bottom electrodes were formed after fatigue , as found by observing Auger electron spectroscopy (AES) depth profil es. Time-zero current-voltage (I-V) characteristics show that ohmic le akage current increased as the switching cycles increased during fatig ue. This indicates that oxygen vacancies as donors arising during fati gue may compensate the lead vacancies as accepters. The electric field dependence of P-r+-P-r- and that of the dielectric constant show that the motion of domains, which can move in the electric field near a co ercive field, is suppressed after fatigue. We conclude that the oxygen vacancies suppress the domain motion and cause remanent polarization degradation. Since the biased-dielectric constant beyond 150 kV/cm sho wed no significant change after fatigue, it seems that no low-dielectr ic-constant regions adjacent to the electrode were generated during fa tigue.