DEPOLARIZATION CHARACTERISTICS IN SOL-GEL FERROELECTRIC PB(ZR0.4TI0.6)O-3 THIN-FILM CAPACITORS

Studies of depolarization characteristics have been carried out on so-gel lead zirconate titanate (PZT) ferroelectric thin-film capacitors by electrical evaluation of the pulse switching response employing a capacitor-loaded circuit. Pour consecutive positive pulses were used to evaluate the depolarization effect after negative writing, instead of conventional positive and negative double pulses. The extended evaluations were carried out for, e.g., pulse height, pulse width, temperature dependence, and space charge effect. The amount of depolarization strongly depended only upon the value of load capacitance. The transition and hysteresis loops from pulse switching clearly showed that the depolarization occurred due to the depoling (partial switching) of domains by an opposite-directional depolarization field which arose from accumulated switched charge on the load capacitor. We considered that depolarization occurs as a result of both external depolarization field from an external load capacitor and internal depolarization field from interfacial layers within ferroelectric material.