Role of IrO2 Electrode in Reducing the Retention Loss of Ir/IrO2/Pb(Zr, Ti)O3/Ir Capacitors

Oxide electrodes are known to significantly improve reliability problems, such as fatigue and retention, in Pb(Zr, Ti)O3(PZT)-based ferroelectric capacitors. To understand the roles of the oxide electrodes on the opposite-state retention, we investigated the isotope tracer experiments and hysteresis measurements on Ir/IrO2/PZT/Ir and Ir/PZT/Ir capacitors before and after the retention tests. The depth profile of isotopic 18O in the Ir/IrO2/PZT/Ir capacitor, measured by the second ion mass spectroscopy, shows little changes in the 18O and 16O distributions at the IrO2/PZT interface. In addition, the hysteresis measurements showed that the internal field created by the retention tests should be nearly the same for both capacitors, indicating that the IrO2 layer should not play an important role in compensating the interface defect charges (possibly, the oxygen vacancies).