Electrical Comparison of Sol-Gel Derived Lead-Zirconate-Titanate Capacitors with Ir and Pt Electrodes

The electrical properties of sol-gel-derived Ir/lead-zirconate-titanate (PZT)/Ir and Pt/PZT/Pt capacitors were carefully investigated. PZTs with columnar structures were well crystallized on both Ir and Pt substrates. 250-nm-thick PZT films deposited on Ir and Pt showed random and <111>-preferred orientations, respectively. The Ir/PZT/Ir capacitor showed large remanent polarization density of 20.7 µ C/cm2 at applied voltage of 2.5 V even though this PZT is randomly oriented. This value is almost equal to that of <111>-oriented film prepared on Pt. Furthermore, coercive field of the Ir/PZT/Ir capacitor is much lower than that of the Pt/PZT/Pt one. For endurance property for switching, Pr of Pt/PZT/Pt capacitor was degraded to 45% of the initial value by switching of 1×105 cycles. On the other hand, that of Ir/PZT/Ir capacitor was decreased to 45% by 1×107 switching cycles. Degradation of remanent polarization density by switching was reduced considerably by using Ir electrodes.