Degradation of asymmetrical Pt/SRO/PLZT/Pt capacitors: Role of Pt and oxide electrodes

Role of Pt and SRO electrodes in polarization fatigue of PLZT film ferroelectric capacitors is studied. We show that asymmetrical Pt/SRO/PLZT/Pt structure exhibits unusual dependence of the endurance of switching polarization on the driving ac electric field amplitude. Specifically, for high ac electric field amplitude it shows a good switching endurance similar to SRO/PLZT/SRO capacitors, whereas for amplitude lower than 80 kV/cm a pronounced polarization fatigue similar to that of conventional Pt/PLZT/Pt capacitors is observed. Based on the analysis of these results we conclude that the polarization switching endurance under high-amplitude fatiguing cycling is governed only by the top SRO-interface which is not subjected to degradation, whereas the degradation properties of the bottom Pt-interface do not play any role. Comparative analysis of leakage conduction of Pt/PLZT/Pt (i) and Pt/SRO/PLZT/Pt (ii) capacitors in virgin and fatigued states shows that both interfaces of capacitor (i) are subjected to degradation whereas both interfaces of the capacitor (ii) are not degraded. According to our analysis, in asymmetrical Pt/SRO/PLZT/Pt structure the top SRO-interface can protect the bottom Pt interface from degradation if the following conditions are met: 1. Top SRO interface is degradation-free 2. Switching rate at the top electrode is higher than at the bottom one