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 ferroele ctric capacitors is studied. We show that asymmetrical Pt/SRO/PLZT/Pt struc ture exhibits unusual dependence of the endurance of switching polarization on the driving ac electric field amplitude. Specifically, for high ac elec tric field amplitude it shows a good switching endurance similar to SRO/PLZ T/SRO capacitors, whereas for amplitude lower than 80 kV/cm a pronounced po larization fatigue similar to that of conventional Pt/PLZT/Pt capacitors is observed. Based on the analysis of these results we conclude that the pola rization switching endurance under high-amplitude fatiguing cycling is gove rned only by the top SRO-interface which is not subjected to degradation, w hereas the degradation properties of the bottom Pt-interface do not play an y role. Comparative analysis of leakage conduction of Pt/PLZT/Pt (i) and Pt/SRO/PLZ T/Pt (ii) capacitors in virgin and fatigued states shows that both interfac es of capacitor (i) are subjected to degradation whereas both interfaces of the capacitor (ii) are not degraded. According to our analysis, in asymmet rical 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.