Investigation of interface and bulk fatigue scenarios in sol-gel derived Pb(Zr_0.5Ti_0.5)O₃ films by asymmetric field driving

A method to distinguish the bulk and interface scenarios of fatigue in sol-gel derived Pb(Zr_0.5,Ti_0.5)O₃ (PZT) thin films on Pt and LaNiO₃ (LNO) substrates is proposed based on the asymmetric electric field driving of capacitors. The "hard" and "soft" failures of polarization, which are typical for sputtering and sol-gel deposited PZT, respectively, are realized in sol-gel derived Pt/PZT/Pt capacitors by changing the asymmetricity of driving pulses, indicating that the interface plays an important role in the polarization breakdown. For Pt/PZT/LNO capacitors, it is shown that the bulk pinning of domains appears to be more evident than the interface pinning. A model based on the electromigration and entrapment of charged defects subjected to the asymmetric field is also given, and the plausible approximation of space charge field versus charge density is discussed.