Constant-current study of dielectric breakdown of Pb(Zr,Ti)O-3 ferroelectric film capacitors

This paper addresses the problem of time-dependent dielectric breakdown of Pb(Zr,Ti)O-3 (PZT) thin films. It is shown by using constant-current breakd own measurements, that for PZT film capacitors with Pt and SrRuO3 (SRO) ele ctrodes the breakdown onset is controlled by charge to breakdown (Q(BR)) ra ther than the voltage applied to the capacitor. The QBR value for the asymm etrical Pt/SrRuO3/PZT/Pt capacitors is found to be much higher that for the Pt/PZT/Pt system. Polarization fatigue caused by bipolar voltage stress pr ovokes a substantial decrease in charge to breakdown. These results can be interpreted in terms of percolation model used for breakdown in SiO2, where the QBR is associated with injected-carrier-assisted creation of the criti cal concentration of defects required for formation of the breakdown paths. The observed variation of the QBR values depending on the electrode materi al (i) and polarization fatigue (ii) are interpreted in terms of current re distribution across the area of the capacitor, specifically current redistr ibution between grains and grain boundaries (case (i)) or current redistrib ution between fatigued and nonfatigued areas (case(ii)).