An investigation was made of the discrepancy between the significant 18O isotope motion observed after bipolar voltage cycling used to induce ferro-electric fatigue in unannealed Pt/Pb(Zr,Ti)O3/Ir (PZT) capacitors and the lack of an observable O tracer motion in annealed capacitors. It was found that, whereas unannealed Pt electrodes were permeable to O, annealed Pt electrodes were O-impermeable. Moreover, when the initial O tracer profile did not vary strongly with depth, the ability to detect O motion during fatigue voltage cycling depended critically upon the O permeability of the top electrode of the capacitor. The results indicated that O exchange between the PZT film and external O sources and sinks during voltage cycling was not necessary for ferro-electric fatigue to be manifest. In addition, studies of the dependence of ferro-electric materials properties on ambient gases should be accompanied by analysis of the permeability of exposed surfaces to the gases of interest.

Oxygen Permeability of Ferroelectric Thin Film Top Electrodes and its Effect on Detectable Fatigue Cycling-Induced Oxygen Isotope Motion. L.F.Schloss, H.Kim, P.C.McIntyre: Journal of Materials Research, 2004, 19[4], 1265-72