Hydrogen-induced degradation mechanisms in ferroelectric PbZr0.4Ti0.6O3 and Bi3.25La0.75Ti3O12 thin films

Abstract

Hydrogen-induced degradation in PbZr0.4Ti0.6O3 and Bi3.25La0.75Ti3O12 (BLT) capacitors was investigated after forming gas annealing (FGA). By comparison, the BLT capacitors were found to have a high resistance against hydrogen-induced degradation at the low temperature FGA below 350degreesC. The BLT capacitors showed only a small reduction of remanent polarization and no deformation of hysteresis loops while the PZT showed a large polarization degradation after the same FGA process. The degradation of PZT at the low temperature FGA was investigated systematically by measuring the voltage shifts of hysteresis loop, and current-voltage and capacitance-voltage characteristics. Different degradation. mechanisms are suggested for PZT and BLT by comparing experimental results including those of thermogravimetric analysis. For PZT films, pinning of domains and defect dipoles due to charged defects is inferred to dominate the initial stage of the degradation. On the other hand, for BLT films, hydrogen-induced decomposition seems to govern the degradation resulting in the increase of leakage current density and production of non-ferroelectric oxide(s).