Top electrode dependence of forming gas annealing effects on ferroelectric films

The effects of forming gas annealing have been studied on PZT [Pb(Zr,Ti)O-3] and SBT (SrBi2Ta2O9) samples with a variety of top electrode materials. It's been found that forming gas annealing causes changes in the remanent polarization, coercive field,;nd leakage current in both types of samples, and these changes depend strongly on the top electrode material. Among the 6 electrode materials that we have studied (Pt, Au, Ag, Cu, Ni, and In2O3), Pt tends to lead to the most severe degradation, while the oxide electrode tends to withstand better the forming gas anneal. To explain the results, a model has been proposed which is based on the catalytic activities of the top electrode to dissociate hydrogen molecules into hydrogen atoms, and the latter then migrate into PZT or SBT films to cause oxygen deficiency.