Mechanism of high temperature hydrogen reduced polarization degradation in Pb(Zr1−xTix)O3 ferroelectric thin film capacitors

Abstract

AbstractAnnealing Pb(Zr1−xTix)O3 (PZT) thin films in the hydrogen ambient can result in the unacceptable degradation of ferroelectric properties due to interaction of H2 forming gas with the ferroelectric materials. Since the understanding of this degradation mechanism is limited, this issue arouses a big problem for the application of PZT in high‐density non‐volatile ferroelectric random access memories (NVFRAM). In order to resolve this problem, we investigate Pt/PZT/Pt capacitors before and after H2 annealing at various temperatures. The capacitors lost their ferroelectric properties during hydrogen annealing. The measurements of polarization hysteresis loops and leakage currents suggest that there are different degradation mechanisms for the reduced PZT films. Although hydrogen induced degradation can be partially recovered by post‐annealing of the thin films in the O2 ambient, all the remanent polarizations after recovery are much smaller than their virgin values, which indicates the irreversible damage of the ferroelectricity during the forming gas annealing (FGA) process. In order to investigate the degradation mechanism, X‐ray diffraction was performed before and after FGA, and atomic force microscopy images were taken to observe the topograghy and microstructure changes. A conductive Pt‐coated piezoelectric force microscope probe was used as a mobile top electrode to check ferroelectric and piezoelectric properties within microregions of PZT films before and after FGA.