Fatigue of Pb(Zr0.53Ti0.47)O3 ferroelectric thin films

Fatigue of Pb(Zr0.53Ti0.47)O-3 ferroelectric thin films has been studied with several novel electrode modifications. Doped amorphous silicon is used as a gating layer between the ferroelectric and metal electrode to regulate the type of charge carrier injection during switching of the ferroelectric. This configuration requires a low switching frequency in order to avoid the relaxation effect that arises from the limited charging ability of the semiconductor. In addition, charge depletion in the semiconductor causes a polarization asymmetry that reflects a depolarization field due to incomplete compensation of the polarization charge. Fatigue tests reveal that electron injection is a necessary condition for polarization degradation, whereas hole injection is not. Blocking interfaces by SiO2 or c-oriented Bi4Ti3O12 can also mitigate fatigue, albeit at a reduced polarization level. On the other hand, compensation of Pb loss through PbO undercoat layer has little effect on fatigue. Based on these observations, injected electrons in association with oxygen vacancies generated during cycling are proposed as the defects responsible for fatigue. These defects may impede domain switching by segregation at the electrode interface or at domain boundaries, with an enhanced kinetics because of the lower valence of the partially de-ionized entity. (C) 1998 American Institute of Physics.