Ferroelectric thin films of bismuth-containing layered perovskite Bi 4 Ti 3 O 12 have been fabricated by a metalorganic decomposition (MOD) method. Crack-free and crystalline films of ∼5000 Å thickness have been deposited on Pt/Ti/SiO 2 /Si substrates. Different heat treatments have been studied to investigate the nucleation and growth of perovskite Bi 4 Ti 3 O 12 crystallites. If the same composition and final annealing temperature are used, films with different orientations are obtained by different heating schedules. These films show a large anisotropy in ferroelectric properties. Theoretical considerations are presented to suggest that nucleation control is responsible for texture and grain-size evolution. Moreover, the origin of the ferroelectric anisotropy is rooted in the two-dimensional nature of layered polarization.
Fatigue of Pb(Zr0.53Ti0.47)O3 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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.