Reconstruction of IrO2/(Pb, La)(Zr, Ti)O3 (PLZT) interface by optimization of postdeposition annealing and sputtering conditions

Abstract

We reconstruct the interface between ferroelectric (FE) lanthanum-doped lead zirconate titanate (PLZT) and an iridium oxide (IrOx) top electrode (TE), taking advantage of the interdiffusion of Ir and Pb during postdeposition annealing. The tetragonal perovskite phase with a low c/a axis ratio at the IrOx/PLZT interface is observed by X-ray diffraction. It is suggested that the low c/a axis ratio in the interfacial layer is due to the effect of diffusion of Ir from the TE-IrOx. It is also considered that the low c/a axis ratio interfacial layer functions as a nucleation layer for reversal of polarization, thereby achieving a low coercive electric field. The formation of the interfacial layer is very sensitive to the O2 content of the Ar/O2 atmosphere during TE-IrOx deposition. Although an optimized Ar/O2 ratio achieves excellent polarization characteristics (high polarization value and low coercive field), the optimum Ar/O2 region is very narrow at around 36% O2. In other Ar/O2 regions, a pyrochlore phase is formed at the interface owing to interdiffusion of the TE and FE films, and polarization characteristics deteriorate.