Characterization of metalorganic decomposition-derived SrBi2Ta2O9 thin films with different thicknesses

Abstract

Ferroelectric capacitors having sputtered Pt bottom and top electrodes and metalorganic decomposition derived ferroelectric thin films of SrBi2Ta2O9 (SBT) were prepared. The thickness effects on the structure, surface morphology, and electrical properties of SBT thin films were studied and discussed. Structure and surface morphology were analyzed by x-ray diffraction and atomic force microscope. The electrical properties were characterized by the measurements of hysteresis, capacitance, and pulse switching. The crystalline structure, grain size, and electrical properties do not depend on film thickness when films are less than 440 nm thick. A larger grain size is observed for films thicker than 440 nm, which results in a larger remnant polarization. The thickness dependence of the coercive voltage and reciprocal capacitance can be explained by an interfacial layer model. The thickness-independent coercive field and dielectric constant, calculated from the interfacial layer model, are around 19 kV/cm and 343, respectively. Nonvolatile polarization (Pnv), obtained from pulse-switching measurements, increases with the applied electric field and finally saturates with a slight thickness effect. The relaxation of the remnant polarization that occurs at zero-voltage intervals between the pulses and the thickness-independent behavior of Pnv are explained based on depolarization fields within the ferroelectric due to nonswitching interfacial layers at the film/electrode interfaces.