Effects of processing on the characteristics of SrBi<inf>2</inf>Ta<inf>2</inf>O<inf>9</inf> films prepared by metalorganic decomposition

Abstract

SrBi2Ta2O9(SBT) films were prepared by metalorganic decomposition technique. The films were obtained by spin-on pyrolysis of the precursor solutions on various substrates and then annealed at 550-850°C in dry oxygen, wet oxygen, or Ar. Effects of precursor solution concentration, anneal temperature, anneal atmosphere, substrate and Ar ion sputtering on the microstructure, morphology and electrical properties were investigated by means of x-ray diffraction, scanning electron microscope, atomic force microscope, x-ray photoelectron spectroscopy, and electrical measurements. The results indicated the grain size, and the remnant polarization (Pr) increased with increasing the anneal temperature up to 800°C and the significant hysteresis loop could be obtained only after anneal above 700°C. At 850°C, the pyrochlore phase and other secondary phases were observed along with the SBT phase, leading to the decreasing Pr and dielectric constant. In addition, the development of crystalline phase and electrical properties were affected by anneal atmosphere. When annealed in Ar at 750°C, the layered SBT structure was destroyed with evident Bi loss. As though the original structure could be restored basically by subsequent adequate O2 anneal, the electrical properties were deteriorated seriously due to the shorted capacitor. Wet oxygen anneal evidently deformed the morphology and the hysteresis loop. This was attributed to the effect of possible produced slight H2 due to the reaction between H2O and residual carbonaceous in films under Pt catalyst. Substrates also played an important role on film crystallinity. The films deposited on Si, SrTiO3, and crystal quartz at 750°C had a layered perovskite polycrystalline structure while the films on fused quartz exhibited poor crystalline nature even after 800°C anneal and films on NaCl showed (200)-predominant orientation of SBT phase with some pyrochlore. In addition, Ar ion sputtering might lead to the severe Bi and oxygen deficiency in the surface of the sputtered film. © 2000 American Institute of Physics.