Investigation of the structural and electrical properties of Sr1ÿxBi2.2Ta2O9 thin ®lms with de®cient Sr contents

Strontium bismuth tantalate Sr1ÿxBi2.2Ta2O9 (SBT, x ˆ 0, 0.1, 0.2, 0.3, 0.4, 0.6) thin ®lms with de®cient Sr contents were prepared at 7508C on Pt/TiO2/SiO2/Si substrates using metalorganic decomposition (MOD) spin-on technique. Effect of Sr de®ciency compositions on the structural and electrical properties were investigated by means of X-ray diffraction (XRD), inductively coupled plasma (ICP) analyses, electronic probe microanalyses (EPMA), atomic force microscope (AFM), scanning electron microscope (SEM) and electrical measurements. The XRD results indicate the ®lms with Sr de®ciency content at 40% and below have layered perovskite structure with the distorted lattice. For ®lms with 60% de®cient Sr, the layered structure cannot be formed. SEM and AFM micrograph shows the surface morphology is very sensitive to the Sr de®ciency. With increasing the Sr de®ciency to 40% and above, the ®lms exhibit the extremely inhomogeneity and poor crystallinity. The remnant polarization (Pr) gradually reduces with Sr de®ciency. This is attributed to the distorted layered structure and the formation of amorphous phase. In summary, SrBi2.2Ta2O9 is found to be the optimum composition with respect to grain size, morphology, and electrical properties. # 2001 Elsevier Science B.V. All rights reserved