Composition-related effects of microstructure on the ferroelectric behavior of SBT thin films

Non-stoichiometric strontium bismuth tantalate, Sr1-xBi2+yTa2O9 (SBT) thin films with different cation ratios have been deposited by metalorganic decomposition (MOD) on Pt/TiO2/SiO2/Si(1 0 0) substrates, using strontium (2,2,6,6-tetramethyl-3,5-heptadionate). bismuth (2,2,6.6-tetramethyl-3,5-heptadionate), and tantalum ethoxide as precursors. Crystallization of the films was carried out at 750 degreesC under an atmosphere of O-2, following a firing step at 550 degreesC. The crystal phase and orientation of the 300 nm thick films were studied by XRD (CBXRD and GIXRD). The surface morphology of the films was examined by AFM. For an Sr:Bi ratio of 0.8:2.2, the films are formed by large clusters of elongated grains corresponding to the SET phase embedded in a matrix of a Bi-deficient pyrochlore phase. For Sr:Bi ratios of 0.7:2.2 and 0.7:2.3, we obtained single-phase orthorhombic SET films formed by densely packed elongated grains, whose axial ratio was dependent on the specific cation ratio used. Single-phase SET films showed very low polarization fatigue after 10(11) switching cycles and good retention properties. (C) 2001 Elsevier Science B.V. All rights reserved.