Substrate temperature studies of SrBi2„Ta1ÀxNbx...2O9 grown by pulsed laser ablation deposition

Ferroelectric SrBi2(Ta12xNbx)2O9 ~SBNT! thin films were deposited on Pt/TiOx /SiO2 /Si substrates at various substrate temperatures by the pulsed laser ablation deposition method. X-ray diffraction shows that the film has a fluorite structure at a substrate temperature of 500 °C. The fluorite structure was transformed into perovskite phase at 550 °C and was fully crystallized at temperatures >700 °C, with a secondary phase present. Secondary ion mass spectroscopy and x-ray photoelectron spectroscopy studies reveal that the secondary phase was a nonferroelectric Bi-deficient pyrochlore phase at the SBNT/Pt interface and the film surface. The pyrochlore structure has a detrimental effect on the ferroelectric properties ~i.e., the remanent polarization, coercive field, leakage current and fatigue! of the film. The remanent polarization and coercive field for the film grown at a substrate temperature of 700 °C were 4.79 mC/cm and 68.68 kV/cm, respectively, with leakage current ,10 A/cm even at an applied voltage of 8 V and 30% degradation in endurance against fatigue after 2310 switching cycles. © 2002 American Vacuum Society. @DOI: 10.1116/1.1426364#