Substrate temperature studies of SrBi2(Ta1−xNbx)2O9 grown by pulsed laser ablation deposition

Ferroelectric SrBi2(Ta1−xNbx)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 μC/cm2 and 68.68 kV/cm, respectively, with leakage current <10−7 A/cm2 even at an applied voltage of 8 V and 30% degradation in endurance against fatigue after 2×1012 switching cycles.