Abstract
Sr-deficient SrBi2Ta2O9 (SBT) thin films for nonvolatile ferroelectric random access memory applications were deposited by radio-frequency magnetron sputtering on Pt∕Ta∕SiO2∕Si substrates. The effect of deposition parameters on microstructures and chemical composition were studied using x-ray diffraction (XRD), field emission scanning electron microscopy, and x-ray photoelectron spectroscopy (XPS). The composition of the films was dependent on the sputtering conditions. The undesirable pyrochlore phase could be eliminated by adjusting process pressure, target power density, and target-to-substrate distance. The evolution of microstructures at various deposition conditions was attributed to changes in the Bi∕Ta and Sr∕Ta ratios. When Sr became deficient and Bi excessive (Sr0.74Bi2.2Ta2O9+x as determined by XPS), no pyrochlore phase was detected with XRD. Under an electric field of 240kV∕cm, the Sr-deficient SBT film demonstrated a remnant polarization (2Pr) of 11.6μC∕cm2 and a coercive field (2Ec) of 96kV∕cm.
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