Ferroelectric properties and interfacial characteristics of Ca substituted strontium bismuth tantalate thin films

In this study, we have investigated the structural, interfacial and ferroelectric properties of Sr1-xCaxBi2Ta2O9 thin films grown on Pt/TiO2/SiO2/Si substrates using pulsed-laser-deposition technique. The decrease in lattice parameters with increasing Ca content was attributed to the smaller ionic radius of Ca. Atomic force microscopy shows that the average grain size and surface roughness of the films increases with the incorporation of Ca. Films with x = 0.2 exhibited a maximum remanent polarization of similar to 23.8 mu C/cm(2) with a coercive field of 175 kV/cm. The higher remanent polarization was attributed to the increased grain size and to the increase in the lattice mismatch between TaO2 and SrO planes. The presence of metallic bismuth at the interface of the film and the substrates was confirmed using XPS depth profile analysis. The current transport property of the thin film capacitors suggests a bulk-limited dc-current conduction mechanism.