Influence of the morphology of ferroelectric SrBi2Ta2O9 thin films deposited by metal organic decomposition on its electrical characteristics

The morphologies of SrBi2Ta2O9 (SBT) thin films deposited by metal organic decomposition and crystallized at temperatures between 600 and 800 °C for 45 min are studied by atomic force microscopy (AFM) and X-ray diffractometry (XRD). From these analytical investigations a detailed quantitative description of the phase transformation from the non-ferroelectric fluorite to ferroelectric Aurivillius phase including changes in the microstructure and surface roughness are extracted. These results are correlated to electrical characteristics from hysteresis loop and leakage current measurements of corresponding Pt/SBT/Pt capacitor modules. As a result, increased values of remnant polarization can directly be correlated to the Aurivillius surface coverage. It is shown that the measured leakage currents are dominantly influenced by the grain boundaries and, therefore, are very sensitive on the overall film granularity. The SBT roughness is not predominant for the leakage currents, but is very critical for capacitor shorting. Potentially, the results provided with this work provide instruments for design of electrical characteristics, to meet desired FeRAM specifications.