Role of bismuth precursor in crystallization of SrBi2Ta2O9 thin films

Crystallization of SrBi2Ta2O9 (SBT) thin films was studied as a function of viscosity of bismuth precursor and baking temperature, in order to fabrica te capacitors with improved ferroelectric properties. SET thin films were d eposited on to Pt substrates using a chemical solution deposition (CSD) tec hnique. Post-deposition anneal at 750 degrees C for 1 h in oxygen atmospher e revealed a significant influence of baking temperature and the viscosity of bismuth precursor on the microstructure and the ferroelectric properties of SET thin films. A high baking temperature (350 degrees C) and a low vis cosity of bismuth precursor (8 cp) yielded larger amounts of Bi2O3 secondar y phase, smaller SET grains (104 nm), and lower remanent polarization (P-r = 2.0 mu c/cm(2)). Additionally, these films exhibited a very high rate of ageing (> 45% reduction in P-r after 7 days). A modified CSD process is sug gested, which could suppress the formation of Bi2O3 secondary phase. Films fabricated using modified CSD technique exhibited a much larger grain size of 165 nm, higher P-r of 7.2 mu c/cm(2), and significantly improved ageing characteristics (< 1% reduction in P-r after 7 days). A qualitative model t o describe the ageing in SET-based capacitors is also suggested.