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.