St. Tay et al., Influence of annealing temperature on ferroelectric properties of SrBi2Ta2O9 thin films prepared by off-axis radio frequency magnetron sputtering, J APPL PHYS, 88(10), 2000, pp. 5928-5934
Ferroelectric SrBi2Ta2O9 (SBT) thin films were deposited on Pt/TiOx/SiO2/Si
substrates using the off-axis radio frequency magnetron sputtering techniq
ue. X-ray diffraction and atomic force microscopy experiments showed that t
he crystallization of SBT thin films at > 700 degreesC correlated with the
formation of rod-like grains. Cross-sectional field emission scanning elect
ron microscopy images revealed that the apparent thickness of SBT decreased
while the thickness of Pt increased as the annealing temperature was incre
ased. The apparent decrease in the thickness of SBT was attributed to cryst
allization and densification in the film whereas the apparent increase in P
t thickness was due to diffusion of Ti and Bi into the Pt layer. This diffu
sion at high annealing temperatures (800 degreesC and above) alters the Pt
purity and degrades the Pt as the bottom electrode for the ferroelectric ca
pacitor. Good insulating properties were obtained when the SBT film was ann
ealed at 700 and 750 degreesC whereas higher leakage currents were observed
at annealing temperatures > 800 degreesC. A remnant polarization (P-r) of
4.35 muC/cm(2) and coercive field (E-c) of 31.5 kV/cm were obtained for the
SBT thin film annealed at 750 degreesC with a leakage current density of <
10(-7) A/cm(2). (C) 2000 American Institute of Physics. [S0021-8979(00)073
22-9].