Effects of Annealing in Ar Gas on Ferroelectric Properties of SrBi2Ta2O9 Thin Films

The effects of annealing processes at 700°C in Ar gas, added prior to the oxidizing processes of SrBi2Ta2O9 (SBT) films at the lowered temperature of 700°C, are investigated in terms of the ferroelectric properties of the films. SBT films 200 nm thick were spin-coated on Pt(200 nm)/Ti(30 nm)/SiO2(200 nm)/Si substrates by using the chemical liquid deposition method. The annealing was found to be effective in obtaining a large saturated polarization and a remanent polarization 2P r of more than 10 µC/cm2 with leakage current less than 1×10-6 A/cm2 at the process temperature of 700°C. Structural and compositional analyses suggest that some Bi atoms in the films become free of oxygen and arrive at the lattice sites as a result of the annealing in non-oxidizing Ar gas for periods shorter than 100 s. Consequently, the crystallization of SBT layered structures may be promoted even at temperatures as low as 700°C.