In situ Observation of the Crystallization Process of Ferroelectric Thin Films by Raman Microspectroscopy

Crystallization processes of ferroelectric strontium bismuth tantalate (SrBi2Ta2O9; SBT) films with a Bi-layered structure and lead zirconate titanate [Pb(Zr0.5Ti0.5)O3; PZT] films with a perovskite structure have been investigated by Raman microspectroscopy. Amorphous films were prepared by rf-magnetron sputtering at room temperature using nearly stoichiometric ceramic targets. In situ Raman observations were performed at intervals with increasing sample temperatures. Under a heating rate of 20°C/min, the SBT films began to crystallize at 710°C, and completed crystallization at 850°C. It was found that SBT film crystallization advanced rapidly in the temperature region from 750 to 800°C. Raman mapping measurements of the SBT films at room temperature after annealing at 700 and 800°C clearly indicated the nucleation and growth processes of the crystal grains, respectively. The Raman peaks of the PZT films, which were observed in situ in spite of the cubic symmetry at the annealing temperatures, showed perovskite structure formation at temperatures as low as 500°C.