PREPARATION OF BI-BASED FERROELECTRIC THIN-FILMS BY SOL-GEL METHOD

The effects of Bi/Ta and Sr/Ta mole ratios on ferroelectric properties of SrxBiyTa2O2 [SBIT(x/y/2.0); 0.7 less than or equal to x less than or equal to 1.0, 2.0 less than or equal to y less than or equal to 2.6] thin-film capacitors were investigated. The SBIT films were grown by the sol-gel method using a spin-on coating on Pt/Ta/SiO2/Si and Pt/Ti/SiO2/Si substrates. The films were annealed at 800 degrees C for one hour in oxygen atmosphere. Remanent polarization (Pr) depended strongly on the Sr/Ta mole ratio, and increased with decrease of the Sr/Ta mole ratio. On the other hand, Pr was almost independent of the Bi/Ta mole ratio. Scanning electron microscopy (SEM) images show that crystal grains grew with decrease of the Sr/Ta mole ratio. Electron probe micro analyzer (EPMA) analysis revealed that Bi content in SPIT films increased with decrease in Sr composition from stoichiometry.