PREPARATION AND PROPERTIES OF FERROELECTRIC BATIO3 THIN-FILMS BY SOL-GEL PROCESS

Ferroelectric BaTiO3 thin films have been successfully prepared by sol-gel process using barium and titanium isopropoxides as precursor solutions for dip-coating. Homogeneous BaTiO3 thin films have been obtained on various substrates by preheating gel films at 120-degrees-C in a flow of oxygen/water vapor mixed gas, and successive heating at 650-degrees-C in oxygen atmosphere. The introduction of water vapor during preheating is very effective for the crystallization of BaTiO3 at relatively low temperatures. These films exhibit good crystallinity and smooth surfaces with grains as small as about 50 nm. BaTiO3 thin films prepared on Pt/SiO2/Si substrates with a thickness of about 0.5 mum show dielectric constants of 800 approximately 1000 and loss tangents of 0.07-0.09 at 1 kHz. Ferroelectric hysteresis loops were observed for these thin films which possessed the remanent polarization of 8 muC/cm2 and the coercive field of 25 kV/cm.