Control of the Orientation of Ferroelectric Bi₄Ti₃O₁₂ Thin Films by Multi-step Metal Organic Decomposition Process

Abstract

We have proposed a multi-step metal organic decomposition (MOD) process for Bi 4 Ti 3 O 12 thin films in which some layers were formed in stages using precursor solutions including different amounts of Bi constituent. One step of the MOD process consisted of spin-coating at 3000–4000 rpm for 20 s, drying at 110°C for 5 min, calcination at 400°C for 5 min and sintering at 800°C for 30 min. The orientation index along the c -axis of Bi 4 Ti 3 O 12 thin films was controlled in the range from 0 to 94% by changing the first coating solutions. Bi 4 Ti 3 O 12 thin films with different orientation indexes were fabricated using precursor solutions including excess Bi atoms in ratios of 10 and 40 mol% and exhibited ferroelectric properties. The polarization values at zero field of the random orientated film and the strongly c -axis oriented one were 1.9 and 2.5 µC/cm 2 , respectively, when the same voltage was applied.