Novel Ferroelectric Candidates in a Series of ABi₄Ti₄O₁₅ (A: Alkaline Earth Metals) Thin Films

Abstract

ABi₄Ti₄O₁₅ (A: alkaline earth metals) thin films were prepared on Pt-passivated Si substrates by using the precursor solution of metal alkoxides. As-deposited thin films initiated crystallization below 550°C and enhanced the crystallinity at higher temperature via rapid thermal annealing in oxygen. The crystallinity of the ABi₄Ti₄O₁₅ thin films depended on the A-site cation of the alkaline earth metals but the content of the pyrochlore phase as a second phase was independent of the cation. The phase purity of BLSFs strongly depended on the crystallinity and crystallographic orientation of the Pt bottoms. The 650°C-annealed CaBi₄Ti₄O₁₅ thin films on the relatively low-crystalline Pt was a single phase of the BLSFs and exhibited better ferroelectric properties.

Keywords:

• ABi₄Ti₄O₁₅ thin films
• the Aurivillius family
• chemical solution deposition
• low-temperature processing
• phase purity
• Pt bottom electrodes