Enhanced remnant polarization in ferroelectric Bi6Fe2Ti3O18 thin films

Abstract

For practical applications of ferroelectric memory, a large remnant polarization in nontoxic Pb-free ferroelectric materials is required. We prepared Bi₆Fe₂Ti₃O₁₈ thin films on Pt/Ti/SiO₂/Si (100) substrates by chemical solution deposition using different annealing processes and found that a well-defined ferroelectric hysteresis loop with a rather large remnant polarization (P_r ≈ 21.5 μC cm⁻²) occurs in Bi₆Fe₂Ti₃O₁₈ thin films prepared by rapid thermal annealing in air. This value of remnant polarization is superior to those of other ferroelectric Aurivillius compounds such as Bi₂WO₆, Bi₃TiNbO₉, Bi₄Ti₃O₁₂, Bi₅FeTi₃O₁₅, and Bi₆Fe₂Ti₃O₁₈ thin films prepared by chemical solution deposition and pulsed laser deposition. The results of X-ray diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy and ferroelectric P–E hysteresis loops revealed that the grain size, surface morphologies, oxygen vacancies and lattice distortion play very important roles in the determination of the remnant polarization. The present study provides an effective route to prepare layered Aurivillius thin films with a large remnant polarization by chemical solution deposition.