Effect of thickness and crystalline morphology on electrical properties of rf-magnetron sputtering deposited Bi₄Ti₃O₁₂ thin films

Bi₄Ti₃O₁₂ (BiT) thin films with thicknesses ranging from 535 to 870 nm were deposited on Pt(111)/Ti/SiO₂/Si substrates by rf-magnetron sputtering method. The films were crystallized by direct thermal annealing in air at 650 °C. The effects of film thicknesses and crystalline morphology on ferroelectric, leakage current conduction and dielectric properties were investigated. XRD and SEM analysises reveal that BiT thin film deposited at 400 °C is amorphous and exhibits a non-crystalline morphology. After annealing treatment, the amorphous film transformed into Aurivillius Bi₄Ti₃O₁₂ crystalline phase with rodlike grains. The electrical properties show that the as-deposited thin film is a lossy dielectric with absence of ferroelectricity. The remnant polarization of crystalline BiT thin films increases slightly with decreasing thickness. The leakage currents of annealed BiT films exhibit ohmic behavior in low voltage region and Schottky emission conduction characteristic in high voltage region, respectively. For crystalline BiT films, the dielectric constant decreases significantly with increasing film thicknesses.