Optical characteristics of Bi_4-xEu_xTi₃O₁₂ ferroelectric thin films on fused silica substrates

Abstract

Bi_4-xEu_xTi₃O₁₂ (BEuT) ferroelectric thin films were prepared on fused silica substrates by using chemical solution deposition technique. The attained samples had a polycrystalline bismuth-layered perovskite structure, and their optical properties were composition dependent. The thin film samples had good optical transmittance above 500 nm wavelength. A blue shift of the optical absorption edge was observed in the BEuT thin films with increasing Eu³⁺ concentration. The optical band gaps of BEuT thin films were estimated to be about 3.57, 3.60, 3.61, 3.63, and 3.69 eV for the samples with x = 0.25, 0.40, 0.55, 0.70, and 0.85, respectively. Photoluminescence measurements showed that two emission peaks of BEuT thin films originated from two transitions of ⁵ D ₀ → ⁷  F ₁ (594 nm) and ⁵ D ₀ → ⁷  F ₂ (617 nm) had maximum intensities when Eu³⁺ concentration was x = 0.40. The relatively high quenching concentration of Eu³⁺ content was thought to be related to the layered structure of BEuT thin films. These results suggested that multifunctional BEuT thin film materials could have promising applications in optoelectronic devices.