Structural and pyroelectric properties of sol–gel derived multiferroic BFO thin films

Multiferroic BFO/PZT multilayer films were fabricated by spin-coating method on the (1 1 1)Pt/Ti/SiO2/Si substrate alternately using PZT(30/70), PZT(70/30) and BFO alkoxide solutions. The structural and ferroelectric properties were investigated for uncooled infrared detector applications. The coating and heating procedure was repeated six times to form BFO/PZT multilayer films. All films showed the typical XRD patterns of the perovskite polycrystalline structure without presence of the second phase such as Bi2Fe4O3. The thickness of BFO/PZT multilayer film was about 200–220 nm. The ferroelectric properties such as dielectric constant, remnant polarization and pyroelectric coefficient were superior to those of single composition BFO film, and those values for BFO/PZT(70/30) multilayer film were 288, 15.7 μC/cm2 and 9.1 × 10−9 C/cm2 K at room temperature, respectively. Leakage current density of the BFO/PZT(30/70) multilayer film was 3.3 × 10−9 A/cm2 at 150 kV/cm. The figures of merit, FV for the voltage responsivity and FD for the specific detectivity, of the BFO/PZT(70/30) multilayer film were 6.17 × 10−11 Ccm/J and 6.45 × 10−9 Ccm/J, respectively.