Structural and electrical properties of sol-gel-derived Al-doped bismuth ferrite thin films

Al-doped BiFeO₃ (BiFe_(1-x)Al_xO ₃) thin films with small doping content (x=0, 0.05, and 0.1) were grown on Pt(111)/TiO₂/SiO₂/Si substrates at the annealing temperature of 550 °C for 5 min in air by the sol-gel method. The crystalline structure, as well as surface and cross section morphology were studied by X-ray diffraction and scanning electron microscope, respectively. The dielectric constant of BiFeO₃ film was approximately 71 at 100 kHz, and it increased to 91 and 96 in the 5% and 10% Al-doped BiFeO₃ films, respectively. The substitution of Al atoms in BiFeO₃ thin films reduced the leakage current obviously. At an applied electric field of 260 kV/cm, the leakage current density of the undoped BiFeO₃ films was 3.97×10^-4 A/cm², while in the 10% Al-substitution BiFeO₃ thin films it was reduced to 8.4×10^-7 A/cm². The obtained values of 2P_r were 63 μC/cm ² and 54 μC/cm² in the 5% and 10% Al-doped BiFeO ₃ films at 2 kHz, respectively.