Great enhancement of ferroelectric properties of Al2O3-modified BiFeO3 thin films obtained by sol-gel method

Thin films prepared by sol-gel method usually have a large leakage current, which hinders their practical applications. Therefore, it is extremely important to adopt effective strategies to reduce their leakage current. In this work, BiFeO3 thin films with Al2O3 modification, either in the format of layer insertion or evenly-distributed particles incorporation, are fabricated by a sol-gel method on the Pt(111)/Ti/SiO2/Si substrates. It was found that an optimal amount of Al2O3 in the system can greatly compress the leakage current and enhance the ferroelectric properties. For BiFeO3 films with thickness in the ~300 nm range, remnant polarization (Pr) of ~ 40.82, 80.08, 61,6 μC/cm2, and maximum polarization (Pmax) of ~ 62, 157, 90 μC/cm2 can be achieved for Al2O3 modification via 1/3, 1/5 layer insertion and 1:5 particle incorporation, respectively. Additionally, we systematically investigated the impact of Al2O3 on the phase microstructure, leakage current, and conduction mechanism behavior of Al2O3-modified BiFeO3 films. The results not only promote the sol-gel method as a promising method for preparing high-quality ferroelectric thin films with compressed leakage, but also promote the potential applications of BiFeO3 thin films in electromechanical devices.