Influences of La on Optical and Electric Properties of BiFeO3 Thin Films

Bismuth ferrite (BiFeO 3 , short for BFO) is an important room-temperature single phase multiferroic materials. To further improve electric properties of BFO, La 3+ was introduced. Bi 1− x La x FeO 3 ( x  = 0–0.12) thin films were fabricated by sol-gel method. The microstructure, optical and electric properties of Bi 1− x La x FeO 3 thin films have been investigated. XRD results show that Bi 1− x La x FeO 3 thin films is rhombohedral distortion perovskite structure and the addition of La 3+ can inhibit the formation of impure phase. The substitution of La 3+ for Bi 3+ on A sites can restrain the growth of grain and improve the roughness of thin films. The band gap of Bi 1− x La x FeO 3 thin films is less than that of BFO thin films, and its band gap decreases first and then increases as the content of La 3+ increases, which results from both Burstein-Moss effect and impurity level. A larger amount of La 3+ ( x  = 0.12) can make leakage current of BFO thin films obviously decrease. Moreover, the remnant polarization and coercive electric field of Bi 1− x La x FeO 3 thin films increase with the increasing of La 3+ content. It results from the decrease of oxygen vacancy and effects of grain size. Keywords Bismuth ferrite Lanthanum Optical Dielectric Ferroelectric