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

Abstract

Bismuth ferrite (BiFeO3, short for BFO) is an important room-temperature single phase multiferroic materials. To further improve electric properties of BFO, La3+ was introduced. Bi1−xLa x FeO3 (x = 0–0.12) thin films were fabricated by sol-gel method. The microstructure, optical and electric properties of Bi1−xLa x FeO3 thin films have been investigated. XRD results show that Bi1−xLa x FeO3 thin films is rhombohedral distortion perovskite structure and the addition of La3+ can inhibit the formation of impure phase. The substitution of La3+ for Bi3+ on A sites can restrain the growth of grain and improve the roughness of thin films. The band gap of Bi1−xLa x FeO3 thin films is less than that of BFO thin films, and its band gap decreases first and then increases as the content of La3+ increases, which results from both Burstein-Moss effect and impurity level. A larger amount of La3+ (x = 0.12) can make leakage current of BFO thin films obviously decrease. Moreover, the remnant polarization and coercive electric field of Bi1−xLa x FeO3 thin films increase with the increasing of La3+ content. It results from the decrease of oxygen vacancy and effects of grain size.