Crystal structure and ferroelectric properties of rare-earth substituted BiFeO3 thin films

The influence of ion modification using rare-earth cations on crystal structures, along with the insulating and ferroelectric properties of BiFeO3 (BFO) thin films was investigated. Rare-earth-substituted BFO films with chemical compositions of (Bi1.00-xREx)Fe1.00O3 (x=0-0.15, RE=La and Nd) were fabricated on (111)Pt/TiO2/SiO2/(100)Si substrates using a chemical solution deposition technique. A crystalline phase of rhombohedral BFO was obtained by heat treatment in a N-2 atmosphere at 500 degrees C for 5 min. The crystal anisotropy and the Curie temperature of BFO were degraded continuously with increasing contents of La3+ or Nd3+ cations. Ion modification using La3+ and Nd3+ cations up to x=0.05 lowered the leakage current density of the BFO film at room temperature from approximately 10(-3) down to 10(-6) A/cm(2). A polarization (P)-electrical field (E) hysteresis loop measured at 10 K revealed that the intrinsic remanent polarization of La3+- and Nd3+-substituted BFO films with x=0.05 (44 and 51 mu C/cm(2), respectively) was smaller than that of a nonsubstituted BFO film (79 mu C/cm(2)), which is ascribed to the degradation of crystal anisotropy and the Curie temperature of the BFO crystal. (c) 2006 American Institute of Physics.