Effects of Substitution of Sm for Bi in BiFeO₃ Thin Films Prepared by the Sol-Gel Method

Bi_1-xSm_xFeO₃ films with x= 0, 0.03, 0.05, 0.07 and 0.10 are prepared on LaNiO₃/Si(100) substrates by the sol-gel method. X-ray diffraction patterns reveal that pure phase films with random orientations are fabricated. The results of SEM indicate that films with denser surfaces are obtained by Sm substitution. At the doping level of x=0.05, remnant polarization P_r increases to 3.19 μC/cm² from 1.12 μC/cm² of the un-substituted BiFeO₃ film and shows enhanced ferroelectricity at room temperature. Because of the low leakage current density in the high electric field region, a polarization hysteresis loop with remanent polarization of 5.15 μC/cm² is observed in the 0.10 Sm-substituted BiFeO₃ films at the applied electric field of 226 kV/cm. Through the substitution of Sm, the leakage current density is reduced for the films with x= 0.07-0.10.