Correlation between structure, dielectric, and ferroelectric properties in BiFeO3–LaMnO3 solid solution thin films

Abstract

Chemical solution processed BiFeO3 thin films usually show high leakage currents and poor ferroelectric properties. The optimizations of processing conditions and doping with appropriate elements have been among the most promising strategies to enhance the overall properties of BiFeO3 thin films. However, detailed studies on the effects of doping elements on the structure and through it on the properties are still lacking. In this work we investigate the interplay between structure and dielectric-electric-ferroelectric properties of BiFeO3–LaMnO3 [Bi1−xLaxFe1−xMnxO3 (0≤x≤0.1)] solid solution thin films grown on Pt-terminated silicon substrates. The BiFeO3–LaMnO3 system is shown to undergo a structural transition from monoclinic to orthorhombic-tetragonal with various degrees of orthorhombic distortion. All LMO-containing films show a Debye-like dielectric relaxation with the activation energy of 0.90 eV. Both dielectric relaxation and leakage current mechanisms were interpreted in terms of ionized oxygen vacancy hopping. On the basis of comparative studies on individual doping with La and Mn it is shown that Mn is responsible for the dielectric anomaly and structural transition whereas La alone seems to stabilize the perovskite structure. A correlation between the degree of orthorhombic distortion, leakage current, and polarization properties was also found, with a minimum of leakage current and fairly high polarization at the highest distortion.