Phase transition, leakage conduction mechanism evolution and enhanced ferroelectric properties in multiferroic Mn-doped BiFeO 3 thin films

Pure and Mn-doped BiFeO 3 thin films were prepared by a facile chemical solution deposition process. X-ray diffraction patterns and Raman spectra imply a phase transition from a rhombohedral structure in pure BiFeO 3 film to a nearly tetragonal structure in Mn-doped BiFeO 3 films. Moreover, it is found that doping of Mn could greatly modify the surface morphology, leakage current properties and ferroelectric properties of BiFeO 3 films. Consequently, the lowest leakage current density and the largest remnant polarization are observed in BiFe 0.925 Mn 0.075 O 3 film which could be well explained by the leakage conduction mechanism and its evolution from the space-charge-limited current behavior for BiFeO 3 and BiFe 0.95 Mn 0.05 O 3 films to the Poole–Frenkel emission for BiFe 0.925 Mn 0.075 O 3 film, as well as completely an Ohmic behavior for BiFe 0.90 Mn 0.10 O 3 film. Based on the X-ray photoelectron spectroscopy analysis of Mn ions, we argue that the varied valences of Mn ions such as Mn 4+ , Mn 3+ and Mn 2+ may play an important role in lowering leakage current density and enhancing the ferroelectric properties of BiFeO 3 films.