Phase transition, leakage conduction mechanism evolution and enhanced ferroelectric properties in multiferroic Mn-doped BiFeO3 thin films

Abstract

Pure and Mn-doped BiFeO3 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 BiFeO3 film to a nearly tetragonal structure in Mn-doped BiFeO3 films. Moreover, it is found that doping of Mn could greatly modify the surface morphology, leakage current properties and ferroelectric properties of BiFeO3 films. Consequently, the lowest leakage current density and the largest remnant polarization are observed in BiFe0.925Mn0.075O3 film which could be well explained by the leakage conduction mechanism and its evolution from the space-charge-limited current behavior for BiFeO3 and BiFe0.95Mn0.05O3 films to the Poole–Frenkel emission for BiFe0.925Mn0.075O3 film, as well as completely an Ohmic behavior for BiFe0.90Mn0.10O3 film. Based on the X-ray photoelectron spectroscopy analysis of Mn ions, we argue that the varied valences of Mn ions such as Mn4+, Mn3+ and Mn2+ may play an important role in lowering leakage current density and enhancing the ferroelectric properties of BiFeO3 films.