Structural phase transition and enhanced ferroelectricity in Bi(Fe1 − xMnx)O3 thin films deposited by pulsed laser deposition

• The BiFeO3 and BiMnO3 reveal a rhombohedral and monoclinic structure respectively.
• Proposed a phase diagram of Bi(Fe1 − xMnx)O3 thin films
• BiFe0.5Mn0.5O3 film exhibits high dielectric constant and low leakage current.
• Coexistence of two-phase shows enhanced ferroelectric properties.

In this study, BiFeO3 (BFO), BiFe0.5Mn0.5O3 (BFMO) and BiMnO3 (BMO) thin films were fabricated on LaNiO3 (LNO) coated Si(100) substrates by the pulsed laser deposition method. LNO buffer layer provides epitaxial (l00) growth of pervoskite BFO, BFMO, and BMO thin films. The Raman spectra showed that BFO structure is best described as rhombohedral (R3c), and that doping with Mn causes a substantial modification, Jahn–Teller distortion to octahedral accompanied by structural transition toward mixed phase of orthorhombic and rhombohedral. Field emission scanning electron microscope and atomic force microscope images revealed that the average grain size of the BMO thin film is larger than that of BFO and BFMO thin films. It is also observed that BFMO thin film exhibits improved ferroelectric property compared to pure BFO and BMO films. This enhancement of ferroelectric properties could be due to the Jahn–Teller distortion of octahedral in addition to low defects and oxygen vacancies in BFMO films. The leakage behavior of BFO film endures a transition from an Ohmic conduction to space charge limited conduction with increasing electric field, which was associated with the free carriers trapped by the oxygen vacancies. On the contrary, the leakage currents in BFMO and BMO films were found to be subject to trap-free Ohmic conduction.