The effects of Mn doping on the optical properties of chemically deposited BiFeO3 thin films

A series of Mn-doped BiFeO3 (BFO) thin films were prepared on Pt/Ti/SiO2/Si(111) substrates using a chemical solution deposition method. The structural and optical properties of the Mn doped BFO thin films were studied by X-ray diffraction, Raman spectroscopy and ellipsometric spectroscopy. The X-ray diffraction analysis shows that the films have a single perovskite structure and that a phase transition appears with increasing of the Mn content. The Raman scattering spectra reveal that there are two additional peaks at around 480 and 620 cm− 1 for the Mn-doped BFO samples comparing to the undoped one, indicating the existence of orthorhombic phase. Ellipsometric spectroscopy measurements were carried out in the spectral range of 1-5 eV and the experimental data fitted based on the Tauc-Lorentz model using two oscillators. The optical constants (refractive index n and extinction coefficients k) of the Mn-doped BFO thin films were determined. Moreover, the band gap was found to decrease with increasing of the Mn content.