Structural, optical, and dispersive parameters of (Gd, Mn) co-doped BiFeO3 thin film

Abstract

Nanocrystalline bismuth ferrite thin films co-doped with Gd and Mn were successfully fabricated via sol-gel spin coating method onto the corning glass substrate. The effect of Gd and Mn incorporation at A and B sites of bismuth ferrite perovskite on its structural, microstructural, and optical properties was studied systematically. The starting material for the synthesis of the samples was bismuth nitrate, ferrite nitrate, gadolinium nitrate and manganese acetate. These precursors were dissolved in 2-methoxy ethanol to prepare the sol, which was spin-coated at an optimized rate of 3000 rpm for 30 s on corning glass substrate. The samples were heated subsequently at 350 °C for 5 min on a hot plate in the open air and further annealed at 550 °C for 2 h at a muffle furnace for crystallization of the as-prepared thin film. X-ray diffraction analysis reveals the existence of distorted rhombohedral perovskite structure with preferred orientations along the (101) plane. The incorporation of Gd and Mn in bismuth ferrite perovskite was confirmed from Raman spectra measured at room temperature. Surface morphology and microstructural studies were carried out using Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscopy (FESEM). Several optical parameters like bandgap energy, Urbach energy, Extinction co-efficient, Near Edge Absorption ratio were determined from Ultraviolet–Visible spectra of the film prepared. The variation of refractive index, permittivity, loss tangent as a function of wavelength were plotted and discussed. Real and imaginary parts of dielectric functions as a function of wavelength were reported. The correlation between the structural and the microstructural parameters with the optical parameters was investigated in this work.