Study on pure and Nd-doped BiFeO_3 thin films prepared by chemical solution deposition method

摘要

Polycrystalline BiFeO_3 (BFO) films with varying precursor composition and Bi_(1-x)Nd_xFeO_3 (BNFO, x - 0.06-0.20) films were deposited on FTO substrates by using a chemical solution deposition method. Present data indicated that the precursor played a crucial role, i.e., microstructure, morphology and ferroelectric properties of the BFO film are closely related to the proportion of acetic anhydride. XRD analysis and Raman spectra revealed a structural transition from rhombohedral to tetragonal as the amount of acetic anhydride was increased. The effect of Nd on microstructure, chemical state, dielectric, ferroelectric, magnetic and optical properties has been investigated. A structural transition with increasing Nd content was proved by using XRD and Raman scattering spectra. X-ray photoelectron spectroscopy confirmed the formation of Fe~(2+) and the valence fluctuation of Bi of the BNFO films. The strongest ferroelectric polarization and magnetocapacitance were obtained in the sample with 15% Nd. A dramatic reduction in ferroelectric polarization and the strongest magnetization were observed in the BNFO (x = 0.20) film due to its paraelectric nature and orthorhombic structure. With increasing Nd content, the band gap of the BNFO films decreased with E_g = (2.45 - 0.024x) eV.