Structure properties of BiFeO3 films studied by micro-Raman scattering

Abstract

${\text{BiFeO}}_3$ (BFO) films deposited on ${\text{SrTiO}}_3$ (001) substrates and on ${\text{LaNiO}}_3$ -coated ${\text{SrTiO}}_3$ (001) substrates with different annealing ambiences of oxygen and nitrogen were studied by using micro-Raman spectroscopy and x-ray diffraction (XRD). XRD showed that the films are in single-phase with rhombohedral structure. According to the analysis of the group theory, 13 Raman-active modes, which can be classified as $4A_1$ and $9E$ modes, have been observed in the ${\text{BiFeO}}_3$ films. Raman spectra along the growth direction of the BFO films in the side-view scattering geometry were performed by the Raman mapping technique. The variations of Raman shift and Raman bandwidth in different depths of the films imply the existence of residual strain along the growth direction of the BFO films. These results are very useful for the understanding of the depth dependence of the physical properties including the interface and surface structure of the BFO films.