Polarized Raman scattering of multiferroic BiFeO3 epitaxial films with rhombohedral R3c symmetry

Abstract

Highly (111)-oriented rhombohedral BiFeO3 (BFO) thin films were grown on (111) SrTiO3 substrates by pulsed laser deposition. Polarized Raman-scattering study of the (111)-oriented epitaxial BFO thin film with rhombohedral R3c symmetry was carried out by employing two distinct backscattering geometries. The A(1)-symmetry transverse-optical [A(1)(TO)] phonons were selectively isolated from the E-symmetry transverse-optical [E(TO)] phonons by employing Y-'(ZZ)Y-' polarization configuration in a novel side-view backscattering. By comparing the Y-'(ZZ)Y-' spectrum with the Z((XX')-X-')Z polarization spectrum in a normal backscattering, we were able to assign most of A(1) and E-symmetry normal modes of R3c BFO. In addition, we found that there was a negligible LO-TO splitting in the A(1)-symmetry normal modes.