Evidence of rhombohedral structure within BiFeO₃ thin film grown on SrTiO₃

Comprehensive crystal structure analysis was performed for a BiFeO₃ thin layer (∼30 nm) grown on a SrTiO₃ substrate using cross-sectional transmission electron microscopy along three different zone axes. Nano-beam electron diffraction patterns combined with structure factor calculations and high-resolution transmission electron microscopy images unambiguously revealed that the BiFeO₃ thin layer grew with a rhombohedral structure identical to its bulk form. No evidence of monoclinic and/or tetragonal distortion was found. The rhombohedral BiFeO₃ thin layer was found to grow onto SrTiO₃ by maintaining an epitaxial relationship in a manner minimizing the lattice mismatch at the BiFeO₃/SrTiO₃interface.