The crystal structure of bismuth ferrite (BiFeO 3 ; BFO) epitaxial films was analyzed by X-ray diffraction (XRD) using a two-dimensional detector. The diffraction spots ð2 1 3Þ hex (hexagonal notation was used for the rhombohedral structure in this study) specific to the rhombohedral structure (space group: R3c), which clearly separated from the diffractions in other crystal symmetries of BFO, was used for determining the crystal symmetry. The BFO films on the SrTiO 3 substrates were

more »

... ly identified as R3c with the ð2 1 3Þ hex diffraction spot, whereas highly strained BFO films (space group: Cm) on the LaAlO 3 substrates did not show the diffraction spot. The structure of a single-domain-like sample with R3c could not be determined using variants, i.e., degrees of freedom for crystal orientation, whereas the Bragg's diffraction of ð2 1 3Þ hex can be used to unambiguously distinguish R3c from other space groups. It was proposed that electron diffraction complemented by nondestructive and highresolution XRD is highly effective to obtain wide-area reciprocal space information for identifying low-symmetric-complex materials such as BFO.