Studies on the La substitution site in Bi4−xLaxTi3O12 by polarization-dependent x-ray absorption spectroscopy

We performed polarization-dependent x-ray absorption spectroscopy studies on epitaxially grown Bi4−xLaxTi3O12 thin films at the 3p→6s edges to find the La substitution site. Our results show a clear difference between the absorption spectra taken with parallel and perpendicular polarizations, which is consistent with the view that La replaces Bi in the layer rather than at the perovskite site. Calculated absorption spectra also support the interpretation. We therefore conclude that some, if not all, La atoms replace the Bi atoms in the layer.