The recent advances in oxide thin-film fabrications enabled us to obtain high-quality single-crystal oxide thin films and complex artificial hetero-junctions with an atomic-level precision. When we consider the surface or the interface of such thin films, the polarity is a big problem when each layer has a non-zero net charge. In this context, the metallic interface between two band insulators SrTiO 3 (STO) and LaAlO 3 (LAO) has been attracting great interest because this system is composed of non-polar STO and polar LAO. We investigated the electronic structure of the STO-LAO superlattice by resonant soft x-ray scattering . By tuning photon energies to the energy of Ti 2 p →3 d or O 1s→2p absorption edges, one can obtain the information on the electronic structures near the Fermi level, which are composed of Ti 3 d and O 2 p states. From the analyses of reflectivity spectra, focusing on the (003) peak which is forbidden for our “ideal” superlattice structure, we concluded that the LaO|TiO 2 /SrO and the SrO|AlO 2 /LaO interfaces have distinct reconstructions, breaking the heterostructure symmetry. I will also introduce the experimental setup for resonant soft x-ray scattering in Canadian Light Source.
 H. Wadati et al ., J. Appl. Phys. 106, 083705 (2009).